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FHWA Home / Safety / Road Diets (Roadway Reconfiguration) / Road Diet Policies


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Expanding Beyond a Single Implementation

Road Diets reallocate travel lanes and utilize the space for other uses and travel modes. The most common type of Road Diet reduces the number of through lanes from four to two and adds a center two-way leftturn lane (TWLTL). Other uses for the reallocated space include

Example of a Road Diet
Two side-by-side illustrations of the design of the four-lane before configuration and the design of the road diet featuring a single travel lane in each direction, a two-way left turn lane, and a wide shoulder to allow bicycles or parallel parking, if desired.

Aerial photo of a road diet in which two travel lanes are divided by a combination of painted lines and medians that serve as pedestrian refuges. To the left, a line of transit buses occupies a converted travel lane closest to the curb, and to the right is a row of parallel parked cars to the right of the travel lane. Source: New York City Department of Transportation.
A painted center median with left-turn bays and pedestrian safety islands were installed along Luten Avenue from Amboy Road to Hylan Boulevard to calm traffic and enhance safety for all road users

A pedestrian shelter is located on a raised median separating the travel lanes, where a bus is pulling up to load passengers, from a bike lane.
This roadway configuration, incorporating a protected bike lane and a raised bus stop, could be achieved by implementing a Road Diet

This document describes the benefits and highlights real-world examples of agencies including Road Diets within new or revised transportation policies and guidance.

Policy Benefits

A single Road Diet project can yield numerous safety, operational, and multimodal benefits. Additionally, developing Road Diet-related policies and guidance – and therefore encouraging implementation on a large scale – can result in widespread advantages:

Improve Safety. Increasing Road Diet implementation can translate to more lives saved. An FHWA study1 found that converting a road from four to two though lanes with a center TWLTL can reduce overall crashes by 19 to 47 percent.

Save Time. Agency-standardized guidance or policy allows engineers to use an approved Road Diet template, framework, or set of design criteria that can jumpstart the design and implementation process. Non-standardized or "first time" designs tend to require more levels of management scrutiny and approval.

Save Money. Road Diets are already a relatively inexpensive countermeasure, but incorporating them into policies can provide the foundation for combining Road Diets with other efforts (e.g., resurfacing) to reduce costs further.

Increase Multimodal Use. Road Diets can raise property values and improve the "livability" of an area by reallocating space for bicycle or pedestrian facilities along a corridor. Systemic or wide-spread Road Diet implementation can create safer and more convenient pedestrian and bicyclist transportation networks.

Facilitate Public Acceptance. A Road Diet policy can build public confidence in the treatment. Such documentation can set a foundation for communication between the agency and the public and convey the Road Diet's benefits.

Examples of Road Diet Policies and Guidance

Many agencies across the United States have already incorporated Road Diets into their policies and guidance documents. Some developed standalone Road Diet documentation, while others chose to incorporate Road Diets into broader, pre-existing policies. The following sections provide examples of different types of Road Diet policy integration:

Standalone Policies

Standalone policies turn Road Diets into one of an agency's first-tier solutions. The following resources are examples of standalone Road Diet policies and guidance documents developed by State and local agencies.

Florida Department of Transportation's (FDOT) Statewide Lane Elimination Guidance2, 3, provides Road Diet and space reallocation guidance (referred to as lane eliminating). These documents include examples and impacts of Road Diets in Florida, a description of FDOT's Road Diet review process, and a discussion of issues associated with the improvement.

Maine Department of Transportation's (MaineDOT) Guidelines to Implement a Road Diet or Other Features Involving Traffic Calming4 provides Road Diet guidance for Maine municipalities. The document includes a brief overview of the treatment, Maine specific implementation guidance, an overview of the countermeasure's limitations, and a list of minimum study requirements.

Michigan Department of Transportation's (MDOT) Road Diet Checklist5 is a step-by-step list used by agency personnel when considering a Road Diet's appropriateness and applicability in a given situation.

St. Louis County's (Missouri) Road Diet Policy6 provides factors to consider when determining if a Road Diet is feasible for a location, including average weekly traffic (AWT) volumes, directional peak hour volumes, left turns, intersection impacts, alternate bypass routes, bus transit, bicyclists, and pedestrians.

