It’s quite technical but the Federal Highway Administration (FHWA) has released what it considers a comprehensive guide for transportation officials to measure trade-offs and determine what type of bikeway to build and where. The Bikeway Selection Guide shows, for instance, how to consider auto traffic volume and speed and number of lanes. It discusses all the possibilities from narrowing and removing auto lanes to the preferred shoulder width on rural roads (10 ft.).
Among the many generalities: It’s usually better to include a bike lane even next to parking, despite the possibility of dooring, which accounts for 5-10 percent of bicycle accidents. And generally, one-way bike lanes are better on two–way streets than two-way bike lanes on one side.
It is also worthwhile to provide protection at intersections and continue bike lanes through them. “Intersection approaches with mixing zones require motorists to yield to bicyclists before entering or crossing the bike lane. This clarity can be further enhanced with bicycle lane extensions through the intersections, green colored pavement, and regulatory signs. Research shows protected intersections have fewer conflicts and are therefore preferable, the guide says.
The manual discusses the many factors that should go into deciding whether to separate autos from bikes. If they can’t do so, planners can consider other measures, such as reduced speed limits.
Bicyclists do tend to feel more comfortable on separated lanes.
View the Bikeway Selection Guide at: https://safety.fhwa.dot.gov/ped_bike/tools_solve/docs/fhwasa18077.pdf