National Cooperative Highway Research ProgramFiscal Year 2003 April 2002

Announcement of Research Projects

The National Cooperative Highway ResearchProgram (NCHRP) is supported on a continuing basisby funds from participating member departments of theAmerican Association of State Highway andTransportation Officials (AASHTO), with thecooperation and support of the Federal HighwayAdministration, U.S. Department of Transportation. TheNCHRP is administered by the National ResearchCouncil’s Transportation Research Board (TRB). TheNCHRP is an applied contract research program totallycommitted to providing timely solutions to operationalproblems facing highway and transportation engineersand administrators.

Each year, AASHTO refers a research programto the TRB consisting of high priority problems forwhich solutions are urgently required by the states. TheAASHTO program for FY 2003 is expected to include17 continuation and 42 new projects.

This announcement contains preliminarydescriptions of only those new projects expected to beadvertised for competitive proposals. Detailed ProjectStatements (i.e., Requests for Proposals) for these newprojects will be developed beginning in August 2002.

Please note that NCHRP Research ProjectStatements for soliciting proposals are available only

on the World Wide Web. Project Statements are notmailed. If you have an interest in receiving ResearchProject Statements, you must periodically browse theNCHRP/World Wide Web site or register on the website (http://www4.trb.org/trb/crp.nsf). If you register,you will receive an e-mail notification of everyProject Statement posting and an e-mail notificationof new anticipated projects in future years.

Because NCHRP projects seek practicalremedies for operational problems, it is emphasized thatproposals not evidencing strong capability gainedthrough extensive successful experiences in the relevantproblem area stand little chance of being selected.Consequently, any agency interested in submitting aproposal should first make a frank, thorough self-appraisal to determine whether it possesses thecapability and experience necessary to ensure successfulcompletion of the project. The specifications forpreparing proposals are quite strict and are set forth inthe brochure entitled Information and Instructions forPreparing Proposals. Proposals will be rejected if theyare not prepared in strict conformance with thesection entitled “Instructions for Preparing andSubmitting Proposals.” The brochure is available onthe Internet at the website referenced above.

IMPORTANT NOTICE

Potential proposers should understand clearly that the research program described herein is tentative. The final program willdepend on the level of funding available from the Federal-aid apportionments for FY 2003. Meanwhile, to ensure that researchcontracts can be executed as soon as possible after the beginning of the fiscal year, the NCHRP is proceeding with the customarysequence of events through the point of agency selection for all projects. The first round of detailed project statements will beavailable in August and September 2002; proposals will be due in October and November 2002, and agency selections will be made inNovember and December 2002. This places the risk of incurring proposal costs at the election of the research agencies. Beyond thepoint of selecting agencies, all activity relative to the FY 2003 program will cease until the funding authorization is known. Thesecircumstances of uncertainty are beyond NCHRP control and are covered here so that potential proposers will be aware of the riskinherent in electing to propose on tentative projects.

Address inquiries to:Crawford F. Jencks, P.E.

Manager, National Cooperative Highway Research ProgramTransportation Research Board2101 Constitution Avenue NW

Washington, DC 20418cjencks@nas.edu

National Cooperative Highway Research ProgramProjects in the Fiscal Year 2003 Program

ProjectNumber Title Page

No.

01-40 Facilitating the Implementation of the 2002 Guide for the Design of New andRehabilitated Pavement Structures

1

01-41 Selection, Calibration and Validation of a Reflective Cracking Model for AsphaltConcrete Overlays

2

01-42 Identification of the Design Conditions and Critical Factors That Are Related to the TopDown Fatigue Cracking Mechanism

4

01-43 Update of Guidelines for Skid Resistant Pavement 6

03-67 Expert System for Setting Speed Limits 7

03-68 Freeway Performance Monitoring, Evaluation, and Reporting 8

03-69 Geometric Design for Work Zones on High-Speed Facilities 10

03-70 Multimodal Arterial Level of Service 11

03-72 Lane Widths, Free-Flow Turn Lanes, and Right-Turn Deceleration Lanes in Urban Areas 13

03-73 Separation of Vehicles - CMV Only Lanes 15

04-31 Relevant Acceptance Test Procedures for Recycled Materials Produced from PCC andHMA Used as Unbound Pavement Base or Subbase Aggregate

17

06-15 Standardized Testing Methodology for RWIS Surface and Subsurface Sensors 19

06-16 Environmental Impacts of Snow and Ice Control Chemicals and Their Relationship toCost and Effectiveness

20

07-14 A Cost-Benefit Analysis of Bicycle Facilities 22

08-46 How to Include Access Management Strategies in State and Metropolitan PlanningOrganization Transportation System Plans

23

08-47 Policy, Planning, and Programming for Goods Movement and Freight in Small and Mid-Sized Metropolitan Areas

25

08-48 Using American Community Survey Data for Transportation Planning 26

09-36 Improved Procedure for Laboratory Aging of Asphalt Binders in Pavements 28

09-37 Aggregate Surface Energy: Measurement and Use in Selecting Materials for Pavements 30

ProjectNumber Title Page

No.

10-62 Acceptance Test for Surface Characteristics of Uncoated Strands Used in PretensionedPrecast Concrete Applications

32

10-63 Heat-Straightening Repair of Damaged Steel Bridges 34

10-64 Field Inspection, Maintenance, and Repair of Existing FRP Bridge Decks andSuperstructures

35

10-65 Demonstration Project: Using Nondestructive Testing Technology for Assuring theQuality of New Flexible Pavements

36

10-66 Methodologies to Account for Realistic Environmental and Time Influences inAccelerated Pavement Testing

38

12-62 Refined Live-Load Distribution-Factor Equations 40

12-63 Comparison of Legal Truck Loads to AASHTO Typical Posting Vehicles 42

12-64 Application of the LRFD Bridge Design Specifications to High-Strength StructuralConcrete Members (Phase 3 – Flexure and Axial Loads)

43

12-65 Development of a Full-Depth Precast Concrete Bridge Deck Construction System Suitablefor Direct Contact Traffic

45

15-24 Hydraulic Loss Coefficients for Culverts 46

16-04 Development of Designs and Guidelines for Safe and Aesthetic Urban RoadsideTreatments

49

17-25 Development of Crash Reduction Factors for Traffic Engineering and ITS Improvements 51

17-26 Development of Models for Prediction of Expected Safety Performance for Urban andSuburban Arterials

53

20-60 Transportation Performance Measures and Performance Target Establishment for AssetManagement

55

24-21 LRFD Soil Nailing Design and Construction Specifications 56

24-22 Economical and Performance Optimization for Using a Wider Range of Backfill Materialsfor Retaining Wall Structures

57

24-23 Riprap Design Criteria, Specifications, and Quality Control 60

25-26 Development of a Low-Impact Development Design and Construction Manual forTransportation Systems

62

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SUMMARY OF APPROVED RESEARCH PROJECTS

♦ Project 01-40Facilitating the Implementation of the 2002 Guide for the Design of New and Rehabilitated PavementStructures

Research Field: DesignSource: AASHTO Joint Task Force on PavementsAllocation: $300,000NCHRP Staff: Amir N. Hanna

At the request of the AASHTO Joint Task Force on Pavements (JTFP) and with the endorsementof the AASHTO Standing Committee on Research (SCOR) and approval of the AASHTO Board ofDirectors, NCHRP initiated Project 1-37A to develop a guide for the design of new and rehabilitatedpavement structures. By July 31, 2002, NCHRP Project 1-37A will deliver the 2002 Guide for theDesign of New and Rehabilitated Pavement Structures accompanied by the necessary computationalsoftware, for adoption and distribution by AASHTO. In contrast to the 1986 and 1993 versions of theAASHTO Guide for Design of Pavement Structures, the 2002 Guide will be based on mechanistic-empirical principles; provide a uniform basis for the design of flexible, rigid, and composite pavements;and employ common design parameters for traffic, subgrade, environment, and reliability. However,because the 2002 Guide is based on mechanistic-empirical principles and incorporates concepts thatmany pavement designers at state departments of transportation (DOTs) may not be familiar with, thereis a need for a coordinated effort to acquaint state DOT pavement designers with the principles andconcepts employed in the 2002 Guide and assist them with the interpretation and use of the Guide andits software. This effort will facilitate implementation and use of the 2002 Guide by state DOTpersonnel, and help pavement designers to identify, for specific conditions, pavement structures andfeatures that would best provide intended performance and service life.

The objective of this research is to facilitate implementation of the 2002 Guide by providing ameans for assisting state DOT personnel with the interpretation and use of the Guide. Accomplishmentof this objective will require at least the following tasks: (1) Convening a national workshop—This taskwill involve organizing and convening a national workshop to acquaint state DOT personnel with the2002 Guide. It is expected that one individual from each state DOT, preferably the chief pavementdesigner, will participate in the workshop. Project funds will cover travel expenses of the invitees. Theworkshop will focus on use of the 2002 Guide and its software for the analysis and design of new andrehabilitated pavement structures; case studies will be used for illustration. Also, a brief review of theprinciples and concepts incorporated in the Guide will be included. (2) Providing customer service—This task is concerned with providing a service to Guide users over a 12-month period. This service willfocus on responding to inquiries from state DOT personnel regarding use of the 2002 Guide and itssoftware. (3) Preparing reports and documentation—This task will involve documenting issues raisedduring the workshop and interactions with Guide users that should be considered in future enhancementsof the Guide and its software. Consideration will be given to issues pertaining to Guide content, datarequirements, ease of software use, research needs, or related matters. When appropriate, the importanceof these issues will be assessed, and corrective actions may be taken under this project or future actionsmay be recommended.

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♦ Project 01-41Selection, Calibration, and Validation of a Reflective Cracking Model for Asphalt Concrete Overlays

Research Field: DesignSource: AASHTO Joint Task Force on Pavements/Maryland/TexasAllocation: $500,000NCHRP Staff: Amir N. Hanna

Reflection cracking is recognized as one of the principal forms of distress in hot mix asphalt(HMA) overlays of resurfaced flexible and rigid pavements. These cracks can be induced byenvironmental or traffic loads, and/or a combination of the two. When these cracks propagate throughthe AC overlay, infiltration of water and de-icing salts can cause rapid deterioration of the underlyingpavement structure and foundation. The basic mechanisms leading to the development of reflectioncracking are horizontal and differential vertical movements between the original pavement and HMAoverlay. However, the present state-of-the-art for preventing reflection cracking in HMA overlays overflexible and rigid pavements is, to a large degree, still based on experience gained from trial and errormethods of in-service highways and has been empirical in nature.

Reflection cracking has been recognized as one of the distresses or failure mechanisms thatshould be considered in an HMA overlay design procedure. Both reflection cracking itself and the rateof crack deterioration of the reflected cracks in HMA overlays are considered to be an important designconsideration for both structural and mixture design characteristics of HMA overlays over existingpavements. Recent work performed under NCHRP Project 1-37A, Development of the 2002 Guide forthe Design of New and Rehabilitated Pavement Structures: Phase II, found that the severity of reflectioncracks (transverse and longitudinal) significantly affects ride quality as measured by the InternationalRoughness Index (IRI). However, a mechanistic-based model to predict reflection cracking in HMAoverlays and composite pavements will not be incorporated into the design guide being developed aspart of NCHRP Project 1-37A because such a model is not readily available. Also, there is no knownongoing national research effort to develop a model that accurately predicts reflection cracks. Forexample, fracture properties and characteristics of HMA mixtures are being studied in detail in NCHRPProject 9-19, Superpave Support and Performance Models Management, but development of a crackprediction model and consideration of the rate of deterioration are well beyond the scope of work forthat project. Other studies and tests are being conducted by state highway agencies (e.g., Caltrans) foruse in evaluating a mixture's resistance to reflection cracking of existing cracks and/or joints in portlandcement concrete (PCC) pavements. Some of the more recent models and procedures that have been usedto design HMA overlays to resist the detrimental impact of reflection cracks on HMA overlayperformance have been reported in the literature (e.g., Proceedings of the 4th International RILEMConference on Reflective Cracking held in March 2000, in Ottawa, Canada).

The overall research objective is to select from current "state-of-the-art" models the mostappropriate mechanistic-based model for reflective cracking in AC overlays. The model will becalibrated, validated, and incorporated into the framework and procedure (software) being developedunder NCHRP Project 1-37A. The specific tasks are as follows:

Phase I: (1) Collect and review information related to the existing reflective cracking models.This information may be obtained from domestic and foreign literature, contact with other agencies andindustry organizations, and other sources. Identify, based on current practices and other information, thefactors that are likely to influence reflective cracking. Also, identify the reflective crack modelscurrently used worldwide, especially those that are part of recent research. (2) Evaluate the merit anddeficiencies of the reflective models identified in Task 1—with consideration to capability, accuracy,practicality, sensitivity to the factors (e.g., structure, crack severity, materials, traffic, and climate),

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applicability, and especially the measurement of asphalt concrete (AC) property of resistance toreflective cracking. Identify the most promising reflective cracking models and, if necessary, newmodels or modifications to existing models for further evaluation in Task 6. These models must besuitable for use by state DOTs. (3) Review the relevant data available in the LTPP database and othersources, and identify the possible sections to calibrate and validate the reflective cracking models. (4)Develop the research plan, to be executed in Task 6, to evaluate and validate the reflective crackingmodels proposed in Task 2. In the plan, discuss the following (a) Identification of the candidatereflective cracking models and associated software to analyze the stress intensity factor and otherfactors. (b) Requirements: for reflective cracking prediction, characterization of pavement structure, andespecially the properties of the asphalt mixture and associated laboratory test procedures or other tools.(c) Candidate sites with various traffic levels, asphalt overlay thickness, environments, and "foundation"types (e.g., old PCC, stabilized base, and old AC). (d) Comparison of the predicted occurrence ofreflective cracking with that observed in the LTPP or other sites, to evaluate the capabilities of thecandidate models. Then, considering implementation, select or modify (or establish) the reflectivecracking model for calibration and validation. (e) Calibration and validation of the selected reflectivecracking models. (5) Prepare an interim report that documents the research performed in Phase I andincludes the updated work plan for Phase II. Following review of the interim report by the NCHRPproject panel, the research team will meet with the panel. Work on Phase II of the project will not beginuntil the interim report is approved and the Phase II work plan is authorized by the NCHRP panel.

Phase II: (6) Execute the plan as approved in Task 5. Based on the results of this work,recommend the reflective model and associated laboratory test to measure the property of reflectivecracking resistance of AC mixtures as a supplement to the 2002 pavement design guide. If a newlaboratory test method is recommended for use, description and details should be provided. (7)Incorporate the calibrated and validated reflective cracking model into the framework and procedure(software) being developed under NCHRP Project 1-37A. (8) Submit a final report that documents theentire research effort. The report shall include an implementation plan for state DOT application.

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♦ Project 01-42Identification of the Design Conditions and Critical Factors That Are Related to the Top DownFatigue Cracking Mechanism

Research Field: Materials and ConstructionSource: FloridaAllocation: $400,000NCHRP Staff: Amir N. Hanna

Fatigue cracking is an important deterioration mechanism of asphalt concrete–surfacedpavement, because of the detrimental effect this cracking has on the overall pavement strength andstiffness. The cracks provide a path for moisture to readily infiltrate the underlying layers and subgradesoils of flexible pavements. Fatigue cracking is caused by repeated wheel loads over time. The pavementstructure, mixture composition and construction are major factors that have an effect on the initiationand propagation of fatigue cracks with load repetitions. More importantly, the environment and climaticfactors also play an influential role on the development of fatigue cracks with time.

Historically, the fatigue or load-associated wheel path cracks have been evaluated in most designand/or evaluation procedures assuming that the fatigue cracks initiate at the bottom of the asphaltconcrete layers and propagate to the surface. The time or number of wheel loads to crack initiation andthe rate of propagation through the thickness of the asphalt concrete layers has previously been related tothe tensile creep characteristics, tensile strength and/or elastic or dynamic modulus of the asphaltconcrete mixtures. Various fatigue relationships have also been developed for predicting the number ofwheel load applications to a predefined level and severity of wheel path fatigue cracks. More recently,however, there has been an increasing number of studies both in the United States and Europe that haveconfirmed that many of the load-related fatigue cracks initiate at the surface of the pavement andpropagate downward through the thickness of the asphalt concrete mixture. This is a more severe casethan the traditional evaluation of fatigue cracks, because it allows water and other foreign debris topenetrate the pavement structure, increasing the stress concentration at the crack tips and propagatingthe crack at an accelerated rate through the thickness of the asphalt concrete. As a result, there is adesperate and critical need to identify the structural-mixture property combinations, in addition to thewheel load characteristics (type of tire, tire pressure, and load), for which the fatigue cracks initiate atthe surface, rather than at the bottom of the asphalt concrete layers.

There have been extensive studies regarding the fatigue characterization of asphalt concretemixtures through the Strategic Highway Research Program and through the FHWA for evaluating thefatigue properties of asphalt concrete mixtures. More importantly, there has been an accelerated use andefficiency in using finite element analysis programs to evaluate and predict where fatigue crackinginitiates throughout the pavement structure. Thus, the tools and mixture characterization procedures arenow available to develop conditions and/or combinations of properties that can be developed fordetermining when fatigue cracks will likely initiate at the surface, as compared with the underlyinglayers. NCHRP Project 1-37A, Development of the 2002 Guide for te Design of New and RehabilitatedPavement Structures: Phase II, will use existing models but will only incorporate a simplistic empiricalapproach to account for top down fatigue cracking. NCHRP Project 9-19, Superpave Support andPerformance Models Management, may incorporate some of the parameters necessary to characterizetop down fatigue cracking, but there is no focus to identify all parameters and model this critical failuremechanism. The results of this research work will have direct application to supporting the mechanistic-empirical design procedure being developed for the 2002 Guide and to support the future and ongoingwork of the Superpave distress prediction software.