Incorporating Road Diets into Existing Agency Plans and Practices

Including Road Diets into an agency's Strategic Highway Safety Plan (SHSP), overall transportation planning process, or design guidance distinguishes the countermeasure as a broader safety improvement strategy. The following are examples of how States have incorporated Road Diets into agency plans, guidance and practices.

Road Diets in Strategic Highway Safety Plans

Every Move You Make: Toward Zero Deaths
Source: Ohio Department of Transportation

Strategic Highway Safety Plans (SHSPs) can facilitate and promote Road Diets within an agency by incorporating the treatment into the agency's safety improvement approach. Several States refer directly to Road Diets in their SHSPs while others use a different name for the same improvement, including:

The table below lists State SHSPs that include Road Diets, the alternate terminology used, and the SHSP emphasis or focus area where it is discussed. All States' SHSPs can be found on FHWA's Office of Safety website.7

Table 1: Road Diets in SHSPs
State Terminology Emphasis or Focus Area
Alabama Lane Conversion Highways
Arkansas Road Diet Bicyclists, Pedestrians
District of Columbia Road Narrowing Pedestrian
Idaho Lane Narrowing Intersection
Michigan Lane Conversion Intersection
Minnesota Road Diet Bicyclists, Pedestrians
Missouri Lane Narrowing Intersection
New Jersey Road Diet Lane Departures, Bicyclists, Pedestrians
Ohio Road Diet Bicyclists, Pedestrians
Rhode Island Road Diet Achievements
South Dakota Road Diet Intersections
Washington Road Diet Bicyclists

Incorporating Road Diets into Planning Processes and Design Guidance

Many State and local agencies incorporate Road Diets into broader polices and guidance like design manuals, Complete Street plans, bicycle and pedestrian plans, or speed management and traffic calming plans. The legend below indicates the types of plans in which agencies have incorporated Road Diets for the following examples.

Legend: Design guide, Complete Streets, Bicycle, Pedestrian, Traffic Calming.

American Association of State Highway and Transportation Officials' (AASHTO) Guide for the Development of Bicycle Facilities, 4th Edition8 provides information on how to accommodate bicycle travel and operations in most riding environments. Road Diets are one of the solutions that the guide recommends to expand a bicycle network and it contains several pages about this countermeasure. The guide presents sound guidelines enabling agencies to meet the needs of bicyclists and other highway users.

Complete Streets, Bicycle, Pedestrian
Charlotte (North Carolina) Department of Transportation's (CDOT) Urban Street Design Guidelines9 contain guidance for designing complete streets in urban and suburban environments with the goal of providing mobility for motorists while improving the safety and comfort of pedestrians, cyclists, and neighborhood residents. Road Diets are one of the tools that CDOT uses to accomplish this goal. Information and high-level guidance about implementing Road Diets is included within the USDG's glossary, and design details that can be used to define resulting cross-sections are found in Chapter 4.

Chicago Department of Transportation's (CDOT) Streets for Cycling Plan 202010 outlines the city's plan to install 100 miles of separated bike lanes that are comfortable for people of all ages and abilities, using Road Diets as a primary tool to meet this goal.

Complete Streets, Bicycle, Pedestrian, Traffic Calming.
University of Delaware Institute for Public Administration's Complete Streets in Delaware: A Guide for Local Governments11 references Road Diets as a roadway-narrowing treatment. It is one of the tools that Delaware's Department of Transportation (DelDOT) recommends local governments use to calm traffic, increase pedestrian safety, and add space for bicyclists.

