tis & parking guidelines

TRAFFIC IMPACT STUDY AND PARKING REQUIREMENT GUIDELINES

UNITED ARAB EMIRATES Department of Municipalities and Agriculture Abu Dhabi Municipality Roads and Transportation Directorate


i

1. INTRODUCTION .................................................................................................1

1.1. Background....................................................................................................1 1.2. Need for Traffic Impact Studies ....................................................................2 1.3. Need for Parking Requirements.....................................................................2 1.4. Objectives of Traffic Impact Study and Parking Requirements ....................3 1.5. How These Guidelines were Developed........................................................3 1.6. References......................................................................................................4

2. APPLICATION OF REQUIREMENTS ...............................................................5 2.1. How Do Traffic Impact Studies and Parking Studies Fit Within the Development Review Process?..................................................................................5

2.1.1. Land Development Review Process ......................................................5 2.1.2. Incorporation of Traffic Impact Study and Parking Study Requirements into the Review Process .........................................................................................6

2.2. When is a Traffic Impact Study Needed? ......................................................6 2.2.1. Criteria for Determining the Need for a Traffic Impact Study ..............8 2.2.2. Procedures for Obtaining Exemptions from the Requirements for Traffic Impact Studies............................................................................................8

2.3. When Do Parking Requirements Apply?.......................................................8 2.4. Qualifications of Study Preparer....................................................................8 2.5. Qualifications of Study Reviewer..................................................................9

3. SCOPE OF TRAFFIC IMPACT STUDY ...........................................................10 3.1. Summary of Traffic Impact Study Process..................................................10 3.2. Initial Meeting and Development of Inception Plan....................................11

3.2.1. Notification ..........................................................................................13 3.2.2. Initial Meeting......................................................................................13 3.2.3. Inception plan for Traffic Impact Study ..............................................13

3.3. Study Area ...................................................................................................14 3.4. Key Facilities to be Analyzed ......................................................................14 3.5. Horizon Year(s) ...........................................................................................15 3.6. Peak Hours of Analysis................................................................................15 3.7. Methodologies and Procedures ....................................................................16

3.7.1. Level of Service Calculation Methodologies.......................................16 3.8. Impact Analysis and Mitigation Strategies ..................................................18 3.9. References....................................................................................................18

4. ANALYSIS OF EXISTING CONDITIONS.......................................................19 4.1. Development Site Location..........................................................................19 4.2. Description of Current Land Uses on Development Site.............................19 4.3. Description of Surrounding Transportation System ....................................21

4.3.1. Study Area ...........................................................................................21 4.3.2. Existing Roadway System ...................................................................21 4.3.3. Existing Public Transport and Taxi Service ........................................23 4.3.4. Existing Pedestrian Facilities...............................................................23

4.4. Data Collection/Traffic Count Requirements ..............................................23 4.4.1. Existing Data to be obtained from the Roads Directorate ...................24 4.4.2. Data to be Collected by Applicant .......................................................24


ii

4.5. Reporting Existing Levels of Service on Key Facilities..............................26 4.6. References....................................................................................................29

5. ESTABLISHING FUTURE YEAR BASELINE CONDITIONS.......................30 5.1. Methods and Data Considerations ...............................................................30 5.2. Assumptions Regarding Future Year Land Use and Population .................30

5.2.1. Regional Growth Assumptions ............................................................31 5.2.2. Related Developments in the Study Area ............................................31

5.3. Assumptions Regarding Future Transportation Improvements...................32 5.3.1. Highway and TSM Improvements.......................................................32 5.3.2. Public Transportation Service and TDM .............................................33

5.4. Determining Future Year Baseline Traffic Volumes...................................33 5.4.1. Manual Method for Determining Future Year Baseline Traffic Volumes 33 5.4.2. Model Method for Determining Future Year Baseline Traffic Volumes 34

5.5. Evaluation of Baseline Traffic Conditions ..................................................35 5.6. References....................................................................................................35

6. TRIP GENERATION ..........................................................................................36 6.1. Development Description ............................................................................36 6.2. Development Trip Generation .....................................................................37

6.2.1. Peak Hours ...........................................................................................37 6.2.2. Trip Generation Rates ..........................................................................38 6.2.3. Primary vs. Linked Trips .....................................................................38 6.2.4. Internal Capture ...................................................................................39 6.2.5. Mode Split Variations ..........................................................................40 6.2.6. Tables of Existing and Future Development Trip Generation.............40 6.2.7. Information On Available Trip Generation Resources........................40

6.3. Choice of Trip Rates ....................................................................................41 6.4. References....................................................................................................41

7. SITE TRAFFIC DISTRIBUTION AND ASSIGNMENT ..................................42 7.1. Trip Distribution ..........................................................................................42

7.1.1. Manual Methods ..................................................................................43 7.1.2. Model-Based Methods .........................................................................45

7.2. Trip Assignment...........................................................................................46 7.3. References....................................................................................................46

8. ANALYSIS OF DEVELOPMENT-RELATED TRANSPORTATION IMPACTS ....................................................................................................................48

8.1. Quantifying Development-Related Transportation Impacts........................48 8.1.1. Traffic Impacts.....................................................................................48 8.1.2. Other Transportation Impacts ..............................................................49

8.2. Thresholds for Determining Significant Transportation Impacts ................50 8.2.1. Approaches to Defining Significance Thresholds ...............................50 8.2.2. Significance Thresholds for Abu Dhabi ..............................................51

8.3. References....................................................................................................52

9. DEVELOPMENT OF MITIGATION PLAN .....................................................53 9.1. Developing the Mitigation Plan ...................................................................53


iii

9.1.1. Objectives of Mitigation Plan ..............................................................53 9.1.2. Quantifying the Benefits of Mitigation Measures ...............................53

9.2. Potential Mitigation Strategies.....................................................................56 9.2.1. Intersection Improvements...................................................................56 9.2.2. New Roadways, Extensions, Roadway Widening, and Interchanges..57 9.2.3. Operational or Transportation System Management Improvements ...57 9.2.4. Transportation Demand Management..................................................57 9.2.5. Modifications to Definition of Development and/or Site Plan ............58

9.3. Implementation and Phasing of Mitigation Measures .................................58 9.4. Review and Approval of Proposed Mitigation Plan ....................................58 9.5. References....................................................................................................59

10. MULTIMODAL SITE ACCESS, CIRCULATION, AND PARKING DESIGN 60

10.1. Importance and Scope of Site Access and Circulation ................................60 10.2. Site Plan .......................................................................................................61 10.3. Site Access, Circulation, and Parking Design .............................................62

10.3.1. Site Access ...........................................................................................62 10.3.2. Access Design......................................................................................62 10.3.3. Internal Roadways ...............................................................................63 10.3.4. Delivery, Service and Emergency Vehicles.........................................64 10.3.5. Taxi and Public and Private Transport Vehicle Access.......................64 10.3.6. Pedestrian and Bicycle Access and Circulation...................................64 10.3.7. Parking Design and Layout..................................................................65

10.4. References....................................................................................................66

11. PARKING REQUIREMENTS............................................................................67 11.1. Overview......................................................................................................67 11.2. Parking Rates in Abu Dhabi ........................................................................67

11.2.1. Parking Rates in CBD and High-Density Sectors................................67 11.2.2. Publicly Available Parking Supply vs. Reserved Parking Supply in the CBD and High-Density Areas .............................................................................69 11.2.3. Parking Rates for All Other Developments .........................................70

11.3. Parking Analysis Requirements...................................................................71 11.3.1. Simple Parking Analysis (Proposed Development Meets Parking Requirements Directly)........................................................................................71 11.3.2. Complex Parking Analysis (Proposed Development Does Not Meet Parking Requirements Directly) ..........................................................................72

11.4. References....................................................................................................74

12. FORMAT OF TRAFFIC Impact Study and PARKING REQUIREMENT STUDY Report ............................................................................................................75

12.1. General Characteristics ................................................................................75 12.2. Structure of Report.......................................................................................75 12.3. References....................................................................................................76


iv

Figure 2-1.......................................................................................................................7 Abu Dhabi Traffic Impact Study and Parking StudyRequirements...............................7 Figure 3-1.....................................................................................................................12 Abu Dhabi Traffic Impact Study Process ....................................................................12 Figure 3-2.....................................................................................................................17 Level Of Service Definitions For Signalized And Unsignalized Intersections ...........17 Figure 3-3.....................................................................................................................17 Figure 6-1:....................................................................................................................39 Trip Types (Source: Institute of Transportation Engineers, Trip Generation

Handbook, 2001)..................................................................................................39 Figure 7-1.....................................................................................................................45 Example Application of Area-of-Influence Method (Source: V. Stover and F. Koepke,

Transportation and Land Development, 2002) ....................................................45 Figure 11-1...................................................................................................................68 Abu Dhabi CBD and High-Density Areas...................................................................68 Table 5-1 Summary Of Future Year Baseline Traffic Conditions...............................35 Table 8-1 ......................................................................................................................49 Quantification of Development Related Traffic Impacts in Study Area .....................49 Table 8-2 ......................................................................................................................52 Significant Thresholds for Development-Related Transportation Impacts .................52 Table 9-1 ......................................................................................................................55 Quantification Of Mitigation Measure Benefits ..........................................................55 Table 11-1 ....................................................................................................................71 Format For Simple Parking Analysis Table.................................................................71


1

1. INTRODUCTION This document is intended to provide public agencies, private landowners, their consultants, and Municipality staff with standards, guidelines, objectives and criteria to be used in the preparation of traffic impact and parking studies for developments. Such studies may be required for proposed developments prior to the issuance of Building Licenses. In order to ensure timely review by the Municipality Roads Directorate, the policies and procedures provided herein are to be followed in the preparation of Traffic Impact and Parking Study reports. This introductory chapter provides background regarding Abu Dhabi’s recent development, and explains the need and main objectives of establishing traffic impacts study and parking requirements. Abu Dhabi Municipality’s Roads Directorate has published these policies and procedures to ensure that appropriate mitigation measures will be identified and implemented for those developments that cause traffic impacts, while not unnecessarily burdening smaller projects or those in less congested areas. 1.1. Background Abu Dhabi is the capital of the United Arab Emirates (U.A.E.), a country established in 1971 as a federation of seven Trucial States: Abu Dhabi; Dubai; Ras Al Khaimah; Fujairah; Umm Al Quwain; and Ajman. The booming economy of Abu Dhabi has led to a large increase in population, rising ownership of cars and trucks, and substantial growth in traffic. The population in the Abu Dhabi Emirate has grown from 200,000 in 1975 to over 900,000 in 2000. Greater Abu Dhabi, including Abu Dhabi Island and neighboring island and mainland developments, has a year 2000 total population estimated at 575,000. Abu Dhabi Municipality has implemented major infrastructure projects to cope with the region’s growth. As a result, the city today has a modern transportation system. The road network is laid out in a rectilinear pattern, and the wide arterial streets typically have dual 3-lane carriageways. Abu Dhabi continues to grow rapidly. Although much of the new growth is in the communities on the mainland, such as Shahama and Shamka, a substantial amount of growth still occurs in Abu Dhabi Island, including the Central Business District (CBD). The CBD is characterized by high-density mixed land uses. Much of the growth in the CBD is in the form of redevelopment of existing buildings to greater intensity. This rapid growth places heavy demands on the transportation system, both in terms of roadway capacity and parking supply. Recognizing the future needs being created by this tremendous growth over the next two decades, the Municipality has proposed a series of strategies and actions to ensure that the city continues to enjoy adequate system performance in the coming years.


2

1.2. Need for Traffic Impact Studies While the Municipality is actively designing and implementing transportation improvements aimed at maintaining and enhancing transportation system performance, it is not possible for the Municipality to anticipate incremental impacts that may occur with the addition of each individual development. In order to ensure that operational problems do not arise at the local level, the MTP proposed that Traffic Impact Study Guidelines be developed as quickly as possible, and that regulations be adopted that require new developments to conduct traffic impact studies prior to obtaining development approval. The MTP further recommended that parking requirements be included in these guidelines. Such guidelines are necessary to ensure a consistent process is followed for all proposed developments. They serve as an important tool for the management of urban growth, and greatly reduce the possibility that additional demand on the transportation network due to new developments results in local problems regarding traffic operations, traffic safety, or other problems. Traffic impact study guidelines include procedures for estimating project traffic impacts on the surrounding transportation network, and for identifying mitigating measures that maintain a satisfactory level of service. Just as important, site access and circulation by automobiles, public transportation, pedestrians, and bicycles, are assessed and improvements recommended. Access requirements for the elderly and physically disadvantaged are also addressed It should be stressed that effective implementation of these guidelines is of benefit to the city as well as the developer asked to prepare the study. Adequate transportation network performance in the area surrounding the planned development benefits those accessing the project as well as the community at large. Moreover, even large and expensive developments often suffer from design oversights in regard to site access and on-site circulation that could lead to serious operational problems if left unsolved. These problems may be difficult and expensive to solve after construction of the development is complete. The Traffic Impact and Parking Requirements will help to identify such problems and develop appropriate solutions. 1.3. Need for Parking Requirements Many cities have learned that the problem of increasing parking shortages can be reduced or eliminated if all new developments are required to meet their own parking needs. It is the objective of these policies and procedures to end the growth in parking shortfalls in the CBD and to ensure that similar parking shortfalls do not occur in other areas of the city. Parking requirements ensure that on-site parking demand is assessed and that adequate parking is provided on-site to ensure that parking problems in the area are not created or exacerbated. Provision of parking by new developments, combined with the ongoing parking structure program of the Municipality and the comprehensive parking management


3

plan that is being developed, will eventually lead to a balance between supply and demand for parking in the city. 1.4. Objectives of Traffic Impact Study and Parking

Requirements Land development in urban areas often impacts the performance of the transportation system. Conducting traffic impact studies and establishing parking requirements is a prerequisite to orderly land development. The overall goal of traffic impact studies and parking requirements is to ensure that any negative impacts of the new development on the transportation system are identified and mitigated. Specific objectives serving this goal include the following:

• To assess traffic impacts on the transportation network surrounding a proposed new development;

• To assess site access and site circulation and propose measures to overcome any problems that are identified; and

• To assess the parking demand of the new development and determine the manner in which that parking demand be met.

The development of guidelines for how to conduct traffic impact studies and determine parking requirements has the following aims:

• To provide decision makers with a basis for assessing the transportation implications of approving proposed development applications;

• To assist developers through the approval process by outlining the requirements and level of detail of traffic analysis that will be required of them during the approval process;

• To standardize the types of analysis required in the assessment of traffic impacts and parking requirements for developments and thereby ensure consistency in the preparation and review of traffic impact studies; and

• To provide a basis for estimating the cost of proposed mitigation measures.

1.5. How These Guidelines were Developed Due to its comprehensiveness, the ITE's "Traffic Access and Impact Studies for Site Development, A Recommended Practice” served as a basic reference for this study. Traffic impact study guidelines and parking requirements prepared for cities in the US, the UK, Dubai, and other locations were also consulted. These guidelines were prepared by reviewing these sources and developing the most appropriate approach for the conditions in Abu Dhabi. A list of all the documents consulted in the preparation of these guidelines is provided in Appendix A. Documents consulted for specific chapters are listed at the end of each chapter.


