When 3 is Better Than 4 (Road Diets)

Posted by on Apr 3, 2018 in Road Safety, Safety, Transportation | No Comments

By Nathan Currie, P.E.

If you’re like me, when you hear the word “diet”, your first reaction isn’t the thought…sign me up! However, in the world of transportation, it may often be an easy solution that provides a very favorable outcome for all involved.

A “Road Diet is essentially a reallocation of space on an existing roadway to better meet the needs of all potential users of that roadway. While road diets can take many forms according to site-specific conditions, the most common form of Road Diet is conversion of a 4-lane, undivided highway to create 2 travel lanes, a two-way left-turn lane in the center, and bike lanes on either side.

The three most significant benefits of implementing a Road Diet are the following:

  • Safety enhancements
  • Increased accessibility for non-vehicular users (pedestrians, bikers, etc.)
  • Low cost improvement

Safety EnhancementsSince 4-lane undivided highways experience relatively high crash frequencies, often due to a high volume of left turn movements conflicting with through traffic, a Road Diet may be a very cost-effective way to reduce crashes and improve traffic operations along a roadway. According to data published by the Federal Highway Administration, Road Diets result in a 19 to 47 percent reduction in crashes, when converting 4-lane, undivided highways to 3-lane roadways, in the manner described above.

Increased Accessibility for Non-Vehicular Users (pedestrians, bikers, etc.) – As demand for bike lanes and walkability continue to increase, Road Diets present an excellent opportunity to accommodate these non-vehicular users in a very cost-effective way, especially for communities looking to increase livability and implement “Complete Streets” policies along existing roadway corridors. Not only can reclaimed pavement be used for bike lanes, but it may also be available for on-street parking, bus lanes, or walkways and landscaping.

Low Cost ImprovementIn many cases, implementing a Road Diet can be achieved simply by restriping an existing roadway, resulting in no impacts to existing curb lines or adjacent roadway shoulders and right-of-way boundaries. As a result, cost effectiveness is maximized and construction can be achieved in a relatively short timeframe.

The Federal Highway Administration has published a variety of resources related to Road Diets, including a summary of potential cost benefits available online at https://safety.fhwa.dot.gov/road_diets/resources/fhwasa16100/. Also worth noting, since Road Diets usually enhance safety along a corridor, they are eligible for funding through the Highway Safety Improvement Program (HSIP).

If you think your community has a roadway that would be an excellent candidate for a Road Diet, please contact us. We’d be happy to talk through the possibilities with you. Sain has helped a variety of municipalities throughout the state pursue funding for Road Diets, and we have experience with the planning, design, and construction of Road Diet projects. For one example, see the blog below to review improvements we designed along Cahaba Road adjacent to the Birmingham Zoo and Botanical Gardens.

Cahaba RoadBirmingham, AL


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