Pedestrian Safety Guide and Countermeasure Selection System

 

This rendering shows a four-lane road with a midblock crosswalk before a road diet. Federal Highway Administration.


Federal Highway Administration. This rendering shows how a road diet on a street that was previously four lanes can create space for features like bicycle lanes and a pedestrian refuge island.
Federal Highway Administration.

 

Federal Highway Administration. "Before" picture from a typical four-lane to three-lane conversion.
Federal Highway Administration.

 

Federal Highway Administration. "After" picture from a typical four-lane to three-lane conversion.
Federal Highway Administration.

 

pedbikeimages.org - New York City DOT. Side-by-side before and after pictures of a road diet with a pedestrian refuge island.
pedbikeimages.org - New York City DOT.

Lane Reduction (Road Diet)

Lane reductions and road diets can decrease the lane crossing distance and reduce vehicle speeds. Multilane roads can take longer for pedestrians to cross and vehicle speeds may be high. A typical road diet converts an existing four-lane, undivided roadway to two through lanes and a center, two-way left turn lane (TWLTL). This design allows left-turning drivers to exit the traffic stream while waiting for a gap to complete their turn and frees up space that can be reallocated to other uses, including:

Pedestrian refuge island
Crosswalk visibility enhancements, such as curb extensions
• On-street parking, with parking restrictions on crosswalk approaches
• Widened sidewalks and landscaped buffers
Bicycle lane and/or transit lanes

There are many other opportunities to perform road diets, particularly on roadways with wider cross sections, one-way streets (which may have excess capacity), and although not as common, where volumes are low a three-lane road (one lane in each direction with a TWLTL) can be converted to two. Road diets are often supplemented with painted, textured, or raised center islands.

Purpose

Lane reductions (i.e., road diets) optimize street space to benefit all users. Lane reductions help improve safety and comfort for pedestrian as well as bicyclists. Reducing the number of lanes on a multilane roadway can reduce crossing distance and exposure for pedestrians while also reducing vehicle speeds and the potential for rear-end collisions. Road diets also improve sight distances for left-turning vehicles.

Considerations

• Road diets may be uncommon in a community. Consider conducting an outreach effort to educate the public on the purpose and potential benefits.
• Four to three lane conversions should be considered for roadways with documented safety concerns, moderate volumes (less than 15,000 ADT, up to 25,000 ADT in special cases), and along priority bicycling and walking routes.
• FHWA’s Road Diet Informational Guide recommends communities consider a range of factors including:
  • Vehicle speed
  • Level of Service (LOS)
  • Quality of Service
  • Vehicle volume (ADT)
  • The operation and volume of pedestrians, bicyclists, transit, and freight
  • Peak hour and peak direction traffic flow
  • Vehicle turning volumes and patterns
  • Frequency of stopping and slow-moving vehicles
  • Presence of parallel roadways
• Determine if and how alternative routes will be impacted by a lane reduction.
• Consider the importance a particular street plays in the pedestrian or bicycle network and the relationship between creating more livable streets and supporting economic development.
• Consider designs that incorporate raised medians and left-turn bays to help eliminate the potential for TWLTL to be used as acceleration lanes by some motorists.
• The common four-to-three-lane road diet is very compatible with single-lane roundabouts.
• Strongly consider conducting before-and-after studies of the conversion for safety and traffic flow conditions.1,3,5,6,7,8

Estimated Cost

The cost associated with a road diet can vary widely. The countermeasure can be a relatively low-cost safety solution if only pavement marking modifications are required to implement the reconfigured roadway design. Restriping costs for the three lanes plus bicycle lanes are estimated at $25,000 to $40,000 per mile, depending on the amount of lane lines that need to be repainted. However, work involving geometric features like extended sidewalks, curb extensions, a raised median, or refuge island can increase the cost to $100,000 or more per mile.

When planning in conjunction with reconstruction or overlay projects, the change in cross section may be completed without any additional cost. If a reconfiguration is done after repaving or with an overlay, and curbs do not need to be changed, there may be no additional costs for the reconfiguration or pavement markings. Reconstruction projects may also allow for curb lines to be moved to narrow the roadway.

Safety Effects

A summary of studies that have looked at the safety effects of road diets can be found here.

Case Studies

Oneonta, NY
West Palm Beach, FL
University Place, WA
Cleveland Heights, Ohio
El Cajon, California
New York, New York
Tampa, Florida
Seattle, Washington
Hendersonville, North Carolina
New York City, New York