4

1.6. References 1. Institute of Transportation Engineers, Traffic Access and Impact Studies for Site Development, 1991.

2. V. Stover and F. Koepke, Transportation and Land Development, 2002.


5

2. APPLICATION OF REQUIREMENTS Traffic impacts study and parking requirements are only one element of the land development review process. This chapter summarizes the manner in which planned developments are reviewed before approval for construction, and explains how the review process can include the traffic impact study and parking requirements. Criteria are also defined that specify under which conditions a traffic impact/parking requirements study is required.. The chapter concludes with a discussion of the qualifications required of the transportation professionals who prepare or review these studies. 2.1. How Do Traffic Impact Studies and Parking Studies Fit

Within the Development Review Process? In this section, an outline of the land development review process in Abu Dhabi is followed by a description of how the traffic impact study and parking requirements are to be inserted into that process. 2.1.1. Land Development Review Process Before a development can proceed into construction, the development must successfully pass through the land development review process. This process includes review by the Municipality’s Town Planning, Engineering, and Sewerage Sections, as well as the Civil Defense Department. With the publication and application of these guidelines, this review process will also include a review by the Roads Directorate. This section summarizes the main features of the land development review process. Once a parcel of land has been granted to a private individual or a public agency, and the land use specified, the land development review process of the Abu Dhabi Municipality and Town Planning Department ensures that the actual development of the land meets Municipality requirements. The landowner or the consultant hired to design the facility may notify the Town Planning Department of its plans and proceed with obtaining the necessary approvals. The Abu Dhabi Municipality and Town Planning have issued a detailed description of all the various regulations and ordinances in the form of a booklet named ‘Code Governing Construction Activities and Executive Ordinance’. The Town Planning Department reviews the site plan, architectural drawings, and proposed land use, and ensures that regulations and guidelines related to architectural standards and building style, as well as building heights/number of floors, setbacks, and others, are observed. Following successful completion of this review, a Building Permit is issued. Despite its name, a Building Permit does not mean that a facility has been approved for development and construction quite yet. The review process then shifts to the Engineering Section, who reviews the engineering drawings for structural adequacy, and issues a permit as appropriate. Additional permits have to be obtained from the Municipality’s Sewerage Section, and from the Civil Defense for compliance with their requirements.


6

This process has recently been streamlined for greater efficiency, and is centrally administered in a separate building next to the ground floor of the Town Planning building. Even the Civil Defense permit can be obtained from within Municipality premises. When all necessary permits have been obtained, the Municipality issues a Building License, which allows the owner to develop the land. 2.1.2. Incorporation of Traffic Impact Study and Parking Study

Requirements into the Review Process With the publication of these guidelines, the land development and review process now includes a review by the Roads Directorate of the Municipality and Town Planning Department. (While the Roads Directorate does not issue a “permit” as such, it does provide a letter signed by the Director of Roads Directorate which indicates that the Traffic Impact and Parking Requirements Study report has been reviewed and approved, or indicates that an exemption has been given enabling the development to proceed without the report). This letter carries the same level of significance as the development review permits described above. It is necessary to obtain the approval letter from the Director of Roads Directorate prior to obtaining the Building License. Depending upon their size and characteristics, proposed developments may be required to have a traffic impact study, a parking study, both, or none. If a proposed development is required to have both a traffic impact study and a parking study, the two study reports may be submitted separately, or submitted in a single joint traffic impact and parking study report.

2.2. When is a Traffic Impact Study Needed? A Traffic Impact Study is generally needed whenever a proposed development is likely to generate sufficient levels of additional traffic to cause an impact on the surrounding transportation system. The Director of Roads Directorate determines whether a Traffic Impact Study will be needed for any individual development proposal. This section provides criteria that will be used, in most cases, to determine the necessity for a Traffic Impact Study. It is possible, however, that other factors may contribute to the determination in some cases.


7

Figure 2-1 Abu Dhabi Traffic Impact Study and Parking StudyRequirements

NOTIFICATION TO ROADS

DIRECTORATE OF PROPOSED

DEVELOPMENT

ROADS DIRECTORATE

REVIEW OF PROPOSED

DEVELOPMENT

ANALYZE TRAFFIC IMPACTS AND

PREPARE MITIGATION PLAN

ANALYZE PARKING

REQUIREMENTS

SUBMIT PARKING STUDY REPORT – DRAFT AND FINAL

SUBMIT OPTIONAL JOINT TRAFFIC

IMPACT AND PARKING STUDY REPORT – DRAFT

AND FINAL

SUBMIT TRAFFIC IMPACT STUDY

REPORT – DRAFT AND FINAL

Traffic Impact Study

Needed?

Yes

No Parking Study

Needed?

No

Yes NO FURTHER ACTION

REQUIRED

NO FURTHER ACTION

REQUIRED


8

2.2.1. Criteria for Determining the Need for a Traffic Impact Study Traffic Impact Studies will generally be required when a proposed development meets or exceeds one or more of the following criteria. 1. A residential development that has 30 or more housing units or

provides housing for 150 or more workers. 2. Any other development that is expected to generate 100 or more

vehicle trip ends (sum of departures and arrivals) during the AM or PM peak hour. Estimates of peak-hour development vehicle trip generation must be consistent with the parameters and procedures in Chapter 6 of these guidelines.

2.2.2. Procedures for Obtaining Exemptions from the Requirements

for Traffic Impact Studies Exemptions from the requirements to provide Traffic Impact Studies may be requested in writing addressed to the Director of Roads. Such requests must include a description of the proposed development and the factors to be considered in considering the request. The Roads Directorate will notify the applicant of its decision in writing within 30 days of receiving the request, indicating whether the request is granted or rejected. The Roads Directorate may request additional information from the applicant while considering the request. 2.3. When Do Parking Requirements Apply? While a traffic impact study is not required of all developments, all proposed developments must demonstrate provision of sufficient parking spaces to meet the parking needs. Chapter 11 of these guidelines details the manner in which parking demand for a development is estimated, and how parking should be provided by the developer. For small developments in certain locations (such as a villa in a particular mainland community), demonstration of adequate parking may be straightforward by submitting the site plan. In sectors with excess parking supply, credits may be granted for nearby excess parking spaces, at the discretion of the Roads Directorate. In sectors with parking shortages, the Municipality may be in the process of building additional parking spaces and it may be possible for the proposed development to benefit from these additional spaces. Financial contributions toward Municipality-supplied parking may be required. The Roads Directorate is developing a comprehensive parking management plan, which may result in additional mechanisms to ensure new developments do not contribute to a worsening of the parking situation. 2.4. Qualifications of Study Preparer Traffic Impact Studies should be prepared under the supervision of a qualified and experienced transportation engineering/transportation planning professional who has training in traffic and transportation engineering and several years of experience in


9

preparing traffic impact studies for existing or proposed developments. A Masters degree in transportation or traffic engineering and 10 or more years of experience is desirable. Approval of the individual responsible for the Traffic Impact Study is at the discretion of the Roads Directorate. The qualifications of the individual responsible for the Traffic Impact Study are to be presented to the Roads Directorate concurrently with the proposed scope of work (see Chapter 3 of these guidelines). 2.5. Qualifications of Study Reviewer Review of Traffic Impact and Parking Requirements Study reports is to be performed by one or more Roads Directorate staff who collectively have training and experience in traffic impact study methodology, land use planning and traffic engineering, including traffic safety and operations. The Head of the Roads Directorate will determine if individuals within the Roads Directorate have these qualifications to review the reports.


10

3. SCOPE OF TRAFFIC IMPACT STUDY The primary purpose of a traffic impact study is to identify impacts of the proposed development on the surrounding transportation network, and to determine appropriate measures to mitigate these impacts. The severity of the traffic impacts depends on the size and characteristics of the proposed development as well as the design and operational characteristics of the surrounding transportation network. For example, if a large shopping mall were planned in a congested downtown area, traffic flow might slow down considerably as a result of the additional traffic generated by the mall, and numerous intersections could be impacted. By comparison, a small planned development in the same area might impact only immediately adjacent roadways and intersections. If the same mall were to be located on the mainland adjacent to a wide and uncongested freeway, however, the nature of the impacts on the adjacent roads might differ significantly. The freeway adjacent to the mall on the mainland might have sufficient unused capacity to handle the increase in traffic, and only immediately nearby interchanges might be impacted measurably. The differences in impacts due to type and size of development and location also result in different approaches to mitigation strategies. In the case of the shopping mall in the congested downtown, significant physical and operational improvements might be required to overcome the decline in level of service. On the other hand, the decline in level of service due to the mall located on the mainland might be too small to necessitate identification and implementation of any mitigation measures. Because of these differences between individual developments, and between the nature of the neighborhood and transportation network within which the developments are located, it is not practical to define a single scope of work that is applicable in every case. This chapter provides procedures to be used in determining the work scope to be applied on a case-by-case basis, and serves as a starting point for consultants who develop a inception plan. The Roads Directorate will review that plan and determine whether additional factors warrant modifications to that plan before approving the precise work scope. Following a summary of the traffic impact study process, this chapter describes how the inception plan is developed, followed by a discussion of how to determine the study area, the key facilities to be analyzed, the horizon years, and the peak hours. The methodologies to be used for assessing the level of service of the facilities to be analyzed in the study area is then provided, followed by a pointer to impact analysis and mitigation strategies discussed in later chapters of this report. 3.1. Summary of Traffic Impact Study Process The overall traffic impact study process is shown in Figure 3-1. This process generally consists of the following steps:


11

1. Introduction – A brief description of the proposed development, issues discussed in the initial meeting, definition of the study area, and overall approach to the traffic impact study.

2. Analysis of existing conditions – Summary of current conditions on the

major arterial streets and internal roads surrounding the proposed development.

3. Establishing future year baseline (without-development) conditions –

Summary of future year conditions without the development, based on assumptions regarding growth and planned transportation improvements in Abu Dhabi approved by Town Planning and the Roads Directorate respectively.

4. Development description and trip generation – Description of development

in sufficient detail to estimate trip generation. 5. Development trip distribution and assignment – Estimates of changes in

traffic on the surrounding major arterial streets and internal roads due to the proposed development.

6. Impact analysis – Determination of traffic impacts due to the proposed

development. 7. Mitigation plan – Summary of proposed measures to mitigate development

traffic impacts. 8. Multi-modal site/sector access and circulation analysis – Evaluation of

access and circulation on-site and within the sector for highway vehicles, public transportation pedestrians and bicycles, and the design of development parking.

9. Parking Requirement – Assessment of the demand for parking generated by

the development, and the manner in which this demand is met. With the exception of the introduction, a separate chapter of this report provides guidelines for each of the above elements. 3.2. Initial Meeting and Development of Inception Plan The first step in the traffic impact study process is to notify the Roads Directorate of intent to perform a study, and to develop a inception plan documenting what is to be done and how it is to be performed. It is strongly recommended that the applicant (landowner, developer, or consultant) notify the Roads Directorate of its intent to perform a traffic impact study, and to meet with the Roads Directorate in order to determine the precise work scope to be followed. Failure to notify the Roads Directorate of the intent to prepare a traffic impact study or to conduct an initial meeting may result in the rejection of the traffic impact study report when it is submitted. Without the notification and initial meeting, the applicant


12

would be conducting the study without an assurance that the Roads Directorate has reviewed and approved the work scope for the study. Figure 3-1 Abu Dhabi Traffic Impact Study Process


13

3.2.1. Notification Notification of intent to conduct a traffic impact study is to be made in writing to the Director of Roads, P.O. Box 263, Abu Dhabi, United Arab Emirates. The notification should include preliminary information about the proposed development, including location, size, and land use(s). 3.2.2. Initial Meeting Depending upon the size and complexity of the proposed development and/or traffic impact study, the initial meeting may be a simple brief meeting or may grow to a series of meetings with many attendees. Issues to be addressed in the initial meeting include:

• Details on Development type and size • How much information is needed for a “complete” study? • What study area should be evaluated? • What should be the horizon year(s)? • What peak hour(s) should be analyzed? • What technical analyses are required? • What technical procedures and parameters should be utilized? • What special requirements, if any, should apply to the traffic impact

study for the proposed development? • Who, within the Roads Directorate, will be assigned to coordinate

with the applicant and review submitted products? • What is the schedule for product submittal and review? • What are the costs, if any, incurred by the Roads Directorate and to

be reimbursed by the applicant? • Other related issues

3.2.3. Inception plan for Traffic Impact Study Either at the initial meeting or subsequent to the meeting, the applicant will submit a inception plan. The inception plan is the proposed work scope for the traffic impact study. It documents the approach agreed upon by the Roads Directorate and the applicant. The inception plan for the traffic impact study should include but is not limited to the following: 1. A general description of the development including:

• Preliminary site plan, including locations of driveways and parking areas;

• Size (number of square meters by use and/or number of residential units by type); and

• Other significant aspects of the development.


14

If the proposed development is to be constructed in phases, then a description of each phase of the development is to be included, together with the anticipated opening date of each phase.

2. A description of the study area, including:

• Intersections and roadway links to be studied; and • The area within the sector(s) to be analyzed.

3. A list of related developments planned within the study area. 4. An overall work scope, identifying those elements of the traffic impact

study process to be included in the study. 5. A description of the methodologies and parameters to be used in

performing the technical analyses. 6. Land-Use/Transportation assumptions to be used. 7. Names and qualifications of preparers. 3.3. Study Area The size of the study area depends upon the location and size of the proposed development and the conditions prevailing in the surrounding area. The impact of large developments proposed in congested or poorly accessible areas may extend several intersections away from the development site. On the other hand, small developments may only require a study area that includes access driveways and immediately adjacent intersections. Thus the definition of the study area should only be as large as necessary to capture all significantly influenced facilities, in order to avoid unnecessary effort being spent analyzing and reviewing the study. Since the area impact by the development is so closely related to both the nature of the development and the current and expected conditions in the surrounding neighborhood, there are no straightforward rules for defining the study area for a traffic impact study. At the minimum, the study area should include all development access points, adjacent intersections in the sector, and adjacent sector driveways, for development located in sectors. For developments elsewhere, the study area should include all development access points, plus major adjacent intersections (signalized and unsignalized). The Roads Directorate will determine the additional facilities to be included in the study area for each traffic impact study based on the specific characteristics of the proposed development, and the traffic conditions and transportation system characteristics of the surrounding area, as well as other concerns, factors, and policies. The inclusion of already congested facilities likely to be impacted by the proposed development will be an important criterion defining the study area. 3.4. Key Facilities to be Analyzed The key facilities to be analyzed in traffic impact studies are determined by the Roads Directorate. In most cases, key facilities will include:


15

• All signalized intersections within the study area; • All roundabouts connecting streets classified as collectors or higher

within the study area; • All all-way-stop-controlled intersections of streets classified as

collectors or higher; • All ramps connecting streets classified as arterials or higher within

the study area; • All freeways and expressways in the study area; • All local circulator roads within the study area; and • All sector/arterial driveways within the study area.

3.5. Horizon Year(s) The horizon year will generally be the year that the proposed development is expected to be fully operational. For phased developments, separate horizon years representing the anticipated completion date of each phase may be required. For very large developments, in which the anticipated completion year is uncertain, a fifteen or twenty-year time horizon may be required. The Roads Directorate will determine the horizon year(s) for the study. The Abu Dhabi Travel Demand Forecasting Model forecasts for the years 2005, 2010, 2015, and 2020. Future updates to the model will extend the horizon years modeled. When modeling is used in the analysis, as described in section 3.7, the Roads Directorate may elect to define a horizon year as the nearest year modeled after development buildout. 3.6. Peak Hours of Analysis The peak hours to be analyzed will be determined during the initial meeting and documented in the Inception plan. Typically two peak hours of analysis will be required. The hours selected for the analysis will be based on peak hour trip generation estimates for the proposed development and the peaking patterns of traffic on the roadway system within the study area. With the possible exception of some retail developments, the morning peak hour (7:00-8:00 AM) will most likely be required for all traffic impact studies. Depending upon the type of development, the second peak hour may be the noon (11:00 AM-noon), afternoon (2:00-3:00 PM), or evening (7:00-8:00 PM) peak hour. For example, if the proposed development is located in a downtown sector, the noon or evening peak hour may be selected. If the development is not in a downtown sector, the afternoon peak hour may be selected. If the proposed development is a school, the afternoon peak hour may be selected regardless of the school’s location. Exceptions to the choice of peak hour may be made in response to specific local or global conditions.