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The objectives of this research are (1) to determine and quantify the structural and environmentalconditions and mixture property interactions most conducive for fatigue cracks to initiate at the surfaceand propagate downward through the pavement structure and (2) to develop a model that incorporatesstructural, environmental and material conditions. The following tasks will be performed: (1) Reviewexisting literature and existing models to identify potential mechanisms for top down fatigue cracking.Identify structural, environmental, and material characteristic variables that would support thesemechanisms. (2) Design an analytical experiment that would identify the critical structural,environmental, and material characteristic properties that support top down fatigue cracking. Identifyexisting databases that will be used in the experiment, and identify any additional lab testing of materialproperty characteristics necessary. (3) Submit an interim report that documents the work in tasks 1 and2. (4) Conduct the analytical experiment and any additional lab testing required in order to develop amodel for top down fatigue cracking. The variables to be included in the experiment shall includepavement structure, environmental conditions (temperature, aging, moisture), material characteristicproperties, and loading conditions. (5) Prepare a final report that includes as a deliverable a model of topdown fatigue cracking that could be incorporated into the 2002 pavement design guide andNCHRP/AASHTO projects related to pavement design and material specifications.

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♦ Project 01-43Update of Guidelines for Skid Resistant Pavements

Research Field: Materials and Construction/DesignSource: AASHTO Joint Task Force on Pavements/South DakotaAllocation: $350,000NCHRP Staff: Amir N. Hanna

While the importance of providing skid resistant pavements is acknowledged to be of highimportance, the most recent AASHTO guidelines on the subject are more than 20 years old, the lastversion being published in 1976. Many changes in vehicle characteristics, as well as changes in themethods of collecting friction data, make a revision long overdue.

The objective of this research is to develop a more comprehensive guide that addresses frictionalperformance of asphalt concrete (AC) and portland cement concrete (PCC) pavements and considersrelated highway traffic noise issues. The research would expand on the results of NCHRP Synthesis 291:Evaluation of Pavement Friction Characteristics and apply its results to the development of the guide.This synthesis contains information and reports on the full range of the friction issues, from best practicedesign to long-term performance and state-of-the-art testing procedures. The guide will consider theinfluence of aggregate selection, micro and macro texture, geometrics, and weather on frictionalresistance and will relate data collection equipment, procedures, and calibration methods. The guideshould address related highway traffic noise issues.

Regarding highway traffic noise issues, the guide should define the current situation nationallywith respect to surface friction and noise, identify strategies for maintaining adequate skid resistance onpavement surfaces of all types without generating unacceptable noise pollution, and demonstrate theappropriateness and practicality of these strategies. This effort will involve the following: (a) Review ofpertinent literature and current research and survey of the states to determine the extent of the problem.(b) Examination of legal issues with regard to pavement skid resistance and noise abatement. (c)Interaction with vehicle and tire manufacturers to determine the current status of future designmodifications that may help to alleviate the potential for noise generation while maintaining adequatetraction. (d) Development of a systematic approach to determining the extent of the skid resistance/noiseproblem and possible scenarios for minimizing its impacts, including the feasibility of new surfacetreatments and modified tire tread designs. (e) Conduct of research necessary to clarify potentialsolutions. (f) Evaluation of safety, practicality, and economic feasibility of strategies for noise abatementand examination of related legal and liability issues. (g) Development of guidelines to assist pavementengineers in making appropriate design decisions. (h) Identification of relevant findings and conclusionsfor incorporation in the guidelines for skid resistant pavements.

Note: The AASHTO Standing Committee on Research combined Problem No. 2003-C-35, “Guidelinesfor Quiet and Safe Pavement Surface Textures,” and Problem No. 2003-D-25, “Update of Guidelines forSkid Resistant Pavement.”

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♦ Project 03-67Expert System for Setting Speed Limits

Research Field: DesignSource: Federal Highway AdministrationAllocation: $300,000NCHRP Staff: B. Ray Derr

The management of speed through appropriate speed limits is an essential element of highwaysafety. In a recent study of current practice for setting speed limits, a TRB special committee concludedthat setting speed limits on the 85th-percentile speed might not always be appropriate on roads in built-up areas with a mix of road users and high traffic volumes and roadside activity. There are any numberof factors bearing on reasonable and safe speed but little agreement about the importance and weight ofthe myriad of factors among residents, drivers, public officials, enforcement officers and engineers. As aresult of these pressures, many speed zones appear unrealistic and inconsistent. TRB Special Report 254:Managing Speed: Review of Current Practices for Setting and Enforcing Speed Limits recommends thatan expert system approach be developed to advise and assist the practitioners in setting speed limitswithin speed zones.

The objective of this research will be to develop a computer-based expert system for speed zonedetermination that results in rational and consistent speed limits. The objective will be met through thefollowing tasks: (1) Review current speed zoning guidelines, criteria and procedures used forestablishing reasonable and safe speed limits in the United States. Review experience with the operationof the XLIMITS system in Australia and assess its applicability to the United States. (2) Identify the keysite and traffic factors affecting the determination of reasonable and safe speed limits using a panel ofexperienced traffic and safety professionals, literature review, and field studies as necessary. (3) Buildthe knowledge base for the expert system based on the knowledge induced from the expert panel,literature review and field studies. (4) Develop prototype expert system software for speed zoning. Thesystem should be user friendly and include on-line help. (5) Conduct beta test with practitioners.Evaluate in terms of completeness, logic, ease of use, and other elements. Modify the system to take intoaccount results of the test and evaluation. (6) Prepare a final report documenting the research effort,including a User’s Guide as an Appendix.

Public pressure from special interest groups and elements of government are difficult to resistwhen procedures are seen as imprecise and subjective. This often leads to arbitrary and unrealistic speedzones that inefficiently allocate resources of enforcement agencies and courts to deal with technicalviolators when they should be focused on hazardous behavior. This project will provide an objective,quantifiable, and systematic tool to assist practitioners in implementing credible speed zones in built-upareas resulting in more consistent and safe speed limits. Rational limits implemented statewide will leadto better management of crash risk by targeting enforcement at drivers operating at unreasonable andunsafe speeds.

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♦ Project 03-68Freeway Performance Monitoring, Evaluation, and Reporting

Research Field: TrafficSource: Federal Highway AdministrationAllocation: $300,000NCHRP Staff: B. Ray Derr

The freeway system in urban areas involves a complex collection of interdependentinfrastructure components, facilities, management systems, operating strategies, service providers, andmodes. Public agencies are concerned with preserving the mobility, improving the reliability, enhancingthe productivity, and meeting the public's expectations for efficient and effective travel. Meeting thesechallenges requires agencies to realize the full potential of the investment that has already been madeand will continue to be made in the freeway system.

In order to effectively manage and operate a freeway, an accurate minute-by-minute monitoringof the facility’s performance is necessary. Monitoring the operation or performance of a freeway iscritical for both the agency responsible for managing the facility and for the various users. The freewaymanager monitors the performance of the facility to assess existing conditions for short-termnonrecurring events and longer-term recurring congestion, determines and implements operational plans,and informs freeway users of existing and predicted near-term conditions. The freeway manager alsouses the results of the performance monitoring to identify deficiencies in the physical freeway systemand provides planners and designers with the necessary information and input to incorporate into theplanning and design of future improvements to the facility.

The use of performance measures in transportation planning and decision-making processes ofpublic agencies has increased significantly. This demand has led to the need for information andguidance on how to integrate the consideration of freeway performance into these processes. There isgeneral agreement among transportation practitioners that freeway system performance monitoring,evaluation, and reporting should be performed and continuously supported by operating agencies.

A consensus does not exist and technical guidance has not been developed regarding theappropriate measures, methods, data requirements, evaluation tools, procedures, level of effort, andresources required to properly support the monitoring, evaluation, and reporting of freewayperformance. Research and technical guidance is needed to provide direction and ensure thattransportation professionals are effectively integrating the performance of freeways into the appropriateplanning and decision-making processes of agencies.

The objective of this research is to develop a framework and recommended procedures for publicagencies to use in the monitoring, evaluation, and reporting of the performance of freeway facilities. Theresearch is intended to provide transportation organizations and practitioners with the direction,guidance, and technical basis to integrate the consideration of the performance of freeway facilities intoall of the appropriate aspects and phases of the planning and decision-making processes of an agency.This guidance is expected to support the consideration of freeway performance strategic planning,program, facility or system design; travel management; and traffic control. The technical report that isgenerated from this project will bring together the experiences and lessons learned from differentagencies based on the many different applications and approaches with varying degrees of complexity.This effort will reference and, where appropriate, build upon the structure and guidance that weredeveloped in NCHRP Report 446: A Guidebook for Performance-Based Transportation Planning.

This project will include the following tasks: (1) Review and synthesize lessons learned andcurrent practices of different public agencies. This review should include an in-depth review of thepractices of several leading agencies with mature freeway performance monitoring, management, and

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operating systems and should identify future capabilities of these systems and current gaps in practice.(2) Identify the potential components, support services, and resources required for an ongoingperformance monitoring, evaluation, and reporting program. (3) Develop a family of matrices forperformance measures and corresponding data elements to support the consideration of freewayperformance in a wide range of potential agency planning and decision-making applications that mayinclude the following: strategic planning, evaluation, and investment (e.g., regional transportation plans,capital improvement programming); planning (e.g., corridor studies, feasibility studies and improvementalternatives); programs and provision of services; and managing travel and controlling traffic (e.g.,freeway management system functions, ramp metering, lane control). (4) Identify the potentialdimensions and criteria (e.g., measurability, reliability, temporal, geographical, collectability) toconsider when selecting freeway-related performance measures. (5) Identify the recommendedmethodologies, procedures, tools, and level of effort appropriate to support the integration of freewayperformance in the range of potential planning and decision-making applications. (6) Identify acontinuous process improvement (e.g., planning, system engineering process) framework within whichthe theory and methods of performance monitoring, evaluation, and reporting may be appropriate toapply. (7) Identify the issues to consider related to the continuous monitoring, evaluation, and reportingof freeway performance. Issues may include quantity of information and format suitable for differentaudiences; frequency and methods of reporting performance; and techniques to automate the collection,processing, and reporting of data. (8) Identify further research, training, or technology transfer initiativesthat are need to facilitate the successful transfer and incorporation of these practices by operatingagencies.

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♦ Project 03-69Geometric Design for Work Zones on High-Speed Facilities

Research Field: TrafficSource: TexasAllocation: $500,000NCHRP Staff: Charles W. Niessner

The AASHTO Policy on Geometric Design of Highways and Streets (Green Book) providesdesign criteria for permanent construction of highway and street facilities. It does not provide guidancefor the design of temporary features, including ramps and detours that often have high-speed operation.

Goal 19 of the AASHTO Strategic Highway Safety Plan is entitled "Designing Safer WorkZones." AASHTO's plan states that an average of 760 fatalities occurred annually at highway workzones nationwide over the past five years. FHWA states that in 1998, 772 fatalities resulted from motorvehicle crashes in work zones, of which 222 resulted from large-truck crashes. In addition, FHWA statesthat the percentage of fatal work zone crashes occurring on urban interstates was more than twice thepercentage of all fatal crashes occurring at urban intersections (14 percent compared with 6 percent).Approximately 39,000 people were injured as a result of motor vehicle crashes in work zones in 1998.Work zones require increased driver attention to discern special situations requiring special care. Recentdata available for work zone crashes shows a jump of more than 20 percent in work zone fatalities from1999 to 2000.

Detours and temporary ramps on freeways and other high-speed facilities are of particularconcern because freeways carry much of the nation’s traffic, and the consequences of errors made athigh rates of speed are generally severe. FHWA shows that the majority of fatal work zone crashes forall vehicles and large trucks occurred on roads with speed limits of 55 miles per hour or greater (59percent and 71 percent, respectively).

There appear to be two typical schools of thought for designing high-speed work zone detoursand ramps—either 1) design the detour to maintain the high speeds or 2) make the detour curves sosharp that drivers recognize the need to slow down. Designers have little information available tosuggest how these temporary facilities should be constructed to provide for the safety of the travelingpublic. Better information is needed to guide designers toward achieving AASHTO’s goal of reducingwork zone crashes.

The primary objective of the research is to develop design criteria for temporary ramp and detourdesign for high-speed facilities.

The research should include the following tasks: (1) Literature review of various design guidanceavailable, including the AASHTO Green Book and the Manual on Uniform Traffic Control Devices. (2)Review the findings and data gathered as part of the FHWA research effort entitled "Work ZoneAccident Exposure" to identify trends that could be addressed through geometric design. (3) Survey thestates to collect any state design guidance related to these elements. (4) Collect data at various sitesregarding the type of temporary designs constructed and the crash data for the site during the time periodwhen the temporary features are in place. (5) Develop design guidelines for temporary ramp and detourdesign for various classes of high-speed facilities.

Temporary designs are constructed every day in this country that impact the safety of thetravelling public. It is essential that these designs be appropriate for the speeds anticipated in addition tobeing properly marked and signed. Most of the research previously conducted relates to traffic controland operations within the work zone. Little of it relates to geometric design within the work zone,particularly the design of detours and temporary ramps.

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♦ Project 03-70Multimodal Arterial Level of Service

Research Field: TrafficSource: FloridaAllocation: $450,000NCHRP Staff: Dianne S. Schwager

Throughout the United States in virtually every major metropolitan area there is a desire toevaluate the quality of transportation service of roadways from a multimodal perspective. Smart Growthand public concern for curbing urban sprawl demand that transportation systems provide high mobilitywhile minimizing negative community impacts. Non-automobile modes are often stressed in theseviewpoints. The Transportation Equity Act for the 21st Century (TEA-21) and its predecessor, theIntermodal Surface Transportation Efficiency Act of 1991 (ISTEA) call for the mainstreaming of transit,pedestrian and bicycle projects into the planning, design and operation of the U.S. transportation system.In addition to knowing the levels of service for automobile users, it is also desirable to know the qualityof service to transit, pedestrian, bicycle, and truck users along U.S. roadways.

The current Urban Streets chapter of the 2000 Highway Capacity Manual (HCM) essentiallyonly addresses the level of service of the automobile mode. The Urban Streets chapter, perhaps morethan any other chapter of the HCM, should be the centerpiece of a multimodal user orientation.Automobiles, buses, pedestrians, bicycles and trucks are all potential users of an arterial. The modesinteract with each other such that improvements in quality of service to one mode may improve or lowerthe quality of service for another mode.

Major nationally recognized techniques exist for the automobile (HCM) and transit (TransitCapacity and Quality of Service Manual). Techniques for the pedestrian, bicycle and truck modes arenot as well developed and no nationally accepted technique exists for combining the five modes into asimultaneous analysis. Pilot multimodal level-of-service (LOS) research performed for Florida DOT(FDOT) by the University of Florida resulted in the state adopting multimodal LOS measures,methodologies and software. This work is documented in TRB Paper No. 01-3084. This approach needsto be developed and validated at a national level.

Compounding the problem of developing a unified multimodal approach is that, in general,evaluation techniques have been developed from a modal perspective and LOS thresholds may notmatch well when one mode is compared with another. FDOT research conducted by the University ofSouth Florida recommends that currently adopted LOS measures for automobile, truck and transit bevalidated by the appropriate user groups, much as has been done for the pedestrian and bicycle modes.This would allow for appropriate cross-modal comparisons.

The goal of this research project is to develop a multimodal arterial LOS analysis methodologyand to document the methodology in the next update of the HCM. The following tasks will be performedin two project stages:

STAGE I: (1) Develop an LOS technique for the pedestrian mode. Evaluate and integrate leadingpedestrian LOS methodologies from FDOT, the Pedestrian Level of Service Model developed by SCI,the HCM and others. (2) Update the LOS techniques for the bicycle mode. Evaluate and integrateleading bicycle LOS methodologies from FDOT, FHWA's Bicycle Compatibility Index developed byUniversity of North Carolina, the Bicycle Level of Service Model developed by SCI, the HCM andothers. (3) Review LOS techniques for the automobile and truck modes from a multimodal perspective.Review Urban Streets chapters of the HCM with the intent of expansion to a multimodal chapter.Identify key factors needed for and affected by multimodal analysis. Identify any changes needed in themethodologies to accommodate multimodal analysis. (4) Reevaluate and, as appropriate, update LOS

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techniques for the scheduled fixed route bus mode. Evaluate and integrate the Transit Capacity andQuality of Service Manual, HCM, FDOT's TLOS and Multimodal LOS program, and others. (5)Develop a framework for simultaneous multimodal arterial analysis. Evaluate the FDOT MultimodalLOS methodology, Portland Traffic System Performance Evaluation System and others to determine thebest framework for multimodal analysis.

STAGE II: (6) Validate results. Query a statistically valid sample of roadway users in at leastthree areas of the U.S. Design and conduct statistically valid studies of users to validate the multimodalLOS framework in at least three areas of the United States The development of SCI's Pedestrian andBicycle LOS Models and University of South Florida's Midblock Pedestrian Crossing Difficulty providegood examples of validation techniques that can be expanded to encompass each of the modes in each ofthe study locations. (7) Document the methodology in the next updates of the HCM and TransitCapacity and Quality of Service Manual.

Since 1991, ISTEA and TEA-21 have prescribed a multimodal approach to surfacetransportation, yet there still lacks an integrated tool to assess LOS for transit, automobile, pedestrian,bicycle and truck modes. With no nationally accepted standard methodology, there is no yardstick to usefor tradeoff analysis or multimodal planning or operations.

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♦ Project 03-72Lane Widths, Free-Flow Turn Lanes, and Right-Turn Deceleration Lanes in Urban Areas

Research Field: TrafficSource: AASHTO Task Force on Geometric Design/ColoradoAllocation: $450,000NCHRP Staff: B. Ray Derr

Lateral space in urban transportation corridors is becoming increasingly congested. At the sametime, adding width to roadways and streets in urban areas often results in higher running speeds andincreased pedestrian crossing distances, which in turn can act to decrease the safety and livability of thecommunities through which the roadways and streets pass. In addition, space for roadways andwalkways is often extremely limited or simply not possible. Therefore, it is important that the availableroadway width be optimized in terms of safety and operational efficiency. Lane widths of ten, eleven,and twelve feet are the most commonly used design values in these urban situations. Traditionally, thewider lane has been thought to maximize operational capacity across variable low speed urbanconditions. Recently, questions have been raised concerning whether narrower lanes may have similarcapacity capabilities and perhaps enhanced safety characteristics compared with the wider lanes in lowspeed urban applications.