Children and an adult bicycling in a dedicated bicycle lane in a downtown area. Source: PeopleForBikes          Children using a dedicated bicycle crossing to the left of a pedestrian crosswalk at an intersection. Source: PeopleForBikes

Bicycle, Pedestrian
Evansville (Indiana) Metropolitan Planning Organization's Bicycle and Pedestrian Connectivity Master Plan12 outlines a vision for walking and bicycling within the city and recommends Road Diets as a tool to accomplish this goal. The plan discusses Road Diet's operational and safety benefits and recommends city roads that would be good candidates for Road Diets.
Complete Streets, Bicycle, Pedestrian
Genesee County Metropolitan Planning Commission's (GCMPC) Complete Streets Program13 uses a systemic approach to assess every four-lane road within GCMPC's jurisdiction with ADTs under 20,000. Roads with under 10,000 ADT are likely candidates for a Road Diet, while roads with 10,000 – 20,000 ADT may be good candidates, but require further study to make a determination. Level of Service (LOS) is used to determine on a 1 to 4 scale whether a road segment is suitable for four-to-three lane conversion.
Design guide, Complete Streets, Bicycle, Pedestrian, Traffic Calming
Los Angeles County's (California) Design Manual for Living Streets14 recommends Road Diets as a solution for calming traffic, improving pedestrian safety at crossings, adding space for bicyclists, and accommodating large volumes of mid-block left-turning vehicles. It also provides maximum ADT recommendations..

Aerial view of an intersection in which two crosswalks cross a road diet. The far crosswalk features a pedestrian refuge. Beyond the refuge yellow lines close off the central area between the two through lanes. Dedicated lanes for parallel parking is available in both directions.          Diagram depicts two horizontal cutaways of a roadway, the first before the road diet implementation, and the second an after depiction of the repurposed roadway. In the before cutaway, from left to right, are an 8-foot pedestrian path, an 8-foot parallel parking lane, four 12-foot travel lanes (two in each direction), another 8-foot parallel parking lane, and an 8-foot pedestrian path. In the after cutaway, also from left to right, are a 10-foot  pedestrian path, an 8-foot parallel parking lane, a 5-foot dedicated bike lane, an 11-foot travel lane, a 12-foot two way left turn lane broken up by medians, an 11-foot travel lane, a 5-foot bike lane, an 8-foot parallel parking lane, and a 10-foot pedestrian path.

Bicycle, Pedestrian
Minnesota Department of Transportation's Best Practices for Pedestrian-Bicycle Safety (2013)15 presents Road Diets as a solution to more safely accommodate pedestrians and bicyclists on roadways. The document provides Road Diet-related guidance related to ADT, typical construction costs, associated crash reduction rates, and common design features.
Design guide, Complete Streets, Bicycle, Pedestrian, Traffic Calming.
New York City Department of Transportation's Street Design Manual16 recommends Road Diets (referred to as lane narrowing and lane removal) as solutions for calming traffic, adding space for bicycle lanes, improving pedestrian safety at crossings, installing extra parking, and assigning turn lanes. The manual discusses benefits, considerations, appropriate applications, and design guidelines for Road Diets.
Complete Streets, Bicycle, Pedestrian.
New York Department of Transportation's Complete Streets Planning Checklist17 helps determine Road Diet applicability for four-lane undivided urban or suburban roads with annual average daily traffic (AADT) less than 15,000.
Design Guide
Ohio Department of Transportation's (ODOT) Location and Design Manual, Volume 1: Roadway Design18 serves as an example of how Road Diets can be incorporated into a DOT's design standards. Road Diet guidance is discussed in Section 300: Cross Section Design.
Design Guide, Traffic Calming
Pennsylvania Department of Transportation's Traffic Calming Handbook19 proposes lane narrowing as a traffic calming countermeasure and highlights its effectiveness at reducing motor vehicle speeds.
Salisbury's (North Carolina) Comprehensive Bicycle Plan20 recommends Road Diets as an effective solution for expanding the city's bicycle lane network. The document describes a Road Diet, outlines its benefits, proposes a potential geometric configuration, and identifies city roads where the treatment can be applied.
Seattle Department of Transportation's (SDOT) Pedestrian Master Plan21 considers Road Diets as one of the tools in their Pedestrian Design and Engineering toolbox. SDOT is currently updating their plan, but information about it can be found on SDOT's website. SDOT also developed a flow chart for considering Road Diet conversion feasibility.

Road Diet featuring wide pedestrian refuge islands on Ninth Avenue, Manhattan, NY. Source: NYCDOT.
Road Diet on Ninth Avenue, Manhattan, NY.
Road Diet with dedicated bike lanes and on-street parking on Nickerson Street, Seattle, WA. Source: Brian Chandler
Road Diet on Nickerson Street, Seattle, WA.