16

3.7. Methodologies and Procedures Methodologies and procedures to be used in performing the traffic impact studies will be agreed to during the initial meeting and documented in the Inception plan. Some general rules for the choice and use of methodologies for level-of-service calculation of signalized and unsignalized intersections, roundabouts, and road segments are discussed in this section. Manual and model-based methods of forecasting travel for future scenarios both with and without the proposed development are discussed in Chapters 6-7 of this report 3.7.1. Level of Service Calculation Methodologies Level of service analysis must be conducted in conformance to these guidelines. Alternative methodologies may be proposed by the applicant and, following review by the Roads Directorate, may be accepted. Signalized and Unsignalized Intersections Levels of Service for signalized and unsignalized intersections shall be based on average control delay following methodologies and procedures outlined in the most recent edition of the Highway Capacity Manual (HCM) published by the Transportation Research Board (1). Figure 3-2 defines the levels of service for signalized and unsignalized intersections. Commonly used software packages utilizing HCM methodologies and procedures such as HCS and SYNCHRO (using the HCM Signals Report to determine delay) are acceptable for determining levels of service on signalized and unsignalized intersections. Use of other methodologies and procedures will be accepted only after Roads Directorate review and approval of the proposed methodologies and procedures. In reviewing other methodologies, the Roads Directorate will assess whether the proposed methodology provides results that are comparable to the results obtained using HCM-based methodologies. For both signalized and unsignalized intersections, it is not only the average intersection control delay that determines the level of service of the intersection. Approach LOS and movement LOS are also important. If any approach or movement at an intersection is LOS F, then the intersection is considered to be LOS F. As long as all approaches and movements of the intersection are at LOS E or better, then the average intersection control delay will be the basis for determining the LOS. Roundabouts Levels of service for roundabouts shall be based on average queuing delay following methodologies and procedures developed by the Transport Research Laboratory (TRL) and documented in the ARCADY 5 (International) User Guide (3) or later version for right-hand-side driving. Figure 3-3 defines the levels of service for roundabouts. Use of ARCADY or other software based on the TRL methodologies and procedures are acceptable for determining levels of service on roundabouts. Use of other methodologies and procedures will be accepted only after Roads Directorate review and approval of the proposed methodologies and procedures. In reviewing other methodologies, the Municipality will assess whether the proposed methodology


17

provides results that are comparable to the results obtained using TRL-based methodologies. Figure 3-2 Level Of Service Definitions For Signalized And Unsignalized Intersections SIGNALIZED INTERSECTIONS

LOS Average Control Delay in seconds (1)

Description of Traffic Conditions (2)

A 0 – 10.0 Excellent. No vehicle waits longer than one red light and no approach phase is fully used.

B 10.1 – 20.0 Very Good. An occasional approach phase is fully utilized; many drivers begin to feel somewhat restricted within groups of vehicles.

C 20.1 – 35.0 Good. Occasionally, drivers may have to wait through more than one red light; backups may develop behind turning vehicles.

D 35.1 – 55.0 Fair. Delays may be substantial during portions of the rush hour, but enough lower volume periods occur to permit cleaning of developing lines, preventing excessive backups.

E 55.1 – 80.0 Poor. Represents the most vehicles that intersection approaches can accommodate; may be long lines of waiting vehicles through several signal cycles.

F 80.1 and above

Failure. Backups from nearby intersections or on cross streets may restrict or prevent movement of vehicles out of the intersection approaches. Tremendous delays with continuously increasing queue lengths.

Figure 3-3

UNSIGNALIZED INTERSECTIONS

LOS Average Control Delay (Sec)1

Description of Traffic Conditions

A 0 – 10.0 Excellent.

B 10.1 – 15.0 Very Good.

C 15.1 – 25.0 Good.

D 25.1 – 35.0 Fair.

E 35.1 – 50.0 Poor.

F 50.1 and above Failure.

For roundabouts, it is not only the average intersection queuing delay that determines the level of service of the intersection. Approach LOS is also important. If any approach leg at a roundabout is LOS F, then the roundabout is considered to be LOS F. As long as all approach legs of the roundabout are at LOS E or better, then the average roundabout queuing delay will be the basis for determining the LOS.


18

Links Levels of service for segments of roadways and ramps shall be based on volume-to-capacity ratio (V/C). V/C is determined by comparing the observed hourly traffic volume to the capacity of the link. Link capacities are assumed as follows (4):

• Expressways and freeways, 2,000 vehicles per hour per lane; • Arterial streets, 780 vehicles per hour per lane; • Arterial streets in the CBD, 580 vehicles per hour per lane; • Local roads, 580 vehicles per hour per lane; and • Ramps, 1,500 vehicles per hour per lane.

Other Operational Analyses The Roads Directorate may request additional analyses, such as weave analyses or merge/diverge analyses, based on its review of a specific proposed development and its potential impacts. Such analyses must conform to the methodologies and procedures outlined in the latest edition of the Highway Capacity Manual. 3.8. Impact Analysis and Mitigation Strategies The criteria and methods the consultant should use for defining and computing development impacts are discussed in Chapter 8. The chapter also discusses methods to determine whether these impacts are serious enough to warrant development of mitigation strategies. Chapter 9 discusses the manner in which mitigation strategies are to be developed. The manner in which on-site access and circulation are evaluated and improvements proposed is discussed in Chapter 10. 3.9. References 1. Los Angeles County Metropolitan Transportation Authority, 1997 Congestion

Management Program for Los Angeles County, November 1997.

2. Transportation Research Board, Highway Capacity Manual, 2000.

3. Transportation Research Laboratory, ARCADY 5 (International) User Guide, 2000.

4. Abu Dhabi Municipality and Town Planning Department, Abu Dhabi Master

Transportation Plan, Phase II Report, July 2002.


19

4. ANALYSIS OF EXISTING CONDITIONS At the outset of a study it is necessary to characterize the existing conditions in and around the site under investigation, as well as to describe the area to be affected by the development. The characterization should represent current conditions and should generally be no more than one year old. These baseline data will provide a foundation for assessing the land use and transportation implication of changes over time. This chapter establishes requirements for the data to be collected and used in the study, as well as specifying the requirements for the existing conditions analysis. It specifies the required information to be included in the “Analysis of Existing Conditions” chapter of the traffic impact study report. 4.1. Development Site Location A map showing the study site in relation to the surrounding roadway must be provided in the traffic report. The map must be legible, and the size of the site and the amount of frontage available on all adjacent streets must be noted on it or in the accompanying text. Figure 4-1 is a sample of a site location map. 4.2. Description of Current Land Uses on Development Site Current land uses on the development site are to be described. Current land use is defined as the most intense use during the six-month period prior to approval of the preliminary plan. If the site currently contains structures or other uses, these are to be described in sufficient detail to allow for trip generation estimation. The description of current land uses on the development site includes:

• Number of dwelling units by type (villas, apartments, etc.); • Number of hotel rooms; • Number of group quarter units (labor camp rooms, student housing rooms,

etc.); • Intensity of non-residential use quantified in square meters (gross floor area)

and classified as retail, school, office, industrial, social-recreational, or medical; and

• Other uses not identified above, quantified in square meters of gross floor area (where applicable) and/or estimated peak hour trip generation (for the peak hours to be analyzed in the traffic impact study as discussed in Chapter 6) if available.


20


21

Footprints of existing structures and other uses are to be shown on a map. Figure 4-2 is an example of a Current Site Land Use map. Where reasonable, footprints of current uses can be included in the Site Location Map. 4.3. Description of Surrounding Transportation System The traffic study shall include a description of the study area and the existing transportation system serving the site including any specific operational issues. The following will be addressed in this section:

• Study area; • Existing roadway system and parking facilities; • Existing public transportation and taxi service; and • Existing pedestrian facilities.

4.3.1. Study Area This section will describe the boundaries of the study area and give a general description of the land uses therein. Typically, the study area boundaries will be determined in the initial meeting and documented in the Preliminary Plan. In some cases, generally for large developments, the study area is defined following an analysis of development trips as described in Chapter 3. 4.3.2. Existing Roadway System Detailed information regarding the physical and functional characteristics of the roadway system in the study area is provided in this section. Roadways to be described include all freeways, expressways, arterials and collectors that pass through the study area or pass within one-half kilometer of any part of the development site. If the development site is located in a downtown Abu Dhabi sector, a map of the sector is to be included and all local circulation roads in the sector are to be described. It is possible for some facilities outside the study area to be included in this description. Facilities may be added or subtracted at the discretion of the Roads Directorate. Descriptions of facilities will include:

• Name of facility; • Physical characteristics of the facility (e.g., number of travel lanes, median,

sidewalks, amenities, etc.); • Posted speed limit; • Location and type of control used of key junctions on the facility within the study area

(a key junction is defined as an intersection or roundabout, signalized or unsignalized, or a ramp connecting two or more facilities classified as arterials, expressways or freeways);

• Parking facilities and regulations; and • Existing peak traffic volumes on the facility within the study area or (if outside of the

study area) at its nearest location to the development site for all peak hours to be analyzed in the traffic impact study.


22


23

An example of a facility description is as follows: “Khalifa bin Zayed Street is an east-west arterial with dual carriageways separated by a raised median, with a posted speed limit of 60 kph. Each carriageway has three lanes, with additional turning lanes at signalized intersections. Khalifa bin Zayed Street serves mixed land uses in the study area. Within the study area, Khalifa bin Zayed Street has signalized intersections at Fourth Street, Liwa Street and Airport Road. Parking is prohibited on both sides of the street in the study area. Current daily and peak hour traffic volumes on Khalifa bin Zayed Street are shown in the following table.”

4.3.3. Existing Public Transport and Taxi Service In Abu Dhabi, public transport currently consists of a regularly scheduled bus service. This section of the traffic impact study report will include a description of all bus transit lines providing service in the study area. A description of each bus line including route number, alignment within the study area, terminal locations, frequency during peak hours and operating hours, should be included in the report. A map showing the routing of each of the bus lines in the study area may help clarify the narratives. Any taxi station or major taxi staging area located in the study area should be described in the report. 4.3.4. Existing Pedestrian Facilities Main pedestrian facilities such as crossings at signalized intersections, mid-block crossings, pedestrian underpasses, should be identified and marked on a map. Within sectors, sidewalks should be identified. 4.4. Data Collection/Traffic Count Requirements Prior to any fieldwork, consultation between the Roads Directorate and the applicant is recommended to reach consensus on data to be used in the traffic impact study. This consensus is typically achieved at the initial meeting and documented in the Preliminary Plan. Current year traffic counts are required for all key facilities analyzed in the traffic impact study. Counts conducted during the twelve months prior to approval of the Preliminary Plan will be considered current. Counts conducted earlier than twelve months but not more than 24 months before approval of the Preliminary Plan will require a growth factor adjustment before being considered current. The Consultant should develop appropriate growth factors and seek the Roads Directorate’s approval before their use. Within sectors, peak-hour link volume counts are required for all segments of the local circulator roads. A segment is defined as the portion of the road between two other roads that are classified as local circulator roads or higher. Turning movement counts are required at all


24

junctions of local circulator roads. Sector/arterial driveways within the study area are key facilities that require peak hour counts. Outside of the sectors, all junctions of collectors, arterials, expressways and freeways, including roundabouts (signalized and unsignalized) and intersections (signalized and all-way-stop-controlled) within the study area require peak hour turning movement counts (except ramps, which require directional counts). Freeways, arterials, and ramps within the study area require directional counts on all segments. A freeway or expressway segment is defined as the portion of the facility between interchanges/ramps or junctions with any other roadway facility. Data to be used in the traffic impact study fall into one of two categories:

• Existing data to be obtained from the Roads Directorate; and • New data to be collected by the applicant.

4.4.1. Existing Data to be obtained from the Roads Directorate The consultant is to explore the availability of existing data relevant to the study with the Roads Directorate. The Roads Directorate may be in possession of data themselves or may refer the Consultant to another party. A charge may be levied by the Roads Directorate for providing certain data. Data that may be available through the Roads Directorate include:

• Traffic counts; • Maps showing land uses or street networks, or design plots of developments; • Recent studies – Copies of recent traffic impact studies in the study area and area-

wide studies that include the development site, if applicable. • Plots of traffic volumes – Plots of current year and future year peak hour traffic

volumes on freeways, expressways, arterials and collectors developed from Abu Dhabi Travel Demand Model assignments.

4.4.2. Data to be Collected by Applicant Any data required for the traffic impact study and not available from the Roads Directorate must be collected by the applicant. The assembly of available data should be accompanied by a detailed reconnaissance of the development site, area roadways, and the surrounding vicinity. This should include recording all relevant characteristics needed for the analysis, plus observations of existing traffic conditions. Only data required to address issues to be studied in the traffic impact study need to be collected. Traffic volume counts must be collected in accordance with the procedure and requirements in these guidelines. Peak hour counts are to be collected for each peak hour to be evaluated in the traffic impact study. Morning peak hour counts are to be collected for the period from 6:30 to 8:30 AM. Noon peak hour counts are to be collected for the period from 10:30 AM to


25

12:30 PM. Afternoon peak hour counts are to be collected for the period from 1:30 to 3:30 PM. Evening peak hour counts are to be collected for the period from 6:30 to 8:30 PM. All peak hour and daily counts are to be taken on Sundays, Mondays, and Tuesdays during the period beginning on 15 September and ending on 15 May, and are not to coincide with holidays or Ramadan. Counts taken at other times must be reviewed by the Roads Directorate, and may need to be adjusted before being used in the traffic impact study. Turning Movement Counts at Signalized or Unsignalized Intersections Turning movement counts at intersections are to be conducted manually, either via direct observation or through the use of continuous video surveillance. The counted volumes are to be documented in tabular format as shown in Figure 4-3. An Excel spreadsheet containing the table is to be put on a disk, CD, or other electronic medium and submitted to the Roads Directorate prior to or at the time the draft traffic impact study report is submitted. Roundabout Counts The format for reporting roundabout counts is the same as for intersections. Obtaining reliable turning movement counts at roundabouts is a task that requires careful planning and competent execution. Roundabout counts should only be conducted by trained personnel. Acceptable methodologies for conducting roundabout turning movement counts include:

• Video surveillance, provided the entire roundabout and entry/exit arms are visible continuously throughout the survey period;

• License plate surveys, provided the error rate is acceptable to the Roads Directorate; and

• Procedures documented in “Counting Roundabouts, A Model to Obtain Detailed Roundabout Turning Movements” (1).

Other procedures for counting roundabout turning movements will require review and approval of the Roads Directorate before being accepted. Link Counts Link counts include directional traffic volume counts on roadway segments and ramps. The counted volumes are to be documented in tabular format as shown in Figure 4-4. An Excel spreadsheet containing the table is to be put on a disk, CD or other electronic medium and submitted to the Roads Directorate prior to or at the time the draft traffic impact study report is submitted. Acceptable methodologies for conducting link volume counts include:

• Manually, via direct observation; • Manually, via video surveillance; • Magnetic detectors; • Pneumatic tubes; and


26

• Any other proven technology. • Other procedures for counting link volumes will require approval of the Roads

Directorate before being accepted. 4.5. Reporting Existing Levels of Service on Key Facilities The analysis of existing conditions must include a summary of levels of service on all key facilities. Methodologies and procedures for determining levels of service are described in Chapter 3. All counts used in the report, whether obtained from the Roads Directorate or collected by the applicant, are to be included in an appendix to the report, both in printed and electronic format.


27


28


29

4.6. References 1. Kathairi, R. Mufti, A. Garib, E. Bierce, and B. Williams (2001). “Counting

Roundabouts: A Model to Obtain Roundabout Turning Movements”, Transportation Research Record, Vol. 1769, pp. 103-112.