Free-flow turn lanes have become increasingly common in urban areas over the last twentyyears. The free-flow lanes are often provided for right turn situations, but are also used for left turnmovements onto one-way roadways. The use of free-flow turn lanes has significantly reduced vehicleemissions while idling as well as enhanced intersection capacity and operations for vehicle movement.However, questions have been raised concerning the contribution of free-flow turn lanes tovehicle/pedestrian conflicts. While free-flow turn lanes can orient the driver's attention toward oncomingtraffic and away from possible pedestrian crossings, there is no consensus on the magnitude ofvehicle/pedestrian conflicts induced by free-flow turn lanes. Further, the effect that factors such aschannelization, signalization, acceleration/deceleration lanes, turn radii, and island placement may haveon these conflicts is unknown.

Right-turn deceleration lanes reduce the incidence of rear-end collisions from vehicles slowing tomake right-turn maneuvers. Right-turn deceleration lanes also improve arterial capacity by removingslower moving turning vehicles from the main traffic stream. New access points, particularly busyprivate commercial driveways, often contribute noticeably to the congestion and reduced outside travellane capacity. Several states have established warrants and design criteria for right-turn decelerationlanes for driveways and intersections, but the criteria vary widely. In addition, there is little informationon the design and placement of bicycle lanes and handling of adjacent pedestrian paths at locations withright-turn deceleration lanes. Information that transportation agencies can use to determine when adeceleration lane is needed and to design that lane is desirable.

The objective of this research is to assess the state of the practice in geometric design of lanewidths, free-flow turn lanes, and right-turn deceleration lanes in urban areas. This assessment shouldspan the range of conditions found in urban areas, and particular attention should be paid to the impactof the designs on vehicle/pedestrian conflicts.

The project will include the following tasks: (1) Review previous research on the safety andoperational effects of lane widths on low speed urban arterial/collector roadways. Evaluate whethersignificant safety, operational, or capacity differences can be associated with lane widths of ten, eleven,and twelve feet on low speed (25 mph to 45 mph) urban collectors and arterials. Local streets are notpart of this research effort. The research should include large and small urban areas, and heavilycongested and less congested facilities. If significant differences are found, recommend criteria upon

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which a design decision on lane width can be made. (2) Review previous research on the effects of free-flow turn lanes on vehicle/pedestrian conflicts. Evaluate the magnitude of vehicle/pedestrian conflictsinduced by free-flow turn lanes. If significant conflicts are found, evaluate the effects of speed,signalization, turn lane width, corner radii, island placement, presence of acceleration/deceleration lanesand intersection skew on these conflicts in congested and uncongested collector and arterial situations.Estimate the effect on vehicle operations and emissions if free-flow turn lanes were eliminated.Summarize the situations where free-flow turn lanes may significantly influence vehicle/pedestrianconflicts and those situations where such influence is minimal. Offer design recommendations forintersection geometrics and operations to minimize vehicle/pedestrian conflicts. (3) Determine thecurrent practice for warranting and designing right-turn deceleration lanes through a literature reviewand survey. Detailed interviews with states with comprehensive right-turn deceleration lane criteria (e.g.,Colorado, Delaware, Michigan, Oregon, Virginia) may be desirable, particularly in assessing theeffectiveness of their criteria. Evaluate the safety and operational benefits of right-turn decelerationlanes. Identify the various factors that would affect the implementation of right-turn deceleration lanes.This would possibly include arterial traffic volume levels, right-turn traffic volume, functionalclassification, crash rates, posted speed, density, corner clearances, bicycle and pedestrian improvementsand land values. Develop criteria for deciding where deceleration lanes should be installed (for newaccess and retrofit) and recommend design parameters. Information should be presented in simpleguidelines and charts. Simple simulation models could be developed to evaluate the traffic operationaleffectiveness of different design configurations at various traffic levels. (4) Develop a final report thatsummarizes the research conducted. Recommended changes to the AASHTO Policy on GeometricDesign of Highways and Streets and other AASHTO publications should be included in an appendix tothe report.

Note: This project is a combination of Problem No. 2003-G-06, “Development of Right-TurnDeceleration Lane Warrants and Design Criteria”; Problem No. 2003-G-56, “Free-Flow Turn Lanes inUrban Areas”; and Problem No. 2003-G-57, “Lane Width in Urban Areas.”

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♦ Project 03-73Separation of Vehicles - CMV Only Lanes

Research Field: TrafficSource: MarylandAllocation: $100,000NCHRP Staff: Ronald D. McCready

Congestion on our nation’s highways is a leading contributor to the rising number of accidents.The interaction between cars and commercial vehicles, namely large trucks, having significantlydifferent sizes/configurations, weights and operating capabilities acts to exacerbate the problem. Aspressure mounts to increase the legal size and weight restrictions for commercial motor vehicles(CMVs), coupled with an increase in the number of vehicles on the nation’s highways, government istasked with trying to manage a transportation system with severely limited resources. Although the issueof CMV-only lanes is raised from time to time, as a potential method for both easing congestion andreducing the number of accidents, little if any, real data exist to enlighten transportation officials as tothe efficacy of such lanes.

The Federal Highway Administration (FHWA) has performed preliminary research andconducted modeling scenarios on lane separation for different classes of vehicles. Additionally, the NewJersey Turnpike Authority (NJTPA) has vast experience in the area of lane separation for different typesof vehicles. During the latter part of the 20th Century, the NJTPA opened two lanes in each direction onthe New Jersey Turnpike (NJTP) that are physically separated from other traffic and that are specificallydedicated to CMV traffic. Statistics from 1998 revealed this portion of highway had a 36 percent loweraccident rate than the stretch of Turnpike which has lanes open to all traffic. Furthermore, evidencesuggests that other countries around the globe have experimented with the concept of lane separation fordifferent classes of vehicles.

In summation, the concept of CMV lanes for large vehicles that travel our nation’s highways isnot a new one, however, considering the lack of any previous research into the aforementioned topicthere is a real need for an in-depth review of existing data in this area. An examination of the currentapplications (NJTPA experience) and others would provide valuable information that could be utilizedby transportation officials in determining the future of highway planning in their respective areas.

The objectives of this research project are to (1) examine the various performance characteristicsof a CMV-only lane application within a highway (e.g., reduced congestion, accident reduction, etc.);(2) examine relative items such as cost variables, aspects of reduced and/or increased pavement wear;(3) examine/explore modeling scenarios which have been completed by others; (4) examine/explore thebenefits to Intelligent Transportation Systems (ITS) technologies that are being used by various states[i.e., Automated Vehicle Identification (AVI) readers, Driver-less Vehicle Systems (DVS), ElectronicTraffic Control and Monitoring (ETCM) system as well as other systems]; (5) examine/review thefeasibility of increased size and weight standards on CMV only lanes; and (6) prepare a report ofpertinent data and findings that includes economic implications, transportation performance, safetybenefits, and other impacts associated with the application of CMV-only lanes.

The projected increase in traffic and specifically commercial vehicle traffic on the highwaysnationwide makes this study critically important for future highway design and planning. As highwayengineers and transportation officials across the nation struggle to resolve traffic congestion, as well asother issues involving the movement of vehicles on our highways, it becomes vitally important that allavenues are explored.

The motoring public is clamoring for a transportation system that is responsive to its needs.Drivers across the nation have made it clear: they want a system that reduces congestion and reduces

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accidents. Moreover, they have expressed their displeasure of having to intermingle with large vehicles(namely trucks and buses) on the Interstate System and believe this to be a deadly combination thatcourts disaster.

The study would provide great incite into the most effective methods for accommodating a broadspectrum of commercial and noncommercial vehicles on our major highways.

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♦ Project 04-31Relevant Acceptance Test Procedures for Recycled Materials Produced from PCC and HMA Used asUnbound Pavement Base or Subbase Aggregate

Research Field: Materials and ConstructionSource: New YorkAllocation: $100,000NCHRP Staff: Amir N. Hanna

Due to decreased availability of natural aggregates and increased pressure to incorporaterecycled materials in public construction, it has become important to find tests that properly evaluate thecritical properties of non-traditional construction aggregate materials used in unbound pavement layers.Standard tests developed specifically for natural materials may not yield realistic results when applied torecycled portland cement concrete (PCC) or hot mix asphalt (HMA) materials. For example, magnesiumsulfate soundness testing of recycled concrete aggregate may yield very low loss rates due to theinability of the magnesium sulfate solution to penetrate the portland cement paste on the stone and notnecessarily the innate quality of the aggregates. Also, gradation is normally a critical property forunbound materials, yet recycled HMA defies traditional sieving due to the presence of the asphaltcement. However, some states have found that leachate from PCC precipitating in the underdrains was acritical problem.

Research done in this field has been primarily to determine if these materials may be used forthese applications, and the answer has been a resounding "yes." Now research is needed to find andexamine test methods that accurately depict the critical properties of these materials. The tests must besimple enough to be run in production volumes, yet comprehensive enough to ensure satisfactoryproperties of these materials in constructability, performance, and durability.

To be more efficient with materials, PCC and HMA that were formerly waste products are nowbeing used by state transportation departments as aggregates in unbound granular layers in highwayconstruction applications. The tests that have been developed for traditional, natural materials may notbe reliable on these recycled materials or may not determine properties that are particularly relevant tothe materials’ unusual characteristics. Typically, tests are done for durability and gradation, but aleachate or chemical content test may be more important for these products in this application.

The objectives of this research are to assess the applicability of the standard tests for evaluatinguse of recycled PCC and HMA materials in pavement bases and subbases and establish relevantproperties and test methods for these applications. The existing tests may suffice in many cases, withchanges in the boundary values, or different tests may be more applicable. Specific tasks that may berequired for this research would include the following: (1) Literature Search—To determine the state ofthe knowledge and art in the use of recycled concrete materials (HMA and PCC) as unbound aggregatelayers. This will be useful not only for learning what others are using as tests for these materials, butalso just how commonly these materials are being recycled. (2) Survey of Practice—To better definewhen these materials are being recycled and for what uses, as well as what steps are being taken toensure their suitability. This should also uncover other unbound applications for which there is a desireto use recycled aggregates, but for which no reliable test methods yet exist to determine criticalproperties. (3) Applied Research—To determine which properties are most relevant to these unboundpavement layer applications, which tests best determine those properties, and what gaps may be in thecurrent knowledge or available test methods to determine these properties. (4) Testing Program—To doactual laboratory testing as necessary to validate the findings in Task 3. Check for reliability, accuracy,and repeatability, as well as for practicality of the proposed test methods. (5) Summarize—To produce afinal product that lists unbound pavement layer applications for which these materials are appropriate,

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that cautions about inappropriate uses, and that provides the tests that best define the properties mostlikely to apply to proper uses.

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♦ Project 06-15Standardized Testing Methodology for RWIS Surface and Subsurface Sensors

Research Field: MaintenanceSource: VirginiaAllocation: $300,000NCHRP Staff: Crawford F. Jencks

At least 42 state-level DOTs use road weather information systems (RWIS). These agenciesspecify standards for the accuracy of surface and subsurface sensor measurements. At present, mostagencies use vendor-developed calibration procedures or accept the data without verification. There is aneed for standardized, internationally accepted testing and calibration methods. Aurora, a consortium ofUnited States and Canadian DOTs and the Swedish National Road Administration formed to promoteRWIS research and implementation, has investigated the state of the practice for testing and calibratingRWIS surface and subsurface sensors. A December 1999 report indicates that a number of nations andorganizations are developing standards for testing and calibrating road weather sensors, but as of thereport date, only the Ministère de l’Equipment des Transports et du Logement of France has adopted andimplemented standards.

The objective of the research is to develop detailed standards, specifications and procedures forthe testing and calibration of surface and subsurface sensors. The standards, specifications andprocedures will be applicable for both laboratory and field use. Tasks include(1) An examination of the literature and review of previous work undertaken into the development of

testing methodologies relating to RWIS components (more specifically, pavement and atmosphericsensors). This task could build on a state-of-the-practice report undertaken by Aurora and onatmospheric sensor standards developed by the National Weather Service and the meteorologicalcommunity.

(2) Draft testing and evaluation guidelines, the purpose of which is to develop a preliminary set ofprotocols that will be relevant in testing RWIS sensors.

(3) Beta test a series of pre-selected RWIS sensor products and the testing methodology evaluated. Theinitial examination will be dynamic in nature, allowing for modifications to be made to theguidelines manual based upon decisions made during the test.

(4) Final modifications and testing procedure issues will be addressed and incorporated into a rewrite ofthe preliminary testing protocols. This iteration will be critical because it will reflect the experiencesgained from the initial test of the protocols.

(5) A summary of the findings will be prepared, written for use by public transportation agencyprofessionals. The report will recommend standards and tests that public agencies can adopt to testand calibrate sensors.

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♦ Project 06-16Environmental Impacts of Snow and Ice Control Chemicals and Their Relationship to Cost andEffectiveness

Research Field: MaintenanceSource: New YorkAllocation: $250,000NCHRP Staff: Christopher J. Hedges

Environmental and regulatory agencies have realized the enormous quantities of snow and icecontrol products that are applied to highways and have questioned the impact of these products.Transportation agencies are asked to use less toxic or "environmentally friendly" alternatives whereverpossible, without being given a guide for comparing which products meet this standard. The traditionaluse of road salt has been prohibited in some locations, leaving highway agencies uncertain of how trafficsafety can be maintained in bad weather. Environment Canada, for example, has declared road salt to betoxic under Canadian law, thus setting the foundation for tighter controls and more restrictions on itsuse.

Several new chemical preparations, including some that are trademarked, have entered themarket as both anti-icing and deicing chemicals for use by transportation agencies. One formulation,derived from corn, is advertised as an "environmentally friendly" and biodegradable alternative to saltfor pre-wetting stockpiles or anti-icing. Several states and municipalities have nonetheless prohibited itsuse, even in sensitive environments. Another product uses ethylene glycol (antifreeze) and claims towork well without addressing environmental impacts. Recently, highway agencies have beenencouraged to use molasses to treat salt although the problems of explosive gases from fermentation, theeffect on oxygen, demand on receiving waters, and its effectiveness are unknown. Most studies of themost common chemical alternatives—sodium chloride (salt), magnesium chloride, calcium chloride,calcium magnesium acetate (CMA), potassium acetate (KAc) and urea—have focused on effectiveness,cost, and performance under various weather conditions without evaluating their relative impacts on theenvironment.

The objective of this research project is to examine the environmental impacts of a range of snowand ice control products for several parameters of interest and to identify which products are potentiallyharmful. These products and the parameters would be selected by an expert panel, based on themembers' own experience and on a search of the current literature.

The anticipated products of this research will be recommendations for choosing specificchemicals in environmentally sensitive environments and a sound basis for those choices that the publicand regulatory agencies can support.

The panel members would select parameters of importance to environmental regulatory agenciessuch as biological and chemical oxygen demand (BOD and COD), the contribution of phosphorus orother nutrients that speed eutrophication, or the impact of low pH or heavy metals on the toxicity ofreceiving waters. The panel would choose appropriate laboratory and bench-scale tests, designate thetypes of acceptable analyses, and establish the matrices (soil or water) to be studied. Some laboratorytesting of the products' anti-icing or deicing effectiveness may be necessary in addition to the dataobtained from the literature search.

This project should ideally involve (1) bench-scale testing in a laboratory to derive some simpleleaching relationships and (2) laboratory toxicity tests of a range of the snow and ice control products.The panel may also propose test areas for subsequent field tests of various chemicals and applicationrates. Additional available information on recommended uses under various weather conditions, costs,application requirements, corrosivity to equipment, and effectiveness at preventing a bond between ice

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and pavement should also be collected and compiled with the environmental and toxicity data of thisstudy.

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♦ Project 07-14A Cost-Benefit Analysis of Bicycle Facilities

Research Field: TrafficSource: MinnesotaAllocation: $300,000NCHRP Staff: Christopher J. Hedges

States are examining the role of bicycling in response to traffic congestion, increased traveltimes, and environmental impacts because of changing land-use patterns. Through TEA-21, funding hasbeen made available to develop bicycle facilities, both on- and off-road; however, this public investmentin bicycle facilities has been carried out without a comprehensive analysis of the costs and benefits ofsuch spending. There is little known about the impact of facility development on bicycle use and modeshares or on other transportation, environmental, economic, and social factors. To make the best use oftransportation funds, the costs and benefits of bicycle facility investment should be investigated. Theresults will be useful in making decisions about congestion mitigation, bicycle facility development,transportation demands, and community development.

The objective of this study is to provide state and local government with guidance on bicyclefacility investment based on the projected costs and benefits.

Accomplishment of the project objective will require the following tasks: (1) identify the costsassociated with building and maintaining bicycle facilities; (2) provide a method to determine varyingcosts depending on location, land values, and customers served; (3) identify and document the benefitsassociated with bicycling and bicycle facilities including transportation, environment, intermodality(such as improving effectiveness of transit), economics, society and quality of life; (4) provide ananalysis of maintenance costs of bicycle facilties and identify key components in bicycle facility designthat keeps the facilities pleasant, safe, efficient, and convenient; (5) develop a guidebook that can help tomake decisions such as when and where bicycle facilities are warranted, the most appropriate type offacility (bike lane, shoulder, trail, bridge, or multimodal connections such as bike racks on buses orbike/car park-and-rides for transit), how bicycle facility investment compares with other investments forother modes, and how to incorporate bicycle facility improvements and maintenance into overalltransportation projects and funding allocations.

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♦ Project 08-46How to Include Access Management Strategies in State and Metropolitan Planning OrganizationTransportation System Plans

Research Field: Transportation PlanningSource: ColoradoAllocation: $225,000NCHRP Staff: Dianne S. Schwager

Efficient and effective access management practices provide major implementation strategies forachieving arterial performance and safety objectives. Access management practices incorporated intometropolitan transportation plans can provide major benefits to the use and operation of thetransportation system: (1) the preservation of arterial capacity, (2) the increase of arterial efficiency andits cleaner air dividends, (3) significant improvements in public safety, and (4) reduced cost for highwayimprovements by the preservation of existing performance.

