USA Banner

Official US Government Icon

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure Site Icon

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation
FHWA Highway Safety Programs

3. Feasibility Determination

While Road Diets can improve safety and accommodate motorized and non-motorized transportation modes along a corridor, they may not be appropriate or feasible in all locations. There are many factors to consider before implementing a Road Diet. Agencies should consider the objective of the Road Diet, which could be one or more of the following:

  • Improve safety
  • Reduce speeds
  • Mitigate queues associated with left-turning traffic
  • Improve pedestrian environment
  • Improve bicyclist accessibility
  • Enhance transit stops

Seattle DOT has developed a flow chart to support its Road Diet decision-making process.

The City of Grand Rapids, Michigan, takes a holistic view of Road Diet implementations by first identifying all 4-lane facilities within their jurisdiction.

Identifying the objective(s) will help determine whether the Road Diet is an appropriate alternative for the corridor that is being evaluated. Some example evaluative questions to answer when considering a Road Diet are shown:

Factor Questions
Roadway Function and Environment
  • What is the current, expected, and desired function of the roadway?
  • Is the right of way limited?
  • Will the adjacent land use remain relatively stable throughout the design period?
  • Does the jurisdiction have a context sensitive or Complete Streets policy?
Crash Types and Patterns
  • Can the crashes that are occurring be reduced with a conversion?
  • Will a reduction in speed and speed variability increase safety?
Level of Service
  • What is an acceptable increase in minor street or signal-related delay?
  • What is an acceptable change in queues at intersections?
  • Does the signal timing or phasing need to be changed or optimized?
  • What is the impact on parallel roadways?
Pedestrian and Bike Activity
  • What is the pedestrian and bicyclist friendliness of the roadway?
  • Do pedestrians and bicyclists have safety concerns?
  • Will the addition of a TWLTL assist pedestrians and bicyclists?
  • Can a bike lane be added after the conversion?
Frequent-Stop and/or Slow Moving Vehicles
  • What is the acceptable delay with respect to frequent-stop and/or slow- moving vehicles?
  • Are there locations for pull-outs for these vehicles?
Traffic Volumes and Patterns
  • What are the existing and design year daily traffic and peak hour volumes?
  • Does the current roadway primarily operate as a "de facto" three-lane cross section?
  • Are right-turn lanes needed at particular locations?
  • Does the proposed marking allow the design vehicle to turn properly?
Table adapted from Knapp, Welch, and Witmer, 19996