Incorporating Road Diets into Resurfacing

A roadway in the before configuration featuring two wide through lanes divided by a center double yellow line. Source: Randy Dittberner, VDOT
Resurfaced roadway prior to lane marking. Source: Richard Retting
Resurfaced and marked roadway with a road diet configuration featuring  a two-way left-turn lane, a dedicated bike lane, and parallel parking. Source: Randy Dittberner, VDOT
Resurfacing Project Incorporating Road Diets in Oak St., Merrifield, VA

Incorporating Road Diets into resurfacing efforts can significantly reduce costs associated with the treatment. When a Road Diet includes shifting pavement markings within the existing right-of-way during a resurfacing project, internal planning and design costs are the only expenses incurred. Consequently, some State and local agencies have incorporated Road Diets into their routine review of all roads scheduled for repaving.

City of Oakland's Checklist for Complete Streets / Paving Project Coordination22 is completed for each roadway segment proposed for paving. Road Diets are one of the main elements considered on the checklist.

Rhode Island DOT23 recognized that during resurfacing and restriping, there would be no additional cost to alter pavement markings within the existing right-of-way to incorporate a Road Diet. They now plan their Road Diet installations as part of the overlay.

Seattle DOT24 monitors the city's resurfacing projects to see whether streets scheduled for upcoming roadway overlay projects are good candidates for Road Diets.

Virginia DOT's Northern District25 considers roads that are scheduled for repaving as opportunities to reallocate road space for bicycle lanes and other purposes before new pavement markings are installed.

Federal Highway Administration's (FHWA) Workbook for Building On-Road Bike Networks through Routine Resurfacing Programs26 assists communities in jump-starting their bicycle network development by utilizing Road Diets and capturing space reallocation opportunities as part of routine resurfacing.

Road Diet Guidance Research and Development

A few State DOTs have either conducted research or partnered with universities to further their Road Diet policy development. Iowa, Kentucky, and Michigan DOTs used the findings from State-specific Road Diet studies to improve Road Diet guidance within their respective agencies.

Michigan State University's Safety and Operational Analysis of 4-lane to 3-lane Conversions (Road Diets) (2012)27 was developed for the Michigan Department of Transportation. The study examines the safety- and delay-related impacts of Road Diet conversions in Michigan. It includes guidelines for determining Road Diet feasibility based on ADT and peak hour volume. The study found that four- to three-lane Road Diet conversions could cause delays on roads with ADTs greater than 10,000 and peak hour volumes over 1,000. In almost all instances, crashes reduced after the Road Diet was implemented. This enabled researchers to develop a Michigan-specific Road Diet crash modification factor (CMF).

University of Kentucky's Guidelines for Road Diet Conversion (2011)28 was developed for the Kentucky Transportation Cabinet. The study focused on evaluating and comparing the operation of three- and four-lane roads at signalized intersections. Out of the four Road Diets studied, three demonstrated a safety improvement. Based on this and other findings, the researchers developed operational and safety guidance targeted at helping agencies determine when a Road Diet conversion is appropriate, and increased their recommended maximum ADT threshold from 17,000 to 23,000. The guidance also provides suggested cross-section designs, recommendations for designing the transition to and from a Road Diet configuration, and a flow chart for determining appropriate implementation actions.

Iowa State University's Guidelines for the Conversion of Urban Four-Lane Undivided Roadways to Three-Lane Two-way Left-Turn Lane Facilities (2001)29 was developed for the Iowa Department of Transportation. During the study, researchers summarized previous research on Road Diet conversions located both throughout the United States and in Iowa, analyzed the operational impacts along an idealized conversion corridor, and provided guidelines for Road Diet conversion feasibility. Before-and-after crash results indicated that four- to three-lane Road Diets can increase safety without yielding a reduction in LOS. Based on the analysis, the researchers developed feasibility determination factors including roadway function, traffic volume, and LOS.