30

5. ESTABLISHING FUTURE YEAR BASELINE CONDITIONS

The first step in analyzing the impacts of a proposed new development is to establish future year baseline conditions. The future year baseline conditions represent a future year scenario without the proposed new development. This scenario will subsequently be compared to the with-development scenario to determine the development’s impacts. This chapter describes how the future baseline conditions are established. 5.1. Methods and Data Considerations Future year baseline conditions are a quantitative assessment of traffic conditions in the study area in the horizon year(s), as determined in Chapter 3, assuming the proposed development is not built. Methods used for this step include modeling, manual, and mixed approaches that utilize the model for some steps and manual methods for others. Use of the model is most appropriate for very large developments with area-wide or regional impacts, and in situations in which the model forecasts have local credibility and network detail is consistent with that needed for site traffic analysis in the study area. Manual methods are used for smaller developments, and/or near-future horizon years. A simple manual approach is to apply appropriate traffic volume growth rates in the study area, as described in this chapter. Other manual methods are described in ITE’s Traffic Access and Impact Studies for Site Development the traffic impact handbook (1). For modeling approaches, the future year baseline should include all changes in land use and socio-economic conditions within the study area other than those related to the proposed development. Future baseline conditions are to be established for each horizon year to be evaluated in the traffic impact study. Establishment of future baseline conditions includes:

• Obtaining approved assumptions regarding future year land use and population for related developments in the study area or at the regional level;

• Obtaining approved assumptions regarding future transportation improvements, including highway and public transportation projects;

• Determining future year baseline traffic volumes; and • Evaluating future year baseline levels of service on key facilities.

5.2. Assumptions Regarding Future Year Land Use and

Population Specific assumptions regarding future year land use and population are to be documented when the Abu Dhabi Travel Demand Model is used in the analysis, and when specific related developments are identified and integrated into the analysis. For


31

manual approaches, an assessment of new developments completed by the horizon year(s) may be limited to the study area. For modeling approaches, land use and population must be available or estimated for the entire region covered by the model. 5.2.1. Regional Growth Assumptions When the Abu Dhabi Travel Demand Model is used in the analysis, the traffic impact study report should include an appendix showing assumptions for primary model input variables by zone and by sector, including:

• Number of residential units by type (including group quarters); • Square meters of non-residential land use by type; and • Other data affecting trip generation such as special generators

(airports, parks, etc.). Any changes from the projected land uses in the model’s input database are to be noted in the traffic impact study report. In the future year forecasts, the model input data may already include the development being proposed by the applicant. If this is the case, then the future year land use and demographic assumptions in the model’s input database for the zone (or zones) in which the proposed development is located needs to be appropriately modified such that the proposed development is not included in the baseline assumptions. These modifications must ensure that the intensity of land use and the number of residents of the new development are removed from the totals for these variables in the model database. The zonal totals were generally based on assumptions regarding growth and building height regulations for each sector. The rate of assumed growth within the model’s database for the zone, the size of the proposed development, and current Municipality density/building height regulations for the property to be developed, should all be considered in order to ‘subtract’ or remove correctly the assumed contribution of the new development to the future year database. 5.2.2. Related Developments in the Study Area A related development is defined as a development in the study area that has been approved or is being considered for approval by the Municipality, and is considered by the Abu Dhabi Municipality and Town Planning Department as highly likely to be built and occupied by the horizon year, and is not included in the database of existing development at the time the Preliminary Plan is approved. A list of ongoing related developments should be prepared and, if a model approach is used for the traffic estimation, the model database should be modified to include them. All related developments, both within the same sector as the proposed development and outside the sector but within the study area, are to be integrated into the future year baseline. Each related development to be included in the future year baseline is to be described in sufficient detail to estimate trip generation. Any transportation improvements that are identified as project elements or mitigation measures for a related development are


32

to be included in the description and incorporated into the transportation improvement assumptions for the future year baseline. A map showing the location of the related developments is also to be provided in the report. Procedures for integrating trips generated by related developments are provided in Section 5.4 of this chapter. 5.3. Assumptions Regarding Future Transportation

Improvements The Municipality is continuously improving the transportation system in Abu Dhabi. Since these improvements often impact traffic conditions, it is important that the future year baseline incorporate all committed highway and public transportation improvements that will impact levels of service. A committed transportation improvement is defined as a highway, transportation system management (TSM), public transportation, or transportation demand management (TDM) improvement (physical improvement, operational improvement, service improvement or policy action) that may affect levels of service within the study area and is considered by the Roads Directorate as highly likely to be implemented by the horizon year. Committed transportation improvements may be:

• Under construction; • Funded for construction in an existing budget at the time the

Preliminary Plan is approved; • Project elements or mitigation measures for related developments; • Other improvements being considered by the Roads Directorate that

are considered highly likely to be implemented by the horizon year. Identification of committed transportation improvements will typically be determined during the initial meeting and documented in the Preliminary Plan. If the committed transportation improvements are of sufficient regional significance that they are likely to substantially change traffic volumes on study area roadways, then a model run of the Abu Dhabi Travel Demand Model will be required to establish future year baseline conditions (refer to Section 5.4 of this chapter). The impact of substantial changes to the transportation system on traffic flows is more accurately estimated by the model, which redistributes traffic by taking into to account these changes in transportation system performance. 5.3.1. Highway and TSM Improvements Highway and TSM improvements that may affect levels of service include physical improvements (such as new roads, roadway widening and adding lanes at intersections), signal synchronization and/or revisions to phasing and timing, adding new signals, converting roundabouts to signalized intersections, charging tolls, addition or removal of truck restrictions, and other improvements. When the Abu Dhabi Travel Demand Model is used in establishing future year baseline conditions, all committed highway and TSM improvements are to be incorporated into the highway networks, wherever possible and reasonable, to determine future year baseline traffic volumes. In calculating future year baseline


33

levels of service, physical characteristics of committed transportation improvements (such as number of lanes and signal phasing) are to be integrated into the calculations as appropriate. 5.3.2. Public Transportation Service and TDM Public transportation and TDM improvements that may affect level of service include new public transportation routes or connections (bus or rail), changes in service frequency, changes in public transportation and/or taxi fares, changes affecting public transportation vehicle speeds, creation of new transfer centers, policy actions to reduce the number of taxis in an area such as downtown, changes in parking costs and/or availability, and other improvements. When the Abu Dhabi Travel Demand Model is used in establishing future year baseline conditions, all committed public transportation and TDM improvements are to be incorporated into the highway and/or public transportation networks and into the mode split model parameters, wherever possible and reasonable. 5.4. Determining Future Year Baseline Traffic Volumes Future year baseline traffic volumes on specific roadways may be determined by the Abu Dhabi Travel Demand Model or manual methods. The choice of method depends upon the size of the proposed development and the size of the study area. Future year traffic volumes on local circulator roads will generally be determined using manual methods. Manual or modeling methods may be used to determine future year baseline traffic volumes on arterials and collectors when the study area boundary does not extend beyond the nearest arterial intersection. When the study area boundary includes more than one sector, the Abu Dhabi Travel Demand Model may be used to determine future year baseline traffic volumes on all freeways, expressways, arterials and collectors. However, the model representation of roads in the study area should first be reviewed and modified if possible to provide the necessary detail for an adequate analysis. 5.4.1. Manual Method for Determining Future Year Baseline

Traffic Volumes The manual method for determining future year baseline traffic volumes consists of three steps:

• Quantification of existing volume based on traffic count data; • Application of ambient growth rates; and • Incorporation of traffic from related developments (see Section

5.2.2 above). Procedures for quantifying existing traffic volumes based on traffic count data are provided in Chapter 4. For arterials and collectors, the applicant is expected to propose appropriate ambient growth rates based on traffic count data collected by the Abu Dhabi Municipality


34

Roads Directorate through their Traffic Monitoring Program, information in the Master Transportation Plan, other traffic impact studies for nearby developments, other transportation planning studies, Abu Dhabi Travel Demand Model runs, or other sources. The ambient growth rates for arterials and collectors proposed by the applicant should be submitted to the Roads Directorate for review and approval. For local circulator roads, ambient growth rates are to be determined at the sector level, based on projections of peak hour trip generation in the Abu Dhabi Travel Demand Model. The ambient growth rates are to be applied to the existing traffic volumes to obtain initial future year baseline traffic volumes. If related developments within the sector are to be integrated into the analysis, then related development traffic must be added to the initial volumes to obtain the final future year baseline traffic volumes. If no related developments are located within the sector, then the initial volumes after application of ambient growth rates will be the final future year baseline volumes. Incorporation of traffic from related developments requires an estimate of trips and manual distribution of these trips. Wherever practical, it is recommended that the trip generation and distribution of related developments be obtained directly from the traffic impact study or from the persons performing the traffic impact study for the related development. When this is not practical, the applicant will need to estimate trip generation and distribution for the related developments following the procedures in Chapters 6 and 7 and add these trips to the interim future year baseline traffic volumes. 5.4.2. Model Method for Determining Future Year Baseline Traffic

Volumes In most cases where the Abu Dhabi Travel Demand Model is to be used, the results of the model runs, incorporating appropriate land use/demographic and transportation improvement assumptions, will be used directly to determine future year baseline traffic volumes on freeways, expressways, arterials and collectors. In some cases, the applicant may wish to propose an adjustment to the model output (for example, the applicant may wish to correct for an apparent high or low bias in the model estimate, based on a comparison of the existing conditions model runs to ground count data). Such adjustments must be approved by the Roads Directorate. In some cases, the Abu Dhabi Travel Demand Model is to be used in determining future year baseline traffic volumes on local circulator roads within sectors. As described in Section 5.2 above, this will occur when committed transportation improvements are of sufficient regional significance that they substantially change traffic volumes on local circulator roads. In these cases, model runs are to be performed representing future baseline conditions both with and without the regionally significant transportation improvements. The results of these two runs are then to be used in determining the future year baseline traffic volumes on the affected local circulator roads.


35

5.5. Evaluation of Baseline Traffic Conditions Once the future year baseline traffic volumes have been estimated, an assessment of the future year baseline levels of service is to be performed, following the procedures described in Chapter 4. All key facilities identified in the Preliminary Plan are to be included in the assessment of future year baseline levels of service. These facilities include the links, signalized and unsignalized intersections, and roundabouts in the study area potentially influenced by the new development. Table 5-1 shows the type of information to be included in the evaluation of future year baseline traffic conditions. Table 5-1 Summary Of Future Year Baseline Traffic Conditions

LOCATION EXISTING (Year) CONDITIONS

FUTURE (Year) BASELINE CONDITIONS

Signalized Intersections Delay LOS Delay LOS

Intersection #1 Intersection #2 Intersection #3 Unsignalized Intersections Delay LOS Delay LOS

Intersection #1 Intersection #2 Intersection #3 Roundabouts Delay LOS Delay LOS Roundabout #1 Roundabout #2 Roundabout #3 Links V/C LOS V/C LOS Link #1 Link #2 Link #3

5.6. References 1. Institute of Transportation Engineers, Traffic Access and Impact Studies

for Site Development, 1991.


36

6. TRIP GENERATION In order to identify impacts of the proposed development on the surrounding transportation network and to determine appropriate measures to mitigate development impacts, it is first necessary to estimate the trips generated by the development. The estimation of development trip generation is usually based on a detailed description of the specific types and intensities of the land uses the development comprises. This chapter establishes the necessary elements of the development description, discusses the technical requirements for estimating trip generation, and reviews important sources of trip rates likely to be of use in the conduct of traffic impact studies in Abu Dhabi. The technical requirements for estimating trip generation include the choice of trip rates, the critical time periods to be examined, and the need to take into account internal trip capture, linked trips, and mode split variations, as appropriate. The chapter highlights important aspects of trip rates by means of a discussion of two important sources of such rates. 6.1. Development Description The description of the proposed development includes:

• Preliminary site plan, including locations of driveways and parking areas;

• Size (number of square meters by use and/or number of residential units by type);

• Other significant aspects of the development. In general, the development description provided in the Preliminary Plan may serve as an adequate description for the Traffic Impact Study Report, assuming the definition of the development has not changed and a sufficient level of detail is provided to estimate trip generation. If the development definition has changed since submittal of the Preliminary Plan, then a revised development definition will be required in the Traffic Impact Study report. For developments that are to be constructed in phases, a description of each phase of the development is to be included, together with the anticipated opening date of each phase. The development description should describe the intensity of each land use. For large developments whose precise mix of uses is not known at the time Traffic Impact Study is initiated, an estimated mix of land uses is to be established for purposes of trip generation. The development description should also include a site plan, which shows the locations of driveways, circulation roads, and parking facilities. Numbers of lanes, roadway widths and numbers of parking spaces are also to be included in the development description.


37

6.2. Development Trip Generation The estimation of the traffic generated by the development is a crucial element of the Traffic Impact Study process. This will usually include the use of trip generation rates, as discussed in detail in this chapter. It is the responsibility of the applicant to develop peak-hour trip generation estimates for the proposed development and to fully document the assumptions and methods used in developing those trip generation estimates. The trip generation estimates, with full supporting documentation, are to be submitted to the Roads Directorate for review and approval. In certain rare cases, the proposed development to be studied may be so large as to warrant the use of the Abu Dhabi Travel Demand Forecasting model for estimating trip generation. The possibility of using the model instead of the trip generation rate approach outlined below should be explored with the Abu Dhabi Municipality. 6.2.1. Peak Hours The choice of appropriate peak hours is crucial to the accurate assessment of the impacts. As described in Chapter 3, the specific peak hours to be analyzed will be determined in the initial meeting and documented in the Preliminary Plan. The critical traffic time period for a given development is directly related to the peaking characteristics both of the development-generated traffic and of the adjacent road network. Generally, it has been found that the following peak hours are likely to cover the peak hours for many locations in Abu Dhabi:

• Morning peak hour (7:00-8:00 AM); • Noon peak hour (11:00 AM - 12:00 Noon); • Afternoon peak hour (2:00-3:00 PM); or • Evening peak hour (7:00-8:00 PM).

These should cover typical locations in the CBD. However, local area characteristics may result in other peaks for the adjacent road network, and traffic counts. The peaking characteristics of the adjacent road network can be determined through analysis of traffic count data, which, if not available, may need to be collected for the purposes of the study. The peaking characteristics of the development result from the trip-making characteristics of the land uses within the development site, and may differ from that of the adjacent road network. For the design and evaluation of access drives to the development, the peak periods for development traffic should obviously be used. The periods that result in the highest cumulative directional traffic demands should be used to assess the impact of site traffic on the adjacent road network and to define the roadway configuration and traffic control measures changes needed in the study area. The consultant should explain his choice of peak hours for both the development and the adjacent road network.


38

6.2.2. Trip Generation Rates The most frequently used approach to estimating trip generation is to apply trip generation rates to the number of square meters and/or number of residential units of individual land uses. The trip generation rates typically represent the average number of peak-hour vehicle arrivals and departures per unit of development, established from surveys or other procedures. Trip generation rates estimated for the city of Abu Dhabi do not currently exist. The Roads Directorate will provide samples of approved trip generation estimation procedures from completed Traffic Impact Studies, to assist the applicant in estimating trip generation for the specific development being analyzed. Until local Abu Dhabi data becomes more common or an Abu Dhabi trip rate manual is developed, alternative sources for trip rates, including the Dubai and ITE trip generation manuals (1,2), may be considered. It may be necessary to apply adjustments as appropriate to the trip rates obtained from these sources to obtain suitable peak hour trip generation rates for developments in Abu Dhabi. If in the process of developing trip generation rates the applicant carries out trip generation surveys for existing land uses, whether in Abu Dhabi or elsewhere, then the results of those surveys are to be included in the documentation, and submitted both in printed and electronic format. The Roads Directorate will archive these surveys results. As time progresses, the Roads Directorate will make the growing database of such survey results available to others as appropriate to assist them in developing trip generation estimates. Some important adjustments to trip rates are discussed below. These may need to be performed as a result of the nature of the development and the surrounding road network. Other adjustments may be proposed or used by the consultant. 6.2.3. Primary vs. Linked Trips Trip generation rates such as those reported in ITE and Dubai are derived from actual measurements of traffic generated by individual sites, representing vehicles entering and exiting at the development’s driveways. Therefore, these volumes are appropriate for determining the total traffic to be accommodated by the development’s driveways. There are instances, however, when the total number of trips generated by a development is different from the amount of new traffic added to the surrounding street system. For example, retail-oriented developments such as shopping centers, restaurants, banks, service stations, and convenience markets are often located adjacent to busy streets in order to attract the motorists already on the street. These developments attract a portion of their trips from traffic passing the site on the way from an origin to an ultimate destination different from the new development. Trips attracted in this way clearly do not represent new traffic on the surrounding road network. Such pass-by or undiverted linked trips are defined as trips attracted to a particular development from the traffic “passing by” on the adjacent roadway (3,4). These trips are not newly generated trips made for the purpose of visiting the new development. For such uses, a reduction in the effective trip generation may be warranted when estimating the amount of new traffic on the adjacent road network.