Despite the growing evidence that access management is effective as a relatively inexpensiveenhancement strategy, it has been an underutilized tool. A critical way of introducing systemicacceptance and implementation of access management is to introduce access management strategies intothe transportation system plans (TSPs) produced by metropolitan planning organizations (MPOs).

Starting with identification and analysis of the reasons why access management strategies areunderutilized, this project will identify and describe how to increase the uses of these strategies. Thelatter tasks may range from identifying the need for establishing better or more convincing proof of theclaims made for access management to showing how different and recognized access managementstrategies fit into congestion, safety, and clean air objectives and how to incorporate them into the MPOplanning processes.

The objective of this research is to provide definitive guidance to transportation planners andmanagers on how to incorporate effective access management strategies into their transportation systemplans. This project does not deal with project design or project implementation. It deals with statementsof policies, goals, objectives and identification of implementation actions that need to be included inTSPs for the effective incorporation of access management strategies. To provide good information onpotential operation and safety policies and benefits, substantial data collection relating to planningpractice and legal requirements would be required. The result would be a report used to guide theselection and incorporation of appropriate access management strategies as a function of state andregional specific land-use laws, policies and regulations, access management practices, transportationfinance practices, political preferences, and requirements.

This objective will be accomplished through the following tasks, some of which have beensubstantially advanced in other projects. (1) Establish Links—Through a literature search supplementedby a practice survey (review existing TSPs), identify access studies and data on access managementstrategies and their associated costs and benefits. The researcher should compile the results in acatalogue of established and proven access management techniques with identified results linked tosupportive data and studies and linked also to lists of implementing jurisdictions. (2) Identification andClassification of Access Management Strategies—Determine a comprehensive listing of proven andinnovative access management strategies that could be accomplished by an MPO. The researcher willdevelop a scheme for organizing the strategies by categories. Each strategy will be linked to a cost-benefit analysis, supportive data, and studies and implementing jurisdictions. (3) Identification ofBarriers and Incentives to Inclusion of Access Management Strategies—Conduct a survey of relevantjurisdictions showing access management strategies followed by a thorough assessment of inclusion ofthe strategies. Summarize and analyze successful inclusion and incorporation of access management

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strategies in the TSPs. Summarize and analyze reasons for omission of access management strategies.Selected follow-up interviews should be conducted to identify perceived reasons that would haveoptimized the chances for inclusion of the access management strategies in the TSPs. (4)Implementation Guidelines—Determine under what conditions it is appropriate to implement thevarious access management strategies in the TSPs and provide basic criteria that should determine suchconsideration. These guidelines should address land-use, legal, transportation, financial, and politicalconsiderations. (5) Report Production—Develop a report that will be easily understood and used byplanners and managers. The report should also provide easy access to the links already identified inTasks 1 and 2. The report will incorporate a summary of the research and critical conclusions found inthe literature and practice. Finally, the report should provide sample policy, goal, objectives, andimplementation strategies.

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♦ Project 08-47Policy, Planning, and Programming for Goods Movement and Freight in Small and Mid-SizedMetropolitan Areas

Research Field: Transportation PlanningSource: OregonAllocation: $275,000NCHRP Staff: Ronald D. McCready

The Intermodal Surface Transportation Efficiency Act (ISTEA) and the Transportation EquityAct for the 21st Century (TEA-21) emphasized the need for state and metropolitan multimodal andintermodal transportation policy, planning, and programming activities, including those for goodsmovement. Results of goods movement and freight programs in some of the nation’s large metropolitanareas have been presented at meetings and in publications of federal agencies, the TransportationResearch Board, and other organizations. Information is sketchy about goods movement and freightpolicy, planning, and programming activities in small (less than 500,000 population) and mid-sized(500,000 to 1 million population) metropolitan areas. This research would systematically collectinformation about goods movement and freight programs for small and mid-sized metropolitan planningorganizations (MPOs). The scope would include goods movement on intermodal connector roads andthrough intermodal facilities and terminals. The research is needed to help identify and evaluate howMPOs are implementing federal provisions for goods movement and freight policy, planning, andprogramming. Research results could suggest better ways to accomplish goods movement and freightobjectives in small and mid-sized MPOs.

The objectives of this research are to collect, evaluate, and summarize information about goodsmovement and freight policy, planning, and programming activities in small and mid-sized metropolitanareas and to develop a "best-practices" manual. The research will be implemented in part through asurvey of small and mid-sized MPOs to identify which have established ongoing goods movement orfreight programs. To the extent practical, recent Unified Planning Work Programs (UPWPs) in smalland mid-sized MPOs will be reviewed to identify specific freight-related (including intermodal) policy,planning, and programming activities.

This research will, for the first time, provide comprehensive information on the extent to whichsmall and mid-sized MPOs are incorporating goods movement and freight considerations into overallmultimodal policy, planning, and programming activities. The proposed work will help federal, state,and metropolitan policymakers better understand how small and mid-sized MPOs are implementinggoods movement and freight provisions of TEA-21, other federal initiatives, and state and regionalplanning and programming requirements and guidelines. Results of this work also will help small andmid-sized MPOs implement freight policy, planning, and programming provisions identified in federaltransportation reauthorization legislation. The payoff potential for this research is high. Federal and statepolicymakers could use this information to develop outreach, training, funding, and other programs tohelp small and mid-sized MPOs more effectively incorporate goods movement and freightconsiderations into planning and programming activities and meet the intent of TEA-21 and otherfederal transportation requirements and initiatives. Small and mid-sized MPOs will learn what hasworked elsewhere and what they can do to improve their goods movement and freight policy, planning,and programming efforts.

The ultimate implementers of this research are small and mid-sized MPOs. Other potential usersinclude the Federal Highway Administration, state transportation agencies, local jurisdictions,contractors, and legislators.

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♦ Project 08-48Using American Community Survey Data for Transportation Planning

Research Field: Transportation PlanningSource: Federal Highway Administration/New York/Utah/ArizonaAllocation: $300,000NCHRP Staff: Ronald D. McCready

Transportation planners have relied heavily on the decennial Census "long form" data because itprovides detailed demographic characteristics along with journey-to-work data for small units ofgeography such as census tracts or traffic analysis zones (TAZs). The 2000 Census long form wasprobably the last time the long form will be included in the decennial Census because of Congressionalconcerns about privacy and the burden on the American public. It is the long form that provides the datafor the Census Transportation Planning Package (CTPP), the mostly widely used database fortransportation planning.

The U.S. Census Bureau plans to replace the long form with a continuous data collectionprogram called the American Community Survey (ACS). The ACS differs from the decennial census inmany ways, especially as it represents a change from data collected at a single point-in-time (April 1,2000) to data collected continuously throughout the year and summarized annually for large geographicunits. Data for TAZs or tracts would become available based on a floating average of data accumulatedover 5 to 7 years. The transportation planning community needs to know how to use this new source ofdata in applications such as long-range planning and forecasting, environmental justice analysis, specificproject analysis and descriptive interpretation.

This research will compare results from the ACS test sites (1999 to 2001) and explain how theseresults differ from decennial Census long-form data. The research will provide methods of incorporatingthese differences into existing transportation planning applications, such as travel-demand forecasting,sketch planning and microsimulation, as well as methods for presenting this data for decisionmakers, thepublic, and the media.

1. Compare data from the Census 2000 long form to the data from the ACS test (31 test sites). All 31test sites are not required to be evaluated; however, the research will include sites with differentpopulation characteristics (e.g., seasonal population shifts, degree of urban development and transitaccessibility, racial/ethnic diversity). The comparisons will include journey-to-work characteristics,geographic flow between home and work, and household characteristics. Geographic comparisonswill be made for counties, places, census tracts, and block groups/TAZs. Seasonality, "movingaverages" from accumulations over time, differences in response rates, and sample weighting aresome of the issues to be addressed. Standard errors based on the different surveys (decennial Censuslong-form and ACS) will be calculated for related variables and the geographic units listed above.The research will include the calculation of point-in-time estimates versus moving averages. Areport on the results will be included in this task.

2. Develop recommendations for a CTPP and a schedule of data release, based on the ACS data.Develop recommendations for integrating the CTPP into the standard ACS data disseminationsystem.

3. Prepare guidance manuals for statistical analysis, training courses for metropolitan plnningorganization (MPO) and state DOT staffs, detailed case studies of ACS comparison site data, andguidance materials for presenting continuous census data to decisionmakers, the public, and themedia.

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This is a high-priority issue submitted by three states and FHWA. It is a time-sensitive issuebecause the ACS is currently in a 3-year testing period, with full implementation scheduled to begin in2003. The anticipated products from this research will be used directly by planners at MPOs and stateDOTs.

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♦ Project 09-36Improved Procedure for Laboratory Aging of Asphalt Binders in Pavements

Research Field: Special ProjectsSource: AASHTO/TRB Superpave CommitteeAllocation: $500,000NCHRP Staff: Edward T. Harrigan

In order to fully implement the Superpave asphalt binder specification, it is necessary to have alaboratory binder test procedure that accurately and reliably predicts or ranks the binder aging thatoccurs in the mixture during field mixing and compaction and in-service aging. The resources availableto the Strategic Highway Research Program (SHRP) asphalt research program did not allow a majorinvestigation of either short- or long-term binder aging. The currently used Superpave procedures—theRolling Thin Film Oven Test (RTFOT) and the Pressure-Aging Vessel (PAV)—were selected becauseof previous experience with their use and the promise they showed during development and very limitedvalidation with unmodified binders recovered from in-service pavements.

Recent research and experience shows that the RTFOT, while satisfactory for unmodifiedbinders, is not a satisfactory aging procedure for modified binders. During the test, the film of modifiedasphalt binder does not rotate within the bottle, violating the basic premise of the test method (i.e., thatthe binder is exposed in a continuously moving thin film). This problem was evaluated in NCHRPProject 9-10; the conclusion reached in that research was the same, that the RTFOT does not simulatethe aging that occurs in the field.

There has been considerable activity in recent years, both in the United States and in othercountries, to find a more effective laboratory-aging procedure for asphalt binders. Most of this activityhas focused on mimicking the physical property changes that occur during aging, however, researchershave also considered chemical changes occurring during aging, particularly with respect to the kineticsof long-tern field aging. Therefore, the development of new binder-aging protocols must include bothshort- and long-term aging as well as consider both physical and chemical characterization as was doneduring the SHRP asphalt research program.

Clearly, aging procedures that properly mimic short-term and long-term aging are required tofully implement the Superpave binder specification, now standardized as AASHTO MP1. The first stepin their development is the identification of potential procedures and the their validation and calibrationwith the aging of laboratory mixtures. Field validation and calibration should be pursued in futurestudies.

The objective of this study is to recommend, develop, and validate a procedure for the laboratoryaging of asphalt binders, both neat and modified, such that the procedure mimics the aging that occurs inlaboratory-aged mixtures. The procedure must be suitable for routine specification use, be user friendly,have a short completion cycle, and be potentially applicable to long-term field aging. Ideally, a singleprocedure, as long as it properly represents both short- and long-term field-aging mechanisms, mayultimately replace both the RTFOT and PAV procedures.

The following tasks are anticipated to accomplish this objective: (1) conduct a critical review ofthe literature to establish current practice within and outside North America with respect to laboratory-aging procedures applicable to both neat and modified asphalt binders; (2) design a laboratoryexperiment to validate proposed test procedures that (a) fully considers factors such as binder type(modified and unmodified), the range of modified binders in current and expected field practice, mixturetype and gradation, and aggregate type (source) and (b) provides a-priori criteria for declaring thatequivalent (chemically and physically) aging occurs in both the binder and mixture aging procedure andthat the ranking in both the binder and mixture procedure is equivalent; (3) conduct the experiment

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designed and approved in Task 2; and (4) prepare a final report that summarizes findings, drawsconclusions, documents results, and presents (a) a recommended binder-aging method in AASHTOstandard format and (b) a suggested work plan and budget for an experiment to validate the method withfield data.

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♦ Project 09-37Aggregate Surface Energy: Measurement and Use in Selecting Materials for Pavements

Research Field: Materials and ConstructionSource: UtahAllocation: $450,000NCHRP Staff: Edward T. Harrigan

The surface energy of aggregate particles affects the particle’s affinity for binders as well as forwater. In unbound applications, the aggregates’ surface energy will impact its ability to attract and holdwater, which in turn influences its structural stability. Similarly, the surface energy affects the ability ofbinders to adhere to the particle’s surface, thus affecting the long-term strength and stability of thecomposite. Interactions among aggregate particles, various binders, and water can also occur thatinfluence the development and longevity of binder adhesion—for example, the quality of the hydrauliccement-aggregate bond and asphalt stripping. The ability to characterize aggregates by their surfaceenergy measurements may lead to improved pavement performance through the development ofapplication-specific materials selection criteria, matching of aggregate-binder characteristics, andidentification of aggregate-binder treatments to improve their compatibility.

Although the influence of surface energy properties of aggregates on their performance isbelieved to extend to unbound applications as well as to binders other than asphalt, most recent work hasfocused on asphalt-aggregate combinations. Research at Texas A&M University and the InternationalCenter for Aggregates Research (ICAR) over the past 7 years has focused on the first principles offracture and fatigue in asphalt mixtures. This research has developed a micromechanics model to explainfatigue in hot mix asphalt (HMA) mixtures. In HMA fatigue, two competing processes are at work: (1)crack formation and (2) healing of microcracks. Both processes are theoretically controlled by theprinciples of viscoelastic fracture as set forth by Schapery in 1974. Schapery’s model of fracture andhealing posits that both processes are strongly affected by cohesive (within the mastic) and adhesive(between the aggregate and the bitumen or mastic) surface energies. This is not surprising; surfaceenergies of mixture components are expected to affect bonding strength and, hence, resistance tofracture and fatigue.

Recent work at Texas A&M for the Federal Highway Administration has resulted in a method tomeasure surface energies of aggregates, asphalt cement, and mastic (asphalt cement with mineral dust,other additives, or both). This method is based the Universal Sorption Device (USD). The USD consistsof an extremely sensitive, precise balance in conjunction with a chamber in which the material under testis allowed to sorb (i.e., adsorb, absorb, or both) different gases. In the method developed by Texas A&Mand ICAR, three different gases are used: water vapor (bipolar), MPK (monopolar), and hexane(nonpolar). This method allows researchers to calculate the total surface energy as well as thecomponents of surface energy, including the acid and base components and the Lifshitz–Van der Waalscomponent. This work has shown that the fatigue and healing potential of HMA is directly and stronglyrelated to the surface energies of the components and their compatibility. Asphalt cements that have highacid or base surface energies are more resistant to fatigue than are those that do not because they havebetter fracture and healing properties. The adhesive surface energy between asphalt cement andaggregate is a more complex process and is just as important, if not more important, than cohesivesurface energies of the bitumen or mastic. Testing on aggregates of different mineralogies, sources, andwith different levels of processing has revealed that surface energy is influenced not only by the sourceand mineralogy, but also by the level of processing and surface treatments.

Current work at Texas A&M and ICAR is focusing on the influence of surface energy onmoisture-induced damage and the synergistic effect of moisture during the cyclic loading damage

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process. Because water has a stronger chemical affinity for some aggregates than for others, a logicalnext step is to investigate the effectiveness of using surface energy measurements as a tool for selectingcompatible asphalt cement–aggregate systems that are resistant to fatigue. The current study at TexasA&M/ICAR will introduce moisture vapor during cycling loading to assess the synergistic effects ofload and moisture damage; these results will be compared with surface energy properties.

The objective of this research is to refine the USD methodology for measuring the surfaceenergies of aggregates and binders to the point at which it can be used routinely in constructionmaterials laboratories.

The following tasks are anticipated to accomplish this objective: (1) use the method to evaluate awide range of aggregates (mineralogies, sources, and conditions of processing, e.g., freshly fracturedfaces versus uncrushed aggregate or aggregate crushed, then aged) and binders together with a widerange of treatments such as chemical additives (e.g., hydrated lime slurry, liquid anti-stripping agents,polymer coatings, etc.) and various levels of processing and to assess the effects of material andtreatment on aggregate-binder surface energies; (2) conduct laboratory mechanical testing (i.e., withequipment such as the Superpave shear test device, Hamburg Tester, Asphalt Pavement Analyzer, etc.)of HMA prepared from materials having varying surface energy properties in the presence and absenceof moisture to determine the influence of these properties on permanent deformation and fatiguecracking and then compare the results with field performance; (3) conduct similar testing of materialswith other binders along with appropriate tests to evaluate the relationship of aggregate surface energyto moisture susceptibility in unbound applications; and (4) develop a recommended method in AASHTOstandard format for the use of surface energy measurements in the selection of materials for HMA andunbound pavement layers.

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♦ Project 10-62Acceptance Test for Surface Characteristics of Uncoated Strands Used in Pre-tensioned Pre-castConcrete Applications

Research Field: Materials and ConstructionSource: AASHTO Highway Subcommittee on Bridges and StructuresAllocation: $500,000NCHRP Staff: Edward T. Harrigan

Tests conducted at North Carolina State University in the early 1980s on epoxy-coated strandsalso included tests of uncoated strands. These tests found that the measured transfer and developmentlengths of uncoated strands were in excess of lengths computed using the equation found in theAASHTO Standard Specifications.

Publication of these test results led to concerns by the FHWA that the AASHTO equation wasnot conservative for modern strands with larger diameter and higher ultimate tensile strength. Theseconcerns ultimately resulted in a mandate to increase development lengths by 60 percent over the lengthcomputed using the AASHTO equation.

In response to this mandate, more than 14 test programs were conducted by industry, academia,and state agencies, including a major study by the FHWA. These programs were intended to providedata to reevaluate the transfer and development length performance of modern strands. Test results forbeams were summarized by FHWA, which resulted in the formulation of new equations for both transferand development lengths for uncoated strands.

Following completion of these tests, the industry became aware of variations in the surfaceconditions of strands used throughout the country. This discovery suggested a source for the wide scatterthat was observed in the test data and brought into question the validity of some or all of these data.

