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FHWA Home / Safety / Road Diets (Roadway Reconfiguration) / Road Diet Informational Guide

Road Diet Informational Guide

FHWA Safety Program

Office of Safety logo: Safe roads for a safer future - investment in roadway safety saves lives.

November 2014

Contact: Rebecca Crowe at rebecca.crowe@dot.gov, 202-507-3699

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Table of Contents

[ Technical Report Documentation Page ] [ Acknowledgements ] [ Acronyms ]

Executive Summary

1 Introduction

1.1. What is a Road Diet?

1.2 History of Road Diets

1.2.1 History of Road Diet Installations
1.2.2 History of Road Diet Safety Evaluations

1.3 Purpose and Objectives of the Informational Guide

1.4 Organization of the Guide

2 Why Consider a Road Diet?

2.1 Benefits of Road Diets
2.1.1 Improved Safety
2.1.2 Operational Benefits
2.1.3 Pedestrian and Bicyclist Benefits
2.1.4 Livability Benefits
2.2 Synergies and Trade-offs

3 Road Diet Feasibility Determination

3.1 Safety Factors

3.2 Context Sensitive Solutions and Complete Streets

3.3 Operational Factors

3.3.1 De Facto Three-Lane Roadway Operation
3.3.2 Speed
3.3.3 Level of Service (LOS)
3.3.4 Quality of Service
3.3.5 Average Daily Traffic (ADT)
3.3.6 Peak Hour and Peak Direction
3.3.7 Turning Volumes and Patterns
3.3.8 Frequently Stopping and Slow-Moving Vehicles

3.4 Bicycles, Pedestrians, Transit, and Freight

3.4.1 Bicycle Considerations
3.4.2 Pedestrian Considerations
3.4.3 Transit Considerations
3.4.4 Freight Considerations

3.5 Other Feasibility Determination Factors

3.5.1 Right-of-Way Availability and Cost
3.5.2 Parallel Roadways
3.5.3 Parallel Parking
3.5.4 At-Grade Railroad Crossings
3.5.5 Public Outreach, Public Relations, and Political Considerations

3.6 Case Studies: Feasibility Determination Decision-making

3.7 Funding Road Diets

4 Designing a Road Diet

4.1 Geometric Design

4.1.1 Road Function and Context
4.1.2 Design Controls
4.1.3 Elements of Design
4.1.4 Cross Sectional Elements
4.1.5 Intersection Design

4.2 Operational Design

4.2.1 Cross-Section Allocation
4.2.2 Crossing Pedestrians
4.2.3 Intersection Control Changes
4.2.4 Pavement Marking and Signing
4.2.5 Intersection Design Elements

5 Determining if the Road Diet is Effective

5.1 Safety Analysis of a Road Diet

5.1.1 Data Needs
5.1.2 Observational Before-and-After Studies of Road Diets
5.1.3 Surrogate Measures of Safety for Road Diets

5.2 Operational Analysis

5.2.1 Analyzing Vehicle Operations
5.2.2 Non-Motorized Operations
5.2.3 Tools and Methods to Evaluate Impacts

6 Conclusion

Appendix A – Road Diet Safety Assessment Studies

Appendix B – Feasibility Determination Factors, Characteristics, and Sample Evaluative Questions


List of Figures

Figure 1. Road Diet

Figure 2. Typical Road Diet Basic Design

Figure 3. Focus of Each Informational Guide Chapter

Figure 4. Mid-Block Conflict Points for Four-Lane Undivided Roadway and Three-Lane Cross Section

Figure 5. Crossing and Through Traffic Conflict Points at Intersections for a Four-Lane Undivided Roadway and a Three-Lane Cross Section

Figure 6. Major-Street Left-Turn Sight Distance for Four-Lane Undivided Roadway and Three-Lane Cross Section

Figure 7. Addition of a Bike Lane Creates a Buffer between Pedestrians and Moving Vehicles

Figure 8. Mid-block Pedestrian Refuge Island

Figure 9. Pedestrian Refuge Island on a Road Diet Corridor in Chicago

Figure 10. Road Diet in Flint, Michigan, Central Business District

Figure 11. Four-lane Undivided Roadway Intersection Operating as a de facto Three-lane Cross Section

Figure 12. Road Diet Implementation Maximum Volume Thresholds by Agency

Figure 13. Bus Loading Zone in Seattle, Washington

Figure 14. Buffered Bicycle Lanes on Wabash Avenue in Chicago

Figure 15. Pedestrians Buffered from Traffic in Reston, VA

Figure 16. 55th Street in Chicago: Transit and Bicycles Share an Area at the Intersection (left); Transit Stop and Bicycle Lane (right)

Figure 17. City of Seattle Modeling Flow Chart for Road Diet Feasibility Determination

Figure 18. Painted Buffer Between Through Lane and Bicycle Lane in Lansing, Michigan

Figure 19. Bicycle Lane on Rural 3-Lane Section, Lawyers Road, Reston, VA

Figure 20. Typical Bike Lane Illustration

Figure 21. Paired Parking Cross Sections (Adapted from AASHTO)

Figure 22. Example Parking Lane Transition at Intersection (Adapted from AASHTO, 2011)

Figure 23. Transition from 3-lane to 2-lane Cross Section, Oak Street, Merrifield, VA

Figure 24. Offset Driveways Causing Conflict Points in the TWLTL

List of Tables

Table 1. Problems Potentially Correctable by Road Diet Implementation

Table 2. Practitioner Interview Results Summary: Road Diet Installation Observations

Table 3. Road Diet Implementation Considerations by Agency

Table 4. Quantifiable Characteristics of Land User Contexts (NJDOT & PennDOT, 2008)

Table 5. Regional Arterial Design Matrix (NJDOT & PennDOT, 2008)

Table 6. Maximum Allowable Travel Distance in TWLTL

For More Information:
For more information, visit http://safety.fhwa.dot.gov/

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Page last modified on November 24, 2014
Safe Roads for a Safer Future - Investment in roadway safety saves lives
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