39

A similar type of trips attracted by the proposed development but not newly generated is that of diverted linked trips. These trips divert from their original route to travel to the development site, thereby adding traffic volume to the roadway links that connect the original route to the development. On the other hand, trips that are made solely for the purpose of visiting the development are named primary trips. The different trip types are illustrated in Figure 6-1. The percentage of pass-by and diverted linked trips varies by the type and size of land use, time of day, day of the week, geographic location of the site, and nature of the roadway network serving the site. A reduction in trip generation for the two types of linked trips may hence be applied. Figure 6-1: Trip Types (Source: Institute of Transportation Engineers, Trip Generation Handbook, 2001)

6.2.4. Internal Capture For large mixed-use developments there is potential for interaction in the form of trips made between the different land uses within the development site. This applies


40

especially when these within-site trips can be made on foot. As a result, the total generation of vehicle trips entering and exiting the multi-use site may be less than the sum of the individual, discrete trips generated by each land use. A common example is a multi-use development that contains offices as well as a shopping/service area. Some of the trips made by office workers to shops, banks, or restaurants are accomplished on site. These trips are defined as internal to (i.e. “captured” within) the multi-use site. A reduction in trip generation rates to account for internal capture may therefore be needed in some cases, when applying the trips sequentially to the different land uses comprising the development. (Trip rates calibrated for multi-use developments do obviously not have to be modified). This should be appropriately justified and documented. 6.2.5. Mode Split Variations Whenever the mode split conditions for the traffic impact study are expected to differ significantly from those under which the trip rates were calculated (in a manner that affects vehicle trips), then appropriate adjustments should be made. For example, ITE trip rates are calculated for sites at which the private car is the almost exclusive mode used to access the site. To use ITE areas to estimate trip generation for a development located in an area well served by public transit would require some adjustment to account for the reduced proportion of vehicles traveling to the site that results from the higher public transportation mode share. Smaller mode share for automobiles will reduce vehicle trips if auto trips are replaced by pedestrian or bus trips. In Abu Dhabi, taxis have a larger mode share than typical in North America. However, a taxi trip is still a vehicle trip, and may not reduce total trip generation, only parking demands. A modification to trip generation for mode-split variations may therefore be applied in some cases. This modification should be appropriately justified and documented. 6.2.6. Tables of Existing and Future Development Trip Generation The results of the trip generation estimation procedures are to be documented in the Traffic Impact Study report. Tables of existing conditions on the development site and future conditions after the development is built out and fully occupied are to be developed. Each phase of development is to be included separately in the tables. The tables should include all trips within the development site. If the proposed development is located on a site that contains existing trip-generating land uses, then the tables of existing and future trip generation can be used to calculate the net increase in trips due to the proposed development. 6.2.7. Information On Available Trip Generation Resources Since the objective is to find the number of trips generated by the yet-to-be-completed development undergoing the Traffic Impact Study, some form of estimation must be used. A discussion of both the ITE and Dubai trip rates as sources of trip generation


41

data that may be used in developing trip generation estimates for proposed developments in Abu Dhabi is provided in Appendix A. 6.3. Choice of Trip Rates The consultant is to choose appropriate trip rates, make adjustments as necessary, and provide the estimates together with the assumptions and methods used to the Municipality for review. General advice as to the choice of trip rates would suggest the use of Abu Dhabi trip rates should they be available, followed by resorting to Dubai trip rates if available. For land uses not covered in the Dubai manual, ITE rates may be used. ITE rates are comparable to Dubai rates in light of the limited comparisons made above, and thus may be considered for use for some of the land uses in the ITE trip rates for which no counterpart exists as yet in the Dubai manual. Nevertheless the reasonableness of using ITE trip rates should be decided on a case-by-case basis. 6.4. References 1. Institute of Transportation Engineers, Trip Generation – 6th Edition, 1996.

2. Dubai Municipality, Trip Generation and Parking Rates Manual, 1999. 3. Institute of Transportation Engineers, Trip Generation Handbook, 2001 4. Los Angeles Department of Transportation, Traffic Study Policies and

Procedures, March 2002.


42

7. SITE TRAFFIC DISTRIBUTION AND ASSIGNMENT

The distribution and assignment of traffic generated by the development is necessary so that the impacts of the proposed development on roadway links and intersections within the study area can be analyzed. Trip distribution is the process of establishing where trips destined to the development originated and where trips leaving the development are destined, for each horizon year. Trip assignment is the process of determining the number of proposed development vehicles on each roadway in the study area based on the results of trip generation and trip distribution. This chapter describes methods to be used for the distribution and assignment of traffic generated by the development. 7.1. Trip Distribution Trip distribution is a function of several factors, including:

• Type of the proposed development; • Size of the area of influence of the development, and if

applicable, the location of competing developments. This applies in particular to certain land uses, such as retail facilities, health clubs, etc;

• Surrounding land uses and population distribution; • Layout and efficiency of the adjacent street system; • Access to the site of the proposed development; and • On-site and nearby off-site parking facilities.

Basic methods for trip distribution include manual and model-based methods. The main advantage of the model approach is that trip distribution (and usually assignment as well) is done in an integrated fashion covering the entire metropolitan area and taking into account the impact of changes in the transportation system on both distribution and assignment. There are no hard and fast rules for the choice of method to be used for trip distribution. In general it can be said that the method to be used is determined largely by the size of the study area and the size and complexity of the proposed development in relation to the traffic analysis zone structure and the level of computer representation of the road network. For a study area larger than the sector containing the proposed development and adjacent roads, the model-based method for trip distribution (and assignment) is generally preferred. When the proposed development and the study area fall entirely into one zone, or when the model road network representation does not capture many of the roads of interest in the study area, a manual method may be more appropriate. It is sometimes possible to enhance the model road network or traffic analysis zone representation in the vicinity of the development in order to overcome the problems of using the model for small developments or study areas. The specific method of trip distribution proposed by the Consultant will be reviewed and approved by the Roads Directorate and documented in the Inception Plan. A


43

figure showing the results of the trip distribution step is to be included in the traffic impact study report. 7.1.1. Manual Methods For developments with a small study area (a single sector plus adjacent roads, which may consist of one or a few traffic analysis zones), manual trip distribution consists of determining the percentage of development vehicle trips using each internal circulation road that approach or depart from the development. In these cases, percentages of development trips are to be determined for all roads in the study area and for the links entering and exiting the study area. (Such manual approaches to trip distribution often implicitly include the assignment step, since the vehicle trips are directly loaded onto the network). For developments with a larger study area, the manual method of trip distribution becomes more complex. It becomes necessary to determine the geographic locations of origins for all trips destined to the development site and the geographic locations of destinations for all trips leaving the development site. For these larger developments, the manual distribution may be used with a manual assignment or with an assignment conducted using the Abu Dhabi Travel Demand Model. Some important manual methods of trip distribution to be considered for carrying out Traffic Impact Studies in Abu Dhabi are briefly described below. More information on these and other manual methods for performing trip distribution can be found in traffic engineering and transportation textbooks and Traffic Impact Study guidelines [1,2,3,4,5]. Analogy Method: This method uses trip distribution data from an existing development that is similar to the proposed development. Such data might be in the form of traffic count and turning movement from the similar development. The need to exercise careful judgment in deciding whether and how the results can be adapted for use in estimating trip distribution for the proposed development is obvious. The analogy method is particularly useful when the existing development is near the proposed development, which facilitates the process of “working out” the expected trip distribution for the proposed development (For examples on the procedure, see [1]). This method has been found particularly useful for specific land use types. Examples of facilities that can serve as the analogous development for the proposed development for consideration in Abu Dhabi might include:

• Fast-food restaurants where a competing establishment is near the site;

• Service stations where traffic volumes on the adjacent streets are similar to those forecasted at the site;

• Residential developments on the fringe of an urban area; • Occupied residential developments in an area where the

proposed development is one of the few vacant parcels remaining in an otherwise developed area; and


44

• Occupied office buildings in an office complex being developed in phases.

Origin and Destination Studies: These might be carried out for large and unusual developments, or for relocation, when the “customer base” frequenting the establishment is expected to largely remain the same. Examples are large employers who relocate and expect both to retain most of their employees, and also expect that the relocation will not affect the residential location of those employees. Another example could be a unique government office, such the passport and immigration office. Area-of-Influence Method: When acceptable data is not available, the area of influence method may be used. For a proposed development, the area of influence is the area within which most (say 80 percent or more) of the trips to and from the development are expected to start or end. It is determined by what is seen as reasonable travel times, as well as the location of competing facilities if applicable. The method assumes that these trips start or end at a residence, place of employment, or other measurable land use type. For example, most trips to a shopping center may be assumed to originate at residences. This method then subdivides the area of influence into subareas or zones, estimates the population within each subarea, and computes the percentage of total population in the influence area within each subarea. For each subarea, this percentage figure is then assigned to the available road network. Figure 7-1 demonstrates the approach for the case of a proposed retail development.


45

Figure 7-1 Example Application of Area-of-Influence Method (Source: V. Stover and F. Koepke, Transportation and Land Development, 2002)

7.1.2. Model-Based Methods Model-based trip distribution can be achieved through direct application of the Abu Dhabi Travel Demand Model or other model approved by the Roads Directorate. The Abu Dhabi Travel Demand Model performs trip distribution using the gravity model. However, trip distribution within the Abu Dhabi Travel Demand Model occurs prior to application of the mode choice sub-model and application of vehicle occupancy factors. Care is needed to ensure that the results of applying the Abu Dhabi Travel Demand Model for trip distribution are consistent with the trip generation estimates for the development following the procedures described in Chapter 6 of these guidelines.


46

7.2. Trip Assignment Trip assignment determines the total amount of development-generated trips, by direction and turning movement, on each segment of the study area road network. Trip assignment should be made considering logical routings, available roadway capacities, left turns at critical intersections, and projected (and perceived) travel times. When the development site has more than one access driveway, logical routing and possibly multiple paths should be used to obtain realistic driveway volumes. For large developments, the assignments should be carried through the internal roadways. Trip assignment may be performed manually or by a travel demand model. The arguments for their use are similar to those for trip distribution in the previous section. If a manual approach to trip assignment is used, development trips are to be converted to vehicle trips and added to future year baseline traffic volumes. If the Abu Dhabi Travel Demand Model or other approved model is used, then a development trip table based on the results of development trip generation and distribution is to be added to future year baseline trip table, and the model’s vehicle assignment sub-model is to be applied. Most model-based assignment methods are based on user equilibrium, that is, attempt to assign traffic to the network in such a manner that the resulting flows result in users traveling on the shortest possible route to their destinations. When manual methods are used, it is essential that trip reduction items, such as pass-by trips, be properly accounted for when performing the assignment. Pass-by trips can be deducted from the background traffic when assigning development-generated traffic to surrounding roads, since they are not new trips on the road network but are trips made by traffic already on the roadway(s) that enter the site as an intermediate stop on the way from an origin and primary destination trips turning in and out of the site access intersections. This trip generated does not impact nearby intersections, but does impact traffic flow at the site entrance, and hence pass-by trips should not be deducted when evaluating traffic movements to and from the development at access points. All development-generated trips must be counted in evaluating access requirements and needs such as separate turn lanes. The results of the trip assignment step will be an estimate of total traffic volumes on all roadways in the study area. A figure showing these total volumes is to be included in the traffic impact study report. 7.3. References 1. V. Stover and F. Koepke, Transportation and Land Development, 2002.

2. Florida Department of Transportation, Site Impact Handbook, 1997.

3. Papacostas and Prevedouros, Transportation Engineering and Planning, 1993.

4. Wisconsin Department of Transportation, Traffic Impact Analysis Guidelines, 2002.


47

5. Institute of Transportation Engineers, Traffic Access and Impact Studies for Site Development, 1990.


48

8. ANALYSIS OF DEVELOPMENT-RELATED TRANSPORTATION IMPACTS

Trips generated by a proposed development, including vehicle and public transport trips, will typically add traffic to the existing transportation system surrounding the development. To the extent that new development generates new transportation impacts, it is reasonable to require sponsors of new development to contribute to the mitigation of the impacts. This chapter establishes procedures for quantifying development impacts on the surrounding roadway and public transport systems. It is not always the case that these impacts need to be mitigated. This chapter therefore also defines thresholds for determining when these impacts are serious enough to warrant development of mitigation measures. 8.1. Quantifying Development-Related Transportation

Impacts Additional vehicle traffic generated by the proposed development will cause impacts to the roadway system, some of which may require mitigation. Similarly, development-generated demand for public transport services may impact the existing public transport system, and may require higher frequencies or new routes. 8.1.1. Traffic Impacts The analysis of traffic impacts begins with a comparison of total traffic volumes and levels of service for a future with-development scenario (including all background growth plus the proposed development) to future baseline (including all background growth but without the proposed development) conditions on all intersections and links within the study area. Procedures for estimating future traffic volumes and levels of service have been provided in Chapters 4-7 of these guidelines. Intersections to be analyzed may include access drives. For example, a large mixed retail/commercial building may come with a large underground parking garage whose peak-hour operation must be analyzed to ensure adequate performance and avoid operational problems such as the backing up of vehicles accessing the garage onto the adjacent roadway. Quantification of development-related traffic impacts is achieved by carrying out the necessary analysis to complete the table shown in Table 8-1. For all relevant intersections and links in the study area, delay, V/C, speed, and levels of service are to be computed in a manner consistent with the methodologies and procedures described in Chapter 3 of these guidelines. Assumptions about lane geometry, signal phasing and timing, pedestrian volumes, percentage of trucks, and other characteristics of the facilities and the traffic using them should be the same in the future baseline and future with-development scenarios unless the proposed development description specifically changes the number of lanes or makes other changes to the features or utilization of a facility.


49

In the two columns in Table 8-1 labeled “Development-Related Traffic Impact” the proposed development’s traffic impacts are quantified, and it is determined whether these impacts are significant. The change in delay and/or V/C is determined by subtracting the future baseline value from future with-development value. Whether the impact is considered significant is indicated in the last column. Thresholds for determining if an impact is significant are provided in Section 8.2 of this chapter. Table 8-1 Quantification of Development Related Traffic Impacts in Study Area



FUTURE (Year) WITH-DEVELOPMENT CONDITIONS

DEVELOPMENT-RELATED TRAFFIC IMPACT

Signalized Intersections Delay LOS Delay LOS Delay LOS

Change in Delay

Significant?

Intersection #1 Intersection #2

… Intersection #n

Unsignalized Intersections Delay LOS Delay LOS Delay LOS

Change in Delay

Significant?


… Intersection #m

Roundabouts Delay LOS Delay LOS Delay LOS Change in Delay

Significant?

Roundabout #1 Roundabout #2

… Roundabout #p

Links Speed LOS Speed LOS Speed LOS Speed Significant?Link #1 Link #2

… Link #q

8.1.2. Other Transportation Impacts Based on the specific characteristics of the proposed development and of the surrounding transportation system, the Roads Directorate may request additional issues to be analyzed besides the typical impacts discussed above. Examples of such issues are the operational adequacy of weave and merge/diverge sections, the performance of areas with high pedestrian volumes, etc. Typically these additional impacts will be identified in the initial meeting and documented in the Inception Plan. However, the Roads Directorate may also request that additional impacts be evaluated later in the process, should information gained during the traffic impact study indicate a need to do so.


