Improving Bicycle Safety with More Bikers: An Intersection-Level Study

Conventional thinking among transportation engineers in the U.S. finds a linear correlation between the number of bicyclists on a roadway and the number of crashes involving bicyclists. However, studies from Europe have found that with increased ridership comes increased safety in the form of a reduction in the number of crashes per cyclist. Our study examines whether these trends can also be found in the U.S., to what extent does this hypothesis hold, and what other factors might be playing a role in the results. We conducted this research in Boulder, Colorado using estimates of average cyclists per day based on turning movement counts on corridors with both high and low bicycle traffic and related that to five years of bicyclist crash data. The data suggest that while bicycle crashes do seem to increase with motor-vehicle volumes, bicycle crashes tend to stay constant — or even decrease — with increased bicycle volumes.