Additional Information

For more information about any of these resources or for technical assistance related to Road Diets, please contact FHWA's Road Diet Program Manager:

Rebecca Crowe
FHWA Office of Safety
(202) 507-3699

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1 FHWA "Evaluation of Lane Reduction 'Road Diet' Measures on Crashes." FHWA Report No. FHWA-HRT-10-053. (Washington, D.C: 2010) [ Return to note 1. ]

2 Florida Department of Transportation, Phase 1: Resource Document – Statewide Lane Elimination Guidance, February 2014. Available at: http://www.dot.state.fl.us/rddesign/CSI/Files/Lane-Elimination-Guide-Part1.pdf. [ Return to note 2. ]

3 Florida Department of Transportation, Statewide Lane Elimination Guidance, December 2014. Available at: http://www.dot.state.fl.us/rddesign/CSI/Files/Lane- Elimination-Guide-Part2.pdf [ Return to note 3. ]

4 Maine Department of Transportation, Guidelines to Implement a Road Diet or Other Features Involving Traffic Calming, April 2016. Available at: http://safety.fhwa.dot.gov/road_diets/guidance/docs/maineDOTroad_diet.pdf [ Return to note 4. ]

5 Michigan Department of Transportation, "Road Diet Checklist," MDOT 1629 (02/15). Available at: http://safety.fhwa.dot.gov/road_diets/guidance/docs/mdot_chklist.pdf. [ Return to note 5. ]

6 St. Louis County, MO, Department of Transportation, "St. Louis County Road Diet Policy," (St. Louis County, MO: September 2015). Available at: https://www.stlouisco.com/Portals/8/docs/document%20library/highways/publications/Road_Diet_Policy.pdf. [ Return to note 6. ]

7 FHWA. Office of Safety, "Web-links to State SHSPs" web page. Available at: http://safety.fhwa.dot.gov/hsip/shsp/state_links.cfm [ Return to note 7. ]

8 AASHTO, Guide for the Development of Bicycle Facilities, 4th Edition (Washington, DC: 2012). This publication is available for purchase at: https://bookstore.transportation.org/item_details.aspx?ID=1943 or 1-800-231-3475. [ Return to note 8. ]

9 Charlotte Department of Transportation, Urban Street Design Guidelines, adopted October 22, 2007. Available at: http://charmeck.org/city/charlotte/Transportation/PlansProjects/pages/urban%20street%20design%20guidelines.aspx. [ Return to note 9. ]

10 Chicago Department of Transportation, Chicago Streets for Cycling Plan 2020 (n.d.). Available at: http://www.cityofchicago.org/content/dam/city/depts/cdot/bike/general/ChicagoStreetsforCycling2020.pdf. [ Return to note 10. ]

11 Scott, Beck, Rabidou. Complete Streets in Delaware: A Guide for Local Governments. (Newark, DE: University of Delaware Institute for Public Administration), prepared for the Delaware Department of Transportation. Available at: http://www.ipa.udel.edu/publications/CompleteStreetsGuide-web.pdf. [ Return to note 11. ]

12 City of Evansville, Indiana and the Evansville Metropolitan Plannng Organization, Evansville, Indiana Bicycle and Pedestrian Connectivity Master Plan (n.d.). Available at: http://www.evansvillempo.com/Docs/BikePed/Evansville_BPCMP_Final_Plan.pdf. [ Return to note 12. ]

13 Genessee County Metropolitan Planning Commission, Genesee County Complete Streets Technical Report (n.d.). Available at: http://gcmpc.org/wp-content/uploads/pdf/Complete_Streets/Complete_Streets_Technical_Report_Approved_withAppendix.pdf. [ Return to note 13. ]

14 Los Angeles County, Model Design Manual for Living Streets (Los Angeles County: December 2011), funded by the Department of Health and Human Services through the Los Angeles County Department of Public Health and the UCLA Luskin Center for Innovation. Available at: http://modelstreetdesignmanual.com/ model_street_design_manual.pdf. [ Return to note 14. ]

