Bicycle Safety Guide and Countermeasure Selection System


Lane narrowing (center lane narrowed) creates space to install bike lanes which also provides additional buffer for pedestrians on sidewalks. Seattle, Washington. Photo by Gina Coffman, Toole Design Group

Photo by Bill Schultheiss, Toole Design Group Lane narrowing on Harvard Ave in Boston, Massachusetts.
Photo by Bill Schultheiss, Toole Design Group




Lane Narrowing

Roadway lane narrowing may help to reduce vehicle speeds along a roadway section and enhance movement and safety for bicyclists as well as pedestrians. Lane narrowing is best used where motor vehicle speeds are low to encourage shared lane travel and prevent motorists from attempting to pass bicyclists within the same lane if there is insufficient width. Another use would be to gain space to stripe a bicycle lane or paved shoulder where motor vehicle speeds and volumes are higher.

Lane narrowing can be achieved in several different ways depending on the type and scope of a project. During all projects there are opportunities to reduce lane widths to the recommended minimums (see AASHTO Green Book for further information):

  • 9 feet lanes on rural roadways
  • 10 feet for most vehicular travel lanes
  • 10 feet for turn lanes
  • 11 feet for lanes to accommodate large volumes of trucks, buses, or larger vehicles (typically where volumes of large vehicles are greater than 8 percent)

With the additional space created from narrowing travel lanes, space can be redistributed for the following uses:

  • Bicycle lanes or cycle tracks, parking lanes, or transit lanes.
  • Widened sidewalks, landscaped buffers with street trees, and curb extensions at crossings where on-street parking is present.


On roadways where there are safety and speeding problems, and vehicle lane widths are greater than the recommended minimums, narrowing lane widths (i.e., lane diet), can help improve safety and comfort for pedestrians, bicyclists, transit riders, and motor vehicles. Lane diets provide multiple benefits, including lowering vehicle speeds, reducing crossing widths and pedestrian exposure to motor vehicle traffic, and redistributing roadway space for other users (e.g., create space for bike lanes).


  • Road narrowing projects should always consider the surrounding land uses, parking turnover, vehicular speeds, and the volumes and types of traffic (including pedestrians, bicyclists, transit, commercial, emergency response, and heavy vehicles).
  • Evaluate whether narrowing may encourage traffic to divert to local neighborhood streets.
  • On roadways with excess vehicle capacity, a reduction in the number of travel lanes may be feasible (see lane reduction).

Estimated Cost

Simply adding striped shoulders or on-street bike lanes can cost as little as $0.15-0.20 per linear foot, or approximately $750 to $1,000 per mile. Restriping can cost between $5,000 and $30,000 per mile, depending on how many lanes must be removed, and whether bike lanes are added. Typically the number of striping needed for a block puts the cost between $1,000 and $3,000 per block. If the road must be restriped or reconfigured, the cost is closer to $12,500 per block. Adding a raised median, widening a sidewalk, and adding improvements such as landscaping or curb extensions can significantly increase the cost.


To view references for this countermeasure group click here.

Case Studies

Eugene, Oregon
Eugene, Oregon