Florida DOT Study Reconfirms Ian Walker’s Conclusions
Posted By Sam Ollinger on October 25, 2011
In Traffic, Tom Vanderbilt detailed the study performed by U.K. based researcher, Ian Walker, on passing distance and driving behavior around cyclists based on gender. On his blog, Vanderbilt summarized the study,
To briefly summarize, in his study (published as “Drivers overtaking bicyclists: Objective data on the effects of riding position, helmet use, vehicle type and apparent gender,” in the journal Accident Analysis and Prevention), Walker outfitted a bike with a device that measured the distance of passing cars. He found, among other things, that drivers tended to pass more closely when he was wearing a helmet than when not (he was struck by vehicles twice, both while wearing a helmet).
This was a surprising, somewhat controversial finding that generated a lot of news coverage. To my mind, Walker’s findings were more interesting for what they said about interpersonal psychology on the road than safety itself; mostly because I felt, and Walker seems to agree, that the primary question of bicycle safety had less to do with the helmet than other factors.
In a Florida DOT commissioned study [pdf] published last month, researchers reached a very similar conclusion. Although the study didn’t specifically address helmet usage, the researchers found that their data was consistent with Walker’s conclusions when it came to how closely drivers passed bicyclists based on the bicyclist’s gender and attire. The study found that on average, drivers passed cyclists more closely when cyclists were dressed in “bicycle attire” and if the cyclist was male. The study was unable to determine the reasons on this passing behavior and the authors of the study speculated that, “it [was] possible that motorists perceived less risk passing riders who were in [a] bicycle outfit.”
I suppose effective measures that can be made as a result of the Florida study would be to encourage cyclists to ride in casual clothing rather than bicycle-specific attire. As for the conclusion on passing distance based on the cyclist’s gender, perhaps it is for the best given that men typically outnumber women on the roads.
Comments
5 Responses to “Florida DOT Study Reconfirms Ian Walker’s Conclusions”
Join in the discussion
The passing distance vs apparent gender and attire is interesting, but I think FDOT’s findings WRT cyclist lane position is more important from a safety standpoint. The farther the cyclist rides from the curb, the more passing distance you get (up to a certain point):
“Intuitively, one would expect that the closer you ride to the curb, the more lateral separation you have. On the contrary, the results presented in Table 4 and Figure 6 show that riding closer to the curb results in a smaller separation. Field observations revealed that when bicyclists ride closer to the curb, some motor vehicles, especially compact cars attempt to fit in the lane without laterally shifting to the adjacent lane, hence causing lesser distance.
“On the other hand, the results show that riding too far from the curb also results in a shorter distance. It seems that there is a spot between 3 and 4 ft from the curb that results in the greatest lateral separation between motor vehicles and bicyclists. It should be noted however, that higher standard deviations were observed. This was mainly caused by the fact that some drivers choose to stay within the outside through lane while others laterally shift to the inside lane.”
This study proved both Walker’s and Gutierrez’s results together, which I did think was a new finding.
[...] Bike San Diego, which has more discussion on the gender and apparel aspects of this study. Via Streetsblog [...]
[...] A study from the most dangerous state for cyclists and pedestrians shows that drivers really do base passing distance on cyclist’s sex and attire, as well as how far you ride from the curb; from now on, I’m wearing a dress and taking the lane. [...]
You have to be so careful when riding a bike… cars really don’t see you. I was surprised by that finding, too, but you need a helmet.