15 MnDOT Office of Traffic, Safety and Technology, Minnesota's Best Practices for Pedestrian/Bicycle Safety, Report No. 2013-22 (September 2013). Available at: http://www.dot.state.mn.us/stateaid/trafficsafety/reference/ped-bike-handbook-09.18.2013-v1.pdf. [ Return to note 15. ]

16 New York City Department of Transportation, Street Design Manual, Updated 2nd Edition, (New York: January 2016). Available at: http://www.nyc.gov/html/dot/downloads/pdf/nycdot-streetdesignmanual-interior-lores.pdf. [ Return to note 16. ]

17 New York Department of Transportation, Engineering Division, Office of Design, Highway Design Manual, "Chapter 18, Appendix A - Capital Projects Complete Streets Checklist (18a-2)" (New York: 2015). Available at: https://www.dot.ny.gov/divisions/engineering/design/dqab/hdm/hdm-repository/chapt_18a.pdf [ Return to note 17. ]

18 Ohio Department of Transportation, Location & Design Manual Volume 1, "300 Cross Section Design," (Columbus, OH: January 2016). Available at: http://www.dot.state.oh.us/Divisions/Engineering/Roadway/DesignStandards/roadway/ Location%20and%20Design%20Manual/ Section_300_Jan_2016.pdf. [ Return to note 18. ]

19 Pennsylvania Department of Transportation, Pennsylvania's Traffic Calming Handbook, Publication No. 383 (July 2012). Available at: http://www.dot.state.pa.us/public/PubsForms/Publications/PUB%20383.pdf. [ Return to note 19. ]

20 City of Salisbury Department of Land Management and Development and the NCDOT Divison of Bicycle and Pedestrian Transportation, Salisbury Comprehensive Bicycle Plan, (Salisbury, NC: July 2009). Available at: http://www.salisburync.gov/Departments/CommunityPlanning/DevelopmentServices/ Documents/ SalBikePlan_FINALSUBMITTAL.pdf. [ Return to note 20. ]

21 Seattle Department of Transportation, "Road Diets", Seattle.gov. Accessed May 2016. Available at: http://www.seattle.gov/transportation/pedestrian_masterplan/pedestrian_toolbox/tools_deua_diets.htm. [ Return to note 21. ]

22 City of Oakland, City of Oakland Checklist for Complete Streets / Paving Project Coordination (unpublished). Available at: http://safety.fhwa.dot.gov/road_diets/guidance/docs/oakland_chklist.pdf. [ Return to note 22. ]

23 For additional details and information, please contact Sean Raymond, Sean.Raymond@dot.ri.gov. [ Return to note 23. ]

24 For additional details and information, please contact Dongho Chang, Dongho.Chang@seattle.gov. [ Return to note 24. ]

25 For additional details and information, please contact Randy Dittberner, Randy.Dittberner@VDOT.Virginia.gov. [ Return to note 25. ]

26 Federal Highway Administration, Incorporating On-Road Bicycle Networks into Resurfacing Projects, FHWA-HEP-16-025 (Washington, DC: 2016). Available at: https://www.fhwa.dot.gov/environment/bicycle_pedestrian/publications/resurfacing/resurfacing_workbook.pdf. [ Return to note 26. ]

27 Lyles, R. W. , Safety and Operational Analysis of 4-Lane to 3-Lane Conversions (Road Diets) in Michigan, Michigan State University, RC-1555 (Lansing, MI: 2012). Available at: http://nacto.org/wp-content/uploads/2015/04/safety_and_operation_analysis_lyles.pdf. [ Return to note 27. ]

28 Stamatiadis, N. Guidelines for Road Diet Conversions, University of Kentucky, KTC-11-19/SPR-415-11-1F (Lexington, KY: November 2011). Available at: http://www.ktc.uky.edu/files/2012/06/KTC_11_19_SPR_11_415_1F.pdf. [ Return to note 28. ]

29 Knapp, K. K., et al. , Guidelines for the Conversion of Urban Four-lane Undivided Roadways to Three-lane Two-way Left-turn Lane Facilities, Center for Transportation Research and Education, CTRE Management Project 99-54 (Ames, IA: 2001). Available at: http://www.ctre.iastate.edu/reports/4to3lane.pdf. [ Return to note 29. ]

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March 2016


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