Strand surface condition has a major impact on transfer and development length of strands yethas not been tested as part of the research to date. This variable needs to be quantified, and acceptancetest criteria needs to be developed that will control its impact on transfer and development length. Thisissue has been unresolved for nearly 20 years, resulting in wide variations in the design of beam endsand pile-cap embedments. Results should produce more consistent, economical, and safe designsnationally. Potential for cost savings and national implementation are high.

The objectives of this research project are to (1) identify strand residues that might adverselyimpact or enhance bond development and that result from manufacturing, corrosion inhibitors, rust, orother foreign materials; (2) determine the positive or negative impact of such residues on strandperformance; (3) develop test procedures for qualifying and quantifying such residues; (4) developminimum acceptance criteria for each type of residue; (5) develop and propose methods for removingadverse residues to an acceptable level; and (6) verify or establish design parameters for determiningstrand transfer and development lengths.

The following tasks are anticipated to accomplish these objectives: (1) conduct a critical reviewof the literature, existing test data, and research in progress, particularly the research in NCHRP Project12-60 on bond with high-strength concrete, to identify the factors affecting strand surface conditions; (2)survey owner agencies and industry using written forms and interviews to identify existing parameterswithin the manufacture, delivery, and fabrication process that affect strand bond characteristics; (3)chemically analyze samples of strands from various manufacturers and suppliers to confirm the resultsof the industry/owner survey and to determine the quantity and quality of residues; (4) develop a testprocedure and acceptance criteria for determining strand bond characteristics of the various residues toaugment existing ASTM/AASHTO materials specifications; (5) review the AASHTO-LRFD transferand bond development length criteria in light of the findings and recommendations proposed; and (6)

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prepare a final report that summarizes findings, draws conclusions, documents results, and presents (a)recommended acceptance criteria for bonding of uncoated strands based on proposed testing proceduresand (b) recommended procedures for enhancing strand surface characteristics that may allowimprovement to the AASHTO-LRFD transfer and bond development length criteria.

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♦ Project 10-63Heat-Straightening Repair of Damaged Steel Bridges

Research Field: Materials and ConstructionSource: AASHTO Highway Subcommittee on Bridges and StructuresAllocation: $375,000NCHRP Staff: Edward T. Harrigan

Most DOTs must repair damaged steel bridges on a regular basis because of impact damage.Heat straightening is a cost-effective, fast procedure for field repair that can minimize the requirementsof long detours during repairs, consequently providing for a more efficient system. It is also useful forrepair of steel in fabrication shops. However, many states either do not use heat straightening or severelylimit its use because of questions related to fatigue life as well as past problems with brittle fractureeither during or after heat-straightening repair. In the Heat-Straightening Demonstration Project beingconducted nationwide, attendees invariably suggest additional research to investigate the fatigueproperties of heat straightened steel in bridge applications. The completion of this research would enablestates to adapt heat straightening as a standard repair procedure. Because heat straightening typicallyoffers at least a two-to-one advantage in repair time and in cost, the use of this alternative wouldproduce significant cost savings, estimated in the millions of dollars if the heat-straightening method isadopted systemwide.

Recent research has begun to quantify heat straightening in engineering terms. Key parametersthat have been well defined include heating temperature, heating patterns for specific damageconfigurations, methods for calculating degree of damage, and methods for estimating movement duringheat straightening. In addressing the fatigue characteristics of heat-straightened steel, several specificquestions remain to be answered. What level of fatigue life does heat-straightened steel have? Does thedegree of damage affect the fatigue life of heat-straightened steel? Do the heat-straightening parametersof jacking force and vee angle affect the fatigue life of heat-straightening steel? These questions allrelate to the field conditions in which the fracturing of the repaired beams originally took place.

The objective of this research is to investigate the fatigue properties of heat-straightened steel forbridges.

The following tasks are anticipated to accomplish this objective: (1) determine whether fatiguelife of heat-straightened steel is a function of vee angle, level of jacking force, or degree of damage; (2)evaluate whether fatigue-sensitive details frequently encountered in heat straightening are affected bythe repair process; and (3) develop suitable fatigue specifications for heat-straightened steel bridges,including bridges in seismic regions.

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♦ Project 10-64Field Inspection, Maintenance, and Repair of Existing FRP Bridge Decks and Superstructures

Research Field: Materials and ConstructionSource: AASHTO Highway Subcommittee on Bridges and StructuresAllocation: $400,000NCHRP Staff: David B. Beal

Inspection and monitoring of existing fiber-reinforced polymer (FRP) structures has variedwidely from no monitoring, to periodic visual inspection, to conventional instrumentation and loadtesting, to combinations of conventional and experimental nondestructive evaluation (NDE) techniquesand longer-term monitoring. Reporting on projects has also varied widely, often taking the form ofnontechnical articles in trade publications or popular magazines. States interested in constructing aparticular FRP application have to search to find hard performance data and find it difficult to compareone project with another. There is a need to develop a common reporting format to make suchcomparison possible. In addition, these structures have almost no maintenance and repair history.Routine maintenance practices have not been developed. At some point, the responsibility forinspection, maintenance, and repair of FRP bridges will be handed off entirely to the state’s regularinspection and maintenance personnel.

The objective of this project is to produce guidelines and recommended field procedures for theinspection, maintenance, and repair of FRP bridge decks and superstructures. Research results will beimplemented with the production of an AASHTO Recommended Practice for inspection, maintenance,and repair of FRP bridge decks and superstructures.

The performing agency will be required to develop criteria for field inspection of FRP bridgedecks and superstructures that are based on the identification of critical components of FRP structuresand the determination of critical accumulated damage thresholds in those components. The agency willthen study and determine the ability of available techniques to detect accumulated damage approachingor exceeding these thresholds. The agency will examine both highway agency inspection techniques andFRP-specific inspection techniques employed by aerospace, marine, and other industries using FRP. Theemphasis in this study will be on techniques for point damage detection. Model analysis, globalinspection techniques, and remote monitoring are already being employed on FRP structures for overallcondition assessment and will require only a small portion of the performing agency’s time and effort.The agency will also examine existing maintenance and repair practices. As with inspection, this willinclude both highway agency and FRP-user industry techniques. The agency will evaluate thetechniques for speed and economy in use and for their suitability for integration into the states’ bridgeinspection/maintenance programs. Special consideration will be given to accessibility, that is, to howeasily any required testing, maintenance, and repair equipment can be moved, hoisted, and positioned atthe bridge site. The expectation is that FRP-user industry test, inspection, and repair techniques andpractices, normally conducted in a plant or in a hangar, will have to be adapted and streamlined for useon bridges in service. Training requirements for state and contractor personnel will also be examined.Other inspection issues include accuracy and reliability requirements for inspection data, continuousversus intermittent data collection, reliability requirements for equipment and sensors, and calibration ofthe guidelines with field project data. Deliverables will include recommended inspection andmaintenance schedules, recommended inspection and repair criteria; recommended inspection and repairtechniques, a recommended common reporting format for information developed by the state’sinspections, and recommendations for training inspection and maintenance personnel.

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♦ Project 10-65Using Nondestructive Testing Technology for Controlling the Quality of Flexible Pavement LayersDuring Construction and Assuring the Quality of New Flexible Pavements

Research Field: Materials and ConstructionSource: AASHTO Highway Subcommittee on ConstructionAllocation: $700,000NCHRP Staff: Edward T. Harrigan

Test methods for controlling the construction quality of pavement layers and assuring the qualityof new pavements have changed little in past decades. State DOTs typically base their qualityassessment on localized nuclear density measurements or the results of testing conducted on pavementcores. In many instances, manual profilographs are used to certify that the initial construction hasadequate smoothness.

In recent years nondestructive testing (NDT) technologies have made significant improvements;these include lasers, ground-penetrating radar, and infrared and seismic technologies. Furthermore, thenew AASHTO structural design system is targeting the use of layer moduli as the major thicknessdesign property. Although layer moduli will be used in the design process, they are not typicallymeasured when the DOT is preparing to accept the completed project.

This project will investigate applications of NDT for measuring the quality of individual flexiblepavement layers during or immediately after placement and of the entire flexible pavement immediatelyafter construction. The focus will be on the traditional flexible pavement containing a preparedsubgrade, untreated granular base, and a hot mix asphalt (HMA) surface layer. NDT technologies will beused to test and certify the strength and uniformity of each layer prior to placement of the next layer andto accept the pavement at the completion of construction.

At a minimum, the NDT systems should assess the following performance-related factors: (1)subgrade stiffness, uniformity, and any other performance-related parameters; (2) base layer stiffness,thickness, uniformity, smoothness, moisture content with depth, and any other performance-relatedparameter; (3) surface stiffness, thickness, uniformity, and any other performance-related parameter; (4)initial pavement smoothness; (5) initial pavement skid resistance; (6) structural strength; (7) surfaceuniformity; and (8) layer thickness.

The research will document the status of various NDT technologies, demonstrate their use,identify their strengths and weaknesses, and, if warranted, propose draft test protocols for their use inQC/QA testing of new flexible pavements. The research will examine a range of the most promisingtechnologies and demonstrate their readiness for implementation. The proposed technologies will befield tested during and immediately after the construction of up to six field projects. A key projectdeliverable will be a state-of-the-art report on current NDT technologies that evaluates their feasibilityfor implementation, documents the benefits over existing QC/QA techniques, and providesrecommendations on future developments and implementation efforts.

No new NDT development will be conducted under this contract. The research will use existingtechnologies and demonstrate their readiness for implementation. Where possible, the research willcompare the benefits of the new and traditional methods. The research goal is to provide information onthe quality of the pavement layer during placement so that changes can be made to the operation (e.g.,through the use of an infrared camera to identify temperature segregation problems during HMAplacement) or immediately after finishing to ensure that the structure is ready for the next layer to beplaced (e.g., by locating weak areas in the subgrade that should be correct prior to placing the base).Moreover, the research should provide guidance on issues such as when, where, and how deflection

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testing should be performed to evaluate the structural adequacy of a new flexible pavement, and howdata can be processed to assure the adequacy of the pavement structure.

The objectives of this research are (1) to evaluate NDT technologies that can be used to testindividual flexible pavement layers during construction and measure the quality of the entire flexiblepavement, (2) to determine which technologies are ready for implementation and which need furtherdevelopment, and (3) for those technologies found ready for implementation, to recommend draft testprotocols.

The following tasks are anticipated to accomplish these objectives: (1) conduct a critical reviewof existing NDT technologies in use nationally and internationally and summarize their capabilities toaddress the QC/QA requirements for new flexible pavements through testing directly on top of thesubgrade, flexible base and HMA surfacing; (2) develop a test program for implementing promisingNDT technologies on six construction projects that (a) identifies the type and frequency ofmeasurements to be made and what validation test will be required, (b) describes how the collected datawill be processed and what information will be provided to the participating DOTs, (c) provides forcomparison of the NDT results with those from traditional tests, where appropriate, (d) clearly defineshow each technology will be critically evaluated as to it readiness for implementation, and (e) identifiesperformance requirements that the NDT does not measure that would need to be addressed through othermethods; (3) submit an interim report for review and approval by NCHRP presenting the recommendedNDT techniques and a field test plan proposed for their evaluation; (4) conduct the field test plan on sixfield projects located in two distinct geographic regions including low, intermediate, and high volumeroadways; and (5) prepare a final report that summarizes findings, draws conclusions, documents results,and presents recommended NDT techniques as draft test methods in AASHTO standard format, with adiscussion of their feasibility for implementation, their benefits over existing QC/QA techniques, andfuture development and implementation efforts.

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♦ Project 10-66Methodologies to Account for Realistic Environmental and Time Influences in Accelerated PavementTesting

Research Field: Materials and ConstructionSource: FloridaAllocation: $450,000NCHRP Staff: Amir N. Hanna

The evaluation and validation of new/emerging pavement technologies and innovative conceptsrequire assessing their in-service long-term performance. In-service assessment requires theconsideration of the interaction among traffic loading, material properties, and environmental effects.Among the disadvantages of such an approach is the long time period required before potentiallymeaningful results are obtained and implemented. Additionally, in many instances, it is difficult,impractical, and/or expensive to obtain and account for all the data and information required from in-service experimental set-ups.

The need for faster and more practical evaluation methods under closely simulated in-serviceconditions prompted the consideration of accelerated pavement testing (APT). In recent years, a numberof agencies in the United States have initiated such testing programs. Generally, APT is defined as acontrolled application of a realistic wheel loading to a prototype or in-service pavement system tosimulate in-service long-term loading conditions. This allows the monitoring of pavement systemperformance and response through an accelerated accumulation of damage. APT has the potential toproduce early results while improving the pavement community’s understanding of and ability to predictpavement performance. Still, some issues have not been fully addressed, particularly in consideringaccelerated but realistic environmental effects such as those imposed by changing temperature andmoisture. Researchers in the APT field have generally recognized this shortcoming, and typical effortshave involved attempts to isolate APT tests from the effects due to changes in environmental conditions.APT studies have included artificial aging of asphalt, controlled soil thawing, and intentional moisturemigration. While the effect of environmental factors may be controlled and quantified, the combinedeffects of environment and time have not been successfully simulated. The importance of theseinterdependencies on predicting pavement performance based on APT results was discussed by Hugo inhis “Summary and View Ahead,” during the closing session of the International APT Conference held inReno in 1999.

The objective of this research project is to identify and recommend practical methodologies forrealistically incorporating the interdependent effects of environment, time (aging), and loading intoaccelerated pavement testing. This effort will include (a) reporting on and assessing the effectiveness ofcurrent practices to account for the environment in APT, including instrumentation and monitoringtechniques from both the analytical and experimental points of view; (b) defining detailed impacts ofconstant versus cyclic environment conditions, as well as their interaction with the duration of exposurein APT; (c) reporting on available studies relating APT results to in-service roads, LTPP sections, orfull-scale sites; (d) identifying, if appropriate, and recommending practical techniques for acceleratingthe effects of the environment on pavement materials during APT studies to closely simulate long-termfield conditions; (e) developing or identifying practical methodologies to realistically account forenvironmental and time influences in accelerated pavement testing; and (f) preparing a final report thatsummarizes all the findings, draws conclusions, and presents detailed descriptions of the mostfeasible/practical methodologies and recommendations.

To accomplish this objective, the following tasks will be performed: (1) Conduct a criticalreview of current literature on APT programs and report on findings focusing particularly on (a)

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identifying and reporting on specific studies and available resources relating APT results to those of in-service roads, including full-scale sites and in-service long-term pavement performance studies. Providedetailed scopes as well as performance history, structural designs, material characteristics, traffic,environmental data and potential findings from such studies. Report on any difficulties related to theability for APT to reflect real-world trafficking and environment; (b) identifying and reporting on APTstudies that were potentially hindered by a failure to adequately quantify environmental effects. Describehow the usefulness of these results was impacted; and (c) identifying and documenting methods andtechnologies currently used to quantify and account for the effects of environment during APT. Providea detailed description and assessment of each method as well as its advantages/disadvantages. This willalso consider all current practices for monitoring the environment in pavements (e.g., temperature,moisture, and depth of freezing), including types of instrumentation, their level of success, location ofmeasurements, frequency of measurements, and necessary redundancy. This review will include thesurvey of other ongoing related projects such as NCHRP Project 10-56, Accelerated Pavement Testing:Data Guidelines, and should also make use of the findings of NCHRP Synthesis 235: Application ofFull-Scale Accelerated Pavement Testing. (2) Provide a comprehensive assessment of the needs forimproved accounting of interdependent effects of environment, time, and loading. Address these needsin terms of potential payoff for transportation agencies. (3) Recommend practical techniques or soundpractices for accelerating the environmental effects during APT to closely simulate long-term fieldconditions, as necessary. (4) Review the state-of-practice related to the implementation of APT resultsfor the purpose of improving one’s ability to predict the performance of in-service pavements. Provide adetailed description and assessment of case studies to emphasize weaknesses and strengths of thedifferent practices and techniques. Identify or develop suitable and practical methodologies to accountfor the interdependent effects of environment, time, and loading on APT findings, from both theanalytical and experimental points of view. (5) Prepare a report summarizing all findings.

The proposed project will require a collaborative effort among APT programs, in-service long-term pavement performance and full-scale studies, and the researchers responsible for conducting theproposed study. Also, due to the nature of the study, the proposed project will extend over a number ofyears to ensure that a wide and representative range of climatic influences is included.

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♦ Project 12-62Refined Live-Load Distribution-Factor Equations

Research Field: DesignSource: AASHTO Highway Subcommittee on Bridges and StructuresAllocation: $350,000NCHRP Staff: David B. Beal

Simple "s-over" live-load distribution factors have been used for bridge design since the 1930s.These factors allow the designer to uncouple transverse behavior from longitudinal behavior. Thetraditional factors are easy to apply, but can be overly conservative, and even unconservative, in someparameter ranges. Moreover, even though the traditional factors were developed when spans wererelatively short and simple, and girder spacings were small, designers apply the "s-over" factors forcontinuous spans of significant proportions with relatively wide girder spacings. They are used forsplayed girders, curved girders, skewed supports and virtually all kinds of plan geometry.

New, more accurate, and more complex live-load distribution factor equations were developedby NCHRP Project 12-26, and proposed to AASHTO as replacements for the "s-over" factors in the1980s. Designers find the complexity of the new equations troubling. AASHTO decided to adopt thenew equations as a guide specification, instead of replacing the "s-over" factors. These equations areincluded in the LRFD Specifications instead of the "s-over" factors. The new distribution-factorequations include limited ranges of applicability. The LRFD Specifications mandate that when theranges of applicability are exceeded, refined analysis is required.

Simpler, less complex live-load distribution-factor equations would be welcomed by the designcommunity. Further, less limiting ranges of applicability would result in more economy in the designprocess and less potential error from refined analysis.

