A road diet reduces the number or size of street travel lanes to support multiple modes of transportation, other public utility uses, economic development and/or other amenities. Other terms include lane diets (where lane width is reduced), roadway reallocation or roadway reconfiguration.
Benefits & Problems Addressed
Lower speeds: Results from cities with road diets shows reduced speeds, and as a result fewer crashes. Reduced speeds are not necessarily a reduction from posted speed limits, but rather to tame drivers who view two lanes as a means of passing (at higher speeds).
Reclaiming a single use road for multiple uses: Since streets are a city or town's largest land holding, street redesign can unlock additional uses for multi-modal transportation, infrastructure upgrades and economci development
Asthetic & economic improvements: Road diets end to include additional landscaping and infrastructure improvements (better materials and signage). The improvements can help stimulate economic activity and additional investments in the area.
Tips & Techniques
Choosing candidate roadways for reconfiguration: Successful road diets have been achieved on streets carrying as much as 20,000 auto trips per day. Overly wide streets with high auto crash rates are good candidates. In some cases roadways are not good candidates for example when volumes are greater than 20,000 auto trips per day.
Making the case: Safety improvements are one of the top benefits. Before and after studies from peer cities can help (See the FHWA guide below). Testimonials from citizens and elected officials can also help, especially for projects that initially had significant opposition. Walk tours of nearby projects can also help.
Typical improvements: (1) Adding protected or unprotected bicycle lanes on one or both sides of the road; (2) Adding or widening sidewalks for multiple uses; (3) installing medians for landscaping and/or pedestrian crossing; (4) Adding landscaping for stormwater management; (5) Reconfiguring to add, remove or install a reversable center turn lane; (6)
Hot Buttons: Road diets are often contentious; opponents point to decreased travel time and traffic congestion. Local business often oppose on the percetion that drivers will avoid streets with road diets. Other arguements include impacts on bus service adn emergency response when two lanes are reduced to one. Residents on parallel roads fear spillover traffic if drivers avoid a street with a road diet. Some mobility professionals use other terms since the word diet can have negative connotations.
Road Diet Case Studies - US Department of Transportation, Federal Highways Administration
Road Diet Frequently Asked Questions: US Department of Transportation, Federal Highways Administration
Road diets: designing a safer street: Vox Media 2018
How’s That Diet Working: Performance of Virginia Road Diets - Virginia Transportation Research Council 2020
Image: Alta Planning + Design