Summer’s here. You’ve probably seen more people out on their bikes lately, and if you think you’ve seen more men than women, you’re right.

Cycling is a gendered activity. Dr. Jennifer Dill, an international authority on the gender gap in bicycling, has shown that “women are far less likely to bicycle for transportation than men,” and she cites concerns about safety as a major reason for this disparity.

Recent research here at the Humphrey School of Public Affairs shows that women have real reason to be concerned. In a field experiment, we found that drivers were significantly more likely to encroach—i.e. to pass closer than three feet—on a female cyclists than on male cyclists. Our study illustrate the scope and pervasiveness of the gender gap in cycling, confirms female cyclists’ concerns about safety on the road, and underscore the need for greater investment in safer facilities like protected bike lanes.

In a field experiment, we found that drivers were significantly more likely to encroach—i.e. to pass closer than three feet—on a female cyclist than on male cyclists.

Hennepin County, home to Minneapolis and Minnesota’s largest county by population, is in the midst of building a network of protected bike lanes as part of its efforts to foster and increase the safety of cyclists. In 2017, using grant funds from the Minnesota Department of Health’s Statewide Health Improvement Partnership (SHIP), county planners purchased bike-mounted radar units and GoPro cameras to test their usefulness for safety enforcement by bicycle police patrols. The county, also wanted to collect evidence on the relative risk cyclists face on different types of roads.

Humphrey School students Isaac Evans, Joshua Pansch, and Lila Singer-Berk were recruited to test the equipment and present findings to the County. Their results were subsequently published in the Institute of Transportation Engineers (ITE) Journal.

Working with county staff, students marked ½-mile routes and riding positions on six types of roadways with different types of bicycle facilities. They established the objective of measuring passing distance on a minimum of 400 passing events on each type of roadway, with at least 200 events each for the male riders and the female rider. In total, the students used the handle-bar-mounted radar to measure passing distances for 2,949 passing events: 1,408 for male riders and 1,541 for the female rider. Consistent with the definition in Minnesota law, they classified all passing events less than 36 inches as encroachments.

The gender disparities that emerged in the results were both surprising and worrisome. First, as expected, vehicle passing distance was greatest on roads with protected bicycle facilities, and encroachments were, overall, relatively rare. Vehicle passing distances ranged from a mean of 90 inches on the bollard-protected bike lane to lows of 62-63 inches on roadways with no facilities, shoulders only, and striped bicycle lanes. The rate of encroachment among all passing events was relatively low at 1.12%.

None of the 33 encroachments occurred on the protected bike lane; 64% occurred on the 4-lane roadway without any bicycle facilities. Thus, in general, protected bike lanes that separate cyclists from vehicles clearly accomplish their objectives: they increase passing distance, decrease encroachments, reduce risk, and increase safety.

The finding that surprised and concerned the County’s bicycle advisory task force concerned differences in vehicle passing distances based on the gender of the cyclist. Overall, mean passing distance for the female rider was 68 inches, three inches less than the mean for the male riders (71 inches). And of the 33 encroachments that occurred, 24 (73%) were on the female rider. Statistical modeling showed that, other factors equal, the female cyclist was 3.8 times more likely to be encroached upon.

Statistical modeling showed that, other factors equal, the female cyclist was 3.8 times more likely to be encroached upon.

The County’s bicycle advisory task force observed that, although an encroachment rate of one percent sounds very low, the actual number of encroachments that occur is quite high, given levels of cycling. A recent Minnesota Department of Transportation study estimated that residents of Minneapolis and St. Paul take between 31 and 36 million bicycle trips annually. Assuming just one encroachment occurs on one percent of these trips, there could be between 310,000 and 360,000 instances of encroachment each year in the Twin Cities.

Assuming that the gender-based patterns of encroachment observed here extend into the general population, it appears women riders face additional risk. Indeed, based on these findings, women cyclists likely experience tens of thousands more instances of encroachment each year. Members of the bicycle advisory task force commented on the need to address this disparity, noting that increasing rates of cycling for transportation is a key transportation goal.

Members of the bicycle advisory task force commented on the need to address this disparity, noting that increasing rates of cycling for transportation is a key transportation goal.

Hennepin County undertook this study to establish the feasibility of using bicycle-mounted radar as a tool in traffic enforcement and to generate information to inform planning for protected bicycle lanes. The results confirm the feasibility of using radar to measure passing distance, the effectiveness of protected bicycle lanes, and the need for enforcement of statutes governing encroachment.

However, more unexpectedly, these findings also validate the anecdotal concerns expressed by women about safety as an important consideration in cycling. The gender gap in cycling is likely to persist until disparities such as those revealed in this study are addressed.

Hennepin County and Minneapolis are working to address these concerns. Both have plans to build networks of protected bike lanes, and both are developing plans to increase roadway safety, reduce crashes, and eliminate traffic fatalities. These plans include investments in new facilities, reductions in speed limits, and additional education and enforcement programs. While not all measures are aimed directly at reducing the gender gap, they will address safety concerns cited by women and make cycling safer for all.

The evidence is clear. Cyclists, particularly women, face risks. Separation of cyclists from vehicular traffic reduces encroachments and can address the well-founded concerns women have about safety. Other counties and municipalities can learn from the plans being implemented in Hennepin County and Minneapolis and do more to encourage and protect cyclists—especially women and girls.