50

In addition to the identification of traffic impacts described in this chapter, an analysis of multi-modal site/sector access and circulation is required. This analysis is described in Chapter 10 of these guidelines. 8.2. Thresholds for Determining Significant Transportation

Impacts To determine when development-related transportation impacts are serious enough to warrant development of mitigation measures, all transportation impacts identified in Table 8-1 are categorized as significant or insignificant. Significant transportation impacts are those quantitative impacts on the Level of Service or the average delay considered serious enough to warrant development of mitigation measures. The decision to classify an impact as significant or not is made using the concept of significance thresholds. 8.2.1. Approaches to Defining Significance Thresholds There are two primary approaches to establishing significance thresholds. One approach is to establish LOS standards for the area, and then to consider any impact that causes a facility to become deficient (exceeding this standard) to be significant1. This deficiency approach essentially allows development to occur without mitigation until a deficiency is reached, and then require all development after that time to mitigate its impacts. The second approach is to require developments to participate in the mitigation of impacts even before LOS standards are reached2. This typically requires more developments to implement mitigation measures, and tends to reduce the magnitude of mitigation to be implemented by any one development. It has been decided to use the second approach in which the burden of mitigation is shared among a larger number of developments. This decision is based on the following:

• Strict adherence to the deficiency approach for mitigation could cause a development to implement large and costly mitigation measures even if its impact is small. For example, if an intersection has been fully improved and cannot be improved further with additional lanes or signal enhancements, an impact of as little as a few additional vehicles could force a development to build grade separations or build new roads in order to mitigate its impact.

• Strict adherence to the deficiency approach for mitigation in

areas already congested (such as downtown) could conceivably

1 Examples of agencies that use the deficiency approach include Indiana Department of

Transportation, Dubai Municipality, and Traffic Impact Studies Applicant’s Guide, and the San Diego Traffic Engineering Council.

2 An example of an agency using the shared participation approach is the Los Angeles Department of Transportation.


51

result in a moratorium against any new development because LOS standards in the area have already been exceeded, and the cost of mitigating any new impact may be excessive.

• The deficiency approach could create a situation in which a

very large development is built in an uncongested area with only a few low-cost mitigation measures, but using up all available transportation capacity in the area. A small development following behind it could then be required to implement very costly mitigation measures because all of the transportation facilities in the area have reached their LOS standards.

• The shared-participation approach allows for contributions of

developments toward transportation infrastructure to be calculated based on their relative contributions to traffic growth in the region.

While recognizing that the private sector may contribute to the provision of transportation infrastructure, the Abu Dhabi Municipality and Town Planning Department will continue to take the lead in providing major new roadways and other transportation facilities that benefit the region. The shared-participation approach, which allows the development sector to contribute their fair-share to the program, may begin to be implemented in Abu Dhabi. Together, the public and private sectors can continue to be “ahead of the curve” in building a transportation system to support the future needs of the region. 8.2.2. Significance Thresholds for Abu Dhabi Significance thresholds for development-related transportation impacts in Abu Dhabi that vary with the level-of-service of the facility are defined in Table 8-2. In line with the discussion in the previous section, these thresholds change as the level of service of the affected facility changes. If a facility operates at LOS E or F, then the threshold for categorizing an impact as significant is small. If the level of service of the facility is C or D, the significance threshold is larger. Thresholds used in traffic impact analysis and other types of environmental impact analysis provide a consistent and rational approach to the assessment of impacts of developments or measures that reflects the underlying principles. It should however be borne in mind that the particular values and ranges for the LOS and the impacts that define these thresholds are based on professional judgment and experience, and as such are neither perfect nor the same for all agencies that use this approach to defining thresholds. Even within a particular agency they may be subject to review and modification over time. The particular values listed here are based on the Traffic Impact Study Guidelines of the Los Angeles Department of Transportation and are felt to represent a useful starting set of values for Abu Dhabi. Over time their suitability in the Abu Dhabi context will be evaluated, and in light of the evaluation, these values may be modified.


52

Table 8-2 Significant Thresholds for Development-Related Transportation Impacts

JUNCTIONS

FUTURE WITH-DEVELOPMENT LOS

FUTURE WITH-DEVELOPMENT DELAY

SIGNIFICANT DEVELOPMENT-RELATED IMPACT

Signalized Intersections

F E D C B A

80.1 and above 55.1 – 80.0 35.1 – 55.0 20.1 – 35.0 10.1 – 20.0 0.0 – 10.0

2.0 seconds or above 2.0 seconds or above 4.0 seconds or above 6.0 seconds or above Not Significant Not Significant

Unsignalized Intersections

F E D C B A

50.1 and above 35.1 – 50.0 25.1 – 35.0 15.1 – 25.0 10.1 – 15.0 0.0 – 10.0


Roundabouts

F E D C B A

80.1 and above 55.1 – 80.0 35.1 – 55.0 20.1 – 35.0 10.1 – 20.0 0.0 – 10.0


LINKS

FUTURE WITH-DEVELOPMENT LOS

FUTURE WITH-DEVELOPMENT V/C

SIGNIFICANT DEVELOPMENT-RELATED IMPACT

Freeways, Expressways, Arterial Streets, Local Roads, Ramps, and Driveways

F E D C B A

1.01 and above 0.91 – 1.00 0.81 – 0.90 0.71 – 0.80 0.61 – 0.70 0.00 – 0.60

0.02 or above 0.02 or above 0.04 or above 0.08 or above Not Significant Not Significant

8.3. References 1. Indiana Department of Transportation, Applicant’s Guide to Traffic Impact

Studies, June 1993.

2. Dubai Municipality, Traffic Impact Studies Applicant’s Guide, 1997.

3. SANTEC/ITE,Guidelines for Traffic Impact Studies (TIS) in the San Diego Region, March 2000.

4. Los Angeles Department of Transportation (LADOT), Traffic Study Policies and Procedures, August 2003.


53

9. DEVELOPMENT OF MITIGATION PLAN Once it is established that a proposed development has significant transportation impacts, it becomes necessary to develop a plan to mitigate those impacts. Implementation of mitigation measures concurrent with land development will help to ensure that both the development and the surrounding transportation system will operate satisfactorily. This chapter describes how measures for mitigating impacts to the surrounding transportation system are developed and analyzed. Multi-modal access to the development site, on-site circulation, and parking design and requirements for the proposed development are discussed separately in the next two chapters. It should be borne in mind, however, that all elements function as a system for which changes to one element may impact another. An important example is driveways to the development site, whose design and location significantly determine the development’s impact on the surrounding transportation system. Their analysis may lead to changes in location or configuration that would in turn affect off-site transportation network performance. As such, the analysis of transportation impacts and on-site access, circulation, and parking should be done concurrently to ensure that the most appropriate solutions are identified in a timely manner. 9.1. Developing the Mitigation Plan The mitigation plan is a critical element of the Traffic Impact Study, and will require approval by the Roads Directorate. It is recommended that the applicant discuss potential elements of the mitigation plan prior to submitting the draft Traffic Impact Study report to ensure that the constraints and opportunities affecting the choice of mitigation strategies will be identified. For example, in some areas road widening may be constrained due to a variety of factors, and hence may be eliminated a priori as a possible element of a mitigation plan. 9.1.1. Objectives of Mitigation Plan The first objective of the mitigation plan is to develop feasible measures that, when implemented, will improve levels of service on all significantly impacted facilities such that the impacts are eliminated entirely or reduced to the point that they are no longer significant. The second objective of the mitigation plan is to develop a phasing plan for timely implementation of the mitigation measures. The third objective is to identify funding sources for the proposed mitigation measures. 9.1.2. Quantifying the Benefits of Mitigation Measures Benefits of the proposed mitigation measures are to be quantified in tabular form as shown in Table 9-1. This table is similar to Table 8-1 but has two additional columns. The first describes the future conditions with the mitigation measures; the second lists the impact after mitigation compared to the future baseline (without development) scenario and whether this impact is still significant.


54

Implementation of the proposed mitigation measures may affect other facilities in the area, and these impacts are to be evaluated as well. In some cases, implementation of one mitigation measure may cause another facility to be significantly impacted. When appropriate, the analysis should indicate whether this has happened. Any new significant impacts created by a proposed mitigation measure must also be mitigated in the mitigation plan.


55

Table 9-1 Quantification Of Mitigation Measure Benefits



FUTURE (Year) WITH-DEVELOPMENT CONDITIONS

DEVELOPMENT-RELATED TRAFFIC IMPACT

MITIGATED FUTURE (Year) WITH-DEVELOPMENT CONDITIONS

MITIGATED DEVELOPMENT-RELATED TRAFFIC IMPACT

Signalized Intersections Delay LOS Delay LOS Delay LOS Change

in Delay Significant? Delay LOS Change in Delay Significant?


... Intersection #n Unsignalized Intersections Delay LOS Delay LOS Delay LOS Change

in Delay Significant? Delay LOS Change in Delay Significant?


... Intersection #m

Roundabouts Delay LOS Delay LOS Delay LOS Change in Delay Significant? Delay LOS Change

in Delay Significant?

Roundabout #1 Roundabout #2

... Roundabout #p

Links3 V/C LOS V/C LOS V/C LOS Change in V/C Significant? V/C LOS Change

in V/C Significant?

Link #1 Link #2

... Link #q

3 Links include freeways, expressways, arterial streets, local roads, ramps and driveways.


56

9.2. Potential Mitigation Strategies When significant impacts are discovered, strategies will need to be investigated to mitigate them. From these strategies one or more potential mitigation measures are to be defined and assessed for their effectiveness in mitigating the significant traffic impacts. The strategies may include actions to reduce the level of traffic generated by the proposed development, increasing capacity of the affected roadway system, or implementing other operational improvements that improve the level of service as required. All mitigation measures proposed must meet the design standards of the Abu Dhabi Municipality as documented in Roadway Design Manual – Roads and Bridges and the Abu Dhabi Manual of Uniform Traffic Control Devices (1,2). Some potential mitigation strategies to be considered are discussed below. Additional strategies for consideration are provided in the references listed at the end of this chapter. (3,4) 9.2.1. Intersection Improvements Improvements to impacted intersections, in particular those adjacent to the development site access points, are often the most important elements of a mitigation plan. When a significant impact occurs at a signalized intersection, one strategy to mitigate the impact is to modify the intersection to improve its level of service. Modifications may include:

• Revising signal phasing and/or timing (requires review and approval of the proposed measure by the Abu Dhabi Traffic Control Center);

• Signal coordination and/or Intelligent Transportation Systems (ITS) improvements (requires review and approval of the proposed measure by the Abu Dhabi Traffic Control Center);

• Modifying lane striping to give additional capacity to critical turning movements;

• Eliminating certain turning movements (this requires analysis of impacts to surrounding intersections affected by the elimination of the turning movements);

• Modifying turning lanes (such as extending a left-turn lane for increased queue storage);

• Adding new lanes (this may require acquisition of additional right-of-way and, potentially, removal of existing structures); and

• Creation of grade separations (may require acquisition of right-of-way and, potentially, removal of existing structures). This may result in impacts outside the study area. The impacts outside the study area may have to be evaluated.

When an unsignalized intersection is significantly impacted, potential strategies to improve its level of service might include:

• Eliminating certain turning movements (requires analysis of impacts to surrounding intersections affected by the elimination of the turns);


57

• Signalizing the intersection (Warrants for determining when an unsignalized intersection should be signalized are provided in the Abu Dhabi Manual of Uniform Traffic Control Devices); and

• Adding lanes (may require acquisition of right-of-way). 9.2.2. New Roadways, Extensions, Roadway Widening, and

Interchanges Building new roadways, extending existing roadways, roadway widening, and building new interchanges may be considered in mitigating several types of transportation impacts. This strategy may add capacity to a section of roadway that is significantly impacted by the proposed development, or it may shift traffic away from another impacted roadway or intersection. When this strategy is proposed, an analysis will be required which quantifies any shift in traffic on the surrounding transportation system in response to the added capacity. Proposed new roadways, extensions and road widening should also be evaluated to determine whether they are consistent with the Abu Dhabi Master Transportation Plan or other planning directives. 9.2.3. Operational or Transportation System Management

Improvements Operational improvements or Transportation System Management (TSM) measures to improve levels of service and mitigate significant transportation impacts should be considered. These may include:

• Re-striping merge/diverge or weave sections on existing roads to improve operations;

• Removal of curbside parking (requires analysis of parking impacts); • Prohibition of curb parking during peak hours; and • Conversion of two-way streets to one-way streets.

9.2.4. Transportation Demand Management The Transportation Demand Management (TDM) strategy encompasses actions to reduce peak-hour vehicle travel. As recommended by the Abu Dhabi Master Transportation Plan, broad regional efforts in TDM may be enacted to reduce vehicle travel at the regional level. At the level of Traffic Impact Studies for proposed developments, TDM strategies may include:

• Use of private buses to transport workers; • Employer-sponsored programs to encourage employees to use public

transport or carpool; and • Placement of public transport stations near the site (in conjunction with

public transport service improvements).


58

Analysis of the benefits of TDM measures should include an estimate of the total number of peak hour vehicle trips reduced, and of the number of vehicle trips reduced at each significantly impacted facility. 9.2.5. Modifications to Definition of Development and/or Site Plan Modifications to the definition of the development and/or site plan can reduce significant transportation impacts by reducing the amount of traffic generated by the proposed development or by moving certain traffic volumes to other locations (e.g. moving a driveway to another location to reduce the number of left turns at a nearby intersection. If other reasonable measures cannot sufficiently mitigate significant impacts, modifications to project definition or site design may be the only way to achieve all of the objectives of the mitigation plan. Issues related to the site design will be further discussed in the following chapters. If other reasonable mitigation measures cannot sufficiently mitigate significant impacts, modifications to project definition or site design may need to be investigated as a means to achieve all of the objectives of the mitigation plan. 9.3. Implementation and Phasing of Mitigation Measures An implementation plan is to be included in the mitigation plan to indicate when the proposed mitigation measures will be implemented. The implementation plan should show that the improvements will be implemented in a timely manner so that they are in place by the time they are needed. Large developments may be developed in phases over several years. These large projects may require a comprehensive package of improvements to mitigate the identified significant impacts on the transportation system. The nature of these improvements and their timing can be related to the phasing of the development as well as to changes within the overall study area. In this way, the improvements can be phased such that their implementation occurs at the time they are needed to maintain acceptable levels of service. When developing the implementation plan, care should be used to ensure that the improvement being implemented is directly related to an impact created by the proposed development, both in time and in the nature of the impact to be mitigated. 9.4. Review and Approval of Proposed Mitigation Plan It is the responsibility of the Roads Directorate to review and approve all proposed mitigation measures before approving a Traffic Impact Study report. In reviewing the proposed mitigation measures, the Roads Directorate may have additional questions of the applicant. For this reason, it is strongly recommended that the applicant discuss potential elements of the mitigation plan with the Roads Directorate prior to submitting the draft Traffic Impact Study report to ensure that the proposed mitigation measures will be acceptable. In reviewing proposed mitigation measures, the Roads Directorate will address the following issues:


59

• Has the technical analysis leading to the identification of significant impacts and definition of proposed mitigation measures met the requirements of these guidelines and fulfilled the obligations set forth in the preliminary plan?

• Do the proposed mitigation measures fully mitigate all significant transportation impacts, and are they technically feasible?