The objective of the proposed research is to develop less complex live-load distributionequations with accuracy appropriate for design. These new equations should be less restrictive in theirranges of applicability than the present LRFD distribution factors and represent a more reasonable rangeof bridges being designed today. The proposed ranges of applicability should minimize, to the extentpossible, the need for more refined analysis and facilitate the use of the traditional line girder approach.It is envisioned that the proposed research will involve, at a minimum, the following tasks: (1) conduct aliterature review, building upon the bibliography contained in NCHRP Project 12-26, adding subsequentrelevant research on computation of live load distribution factors; (2) specifically review the findings ofNCHRP Project 12-26 and re-assemble the database of 2-dimensional and 3-dimensional analyses ofbridges used in that study. Re-analyze the database, with the intent to interpret results in a manner thatcan establish more simplified procedures for predicting live load distribution factors, and that correlatewith the results of the NCHRP Project 12-26 database; (3) assemble a new, more limited, database of 2-dimensional and 3-dimensional analyses, using the latest analytical tools, based on a suite of existingbridge plans from various state DOTs. Compare the analysis with the proposed simplified live loaddistributions from Task 2; (4) select a limited number of existing bridges, representative of the typebridges analyzed in Task 3, and field measure the strains due to the passage of known-weight vehicles,comparing the results with the analyses in Task 3; (5) refine the simplified live load distribution factorcalculation procedures proposed in Task 2 based on the results of Tasks 3 and 4. Develop comparisonsof the proposed simplified equations with the methods found in the AASHTO Standard Specifications forDesign of Highway Bridges, 16th edition (S/5.5), the AASHTO LRFD Bridge Design Specifications 2ndedition, and any other promising procedures found in Task 1; (6) prepare a final report based on thebody of work developed in Tasks 1 through 5. The final report must include the text of recommendedrevisions to the AASHTO LRFD Bridge Design Specifications, consistent with the present specification

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language. The proposed specification change may be offered as a substitute method or alternativemethod of computing live load distribution factors.

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♦ Project 12-63Comparison of Legal Truck Loads to AASHTO Typical Posting Vehicles

Research Field: DesignSource: AASHTO Highway Subcommittee on Bridges and StructuresAllocation: $500,000NCHRP Staff: David B. Beal

Certain heavily loaded trucks are allowed to legally operate on the public highways free of anyspecial load permits; yet, they may exceed the capacity of some bridges rated with AASHTO PostingVehicles. Conversely, some bridges are not posted even though they do not have the capacity to carrythe loads of legally operating vehicles. The result is a potentially dangerous situation.

Trucks are typically allowed unrestricted operation and are generally considered “legal”provided they meet the weight guidelines of Federal Formula B. Similarly, bridges in the United Statesare typically not posted if they can carry Type 3, Type 3S2, and Type 3S3 Posting Vehicles as describedin the AASHTO Manual for the Condition Evaluation of Bridges

During the past several years the trucking industry has enhanced the load carrying capacity oftruck vehicles by using a series of closely spaced multiple axles. These axle configurations make itpossible for shorter trucks to carry the maximum load of up to 80,000 pounds and still meet therequirements for Formula B. However, these vehicles cause stresses in bridge structures that exceed thestresses anticipated by the Type 3, 3S2, or 3S3 Posting Vehicles. The end result is legally loaded trucksoverstressing some nonposted bridges

The objectives of this research are to determine the extent of the problem by identifying andquantifying the vehicles causing the overstressing. It will also identify the types of bridges likely to beoverstressed or subject to fatigue damage. Traffic counts, load data from truck weigh station data, andweigh-in-motion data will be used to determine the actual operating loads. Field measurements of trucksizes, axle configurations, and axle loadings will be collected to complement the weigh station data.Mathematical analysis and statistical validation will then be done to compare the stresses from actualtruck loadings to the stresses from the AASHTO Posting Vehicles. It is further proposed to recommenda new family of Posting Vehicles that better represent the current legal trucks for the AASHTO Manualfor the Condition Evaluation of Bridges.

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♦ Project 12-64Application of the LRFD Bridge Design Specifications to High-Strength Structural ConcreteMembers (Phase 3 - Flexure and Axial Loads)

Research Field: DesignSource: AASHTO Highway Subcommittee on Bridges and StructuresAllocation: $600,000NCHRP Staff: David B. Beal

Section 5—Concrete Structures, of the AASHTO LRFD Bridge Design Specifications, states thefollowing: "Concrete strengths above 10.0 ksi (70 MPa) shall be used only when physical tests are madeto establish the relationships between the concrete strength and other properties." This statement impliesthat the LRFD Specifications may not be applicable with concrete members having specified concretecompressive strengths above 10.0 ksi (70 MPa).

When the LRFD Specifications were written, there was a lack of data to demonstrate that theprovisions were applicable with concrete compressive strengths above 10.0 ksi (70 MPa). However,recent research has started to address design issues with higher strength concretes. In addition, theFHWA Showcase Projects are encouraging the use of high performance concretes—including high-strength concrete—in bridge structures. There is, therefore, a need to expand the LRFD Specifications toallow greater use of high-strength concrete. This proposed project will support the research required toremove some of the remaining barriers in the LRFD Specifications regarding the use of high-strengthconcrete. Specific topics on high-strength concrete that remain to be addressed include: design forflexural and axial load effects (including investigations of maximum and minimum flexuralreinforcement limits, cracking limits, and adequacy of compressive stress block assumptions); effect ofhigh-strength concrete on post-tensioning web widths; and long-span segmental bridges.

The objective of the project is to support specific research required to address the effects ofconcrete with strengths above 10 ksi (70 MPa) on flexural and axial load carrying capacity (includinginvestigations of maximum and minimum flexural reinforcement limits, cracking limits, and adequacyof compressive stress block assumptions). In addition, the effects of high-strength concrete on post-tensioning web widths and on the design and behavior of long-span segmental bridges are to beinvestigated. The research findings shall be translated into proposed code language for incorporationwithin the LRFD Specifications.

This research will be accomplished through the following tasks: Task 1—Review research andpractice regarding the flexural and axial load carrying capacity of members with concrete strengthsabove 10.0 ksi (70 MPa). Review research and practice with regard to the effects of high-strengthconcrete on post-tensioning web widths and on the design and behavior of long-span segmental bridges.Task 2—Determine factors (e.g., maximum and minimum flexural reinforcement limits, cracking limits,adequacy of compressive stress block assumptions) that affect the flexural and axial load carryingcapacity and performance of members fabricated with concrete strengths above 10.0 ksi (70 MPa), andidentify additional tests required to determine the effects of these factors. Determine factors that affectweb widths of post-tensioned structures fabricated with concrete strengths above 10.0 ksi (70 MPa) andfactors that affect the design and behavior of long-span segmental bridges fabricated with high-strengthconcrete. Identify any additional tests required to determine the effects of these factors. Task 3—Develop work plan for experimental and analytical investigation regarding the behavior (and factors thataffect behavior) of flexural and axial load carrying members, post-tensioned members, and segmentalbridges fabricated with high-strength concrete (i.e., strengths above 10.0 ksi (70 MPa). Task 4—SubmitInterim Report that documents the research performed in Phase I (Tasks 1–3) and includes an updatedwork plan (Task 3) for Phase II of the project. Task 5—Execute work plan—Experimental and

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analytical research program. The experimental work shall involve large-size members withrepresentative cross sections because of the unknown size effects with small-size specimens. Task 6—Final report including proposed revisions to the AASHTO LRFD Bridge Design Specifications to addressfindings regarding flexural and axial load carrying members, post-tensioned members, and segmentalbridges fabricated with high-strength concrete (i.e., strengths above 10.0 ksi (70 MPa).

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♦ Project 12-65Development of a Full-Depth Precast Concrete Bridge Deck Construction System Suitable for DirectContact Traffic

Research Field: DesignSource: TexasAllocation: $400,000NCHRP Staff: David B. Beal

The impact of highway construction projects on the travelling public is considerable. Increasedtravel times resulting from congested construction work zones and the resultant degradation in trafficsafety are the most readily apparent consequences. Development of a totally precast bridge constructionsystem offers one means of significantly reducing construction barricade time, because forming, casting,and curing operations can be carried out at a remote location with less impact on motorists. Considerabletime could be saved on bridge construction projects through the utilization of precast bent caps,columns, rails, abutments, and other components. One major hurdle to be overcome in developing atotally precast bridge construction system is the issue of deck construction.

Most bridge decks are constructed using either full-depth cast-in-place concrete or precastconcrete panels with a cast-in-place, partial-depth overlay. The use of these conventional deckconstruction techniques with associated curing requirements can easily consume 1 month on a typicalbridge construction project.

Development of a precast concrete deck panel system with a ride quality suitable for high-speed,direct traffic contact would be a major achievement, complementing work being done elsewhere (suchas recent and current research being sponsored by the Texas DOT) in developing a totally precast bridgeconstruction system.

The objective of this research is to develop guidelines for the design and construction of concretebridge decks with full-depth precast panels that address panel casting and placement tolerances, shearconnections, joints, vertical alignment and final grade adjustment, closure techniques, drainage, railconnections, and assurance of final ride quality. Both steel and prestressed concrete superstructuresshould be considered.

The following tasks are anticipated: (1) Literature review. This will be the first step inestablishing the state of the art, (2) Survey of agencies and structural research and developmentinstitutions. This will be the second step in establishing the state of the art. It is important to recognizethat others have done research in this area and have used full-depth precast decks, at times as part ofpost-tensioned structures. (3) Development of a full-depth precast concrete deck system. This systemwill adequately address the issues raised above. Conduct testing as needed. Include design proceduresand details. Emphasis should be placed on constructability. (4) Report presentation. Present the results,including test results, design procedures, and schematics of recommended details in the research report.

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♦ Project 15-24Hydraulic Loss Coefficients for Culverts

Research Field: Soils and GeologySource: AASHTO Task Force on Hydrology and HydraulicsAllocation: $325,000NCHRP Staff: Timothy Hess

A culvert can be a viable and economic option for a stream crossing on small and medium-sizestreams. The culvert structures on environmentally sensitive and fish-bearing streams mustaccommodate fish passage and related aquatic habitat requirements, in addition to the usual hydrologicand hydraulic design considerations.

The hydraulic design of culvert crossings includes an analysis of flow regime, backwater, andvelocity conditions. The water levels at culvert ends and the backwater and flow velocities are criticalparameters in design. Excessive backwater is prohibitive as it may result in adverse flooding impacts onupstream development. Increased velocities at a culvert crossing may cause erosion and scour at thestream and the resulting sedimentation downstream. For sensitive fish bearing streams, the design mustalso provide for fish and other habitats. In addition, excessive erosion and sedimentation must beminimized.

The hydraulic design of a culvert crossing focuses on ensuring that the hydraulic characteristicsof a culvert crossing are not adverse to the site conditions. At the same time, the crossing must provide aflood-free and safe facility for the travelling public. The alternative selected must be cost-effective tojustify the relative priority and spending of public funds.

The principles and the methods for hydraulic assessments and design of culvert crossings are notan exact science. The roughness coefficients, and therefore hydraulic equations, are semi-rational, basedon past laboratory experimentation, and supported by limited prototype testing. Consequently, it isunderstood that the hydraulic analyses and predictions for culverts are approximate and subject torelatively high factors of safety. Recent technical advances have focused mainly on automating theanalysis processes. The basic understanding of the hydraulic loss coefficients for culverts and theirinfluences on analysis and predictions, however, has not been enhanced.

In the current environment, where engineering services are primarily privatized, theresponsibility of applying the methodologies correctly has shifted to consultants and service providers.With emerging new processes such as Value Engineering and the use of fast track approaches ofdelivery of services and programs, the responsibility for design has shifted even further from the ownersto the design and construction consultants and contractors. This is quite often the case for complex andlarge-value projects, which are being delivered through design-build or other similar approaches.Consequently, the owner transportation agencies are focusing on the currency and accuracy of hydraulicdesign methodologies and manuals of practice.

Considering the current design environment with its hands-off approach by the ownertransportation agencies, the need to improve the hydraulic loss coefficients for culverts for hydraulicanalysis and design, and to address the environmental requirements cannot be over-emphasized. Theareas in hydraulic design of culverts, which are relatively less understood, are:

• Entrance and Exit Loss Coefficients for varying shapes of pipe. The culvert shapes normally used forsteel pipes are the round, elliptical, and arch. The shapes used in concrete pipes include square,rectangular, round, and arch.

• Bend Losses Coefficients. A bend in a culvert may vary from gradual to major. A bend may varyfrom a minor deflection 1–2 degrees to 90 degrees.

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• Head Loss due to lowered culvert invert. The invert of a culvert may be lowered by a certain depthbelow stream invert to allow for fish passage.

• Effect on the overall hydraulic roughness of substrate and baffles at culvert bottom.• Head Loss Coefficients for various baffles in culverts for fish passage.• Head Loss Coefficient for multiple culverts, resulting in flow split.• Head Loss Coefficient for submerged culverts.• Practical culvert transitions and end treatments, resulting in reduction in head loss and backwater.• Generalized width-depth-shape-velocity-discharge relationships, relating channels and culverts,

which may be used as guidance.• Effect of concrete and steel surface finishes on hydraulic roughness.• Effect of culvert rehabilitation measures on hydraulic roughness and performance.

The objectives of this proposed research are:

• To update the state of knowledge on hydraulic design for culverts in the areas listed above.• To develop documentation of the most updated findings.• To investigate/conduct studies to further define/rationalize the hydraulic relationships for the above

areas.• To develop generalized relationships to aid in arriving at refined/improved culvert designs.

To accomplish the research objectives the following work phases and tasks are recommended:(1) Critically review the literature from foreign and domestic sources to develop a synopsis of the stateof knowledge and research. Assess the utility of the past investigations in meeting the aboverequirements and filling the gaps in the research. Determine if some of the required hydraulicrelationships can be readily extrapolated from the earlier research. Establish the scope of assignmentneeded to deliver the above. Search for findings and data that may be used and expanded to assess andcalibrate the above relationships. Develop the outline for the next phase of work. Submit an interimreport describing the above findings. (2) Develop a detailed plan and steps, to investigate the abovehydraulic aspects in culvert design, in keeping with the current state of knowledge and research.Determine the study approach for the investigation and follow-up testing. It is assumed that acombination of physical, numerical, and computer modeling will be used to assess and calibrate thevarying hydraulic conditions, to arrive at the generalized relationships. Identify the parameters needed tobe developed and the related laboratory modeling and experimentation required to achieve the above,including the duration and manpower. Also identify any field instrumentation or measurements, ifrequired. Submit a report of the above. The report will document all the tasks and the correspondingsteps needed to achieve the above. (3) Conduct the physical, numerical, and computer modelingnecessary to assess the hydraulic influence of the above on the flow, velocities, and backwater forvarying conditions. The modeling should be sufficient enough to develop the generalized relationshipsrequired. Critically assess and measure the differences and variability with appropriate instrumentationand modeling. Validate and document the findings and their limitations. (4) From the work andexperimentation carried out, develop the generalized relationships, equations, and curves to be used asaids in hydraulic assessments, predictions, and design. Document the development carried out and thelimitations of the findings. (5) Submit a final report that documents the total research effort, and presentsthe prediction methodology, the design aids, and the illustrative examples for application.

The AASHTO Task Force on Hydraulics and Hydrology selected this research as a priority. Byincorporating an accurate method for hydraulic design of culverts in the AASHTO, FHWA and statemanuals, the guidance will be available to hydraulic engineers. Using the most accurate relationshipswill allow engineers to refine design predictions and reduce tolerance and safety factors that may be

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otherwise necessary to compensate for the reduced technological accuracy. The inclusion of an accuratehydraulic design method in the manuals supports the acquisition of engineering and design servicesunder hands-off privatized and fast track approaches.

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♦ Project 16-04Development of Designs and Guidelines for Safe and Aesthetic Urban Roadside Treatments

Research Field: DesignSource: AASHTO Task Force on Roadside Safety/WashingtonAllocation: $350,000NCHRP Staff: Charles W. Niessner

Many challenges are encountered when designing highway projects that pass through urbanareas. Arterial highways are intended to connect communities and are typically designed for movingmotorized vehicles as quickly and efficiently as possible. However, many times these highways are thecenters of the communities that have developed around them. Increasingly, these communities haverequested that these highways be redesigned using "Context Sensitive Design" principles that enhancethe appearance and, in some cases, the function of the highway.

Many of the context sensitive designs involve introducing landscape features such as trees,sculptures, and signs, in a median or roadside. In addition to enhancing the appearance of thesehighways, these designs are often also intended to slow or "calm" traffic in order to enhance pedestrianand bicycle safety. However, many of these features are usually considered fixed objects, as defined inthe AASHTO Roadside Design Guide, and will often be located within the design clear zone.Recommended clear zone dimensions generally represent minimum offset distances. Thus, reducingexisting, wider clear zones by introducing fixed object hazards even at these minimum distances reducesthe space available for a motorist to avoid a serious crash. In addition, slowing traffic may causechanges in traffic patterns as motorists seek alternate routes. Therefore, it is crucial that the impacts ofthese designs be understood so that decisions can be based on facts. There is also a need to identifydesigns that have performed acceptably, and a need to develop new designs and appropriate design-clearzone criteria that enhance the roadside environment while being forgiving to errant vehicles.

The objective of this research is to evaluate the impacts of aesthetic urban roadside designs anddevelop guidelines for design in this environment. These impacts include the effect on motorist andpedestrian\bicycle safety. This research would also develop a toolbox of effective designs that enhanceaesthetics and pedestrian/bicyclist safety but do not compromise the safety of the motorist.

This research would be accomplished as follows: (1) Literature Search—A literature searchwould be conducted to collect existing information regarding the design of urban highways withaesthetic roadside treatments and crashworthy features (such as barriers). (2) Survey of currentpractices—All of the states and selected cities would be surveyed to determine what aesthetic designshave been implemented or are being considered for their urban roadsides. (3) Evaluate—Using thesurvey results, highway sections would be identified where aesthetic treatments have been constructed.Similar highways without these treatments would also be identified for comparison purposes. Data suchas crash histories, traffic volumes, and operating speed would be collected and compared to similarfacilities or data from before the implementation when available. Crash data associated with fixedobjects would be further investigated to identify properties that result in serious injuries (treesizes/species, etc.). (4) Develop and recommend new designs or innovative applications of contextsensitive design principles to provide the appropriate balance between safety and aesthetics for theseapplications. (5) Develop recommendations for clear zones in low speed urban areas. (6) Coordinatewith other interest groups, such as planning, environment, USDA Urban Forestry, landscape architects,Rotary, Council of Local Governments, League of Cities, etc., to review the proposed guidelines.

