Effects of bicycle passing distance law on drivers’ behavior

This paper identifies the effect of passing distance laws on drivers’ perceptions and behaviors when passing bicycles. Using an instrumented bicycle, the study measured bicycle passing in a 25-h naturalistic field experiment using video recording and an ultrasonic distance-measuring device. In order to evaluate the effect of passing distance laws, the study examined jurisdictions with a three-foot passing law, a five-foot passing law, and no passing law. The experiment required a bicyclist to ride the instrumented bicycle in two-lane and three-lane roads to capture the distance between the bicycle and the overtaking motor vehicle. An Ordered Probit model was adopted to describe the relationship between a discrete dependent variable (i.e., passing distance) and independent variables. The results demonstrated that drivers’ overtaking distances were significantly greater in locations with the five-foot passing law than in other areas. The study also found that roads with paved shoulders, wider travel lanes, and a greater number of lanes contributed to greater passing distances. In contrast, we found that the passing distance was shorter on roads with shared lane markings (i.e., sharrows) or a higher share of heat vehicles. Moreover, a survey was conducted in locations with different passing laws and ordinances to determine drivers’ awareness and the effect of such policies on drivers’ behavior. The study illustrates that almost 70% of drivers in areas with a passing law were unaware of any existing laws requiring drivers to maintain a distance from bicyclists. These results can be useful to transportation engineers, policymakers, and legislators who intend to provide efficient designs for road infrastructure to better accommodate bicycles.