• Will additional right-of-way be required, and is it feasible to acquire? • Will the proposed mitigation measures require the removal of any existing

structures, and is this feasible? • Will the proposed mitigation measures be implemented by the time they

are needed? • Have reasonable funding options been developed for implementation of

the mitigation measures? • Have the implementation measures been appropriately phased? • Are there other potential mitigation measures to be considered, and might

they be more appropriate than the measures proposed? Once these issues have been addressed to the satisfaction of the Roads Directorate, the mitigation plan will be approved. Applicants are advised to anticipate the Roads Directorate’s review of the issues above and to provide sufficient information to answer them in the Traffic Impact Study report. 9.5. References 1. Abu Dhabi Municipality Roads Directorate, Abu Dhabi Manual of

Uniform Traffic Control Devices, 2004.

2. Abu Dhabi Municipality Road Section, Roadway Design Manual – Roads and Bridges, 1998.

3. Institute of Transportation Engineers, A Toolbox for Alleviating Traffic Congestion, 1989.

4. Institute of Transportation Engineers, Traffic Engineering Handbook, 2001.


60

10. MULTIMODAL SITE ACCESS, CIRCULATION, AND PARKING DESIGN

This chapter highlights the importance of site access, circulation and parking to developer and Municipality alike and explains the dependence of scope of analysis on development size. This is followed by the requirements of the site plan used as the basis for review by the Municipality. The remaining part of the chapter discusses some principles for the analysis of common items likely to be included in the analysis of site access and circulation. The goal of the multimodal site access and circulation analysis is to ensure safe and efficient movement by all modes to, from and within the site. Movement of passenger vehicles, public transport vehicles, taxis, delivery vehicles, pedestrians, and bicycles are to be considered in this analysis. The design of the parking facilities is also an essential factor impacting access and circulation and is also discussed. A discussion of the parking requirements (i.e. the number of parking spaces to be provided) for new developments is provided separately in the next chapter. 10.1. Importance and Scope of Site Access and Circulation Providing effective site access and circulation is in the direct interest of the developer. The convenience with which a site is accessed, the ease and safety with which one can move on foot or in a vehicle between buildings, parking facilities, and bus and taxi stops, are important factors for its success. They impact how the site will be perceived by its patrons, whether these are residents, employees, visitors, or shoppers. In cases in which a commercial development competes with similar facilities elsewhere, poor site access and circulation may result in disappointing sales performance, since customers have alternative options and can exercise the choice of where to spend their money. Similarly, Abu Dhabi Municipality and Town Planning must ensure that the traveling public encounters a roadway system that is safe and efficient, including those roads that fall within developments that may be under public or private ownership, and the points at which those roads connect to the public road network. The scope of the site access and circulation analysis task is particularly influenced by the size of the development. For single-parcel developments in the CBD, for example, this task may be limited to ensuring that the local shared access is adequate. Small developments that are to have separate access will need an analysis of the access point(s), to ensure that driveway design and location does not lead to operational problems. On the other hand, large developments often have substantial internal roadway systems to facilitate movement to and between the various facilities within the site and the parking lots or structures. The necessary analysis in such a case will be substantial and will deal with numerous issues to ensure the safe movement of vehicles and pedestrians. In some cases, limitations of parcel size compel a developer to provide substantial parking within the buildings comprising the development, in which case the analysis should be logically extended to the roads and ramps within


61

the structure that provide access to and within these parking facilities. This is often the case in Abu Dhabi’s CBD. In addition to the scope of this task being highly variable, the analysis to be carried out is generally less structured than say the computation of the LOS of a signalized intersection when calculating off-site traffic impacts. The use of specific analytical procedures is not mandated in these guidelines. In particular the applicant is to consult Abu Dhabi Municipality Roads Directorate’s available design standards, manuals, and standard drawings. These sources are to be complemented by standards and references from other sources reflecting current traffic engineering practice to assist in both the design and the analysis of specific items. Furthermore, depending upon the complexity of the situation, the Roads Directorate may request the analysis of certain items in advance to be sure that specific concerns are addressed. The applicant has the responsibility to provide sufficient data and analysis in support of any conclusions. 10.2. Site Plan The applicant is required to submit a detailed map of the site. This map should show all relevant features of the site related to access, circulation and parking, as applicable. Depending on the size and nature of the development, the features to be shown may include all of the following:

• Building footprint and location, and sector layout; • Building entrances, loading docks, and service areas; • Pick-up and drop-off lanes or areas; • Location and design of access to the development, such as angle, curb return

radius, throat width, throat length, channelization, turn bays, driveway profile, traffic control, and geometry of shared access drive;

• Distance between driveways and corner clearances; • Location and spacing of median openings; • Geometry of internal roads including lane width, curve radii and vertical

grades; • Geometry and control of internal intersections; • Traffic calming devices such as speed humps and raised crosswalks; • Pedestrian sidewalks, walkways, crosswalks, and bicycle paths, showing

connections between buildings and primary parking areas and between buildings and pick-up/drop-off points for taxis, private transport and public transport;

• Parking layout including parking angle, stall size, aisle width, number of stalls in each row, and end island location and shape indicating if painted, curbed, or landscaped;

• Handicapped facilities including parking stalls and ramps as needed; • Traffic signs and markings; • Landscaping details including buffer areas and end islands.

This list is not meant to be exhaustive. Additional relevant features of the development not included in the list should also be shown.


62

10.3. Site Access, Circulation, and Parking Design This section addresses movements by various modes to, from and within the site. Access in and out of the site focuses on driveways along the site boundary, as well as driveways that provide access to parking lots and other areas located within the site. Circulation within the site focuses on parking lots and structures and internal roadways. The items identified below are to be addressed in the multimodal site access and circulation analysis, if applicable in light of the size and nature of the development. The analysis required for many of the items in this task builds on the findings of the analysis carried out in earlier tasks that estimated the amount and distribution of traffic entering and exiting the site. The total traffic in and out of the site must be distributed to the set and location of access points representing a particular site plan, and on-site flows may need to be computed for certain sections. This in turn allows determination of the required number of lanes for the internal roadways, and required storage lengths of queuing at various locations. A change in configuration will generally necessitate recomputing these parameters. 10.3.1. Site Access The number, location and design of access points or driveways are basic determinants of how the development interacts with the surrounding road network. Issues to be considered in this task include:

• Traffic in and out of access points creates interference with the abutting roadway traffic. As such, the number of access points should be the minimum required to serve the proposed development without negatively affecting safety or operations on the abutting roadway.

• The proposed access drives should be adequately spaced from nearby signalized intersections or unsignalized access points whether public streets or private access drives. The possibility of a shared access drive serving other developments or alternative access should be explored.

• Access to other existing and planned developments should not be significantly affected.

10.3.2. Access Design Proper access design ensures that no local operational problems occur at the interface between the development and the abutting roads. Issues to be considered in this task include:

• Provision of adequate driveway (or throat) length. The throat length should be sufficient for the type and volume of traffic entering and exiting during peak periods to avoid queues that may back up into the abutting roadway, which is particularly undesirable, or block movements on the internal roads. Priority should be given to vehicles entering the development. Estimates of average and maximum queue length may be requested by the Roads Directorate for all peak hours studied. More


63

conservative approaches to determining the throat length based on estimated traffic should be used in situations where physical or other constraints preclude the extension of throat length after the development has been made operational.

• Distances between driveways and adjacent street intersections should be sufficient to minimize driveway blockages by queues from the intersections.

• Auxiliary deceleration lanes should be provided if extreme speed differentials between traffic entering the development and through traffic on the abutting roadway result in a high rear-end crash potential.

• Signing and lighting should provide adequate visual cues to the location and manner of entry to the access point, in order that sudden maneuvers by approaching drivers will be eliminated.

• The vertical profile of the driveway should provide a smooth transition between the roadway and the driveway approach.

• The driveway geometry in terms of curb return radii, lane or throat width should be adequate for the expected type of traffic.

• Developments with restricted access (based on vehicle type or size or user privileges) should allow non-authorized vehicles to return or exit without having to back up through the access.

10.3.3. Internal Roadways The objective for internal roadway analysis is to ensure that vehicles will flow safely and efficiently through the site. For large sites there may be a hierarchy of internal roads similar to the hierarchy of roads on the surrounding road network. There may be a ring road, with access to perimeter roads to the buildings, connected to parking aisles, for example. In some instances, level of service analysis may be requested by the Roads Directorate based on estimated traffic volumes on internal roadways. Issues to be considered in this task:

• The intended circulation pattern within the site should be simple and comprehensible with efficient use of traffic signs and markings.

• Acceptable intersection sight distance should be provided. • High-speed conflicts within the site should be avoided. • On-site circulation should be performed without use of external roadways. • Pick-up and drop-off lanes should provide sufficient stacking length to

avoid spillback onto site perimeter roads or external roads. • Site access and circulation design for drive-thru facilities such as fast-food

restaurants or service stations should clearly identify the intended entry and exit and circulation patterns for drive-thru traffic and other site traffic. The stacking area should be adequate to accommodate expected queues without spillback onto or interference with traffic on the abutting roadway. The location of drive-thru facilities should not create blockages between different queues (for example, between the queues for fuel pumps and automated car-wash facilities at service stations).


64

10.3.4. Delivery, Service and Emergency Vehicles The objective of the delivery and service vehicle analysis is to ensure that a sufficiently sized loading zone is available as needed, and that the delivery vehicles are able to travel to and from the loading and service zone(s) safely and efficiently. Issues to be considered in this task include:

• The number and dimensions of the loading and unloading docks, and of solid waste dumpers, should be adequate for the expected traffic volume. The location of the docks should allow for convenient access.

• Proper access of emergency vehicles to buildings should be provided, as well as adequate room to maneuver.

• Conflicts between service or delivery vehicles and site patrons should be minimized.

• Adequate turning paths for service and delivery vehicles should be provided throughout the site, including access points and internal intersections.

10.3.5. Taxi and Public and Private Transport Vehicle Access The objective of the analysis of taxi and public and private transport vehicle access is to ensure that movement between the stops and the site destinations is safe and convenient. Issues to be considered in this task include:

• For large developments, public transport stops may be located on site. Such stops should be connected to the building entrances by means of safe and convenient walkways. To minimize walking distances and pedestrian-vehicle conflicts, stops should be located near principal building entrances wherever possible. Driveways to be used by public transport vehicles should be appropriately dimensioned.

• Appropriate facilities for private transport vehicles, such as worker and employee buses and vans, should similarly be provided when such traffic is likely to materialize.

• For off-site public transport stops that already exist, the manner in which pedestrians will access the site should be evaluated. New stops that serve the site should be connected by means of walkways that minimize pedestrian-vehicular conflict.

• Taxi pick-up and drop-off areas and lanes should not obstruct main pedestrian paths between building entrances and parking areas. Holding areas for taxis should be adequately designed

10.3.6. Pedestrian and Bicycle Access and Circulation This section addresses the access of pedestrians and bicycles to and their movement within the site. The goal of this analysis is to ensure that pedestrians and bicyclists can safely and conveniently move between different areas within the site as well as travel to and from the site. Issues to be considered in this task include:


65

• The parking and circulation system should be designed to minimize the number and extent of pedestrian-vehicle conflicts, in particular at building faces and at parking lots. For example, vehicles that depart from parking lots to leave the site should not pass through areas of high pedestrian volumes, in particular in front of building entrances. The distance that vehicles travel along the building face should be minimized.

• Low vehicular speeds and volumes whenever such pedestrian-vehicular conflicts do exist. When road width is conducive to high speeds especially along building faces, additional traffic calming measures such as raised crosswalks or speed humps should be used to lower vehicle speeds.

• Adequate sight distances. Drivers and pedestrians should have a clear and unobstructed view of each other along the entire building face where pedestrians may be present. A wide sidewalk should be provided along the building face. Bollards should be provided where necessary.

• For developments that are likely to attract potential cyclists, such as recreational or shopping facilities, the provision of bicycle racks for parking should be considered. A bicycle lane or other measures that enhance bicycle access and safety should be considered especially when the development is close to public bicycle paths.

• Clearly defined pedestrian paths should be provided between the development and any nearby pedestrian underpasses.

10.3.7. Parking Design and Layout Adequate parking, as defined by the number of spaces, type, location, and design and layout, is an essential requirement for a successful development. Basic design standards for parking including stall size, angle of parking, modulation, and pavement markings are provided in the Abu Dhabi Roadway Design Manual and Standard Drawings. Actual design should follow these standards and accepted principles for good parking design and layout. Issues to be considered in this task include:

• The number of parking spaces to be provided is the most important element. The Municipality requirements for this element are discussed separately in the next chapter.

• The number of stalls in a given area should not be maximized at the expense of safe and efficient access, user convenience, and good internal circulation. During peak hours, substantial travel may occur within a parking lot or structure during the search for a parking space of suitable specifications. Difficult-to-access stalls may induce some drivers to forego use of empty stalls until a suitable stall is found.

• The orientation of parking aisles should be perpendicular to the building faces to accommodate convenient pedestrian movements and provide greater visibility to pedestrians and drivers.

• Parking should generally not be provided immediately adjacent to the building.

• Handicapped parking should be conveniently located in relation to elevators, ramps, walkways, and building entrances.


66

10.4. References 1. V. Stover and F. Koepke , Transportation and Land Development, ITE

2002.

2. Florida Department of Transportation, Site Impact Handbook, 1997.

3. Institute of Transportation Engineers, Traffic Access and Impact Studies for Site Development, 1990.

4. Abu Dhabi Municipality, Road Section, Standard Drawings, 1998.

5. Abu Dhabi Municipality, Road Section, Roadway Design Manual, 1998.


67

11. PARKING REQUIREMENTS The parking situation has deteriorated in Abu Dhabi’s CBD and other dense areas during the course of the last two decades. Continued redevelopment to higher densities without an associated rise in parking supply has led to obvious shortages. The problem is not confined to insufficient supply, however; surface parking is congested and illegal parking frequent, while the underground parking supply developed in the last decade to meet the growing demand is underutilized. This chapter provides guidelines to establish parking requirements for new developments. The next section contains an overview of the parking situation in Abu Dhabi. This followed by a discussion of the parking rates to be used in CBD/high-density sectors as well as elsewhere in Abu Dhabi, and how to adjust for whether the parking is public or reserved for private users, in order to estimate the parking demand of the development. The chapter concludes with the procedures to be followed by developers in order to develop a parking plan that meets the estimated parking demand. 11.1. Overview Requiring new developments to meet the parking demands they generate is an essential step towards improving the parking situation in Abu Dhabi. The ongoing activities of Abu Dhabi Municipality and Town Planning to improve parking conditions in Abu Dhabi do not diminish the responsibility of new developments to provide adequate parking supply for their own needs. As new development occurs, parking problems will continue to get worse unless sufficient parking supply is provided for the new development. The practice of new development providing for its own parking needs is growing in Abu Dhabi, but it needs to become universal in order for the growth in parking shortfalls to be halted. 11.2. Parking Rates in Abu Dhabi The amount of parking required is a function of land use type. Retail land uses tend to have high ratios of parking per square meter of floors area, while residential and office land uses tend to have lower ratios. This section establishes procedures for determining appropriate parking rates for proposed new developments. 11.2.1. Parking Rates in CBD and High-Density Sectors In the CBD and other high-density areas in Abu Dhabi, one of the most common types of new development is in the form of high-rise buildings. A map of the areas delineating what is considered CBD/high density and what is considered low density is provided in Figure 11.1. These buildings often contain a mix of residential and/or commercial land uses (such as office, retail, and others such as medical and educational). There are no hard restrictions on the type of land use within a typical residential/commercial building in downtown Abu Dhabi. Land uses within a specific building may therefore change over time, as old tenants are replaced by new tenants (for example, apartments may be converted to offices).


