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Summary:

Among legislative strategies for bicyclists’ safety, the three-foot passing law gained significant interest and operation in the United States. At the time this study was conducted, Michigan was one of the only ten states that had not yet enacted a law that requires motorists to keep a minimum lateral distance while overtaking bicyclists. This study was to compare the effect of a three foot and five foot passing distance law on drivers’ perceptions and behaviors when passing bicycles at sites with a variety of roadway characteristics.

Problem:

Statistics shows that vehicle-bicycle fatality crashes have increased in last decades. Most of these fatalities have occurred in non-intersection urban areas. The crash type with the highest percentage of fatalities is involves a vehicle overtaking a bicycle. The safety concern of bicyclists is increased when there is no limitation for drivers to keep a safe distance from the bicyclist when passing. To date, there is no data on the efficacy of a five-foot bicycle passing law and only limited evidence on the efficacy of a three-foot bicycle passing law. Therefore, there is a strong need to compare the efficacy of a three-foot and five-foot passing laws associated with bicycle infrastructure, cultural differences, and community education and outreach. The purpose of this research is to compare the motorist-bicycle passing distances on urban roads with different roadway characteristics at locations with a three-foot and five-foot bicycle passing law.

Research Findings:

A total of 2857 motor vehicle-bicycle overtaking maneuvers were derived from approximately 25 hours of video recording in four cities with different passing laws, including with 3-foot, 5-foot, and without law. The main findings of the study are listed below:

• Effect of passing law: We also found that passing distances in cities with five-foot law were significantly higher than cities with three-foot law and this result held for all roadways types studied. Passing distance was also influenced by the number of lanes. Analysis specified that that the passing distance in 2-lane roadways with bike facility (bike lane, sharrow, or shoulder) and five-foot passing law was significantly higher than the same roadways in areas without the five-foot passing law. In terms of violation, drivers were more likely to violate the three-foot law when driving on a 2-lane road, or there was no bike lane/shoulder on the road.
• Effect of roadway type:

The results revealed that the passing distance in the roadways with sharrow was significantly less than the roadways with a bike lane, shoulder, and those without bike facility. Unsurprisingly, passing distance in two-lane roadways was significantly less than lateral distance in three-lane roadways, because more lanes provide more room for drivers to keep safe distance from the bicyclist.

• Effect of vehicle type: Heavy vehicle drivers, comparing to regular passenger cars drivers, tended to drive closer to the bicyclist. Moreover, the violation in 2-lane roadways was not significant between vehicle types, however, in 3-lane roadways truck drivers contributed more violations

Results:

We recommend cities with a three-foot state passing law consider adopting a more stringent five-foot passing law inside the city.  We also recommend designing countermeasures to increase passing distance such as enforcement and drivers’ education and awareness. Bicycle infrastructure changes would be also needed to influence better compliance in bicycle passing laws. The results of this study can be used by transportation engineers, policymakers, and legislators to provide efficient designs of road infrastructure associated with bicycle services. Additionally, the output of this study illustrated that LiDAR can be utilized in future research to detect spatial and temporal analysis of vehicle-bicycle trajectory maneuvers, including speed and distance before and after the overtaking zone. The proposed algorithm can also be applied to the variety of traffic applications to provide safe interaction between vehicle and bicycle in smart cities.

Presentation

Final Report