This project would establish the impacts of using aesthetic treatments and provide a basis formaking design decisions. It would also provide designers with a toolbox of proven and potential newdesigns that enhance aesthetics without compromising safety. These guidelines will provide the

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AASHTO Task Force for Roadside Safety critical information needed to update Chapter 10 of theRoadside Design Guide.

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♦ Project 17-25Development of Crash Reduction Factors for Traffic Engineering and ITS Improvements

Research Field: TrafficSource: VirginiaAllocation: $400,000NCHRP Staff: Charles W. Niessner

Practitioners often appreciate crash reduction factors (also known as accident reduction factors oraccident modification factors) because they give a computationally simple and quick way of estimatingcrash reductions. Many states have a set of crash reduction factors that are used for estimating the safetyimpacts of various types of engineering improvements, encompassing the areas of signing, alignment,channelization, and other traffic engineering impacts. Typically, these factors are computed usingbefore-and-after comparisons, although later research has also suggested the use of cross-sectionalcomparisons.

Three main impediments exist for using crash reduction factors widely. First, while presumed tobe based on some type of data analysis, the origin of the factors used in practice is not always clear. Thefact that factors vary from state to state may reflect regional disparity or may indicate a need to updatethese factors. Second, there generally are not crash reduction factors for many ITS improvements, manyof which reflect a wide area of coverage. Third, crash reduction factors are designed for individualimprovements, yet multiple improvements usually occur when an intersection or roadway segment isbeing revamped.

Currently, crash reduction factors (CRFs) are often used at the short-term programming level(e.g., an annual review of hazardous locations statewide coupled with applicable CRFs and expectedcosts quickly yields a list of sites where the "biggest bang for the buck" is likely). While accurate CRFsshould help these users, the larger benefit is that accurate CRFs could be used in long-term planningapplications as well as nontraditional improvements. For example, on an urban freeway, the installationof a full 6 ft. shoulder and the initiation of a safety service patrol both have tangible safety benefits, butCRFs currently exist only for the former.

This research should use a two-pronged approach to develop crash reduction factors based onexperience in the various states. In the short term, one may focus on traditional engineeringimprovements (e.g., addition of a turning lane or improved signing), whereas in the long term oneshould be able to develop factors for select ITS improvements (e.g., changeable message signs thatindicate queues ahead).

Seven key steps are required to achieve the research objective: (1) State practitioners andconsultants should be surveyed as to which types of improvements are employed the most often. Fromthese results, a list of high impact crash reduction factors should be identified. (2) Ongoing studies atFHWA and NCHRP should be reviewed to identify CRFs in step (1) that are not being covered byFHWA and NCHRP. At this time, it is believed that CRFs for urban and suburban roadways, as wellnontraditional CRFs, will not be encompassed in the FHWA and CRF efforts. (3) Data from selectedsites within different states should be obtained to focus on the CRFs suggested in step (2). A balancewill need to be struck between (a) data elements that provide valuable information and (b) data elementsthat are readily available within the limitations of existing information systems. (4) A literature reviewof the various statistical methods used for computing crash reduction factors should be used to develop amethodology. An expert panel should review the findings of Tasks 1, 2, 3, and 4. This is the naturalbreakpoint for a Phase I Report. (5) Where data allow, crash reduction factors should be developed andthe accuracy of the crash reduction factors should be tested, preferably on a different set of data fromthat which was used to develop the factors. (6) Caveats for using the CRFs should be articulated in a

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format that is consistent with TRB’s proposed Highway Safety Manual. TRB Committee A2A02(Geometric Design) notes one objective of the Highway Safety Manual as being to "...raise thecredibility of safety impact analysis." While the use of real data should enhance the credibility of theCRFs, the notation of boundary conditions or situations for which they are not applicable will helpprevent their misuse. This is the natural breakpoint for a Phase II Report. (7) A literature review of ITSexperiences would be conducted in order to learn where ITS factors might be developed. An outcome ofthis task could be a more detailed study of the potential safety benefits of a particular ITS initiative, suchas ramp metering. Tasks 3, 4, 5, and 6 (without the interim reports) should be repeated but with a focuson ITS improvements.

States will continue to use crash reduction factors because they are easy to understand, apply,and explain to decision makers. Although some persons may correctly argue that crashes have manycauses (thereby rendering crash reduction factors problematic in an academic sense) the widespread useof CRFs should be acknowledged and attempts should be made by the transportation community torender these CRFs as practical and accurate as possible. As mentioned above, this "community"currently includes short-term programmers, but, with diverse CRFs, could include a broader range oftransportation planners. As suggested in Task 6, the proposed TRB Highway Safety Manual may workout to be a natural vehicle for disseminating the results of this research.

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♦ Project 17-26Development of Models for Prediction of Expected Safety Performance for Urban and SuburbanArterials

Research Field: TrafficSource: AASHTO Standing Committee on Highway Traffic SafetyAllocation: $500,000NCHRP Staff: Charles W. Niessner

There is a significant need and opportunity for improving the explicit role of highway safety inmaking decisions on roadway planning, design, and operations. Within the Transportation ResearchBoard (TRB), several committees have identified the need to take advantage of a number of recenttechnical advances and synthesize new research on highway safety into a Highway Safety Manual(HSM). It will serve as a useful tool for practitioners in helping them make decisions. It will have manyattributes similar to the extant Highway Capacity Manual. That is, the purpose of an HSM is to providethe best factual information and tools in a useful and widely accepted form in order to facilitate roadwaydesign and operational decisions, based upon explicit consideration of their safety consequences. Thismanual would greatly strengthen the role of safety in road planning, design, and operations decisions.

A workshop was held late in 1999, which produced a preliminary plan for an HSM. The groupoutlined a five-stage process that they estimated to require up to 5 years to produce the first issue andestablish an ongoing process of improvement: (1) Scoping, Organizing & Outreach (6 mos.); (2)Producing a Prototype (1 yr.); (3) Research and Chapter Development—1st edition (2.5 yrs.); (4)Publishing, Marketing & Distributing a First Edition (9 mos.); and (5) Ongoing Improvements.

A Joint Subcommittee for the Development of a Highway Safety Manual was formed within theTRB in January of 2000 to direct the effort to produce an HSM.

NCHRP Project 17-18(4) was funded to facilitate the completion of the first two stages of theprocess. That project is currently about halfway through its 18-month project period. While much of thedetail remains to be worked upon, it has become clear, through the original planning workshop, thediscussions of the Joint Subcommittee, and the work of the research contractor to-date, that a high-priority research need is the development of models for the safety performance of elements of urban andsuburban arterials. This will complement current work within FHWA to produce safety impact modelsfor rural highways

The research shall produce models that allow users to predict the safety performance of elementsof urban and suburban highways. Corollary tasks include (1) Definition of the primary contexts withinwhich the models are anticipated to be applied. (2) Identification of the elements for which prediction ofsafety performance should be sought. (3) Assessment of alternative modeling approaches, andformulation of the approach considered most appropriate for urban and suburban highways (may involvelimited data collection). (4) Collection of data, using existing databases and new data, as appropriate. (5)Model development and validation. (6) Demonstration of the application of the models to practicalexamples. (7) Development of draft materials for the Highway Safety Manual (whole chapter and/orportions of chapters, as appropriate). (8) Development of software to allow computer-basedimplementation of the models. (9) Identification of areas for which further research will be needed toenhance the models (citing specific study protocols, data collection alternatives, appropriate analysistechniques, and potential policy implications).

The establishment of models for urban and suburban highways is anticipated to require extensiveeffort, since almost nothing useful has been done in this area to date. It is logical to expect that aseparate set of models will be required for the analysis of arterial segments and those for arterial

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intersections. Therefore, the research work should (as part of the third task listed above) identify thedifferent modeling approaches to be taken for each.

It is possible that the effort to develop models for both segments and intersections will requiremore than the resources provided. The contractor should be required to document this, if it proves to bethe case. A decision should then be made as to which aspect to pursue within the current project andwhich to delay for a subsequent effort. It is suggested that the decision be made by the Panel inconsultation with the Joint Subcommittee. In addition, the research contractor should be required toproduce a detailed description of the modeling approach and research plan for the subsequent effort (aspart of the ninth task in the list above).

The research contractor should work within the framework established for the HSM by the JointSubcommittee. The successful implementation of the work will be greatly facilitated if a procedure wereto be developed to allow regular review of work by, and interaction with, the Joint Subcommitteethroughout the research period.

It has already been pointed out that it will be important for the contractor to relate to the previouswork of the Joint Subcommittee. In addition the contractor should become familiar with, and relate to,several other initiatives. The FHWA is developing the Interactive Highway Safety Design Model(IHSDM) and the Comprehensive Highway Safety Improvement Model (CHSIM). The TRB also has aJoint Subcommittee for the development of a Human Factors Guide. The AASHTO is developing aTransportation Safety Information Management System (TSIMS), as well as implementing its StrategicHighway Safety Plan. Completion of the proposed project will benefit each of these other initiatives,both directly and indirectly.

The states, and others responsible for the road system, do not currently have very useful tools forreflecting safety in their decisions. The result is a diminishing of the weight of safety considerations inthese decisions. When difficult choices must be made, greater confidence is often taken in predictions ofsuch factors as cost, operational impacts, and environmental impacts. Therefore, an effective resource isurgently needed which predicts the safety performance of the variety of elements considered in roadplanning, design, construction, and operation. Such a resource will be useful to state and localtransportation agencies, as well as in the development of the model systems listed in the previoussection.

The Joint Subcommittee for the HSM seeks to implement the models in the Manual, which is tobe targeted primarily at those on the front-line of daily decision-making within state DOTs, as well aslocal organizations such as MPOs. These would be analysts studying impacts of proposed roadimprovements on users (including the interface with other surface transportation). They would beconducting studies at the planning, design, or operations levels in the system. However, it was alsorecognized that such a manual will be applied by a number of secondary users as well, and the materialshould be produced with these possible users in mind.

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♦ Project 20-60Transportation Performance Measures and Performance Target Establishment for AssetManagement

Research Field: Special ProjectsSource: AASHTO Task Force on Asset ManagementAllocation: $350,000NCHRP Staff: Crawford F. Jencks

Many transportation agencies have developed system performance measures to help track theimpacts of program investments, maintenance, and operations improvements. These performancemeasures are usually technical in nature, capturing an engineering or operational attribute of thetransportation system. A review of these measures is needed to assess their usefulness for assetmanagement (e.g., their application in tradeoff analyses).

In addition, some state DOTs define targets to which current conditions can be objectivelycompared in order to determine whether the transportation system is performing acceptably. The basison which these targets are set varies, and there is no generally accepted methodology for theirestablishment. Research in this area could assist agencies in using the modified method for GASB 34.

The potential research scope includes tasks to (1) Develop a synthesis of current assetmanagement transportation performance measures building on recent related work; (2) Analyze theusefulness and effectiveness of measures as a basis for identifying needs in planning, in programtradeoff analyses, in performance budgeting, in communicating outcomes of investment levels, formonitoring system performance, and other applications of asset management; (3) Identify high-levelperformance measures that have been defined specifically for executives and political leadership. [Thesehigh-level measures may be non-technical, and express trends in program accomplishment (i.e., Is theprogram meeting its targets? How does this year compare to last year?)]; and (4) Develop a frameworkfor establishing performance targets. Rather than recommend specific target values, the framework willestablish a methodology for establishing targets among key performance measures and offer a range ofalternatives as guidance.

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♦ Project 24-21LRFD Soil Nailing Design and Construction Specifications

Research Field: DesignSource: AASHTO Highway Subcommittee on Bridges and StructuresAllocation: $200,000NCHRP Staff: Timothy G. Hess

The soil nailing method of earth structure retention is rapidly becoming accepted as the preferredretaining wall method in cut applications for both temporary and permanent situations. Advantages ofsoil nailed retaining structures include cost, speed of construction, construction flexibility, andaesthetics. The Federal Highway Administration (FHWA) Demonstration Project No. 103 developed acomprehensive design and construction manual for temporary and permanent soil nailed structures. TheFHWA soil nail manual contains a detailed design protocol for working stress design and an early, butincomplete, LRFD approach. The AASHTO Standard Specifications and LRFD specifications lack anyguidance on the design and construction of soil nail structures. Some state DOTs have not fullyimplemented soil nailing due to the absence of AASHTO specifications.

Research is needed to develop soil nailing design and construction guidelines for incorporationwithin the AASHTO LRFD specifications. The existing FHWA LRFD guidance on soil nailing requiresadditional calibration work for both load and resistance factors. In addition the current FHWA guidanceis not in an acceptable AASHTO specification format.

The objectives of the research are to (a) reexamine existing LRFD design and constructionguidance on soil nailed retaining structures and recommend suggested modifications to existing load andresistance factors and (b) develop AASHTO LRFD design and construction specifications for temporaryand permanent applications.

These objectives can be accomplished through the following tasks: (1) Literature search—Usingthe existing FHWA guidelines on soil nailing and other appropriate domestic and international publishedreferences, conduct a comprehensive review of current soil nailing design and construction guidance forboth working stress and LRFD specifications. (2) Analysis—Using model and full-scale data andreliability-based methods where practical, conduct calibration analyses to re-examine or developrecommended load and resistance for soil nailed structures. Utilize current AASHTO load factors or asmodified under NCHRP Project 12-55. Determine appropriate load and resistance factors for global andcompound slope stability failure modes for soil nailed structures. The reexamination of resistance factorsshould account for the frequency of conducting performance and proof soil nail tests duringconstruction. (3) Development—Prepare comprehensive LRFD design specifications using the new orrevised load and resistance factors in combination with existing soil nailing guidance. Development ofthe draft specifications should reflect the technical input of industry and other sources. In addition thistask will develop a comprehensive materials and methods of construction specifications. (4)Reporting—Prepare a report summarizing the research and recommendations to the AASHTOSubcommittee on Bridges and Structures.

Initiation of the work for this project is very important. Soil nailing is widely recognized as acost-effective retaining wall and excavation support technology. FHWA Demonstration Project No. 103documented savings in excess of $52 million on soil nailing. These impressive savings can easily besurpassed on an annual basis by the mainstreaming of this technology. This mainstreaming is currentlybeing inhibited by the absence of AASHTO specifications.

Engineers using the AASHTO LRFD Highway Bridge Specifications will use the end product ofthis research, and payoff to the public will be realized in both the short- and long-term cost savings. Theresearch findings will be implemented through revisions to the AASHTO LRFD specifications.

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♦ Project 24-22Economical and Performance Optimization for Using a Wider Range of Backfill Materials forRetaining Wall Structures

Research Field: Soils and GeologySource: ColoradoAllocation: $600,000NCHRP Staff: Timothy G. Hess

The prevailing specifications for construction of retaining walls require the use of high-qualitygranular and free-draining backfill materials (referred to as Class-1 backfill in CDOT). The availabilityof high-quality structural backfill aggregates for the construction of retaining walls and other structureswill continue to decrease while costs rise, especially in urban areas. FHWA Report SA-96-071 (Page 72)and Keller (1995) indicated that fill materials outside the specified gradation and plasticity requirementsfor Class-1 backfill material have shown satisfactory performance. Research conducted by CDOTindicated that many onsite materials classified by AASHTO as A-2 soils, and not meeting therequirements for Class-1 backfill, have a very high friction angle (higher than 34 degrees). However,strict Class-1 requirements for percentage of material passing sieve #200 (less than 20 percent) and theplasticity index (less than 6) made the A-2 onsite soils not acceptable materials by the standards for useas backfill materials. A-2 soils are considered in AASHTO soil classification as good materials forsubgrade applications. Requirements for percent of backfill material passing sieve #200 and theplasticity index may be needed to control the permeability, creep, and constructability of backfillmaterials, in addition to strength, but more research is needed in this area. Can we relax theserequirements for possible use of onsite selective backfill materials? What additional measures could beincorporated in the construction that will enhance the performance of these much cheaper soils? Notethat FHWA Report SA-96-071 (Page 71) allows the use of less selected backfill materials forconstruction of reinforced soil slopes (percent passing sieve #200 <50, and PI <20).

The material specifications for Class-1 material encompass a fairly wide range of different soils;some will result in high performance and some in relatively lower performance tolerances for retainingwalls. For a backfill soil meeting the material and construction requirements of Class-1 backfill(gradation, PI, and compaction level), a lower bound frictional strength of 34 degrees is often used in thedesign procedure. Small conventional direct shear tests and large-size direct shear and triaxial strengthtests were performed on the backfill soil employed in the construction of the Founders/Meadows GRSretaining wall structure. In the conventional direct shear tests, the 35 percent gravel portion (material notpassing sieve #4) were removed, but were included in the large-size strength tests. The results of thelarge-size testing program indicated higher friction and cohesion strength than what was measured in theconventional small direct shear tests. Is the measured cohesion part of the shear strength, often neglectedin the design, a real cohesion or apparent cohesion. [How about conducting long-term direct shearstrength tests at saturated conditions to resolve this issue?] It was also noticed that the conventionalguidelines for performing the conventional direct shear test requires specimens compacted at 95 percentof the maximum dry unit weight determined by T-99, while CDOT construction specifications call forcompaction level at 100 percent of T-99.

The objective of this research is to develop selection guidelines, representative designparameters, appropriate testing methods, and feasible construction specifications for a wide range ofbackfill materials for retaining walls that provide the desired optimization between performance andeconomy. The range of candidate backfill soils should encompass all soils rated in AASHTOclassification as excellent to good (A-1, A-2, and A-3),including gravel, sands, and silty or clayey graveland sand. This research should consider providing backfill design and construction provisions for Class

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A and Class B walls (and possibly Class C walls), where Class B walls would have less restrictiveconstruction geometric tolerances (i.e., performance of Class B backfill is less than the performance ofClass A backfill, but meeting the structure performance requirements). Recommendations for feasiblemeasures (practical and economical) with proven field records for enhancing the backfill performance ofrelatively cheaper and lower quality soils are also required in this research.

