3.4 Motorist Passing Bicyclist Laws

Overall Effectiveness Concerns: Although there is some research examining the effectiveness of this countermeasure, there is insufficient evidence to conclude that the countermeasure yields consistent benefits.

The purpose of bicyclist passing laws are to require motor vehicle drivers to leave at least three feet of clearance space between the vehicle and the cyclist when overtaking the cyclist, to minimize the likelihood of a sideswipe, and to reduce the chance of a close encounter that could potentially destabilize or divert the course of a cyclist and cause a crash.

Use: As of July 2018 there were 32 States and the District of Columbia known to have enacted bicyclist passing laws requiring drivers to leave a space of 3 feet or more when passing cyclists (NCSL, 2018). Pennsylvania requires at least 4 feet for passing, and South Dakota requires at least 3 feet for roads with a speed limit of 35 mph or less and at least 6 feet for roads with a speed limit greater than 35 mph. North Carolina requires at least 2 feet for passing, and permits passing a bicyclist in a no-passing zone if the motorist leaves a clearance of at least 4 feet. Three States—Delaware, Kentucky, and Nevada—require the motorist to change lanes to pass a cyclist on roads with lanes in the same direction. Nine other States have laws requiring motorists to pass at a safe distance and speed, but are usually not more specific.

Effectiveness: One analysis of 18,534 bicyclist fatalities from 1990 to 2014 in the United States reported that minimum passing laws may at best prevent approximately one fatal bicyclist crash every 20 months (Nehiba, 2018). Love et al. (2012) evaluated the effectiveness of a passing law enacted in Baltimore, Maryland. The study saw low compliance with the passing law and little to no enforcement of the law by area police. Other factors that influenced passing distance included lane width, bicycle infrastructure, cyclist identity, and street type. The authors concluded that in addition to the passage of a law, interventions such as driver education, signage, enforcement, and bicycle infrastructure changes (such as bike lanes and Complete Streets designs) are needed to influence driving behavior and to increase motorist compliance with the three-foot law. Public education should include some level of description, or say something about equipment to measure or visualize a safe distance, such as imaging the distance of an opened car door.

Bicycle passing laws can be difficult to enforce because it is a challenge to measure the exact distance between bikes and vehicles. Police in Chattanooga, Tennessee, and Austin, Texas, used a device called C3FT, a handlebar mounted ultrasonic device, to measure when a vehicle passes a police bicycle with less than 3 feet of distance (Goodyear, 2015; Davis, 2017). These devices can offer valuable, accurate information to help make passing laws enforceable.

There are some empirical data suggesting that these laws may change driver behavior. A naturalistic observational study of driver passing behavior in Michigan measured vehicle passing distance in five jurisdictions having 3 feet (1 city), 5 feet (3 cities), and no enacted (1 city) passing laws (Van Houten et al., 2018). The results showed that drivers maintained a significantly greater separation distance when they overtook bicyclists in sites with 5-feet laws, compared to sites with 3-feet or no law. Roadway infrastructure also influenced passing behaviors. Roads with paved shoulders, wider roads, and greater number of lanes were associated with greater separations between drivers and bicyclists. Shared use lanes led to closer passing, as did passing situations with larger vehicles.

A study in Queensland, Australia, examined the factors associated with road-user non-compliance with a 2-year trial of a bicyclist passing rule (Debnath et al., 2018; Haworth et al., 2017). Motor vehicle drivers and bicyclists were observed across 15 sites. Apparent rider characteristics (age, gender, helmet use, clothing type) were not associated with compliance with the law. Roadway infrastructure, such as horizontal curves and narrow lanes, resulted in higher observed non-compliance. A concurrent online survey of motorists reported that 43% of respondents were more aware of the presence of bicyclists after the implementation of the law; however, more than 40% reported being uncertain about judging the required 3 feet passing distance. About 73% of cyclists and 60% motorists reported that motorists were leaving more passing distance after the implementation of the rule than before. Further, two focus group discussions with LEOs were conducted. Officers reported that the passing law was difficult to enforce, and that motorists were observed to sometimes allow for much greater than the required distance, leading to erratic maneuvers and increased risk of collision with oncoming vehicles. Appropriate public education with pictures of appropriate distance from the perspectives of different types of vehicles were suggested as potential solutions for enhancing gap judgments. Cyclist fatality rates were not statistically different during the 24 months before and 16 months after implementation of the law.

Costs: Minimal costs could be incurred for informing and educating the public and providing training for enforcement personnel.

Time to implement: A bicyclist passing law can be implemented as soon as the law is enacted.

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