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THE HIGHWAY SAFETY MANUAL

Michael S. GriffithFederal Highway AdministrationJuly 26th, 2004

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Growing Recognition …

Professionals do not have the needed tools to explicitly consider safety when making decisions related to highway facilities.

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What is the Highway Safety Manual (or HSM)?

• Purpose: to provide the best factual information and tools in a useful form to facilitate roadway planning, design, operations, and maintenance decisions based on explicit consideration of their safety consequences

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Targeted Users

• Primarily, analysts studying the impact of actions on roadway users– Planning, design and operations studies

• Secondary users– Management– Educational Institutions

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Research & Development• Relevant NCHRP efforts:

– NCHRP 17-18(4): HSM scoping study and development of prototype chapter on rural two-lane highways: Completed

– NCHRP Project 17-26: Development of Models for Prediction of Expected Safety Performance for Urban and Suburban Arterials: Started March 2003

– NCHRP 17-27: Prepare Parts I and II of the Highway Safety Manual – Started May 2004

– NCHRP 17-29: Safety Prediction Models for Rural Multilane Highways for Use in the Highway Safety Manual – Started May 2004

• Other efforts: SafetyAnalyst, IHSDM, and Human Factors Guide

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Resources

•Development of a Highway Safety Manual - Final Report, March 2004

•Development of a Highway Safety Manual – Research Results Digest, March 2004, Number 286

•Website – http://www.highwaysafetymanual.org/

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Outline for Initial Version of the HSM

Part I – Introduction and FundamentalsPart II – KnowledgePart III – Predictive MethodsPart IV – Safety Management of a

Roadway SystemPart V – Safety EvaluationGlossary

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Part I – Introduction and Fundamentals

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Part I - Chapter 1Introduction and Overview

1.1. Purpose1.2. Background on the Need for HSM1.3. Scope of the HSM1.4. Intended Audience1.5. Intended Use of the HSM1.6. Context for the HSM: Use and

Misuse of the Manual1.7. Nature of the HSM1.8. Organization of HSM

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Part I - Chapter 2Fundamentals

2.1. What is Safety?2.2. How Road Safety is Measured?2.3. Effect of Traffic Volume & Vehicle Mix 2.4. Safety Performance Functions and

Crash Modification Factors2.5. Human Factors in Road Safety2.6. Speed and Safety

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Part II - Knowledge

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Part II - Chapter 3Roadway Segments

3.1. Safety Effects of Highway Design Elements

3.2. Safety Effects of Traffic Control andOperational Elements

3.3. Pedestrian and Bicycle Safety on Roadway Segments

3.4. Safety Effects of Other Elements

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Part II - Chapter 4Intersections

4.1. Safety Effects of Intersection Design Elements

4.2. Safety Effects of Intersection Traffic Control and Other Operational Elements

4.3. Safety Effects of Other Intersection Related Features

4.4 Pedestrian and Bicycle Safety atIntersections

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Part II - Chapter 5Interchanges

5.1. Safety Effects of Interchange Design Elements

5.2. Safety Effects of Traffic Control and Operations Elements

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Part II - Chapter 6Special Facilities and Geometric

Situations6.1. Railroad-Highway Grade Crossings6.2. Construction and Maintenance

Work Zone Areas

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Part II - Chapter 7Road Networks

7.1. Introduction7.2. Safety in Transportation Network

Planning7.3. Safety in the Planning and Design of

Residential Neighborhoods and Commercial Areas

7.4. One-Way Systems and Turn Restrictions 7.5. Safety in Traffic Calming 7.6. Access Management7.7. Road-use Culture

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Part III – Predictive Methods

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Part III - Chapter 8Rural, Two-Lane Roads

8.1. Introduction8.2. Methodology8.3. Applications8.4. Example Problems8.5. References

Appendices

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Prototype Chapter 8 - Overview

• Scope: Estimates the safety performance of a rural two-lane highway segments and at-grade intersections

• Applications– Individual segments and intersections– Overall project

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Prototype Chapter 8 - Overview

• Explicitly Considers:– Roadway Segments (ADT, lane & shoulder

width, shoulder type, horizontal curvature, grade, driveways, and roadside design)

– Intersections (type of control, number of approach lanes & volume, sight distance, skew angle, and turn lanes)

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Part III - Chapter 9Rural, Multi-Lane Highways

9.1. Introduction9.2. Methodology9.3. Applications 9.4. Safety Issues Not Explicitly addressed by

the Methodology9.5. Example Problems9.6. References

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Part III - Chapter 10Urban/Suburban Arterial Highways

10.1. Introduction10.2. Methodology10.3. Application10.4. Safety Issues Not Explicitly addressed

by the Methodology10.5. Example Problems10.6. References

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Part IV – Safety Management of a Roadway System

• Chapter 11. Identification of Sites with Promise

• Chapter 12. Diagnosis of the Nature of Safety Problems at Specific Sites

• Chapter 13. Selection of Countermeasures to Reduce Accident Frequency and Severity at Specific Sites

• Chapter 14. Economic Appraisal of all Sites under Consideration

• Chapter 15. Prioritized Rankings of Improvement Projects

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Part V – Safety Evaluation

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Part V - Chapter 16Safety Evaluation of Implemented

Measures16.1. Introduction16.2. Why Evaluate?16.3. Data Needs and Limitations16.4. Approach to Conducting A Valid

Evaluation

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When available?

• First edition expected to be released in 2007 or 2008.

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Data Requirements for HSM

•Data Requirements Guide will be developed.

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Requirements

R = Data is Required and there is no default value (the process would be incomplete without the user entering the data).

RD = Data is Required and there is a Default Value if the user does not enter the data.

O = Data is used by the process if available but is Optional.

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Basic Data Needs

•Crash

•Roadway

•Traffic

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Prototype Chapter (Rural, Two-Lane Roads)

Crash Data

Traffic Data

Roadway Data

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Crash Data - Required

•Crash History Data

Frequency and Severity Data by Location and by Year

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Traffic Data - Required

Average Daily Traffic by location

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Roadway Data – Horizontal Data ElementsTangentSimple CurveSpiral CurveDeflectionHeading CoordinateStation Equation

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Roadway Data – Vertical

Data Elements

Vertical Point of IntersectionElevationTangentCurve

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Roadway Data – Cross Section

Data Elements

Pavement (Cross Slope)Shoulder (Width and Type)

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Roadway Data – Lane Group

Data Elements

ThruPassingTurnTwo-way left-turnClimb

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Roadway Data – Roadside Group

Data Elements

Driveway Density

Hazard Rating

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Intersection DataTraffic ControlNumber of LegsIntersection Sight DistanceNumber of approach lanes & volumeTurn lanesSkew angle