That headline is one of many comments in response to a study by Ian Walker. The study has been getting a lot of attention in the bicycling community, but is basically junk science. Let’s start with a condensed version of the press release:
“Drivers pass closer when overtaking cyclists wearing helmets than when overtaking bare-headed cyclists, increasing the risk of a collision, the research has found. Dr Ian Walker, a traffic psychologist from the University of Bath in the UK, used a bicycle fitted with a computer and an ultrasonic distance sensor to record data from over 2,500 overtaking motorists in Salisbury and Bristol.Dr Walker, who was struck by a bus and a truck in the course of the experiment, spent half the time wearing a cycle helmet and half the time bare-headed. He was wearing the helmet both times he was struck.
He found that drivers were as much as twice as likely to get particularly close to the bicycle when he was wearing the helmet. Drivers passed an average of 3 inches closer with the helmet than without
The research has been accepted for publication in the journal Accident Analysis & Prevention.
"This study shows that when drivers overtake a cyclist, the margin for error they leave is affected by the cyclist's appearance," said Dr Walker, from the University's Department of Psychology.
"By leaving the cyclist less room, drivers reduce the safety margin that cyclists need to deal with obstacles in the road, such as drain covers and potholes, as well as the margin for error in their own judgements.
To test another theory, Dr Walker donned a long wig to see whether there was any difference in passing distance when drivers thought they were overtaking what appeared to be a female cyclist.Whilst wearing the wig, drivers gave him an average of 5.5 inches more space when passing.
Junk science?
While this article has gotten wide publicity in the cycling community, it’s basically junk science. It’s good for stimulating conversation, but that’s about it.
1. Experimenter bias is likely. Walker’s hypothesis is that drivers are subconsciously making judgments about how close they can pass. But then he goes and does all the experimentation using himself as a subject. It is well known that an experimenter who knows what results he wants, or what results he should get, can unconsciously influence the outcome. That’s been known for decades, and if he is a research psychologist he would have learned this in the first introductory research methods course.This might occur quite easily. One of the cues cyclist give off is how straight a line they maintain versus how wobbly they are. Did he wobble more when he was farther out in the lane, perhaps because he was unfamiliar with being out that far? Did he do the conditions in a certain order, so he was more relaxed with the equipment as he went along? Lots of things can happen, which is why you usually wouldn’t use yourself as the only subject.
2. How bad of a cyclist is he? In the course of the study, he was hit twice. This is in about 200 miles of cycling. This is an incredibly high accident rate, which indicates that something other than normal cycling behavior is going on.
3. Incredible labeling. Walker sometimes rode with a wig in order to gauge motorists reactions to female cyclists. But there’s more to being a female cyclist than just long hair, and looking at Walker’s picture it seems more likely he was measuring the response to cyclists with long hair. But he persists in the article in insisting this indicates something about being female. Why?
The managerial version of the published study is at http://www.drianwalker.com/overtaking/overtakingprobrief.pdf
The press release from Walker can be found at http://www.eurekalert.org/pub_releases/2006-09/uob-wah091106.php
Dr. Ian Walker's picture is below. How feminine is he with a wig?
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