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FHWA Home / Safety / Proven Safety Countermeasures / Road Diets (Roadway Reconfiguration)

Road Diets
(Roadway Reconfiguration)

A Road Diet, or roadway reconfiguration, can improve safety, calm traffic, provide better mobility and access for all road users, and enhance overall quality of life. A Road Diet typically involves converting an existing four-lane undivided roadway to a three-lane roadway consisting of two through lanes and a center two-way left-turn lane (TWLTL).

Graphic: This illustration shows the configuration of a roadway before and after a road diet. The left side of the illustration shows a four-lane undivided highway, marked by a double yellow centerline, solid white edge lines, and dashed white lines distinguishing lanes of travel in the same direction. Four white arrows indicate the direction of travel for each lane, with the two right-most arrows pointing upward in the image and the two left-most arrows pointing downward. The right side of the illustration shows a three-lane highway with a two-way left turn lane in its center. The two way left turn lane is delineated by double yellow lines that are dashed on the inside of the two way left turn lane and solid on the outside of the two way left turn lane. The edge of the general travel lanes are delineated by a solid white edge line. Outside of the general travel lanes are bike lanes marked with a bicycle symbol and directional arrow. Together, the three-lane roadway with adjacent bike lanes occupy the same width of pavement as the previous four-lane undivided highway.

Before and after example of a Road Diet. Source: FHWA

Benefits of Road Diet installations may include:

  • Reduction of rear-end and left-turn crashes due to the dedicated left-turn lane.
  • Reduced right-angle crashes as side street motorists cross three versus four travel lanes.
  • Fewer lanes for pedestrians to cross.
  • Opportunity to install pedestrian refuge islands, bicycle lanes, on-street parking, or transit stops.
  • Traffic calming and more consistent speeds.
  • A more community-focused, Complete Streets environment that better accommodates the needs of all road users.

A Road Diet can be a low-cost safety solution when planned in conjunction with a simple pavement overlay, and the reconfiguration can be accomplished at no additional cost. Typically, a Road Diet is implemented on a roadway with a current and future average daily traffic of 25,000 or less.

Sources

1. Evaluation of Lane Reduction “Road Diet” Measures on Crashes, FHWA-HRT-10-053, (2010).

Safety Benefits:

4-Lane to 3-Lane,
Road Diet Conversions

19-47%

reduction in total crashes.1

Photo: : This photograph, taken above the median of a three-lane highway with a center two way left turn lane, shows the results of a road diet project.  To the outside of the general travel lanes are bike lanes marked with the helmeted bicyclist symbol and directional arrow. Street parking lines the outside of both bike lanes. The two way left turn lane is delineated by yellow retroreflective pavement markers and double yellow lines that are dashed on the inside and solid on the outside of the two way left turn lane.

Road Diet project in Honolulu, Hawaii.
Source: Leidos


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Page last modified on October 28, 2021
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