The following is a list of proposed tasks for this research project (candidate soils are A-1, A-2,and A-3 soils): (1) Perform a comprehensive literature review. (a) Conduct a survey of the designparameters, materials, and construction specifications and cost for backfill materials of earth retainingwalls in the United States and worldwide (no international cost information is needed). Collect anddocument similar information for compacted soils of slopes, embankments, and road bases. Note thatColorado is using a road base with a tighter range of gradation that falls within the gradation of Class-1backfill but costing CDOT less than Class-1 backfill. (b) Collect performance data for backfill materialsoutside the materials requirements for Class-1 material. (c) Perform a literature search of the proper testsfor obtaining the strength, stiffness, creep, and permeability characteristics of compacted backfill soils.(d) Perform a literature search of the material and construction parameters that influence strength,stiffness, permeability, and creep of compacted soils. (e) Collect test results (e.g., on the strength,stiffness, permeability, creep, gradation, compaction level, plasticity) on compacted soils from privatelabs and state DOTs. (f) Summarize measures to enhance the performance of backfill soils that wereused successfully in the field. (2) Compile and synthesize the information of previous task to establishthe state of the practice of backfill materials in retaining walls and lessons learned from the specifiedsoil characteristics employed for construction of road bases, slopes, and embankments. (3) Use theresults of previous tasks to set preliminary limits for the range of potential backfill soils for retainingwalls. The constructability of these soils, especially those outside Class-1, should be addressed. Somenumerical simulations (see Task 7) might be needed in this task. (4) Using the range established in theprevious task for candidate backfill soils, collect a large number of representative and typical soilsamples with sufficient quantities from all over the United States. (5) Develop or identify the properprocedure to test the samples of Task 4 as outlined in Task 6. (6) Conduct a series of tests (identified inTask 5) to obtain the strength, stiffness, permeability, and creep characteristics of the samples identifiedin Task 4 (all soil constitutive and strength parameters). The results on the soil (or group) with the bestperformance will be used as the baseline for all other soils (groups). (7) Using the results of the previoustask, perform theoretical and numerical analyses aid investigations to evaluate the performance oftypical retaining wall structures (i.e., stress, deformation, and build-up of pore water pressure)constructed with different groups of backfill materials. Verify these results (if feasible) with measuredand reported performance results for actual walls. The results on the soil (or group) with the bestperformance will be used as the baseline for all other soils (groups). Compare the performance toleranceof structures using non-Class-1 backfill material with structures employing Class-1 backfill materials.Additional feasible measures (practical and economical) with proven field records for enhancing thebackfill performance should be investigated in this task. (8) Analyze the results of previous tasks todevelop backfill selection limits for different new classes of backfill material with different performancetolerances. For each new class, and for special classes with measures to enhance performance, the resultsof this research should include proper and representative design parameters (i.e., friction angle,cohesion, unit weight, factor of safety), material selection and construction requirements (i.e., gradation,LL, PI, compaction level, strength, stiffness, creep, and permeability tests, number of tests),performance tolerance (i.e., short- and long-term deformation and drainage characteristics), andrecommendations for field applications. The construction requirements are needed to provideconstruction personnel with efficient and practical tools to verify the design parameters selected in thedesign process and to achieve the performance expected in the design. Therefore, additional constructionrequirements (currently in CDOT gradation, PI, and direct shear test, and compaction) such as

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permeability, stiffness, and creep tests may be needed. (9) Document results in a final a report and in atechnical note for possible inclusion in AASHTO specifications.

This research will study less expensive and more readily available alternative backfill materials,possibly available in the close vicinity of the highway project site. This study will lead to bettercharacterization and more economical use of all backfill materials and will provide the desiredoptimization between performance and economy. The use of alternative backfill (i.e., not meetingrequirements for Class-1 backfill) for retaining structures will lead to significant cost benefits both to thecontractor and to the States and local highway agencies. This research also could alleviate someenvironmental and social impacts concerns of aggregate mining, aggregate availability, and quality,especially in the urban areas.

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♦ Project 24-23Riprap Design Criteria, Specifications, and Quality Control

Research Field: Soils and GeologySource: AASHTO Task Force on Hydrology and HydraulicsAllocation: $350,000NCHRP Staff: Timothy G. Hess

A research project was initiated in 1995 by the Transportation Research Board’s NationalCooperative Highway Research Program (NCHRP) to evaluate the state of knowledge regarding bridgescour and stream stability technology. NCHRP Project 24-8 produced a comprehensive plan that, ifundertaken, would begin to fill some of the gaps regarding methods to estimate scour at bridges, protectpiers and abutments from scour, protect channel banks, and understand how scour develops in complexchannel materials. As a result of NCHRP Project 24-8, two NCHRP studies have been funded to developcriteria for the design and installation of scour countermeasures at bridges. NCHRP Project 24-7(2),Countermeasures to Protect Bridge Piers from Scour, will define countermeasures to protect bridgepiers from scour. Similarly, NCHRP Project 24-18, Countermeasures to Protect Bridge Abutments fromScour, will define countermeasures to protect abutments from scour. Most likely, both of these studieswill conclude that riprap is a viable countermeasure to protect piers and abutments from scour. Inaddition, two scanning tours have recently been conducted to assess scour practices andcountermeasures used in other countries. The first scan was conducted in Europe and the second wasconducted in New Zealand. Although NCHRP Project 24-8 does not specifically list riprap designcriteria, specifications, and quality control as a critical research need, many of the research items that arerelated to the design and construction of countermeasures list riprap as a key component.

A brief review of the literature indicates that many different techniques are used to determine thesize and extent of a riprap installation. Depending on the technique used to size the riprap, the answerscan vary widely as far as the computed size of the median particle. Also, most states have their ownspecifications for classifying riprap size and gradation. The construction industry would benefit from aconsistent specification that could be used from location to location. A consistent set of riprapspecifications would also lead to better quality control by reducing confusion among contractors. Thereis also a wide variety of construction practices employed when installing riprap. This research projectwould make recommendations on construction practices and techniques.

The research proposed in this problem statement will evaluate the state of the practice regardingthe determination of riprap size, recommend procedures for riprap size determination, discuss riprapfilters and filter installation, specify a uniform system of gradation and classification, recommendprocedures for installation, and develop a system of guidelines for quality control.

The Federal Highway Administration (FHWA), U.S. Army Corps of Engineers (USACOE), andstate DOTs have developed or utilized methods for sizing riprap for use in protecting embankments,dams, piers, abutments, etc. Most of the methods are based on, or have been derived from, methodsoriginally presented by Isbash or Shields which were first presented in the 1930s. Other methods forsizing riprap have resulted from empirical studies that have been designed to protect specific structuressuch as piers and abutments. It is proposed that a literature review be conducted to assemble all of thewidely used methods for sizing riprap and designing filters. It is further proposed that these methods beevaluated for their use and applicability.

Recommendations will be made on the best procedures to be used. The second portion of thisresearch effort will be to develop and recommend a gradation and classification system that could beadopted as an AASHTO specification. The third portion of this research will be to recommend

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procedures for riprap installation, and the fourth will be to develop a system of guidelines for qualitycontrol.

The objective of this proposed research is to provide improvements to current practices in thefollowing areas:

• Guidelines and techniques for designing and placing riprap on the slopes of spill-through abutments,guidebanks, at the base of piers, on channel banks, etc. This would include guidance on the type andextent of filters that could be used under the protective riprap layer, the riprap extent, and the size ofthe riprap;

• A consistent gradation and classification system that could be adopted for use as an AASHTOspecification;

• Recommended procedures and practices for riprap installation; and• Development of a system of guidelines to improve quality control.

This research will be investigative in nature and will require a survey of existing practices, an evaluationof currently used design techniques, and a critical review of pertinent literature.

To conduct this research, it is recommended that the following tasks be accomplished: (1)Review the technical literature from foreign and domestic sources to assess the adequacy and extent ofexisting information on design equations and techniques for determining the median size of stonerequired for a riprap design. The literature review should critically evaluate the design technique orguidance presented. (2) Conduct a survey of a practices used by federal agencies, state departments oftransportation, and anyone else who routinely designs and constructs projects out of riprap. This surveywill include an evaluation of riprap classification systems and specifications. (3) Based on the findingsof the literature review outlined in Task 1 and the survey conducted in Task 2, perform a criticalevaluation of any design techniques and equations to determine which perform most consistently andreliably. Task 3 will also include recommendations on equations to be used. The work should include,but not be limited to, the following factors: sensitivity of equations being evaluated to ranges in flowparameters, side slopes, etc.; recommended equations to use for different design situations; filter types,design methods, extent, and need; vertical and lateral extent of protection; and durability andsusceptibility to ice and debris damage. (4) Submit an interim report containing a review of theliterature, an evaluation of the state of the practice, and a summary of design equations and applicability.This report will summarize a review of the literature; document Tasks 1, 2 and 3 and include a set ofrecommended design techniques and equations; and discuss the feasibility of an expert system orcomputer program to assist the user in designing riprap protection. (5) Pending a review of the interimreport by the project panel, finalize it into a document suitable for distribution.

Existing techniques and procedures for the design of riprap protection at bridge abutments, piers,channels, guidebanks, and other locations are confusing and difficult to apply. There are many differentequations to choose from which give widely different answers. In addition, there is not a consistentclassification system or set of specifications that can be used when preparing plans or assembling aspecification package for a project. Also, projects requiring the use of riprap have historically sufferedfrom poor construction practices and quality control. The successful completion of this research projectwill provide specific guidelines for the reliable design of projects that include riprap.

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♦ Project 25-26Development of a Low-Impact Development Design and Construction Manual for TransportationSystems

Research Field: Soils and GeologySource: Washington/AASHTO Standing Committee on Planning/AASHTO Standing

Committee on the EnvironmentAllocation: $500,000NCHRP Staff: Christopher J. Hedges

Transportation agencies are required to meet current and future water protection regulations topromote transportation project delivery in the most economically sustainable manner. Low-impactdevelopment technologies provide tools that can promote the dual goals of environmental protectionwith transportation system improvements with maximum efficiency.

Transportation agencies across the nation are faced with the challenge of meeting the public’sincreasing demand for efficient transportation systems while reducing environmental impacts associatedwith transportation projects. Adverse impacts of highway runoff on watershed hydrology and waterquality include the effects on sensitive ecosystems, surface water and groundwater supplies, combinedsewer overflows, and economically important fisheries. Increasingly restrictive regulatory requirementscompound the problem as compliance with the National Environmental Policy Act, National PollutantDischarge Elimination System—Phase II, Total Maximum Daily Loads, and the Endangered SpeciesAct will require mitigation for transportation projects' environmental effects in order to acquirenecessary project-specific permits. These public concerns and regulatory requirements pose significantchallenges in planning, design, construction, and funding for transportation agencies.

Experience and new research has called into question both the ability and long-term economicsustainability of current stormwater management practices to effectively meet these emerging regulatoryand receiving water protection challenges. Even in cases where the roadway or highway constructioncontributions to the total area of impervious surface in a watershed may be small, the hydrodynamicmodifications and pollutant loads generated by highway drainage systems can significantly impactsensitive aquatic species on an individual project basis and on a cumulative basis throughout atransportation corridor.

Because of the limitations in conventional approaches, transportation agencies must develop newand innovative approaches to supplement current technologies and respond to these complex regulatoryand stakeholder requirements. Without new approaches that can be targeted to address complexregulatory and natural resource protection issues, significant delays to the permitting and construction ofnew highway projects and the rehabilitation of existing projects may result. Such delays could greatlyaffect local economic development and cause substantial increases in highway construction costs.

Low-Impact Development (LID) is a very promising innovative technological approach tostormwater management and resource protection that has tremendous potential to be adapted to helpmeet the future environmental and economic objectives of transportation agencies. LID technologies arebased on using the cumulative affects of multiple, redundant, decentralized stormwater managementtechniques to meet quantified stormwater management thresholds. LID is designed to create amultifunctional/multi-beneficial use in every aspect of the urban landscape to manage runoff and, wherepossible, to effectively restore or maintain the natural hydrologic and water quality regimes. The waterquality and economic benefits of LID have been successfully demonstrated for residential, commercial,and industrial development applications in the United States, Europe, and the Pacific Rim nations. Inmany cases, LID has been shown to be more cost-effective as it makes multifunctional use of thelandscape to manage runoff onsite, and, therefore, reduce conventional drainage infrastructure. For

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linear transportation systems, LID can potentially allow transportation agencies to maximize the use ofexisting rights-of-way for stormwater management, reducing the need to procure additional land to meetstormwater management objectives, and thereby reducing project costs. This new approach has showntremendous potential, particularly in highly urbanized areas, for new development, and retrofit projects.At the present time, a design manual exists for suburban residential development in Prince GeorgesCounty, Maryland. LID practices are rapidly being accepted by communities and resource agenciesacross the nation as a new alternative to help meet regulatory requirements and resource protectiongoals.

Since LID is a relatively new practice, many special considerations need to be addressed forlinear transportation systems. Some of the characteristics of linear transportation systems that presentchallenges for LID methods are extensive cut-and-fill situations that cross multiple streams, drainagedivides, limited right-of-way, multiple project phases, and limited maintenance resources. The keyplanning and design LID strategies that have been used for urban retrofits and green developmentinclude impact avoidance, minimization, strategic timing and routing of runoff, uniform distributedintegrated management practices, and pollution prevention. LID stormwater control practices includemultiple combinations of discharge dispersal, infiltration, retention, bioretention, filtration, imperviousdisconnection or removal, detention, amended soils, water reuse, and increasing surface roughness.Integrating LID design principles and practices into every aspect of a highway right-of-way (medians,shoulders, swales, pipes, inlets, streetscapes, slopes, green space, etc.) can be used to create ahydrologically functional transportation system, instead of using drainage infrastructure solely forstormwater conveyance. In urban areas where traditional stormwater management BMPs are ineffectivedue to limited land availability, certain LID practices may offer more cost-effective solutions. It iscritical to evaluate how these techniques can be incorporated into linear systems so that stormwatermanagement, public safety, and construction requirements can be met. It has been shown that many LIDmethods can also be easily maintained or constructed as part of routine road maintenance andconstruction activities, which has the potential to further lower life-cycle costs and the need for ongoingfunding sources for routine maintenance and operations.

Pilot projects conducted by several researchers have demonstrated the potential of LID to meetregulatory requirements, but substantial work needs to be conducted on developing LID designstrategies, performance standards, and specifications. LID’s decentralized approach to stormwatermanagement technology has tremendous potential to supplement or completely replace conventionalcentralized stormwater BMP approaches. However, LID’s applicability, efficacy, and long-termeconomic sustainability have yet to be determined or documented for transportation systems.

There is an urgent need to develop better mitigation technologies to meet current and futureregulatory requirements. The environmental impacts associated with transportation projects are beingchallenged by regulatory agencies, environmental organizations, and the courts. The development ofadditional tools to address environmentally sensitive areas will save transportation agencies both timeand money in planning and designing projects that will ensure environmental integrity. Programs forurban renewal, the TEA-21 environmental components, and "smart growth" concepts present valuableopportunities to integrate stormwater management controls into watershed-based enhancement andredevelopment projects. This presents opportunities for local and regional cost-sharing and partnering toreduce construction and maintenance costs.

For site development and urban renewal projects, the use of LID has demonstrated the ability toeliminate or drastically reduce the pollutant loads of stormwater runoff to streams, wetlands, or othersensitive water resources; reduce concerns about runoff water quality and quantity; and increase directpercolation into sub-soils onsite—all of which can reduce transportation project costs and potentialoffsite water quality or quantity concerns. The next logical step is to adapt these practices totransportation activities that are critical components of the infrastructure. LID methods can potentially

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assist transportation agencies in meeting project delivery schedules by facilitating quicker permitacquisition and fewer project-specific consultations with resource and regulatory agencies.

The proposed guidance document can be an effective tool in designing and constructing LIDfacilities with consistency, which in turn leads to effective technologies that can be monitored andcompared. Several DOTs, including Washington DOT, Maryland State Highway Administration,Virginia DOT, and CalTrans have expressed interest in piloting LID technology due to its potential foraddressing the escalating environmental requirements that are projected.

The objective of this project is to develop a Low Impact Development Design and ConstructionManual for Transportation Systems.

Accomplishment of the project objective will require the following phases:Phase 1—Examine the applicability of existing and conceptual LID technologies to linear

transportation systems by conducting an extensive literature search of existing and potential LIDsystems. LID principles and practices will be identified and documented from existing case studies,demonstration projects, research programs, monitoring efforts, and design guideline documents. Theapplicability of the identified LID practices for use in long, narrow parcels of land that are endemic oflinear transportation systems will be evaluated. The products of the literature search will be compiled ina "white paper" of applicable LID practices for linear transportation systems that can be used bytransportation agencies to determine whether LID is suitable for their particular climate, regulatorymandates, and projects.

Phase 2—Develop practical design standards and practices that meet identified regulatoryrequirements and resource protection goals. The anticipated criteria that will be used to develop the LIDmethods will include regional applicability, highway safety, spatial/temporal requirements, soilcharacteristics, pollutant removal effectiveness, hydrologic benefits, life-cycle maintenancerequirements, and resultant costs. A series of conceptual design standards will then be developed forpractical field evaluation and optimization.

Phase 3—The conceptual designs will then be used in demonstration pilot projects to evaluatedesign and construction issues, determine the cost and environmental benefits, and optimize LIDtechniques for transportation. The field monitoring data will be used to refine construction techniques;develop performance data; identify technical limitations; identify further research needs; developmaintenance protocols; and refine the detailed design guidance, standards, and specifications. Theprincipal investigators will be responsible for developing criteria and coordinating the design,monitoring, and reporting efforts. The construction and final design of these pilot projects would be theresponsibility of participating state highway agencies.