68

Figure 11-1 Abu Dhabi CBD and High-Density Areas

SADIYAT

E48

W62

E25

E49

W50

HARBOUR

W53

W60

W57

E14

E36

W9

W51

W47

E17

W4

W52

E11

ALAK DHAR

W23_01

E3

W64

W35

E19_02

W30

W52_02

W48

E40

W65

FRE EZONE

W16

E41

W59_02

W66

W58

W31

W56

E4_02

E4_01

E22

W54

W59_01

E19

W4_01

W32

E28

W24_02

E12

W49

W11

E43E33

W8

E16

E21

E18_02

W14_02

E31E41_01

W14_01

E42

W21

E32W25W27_01

W22

E18_03

W20

W13_02

W13_01

E8

W26

E18_01

E13

W15_02

W39

E29

W15_01

E10

W29

E38

E35

E6

W33

E37

W67

E30

W3

E34_01

E38_01

W41

W27

E34_02

W23

W17_03

W18_01

E14_01

E1

E15

W18_03

W12

W28

E7

E26

W18_02

W17_01

W6

W17_02

W10

E9_02

E2

W2

E39

E5

W5

W37

E16_01

W19_02

W36

W69

W68

W52_01

W19_01

E20_01

E27

W46

E19_01

E22_02

E23

W28_01

W34

W24_01

W1

W46_02

E20_02

W7_01

W25_01

E24

W46_01

W52_03

E16_02

W40

W38

W45

W44

W43W42

E9_01

W7_02

E22_01

N

Other Areas

CBD/High DensityLegend

Within the CBD and high-density areas, public parking supply is generally available to all land uses on a shared basis. This allows a high turnover, since a given parking space is used at different times by different land uses (for example, the same space might be used by an office worker during the work day, a retail shopper in the evening, and a resident at night). Shared parking is therefore more efficient (needing fewer spaces to meet parking needs) than parking provided separately, and occurs due to the different temporal parking demand patterns of different land uses. A recent analysis of parking demand and supply in six sectors of Abu Dhabi’s CBD estimated that, on average, the demand for publicly available parking spaces equals approximately 4 spaces per thousand square meters of building space (1). Even for a downtown with shared parking, this parking rate estimate for Abu Dhabi is considered low in comparison with estimates for CBDs in cities in Western countries. This reflects the unique characteristics of downtown sectors in Abu Dhabi including:

• An unusually large proportion (more than 50 per cent in 2000) of downtown building space is residential, which typically has parking rates that are much lower per square meter than those of commercial land uses;

• Among downtown residents, automobile ownership is relatively low (approximately 0.9 vehicles per household);


69

• Walking, taxi and private transport modes, which do not generate demand for parking, constitute nearly 50 percent of trips.

11.2.2. Publicly Available Parking Supply vs. Reserved Parking

Supply in the CBD and High-Density Areas The parking rate of 4 spaces/1000 square meters of building space for mixed commercial developments in the CBD and high-density areas is based on the assumption that all parking spaces are available to all users, whether or not they travel to or from the new development. If, however, some or all of the parking spaces are reserved for patrons of the new development, then the parking rate to be used for estimating demand becomes significantly higher. The following discussion highlights the difference in parking space use between public and reserved or private spaces:

• When a parking space is reserved for a specific individual, that space is empty and unavailable for use at all times except when the individual has parked his/her vehicle in the space, so the space is removed from the parking supply whenever it is unoccupied. In a busy area such as downtown Abu Dhabi, a public parking space may experience a very high turnover, with five or even ten vehicles using a space during the course of a day. Thus, reserving parking spaces in areas of high demand and turnover results in empty parking spaces during times of peak demand, and constitutes a very inefficient use of scarce parking facilities when compared to public parking, and;

• The same argument applies when parking spaces are reserved for groups of individuals: the spaces are not a part of the public parking supply since only a select group of individuals are allowed to use them, and hence experience a limited turnover.

In consideration of these issues, determination of parking rates for developments using reserved parking shall be the same as for developments outside the CBD and high-density areas. For developments that propose a mix of reserved and publicly available parking spaces, the required parking rate shall be prorated based on the percentage of reserved and publicly available spaces proposed. For example, suppose a 10,000-square-meter commercial development is proposed in the CBD. Based on a parking rate of 4 spaces per thousand square meters, a total of 37 parking spaces would be required. Suppose further that the land use with the highest potential parking demand has a parking rate of 20 parking spaces per thousand square meters, and the applicant proposes to provide 70 percent reserved spaces and 30 percent publicly available spaces. The required number of parking spaces after considering reserved parking is determined by the following formula: Parking rate = 20 * 70% + 4 * 30 % = 15.2 spaces per thousand square meters.


70

When this parking rate is applied to the 10,000-square meter development, the resulting parking supply requirement is 151 parking spaces. Since each development is responsible for its own parking needs and the land uses within a mixed residential/commercial development may change over time, there is a possibility that the total parking demand of the development may increase over time as well. A periodic review of the building land uses should be performed to ensure that appropriate measures are taken in case the land use changes result in significant increases in the parking demand. 11.2.3. Parking Rates for All Other Developments A table or manual of parking rates by land use type does not currently exist that is specifically designed for Abu Dhabi. For this reason, it may be necessary to obtain parking rates from other sources and then to apply adjustments as appropriate to obtain representative parking rates for developments in Abu Dhabi. If, in the process of developing parking rates the applicant surveys existing land uses, whether in Abu Dhabi or elsewhere, then the results of those surveys are to be included in the documentation. The Roads Directorate will archive these survey results. As time progresses, the Roads Directorate will make the growing database of such survey results available to others as appropriate to assist them in developing parking rate estimates. Parking surveys conducted in Abu Dhabi will be reviewed by the Municipality and depending on the area and land uses covered, may be used to either adjust the existing mixed commercial parking rates for public parking in the CBD or to modify the single use parking rates. For low-density residential developments as well as commercial developments outside the CBD and high-density areas, parking rates may be determined from the following sources:

• Abu Dhabi Municipality Roadway Design Manual (2); • Dubai Municipality Trip Generation and Parking Rates Manual (3); and • ITE Parking Generation (4).

The first of these sources is for Abu Dhabi, but has parking rates for only a few land use types. Use of any particular set of rates, and possible adjustments to the rates, will need to be approved by the Municipality. An example of an adjustment may be the case for a regional mall located in the CBD. While the on-site parking facility is reserved for mall patrons, there may be a greater percentage of walk trips than with a typical suburban regional shopping center that is largely limited to vehicular access. If the argument can be made that some of these walk trips actually substitute for what would be vehicular trips in a suburban location, the parking rate for shopping centers from the Dubai Parking Generation may be reduced by an appropriate factor. A comparison of parking rates for these sources is given in Appendix B. These sources are to be used for single-type land uses. For mixed-use developments outside the CBD and high-density areas, the potential for shared parking exists. The applicant may propose a reduction in the total parking supply in these cases by


71

applying the procedures of the Urban Land Institute’s Shared Parking Demand for Selected Land Uses (5). 11.3. Parking Analysis Requirements A parking analysis will be required for every new development, regardless of size or magnitude of parking demand. This is necessary to ensure that no new development creates a new shortfall in parking supply. The degree of complexity in the analysis will be a function of the project being proposed and the approach to providing the necessary parking supply. In general, the parking analysis to be conducted can be separated into one of two types: meeting the parking rate requirement directly, and using surrounding parking supply for some or all of the required parking supply. 11.3.1. Simple Parking Analysis (Proposed Development Meets

Parking Requirements Directly) If an applicant proposes to provide sufficient parking supply to meet all of the parking demand generated by the proposed development, then the parking analysis can be as simple as a single table accompanied by diagrams illustrating existing parking spaces on the development site and the proposed parking facilities. The table would need to include the information shown in Table 11-1. Table 11-1 Format For Simple Parking Analysis Table

(a) (b) (c) (d) (e) (f) (g) (h)

Phase Description

of Land Use

Parking rate

Parking Spaces

Required for Proposed

Development

Total Parking Spaces

Provided by Proposed

Development

Parking Excess

(Shortfall)

Diagram of

Existing parking spaces

Diagram of proposed

development parking facilities

Use a separate row for each phase of the project

Square meters by land use type or number of residential units by type (see Section 6.1)

Spaces per 1,000 square meters or per residential unit (see Section 11.2)

Square meters x parking rate, by land use type, aggregated to total

Number of spaces to be provided as an element of the proposed development.

Column (e) minus column (d)

Yes/No Yes/No

As long as the information in the table indicates that the number of parking spaces provided by the new development meets or exceeds the development’s anticipated parking demand, the information in the table combined with the diagrams of the existing and proposed parking facilities will be sufficient. If the table does not indicate that sufficient parking supply is to be provided as a part of the proposed development, then a more complex parking analysis will be required as described below.


72

Parking facilities may include surface, underground, or above-ground facilities. All proposed parking facilities require review by the Roads Directorate for design, aesthetics and other considerations, including design, access, and circulation discussed in Chapter 10. Parking facilities provided by the development must meet the requirements of the Roadway Design Manual (1) and other design guidelines established by the Abu Dhabi Municipality and Town Planning Department and other agencies as appropriate. 11.3.2. Complex Parking Analysis (Proposed Development Does Not

Meet Parking Requirements Directly) If the proposed development does not include provision of sufficient parking supply, then a more complex parking analysis will be required that indicates how the remaining parking supply is to be provided. This parking analysis must include the elements described below. Current Parking Demand and Supply in Sector/Study Area For all proposed developments, a complete estimate of parking supply and demand within the appropriate parking analysis study area is to be conducted. The study area for the parking analysis is to be determined jointly with the Roads Directorate and documented in the Preliminary Plan. For developments within the CBD and high-density areas, the parking analysis study area may be as large as an entire sector, and may include parking facilities outside the sector, depending on the characteristics of the sector and the proposed development. The estimate of current parking supply is to be based on an inventory of existing publicly available parking spaces within the sector. Publicly available parking spaces include surface and structured parking that is available (free or paid) to all vehicles. Reserved parking, whether publicly or privately owned or managed, need not be included in this inventory. Parking spaces in areas that are currently under construction or otherwise temporarily unavailable to the public may be included in this inventory. The estimate of current parking demand is to be obtained through a survey of vehicles parked within the sector/study area. Since the objective is to find the maximum parking demand during the day, the survey may be limited to periods of high parking demand. Peak demand periods generally include the morning, evening, and night periods, and may include the afternoon period. Surveys might hence be conducted for up to four periods, and should include the number of vehicles parked (legally or illegally). For a particular study, the Consultant should submit the plan for the parking study, stating and justifying the number and start and end times of the survey periods. For example, the higher the proportion of residential floor space in a sector, the greater the likelihood that the peak demand will be observed during the night period, and the greater the need to include the night period in the survey. The Roads Directorate will maintain a file of recently conducted parking inventories and surveys, and will make them available to any applicant upon request. These recently conducted inventories and surveys may be used in the parking analysis if the survey is less than 12 months old at the time the Preliminary Plan is approved and if the Roads Directorate determines that they continue to be valid.


73

Future Year Baseline Parking Demand and Supply It is generally assumed that any new related developments that may occur within a parking analysis study area will provide for their own parking needs. It is therefore not necessary to conduct a thorough analysis of anticipated new developments within the study area and estimation of their parking impacts. It is important, however, to include in the analysis any known projects that may alter the number of public parking spaces within the study area. For example, if a new public parking structure is under construction, this may need to be included in the future year estimate of future year baseline parking demand and supply. Another example may be an approved development project that will be removing parking spaces within the study area and replacing them with reserved spaces unavailable to the public. These types of known changes are to be included in the estimate of future year baseline parking demand and supply. Once the estimates of future year baseline parking demand and supply are completed, an assessment of the overall study area excess or shortfall in parking supply is to be made. This assessment will be used to determine whether it is possible for the proposed new development to utilize any existing publicly available parking spaces in its parking plan. Project Parking Requirements A table similar to Table 11-1 is to be provided. The parking analysis must include an estimate of total parking rate requirements for the proposed development based on the proposed land uses and the appropriate parking rates for each use. The number of existing parking spaces removed by the proposed new development is also to be determined, and an overall estimate of the difference between parking spaces required and parking spaces provided by the proposed development is to be made. Parking Plan for the Proposed Development A parking plan is to be proposed for the development that indicates how the remaining parking spaces are to be provided. It is the responsibility of the applicant to demonstrate that all of the parking needs of the development can be met without creating or exacerbating a shortfall in publicly available parking supply in the parking analysis study area. Strategies to achieve the objective of the parking plan include:

• Utilization of excess publicly available parking supply within the study area;

• Sharing in the utilization of excess parking supply being provided by another development within the study area (requires agreement by the other developer);

• Implementation of programs to reduce parking demand for the development such as incentives/disincentives to encourage use of public transport or taxis, provision of private transport services, etc.;

• Participation in a joint public/private initiative to increase parking supply within the study area (such as a “parking district,” sector-level parking management plan, etc.); and

• Reducing the size of the proposed development.


74

11.4. References 1. Abu Dhabi Municipality and Town Planning, Abu Dhabi Master

Transportation Plan Technical Memorandum 2.2.9: Parking Policies and Standards, August 2001.

2. Abu Dhabi Municipality, Roadway Design Manual, Road Section, 1998. 3. Dubai Municipality, Trip Generation and Parking Rates Manual, 1999. 4. Institute of Transportation Engineers, Parking Generation, 1987. 5. Urban Land Institute, Shared Parking for Selected Land Uses, September

1983. 6. Abu Dhabi Transportation and Roads Improvement Program, De Leuw

Cather International, Abu Dhabi Parking Structure Program: Planning and Financial Analysis, May 1995.


75

12. FORMAT OF TRAFFIC IMPACT STUDY AND PARKING REQUIREMENT STUDY REPORT

The analysis described in the previous chapters must ultimately be summarized in a technical report for Municipality review and approval. This chapter describes features and structure of the report. 12.1. General Characteristics

The report should have an introduction and an executive summary. The report should be clear and concise. The level of detail of the report should

be sufficient to enable an experienced practitioner to be able to follow all stages and to end up with a similar set of results.

Bulky calculations and software output should be provided separately as an appendix. Since the volume of such output can quickly become very large, the consultant should establish after consultation with Municipality staff the level of detail to be included in the appendix, and whether some detailed additional information should only be provided in electronic format. All data, reports, analysis, and other material relevant to the study report must be submitted in electronic format.

The body of the report should supply key information without forcing the reader to refer to calculations or computer output.

A draft version should be submitted for Municipality review. Draft submissions are also required for any intermediate documents or products.

12.2. Structure of Report The report should contain the following sections. The chapters of these guidelines that provide necessary information relevant to the preparation of each section are listed in parentheses.

Executive Summary Introduction Analysis Parameters: Study Area and Key Facilities (3). Description of study

area within which development impacts will be analyzed, the key facilities and the definition of key analytical parameters such as the peak hours to be analyzed, the study horizon year(s), phasing if applicable. Key assumptions should be listed.

Existing Transportation and Traffic Conditions in Study Area (4). Description of existing conditions on surrounding transportation network.

Future Year Baseline Conditions (5): Traffic on surrounding network for Study Horizon Year(s) without the proposed development.

Trip Generation (6). Trips generated by development based on a detailed description of the land use and intensity.

Trip Distribution/ Mode Choice (7): Distribution of development-generated trips after or before applying relevant mode split model.

Assignment (7): Assignment of development-generated trips. Impact Analysis (8): Analysis of the development’s transportation impacts on

the surrounding transportation network, including the LOS of transportation


76

facilities, based on a comparison of the study area traffic flows with and without the proposed development.

Recommended Mitigation Plan (9): Recommended Improvements to the surrounding transportation network to mitigate development-generated impacts, including timing and phasing of the improvements.

Site Access and Circulation Plan (10), with phasing as applicable. Parking Plan (10, 11): Facilities (on-site and off-site as applicable) and

measures by which development-generated parking is met, with phasing as applicable.

Appendices: Should include all survey data as well as computations used in the analysis. To include traffic count data, survey data, LOS calculations and other analysis data, and pertinent excerpts from reports or documents used in the analysis.

12.3. References 1. Institute of Transportation Engineers, Traffic Access and Impact Studies

for Site Development, 1990.

2. The Institution of Highway & Transportation, Guidelines for Traffic Impact Assessment, 1994