SYDNEY: Drivers pass closer when overtaking cyclists wearing helmets than when overtaking bare-headed cyclists, increasing the risk of a collision, a British researcher has found.
Ian Walker, a traffic psychologist from the University of Bath in the U.K., used a bicycle fitted with a computer and an ultrasonic distance sensor to record data from more than 2,500 overtaking motorists.
Walker – who was struck by a bus and a truck in the course of the experiment – cycled around Salisbury and Bristol in England, and spent half the time wearing a cycle helmet and half the time without. He was wearing the helmet both times he was struck.
The study, published in the British journal Accident Analysis & Prevention, reports that drivers were as much as twice as likely to get particularly close to the bicycle when Walker was wearing the helmet.
Across the board, drivers passed an average of 8.5 cm closer when he was wearing the helmet than when he was riding without a helmet.
“This study shows that when drivers overtake a cyclist, the margin for error they leave is affected by the cyclist’s appearance,” said Walker. “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.”
According to walker, these results relate to how road users perceive cyclists as a group.
“We know from research that many drivers see cyclists as a separate subculture, to which they don’t belong,” he said. “As a result they hold stereotyped ideas about cyclists, often judging all riders by the yardstick of the lycra-clad street-warrior.
“This may lead drivers to believe cyclists with helmets are more serious, experienced and predictable than those without. In reality, there is no real reason to believe someone with a helmet is any more experienced than someone without.”
The study also found that large vehicles, such as buses and trucks, passed considerably closer when overtaking cyclists than cars.
The average car passed 1.33 m away from the bicycle, whereas the average truck got 19 cm closer and the average bus 23 cm closer. However, there was no evidence of four-wheel drives (or sport utility vehicles, SUVs) getting any closer than ordinary cars.
Despite his results, Walker doesn’t suggest all cyclists stop wearing helmets. “We know helmets are useful in low-speed falls, and so definitely good for children, but whether they offer any real protection to somebody struck by a car is very controversial.”
To test another theory, Walker donned a long-haired 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 14 cm more space when passing.
In future research, Walker hopes to discover whether this was because female riders are seen as less predictable than male riders, or because women are not seen riding bicycles as frequently as men … or because he was wearing a wig.
In the meantime, he thinks road users should be better educated about the needs of cyclists. “Most adult cyclists know what it is like to drive a car, but relatively few motorists ride bicycles in traffic, and so don’t know the issues cyclists face,” he said.
“There should definitely be more information on the needs of other road users when people learn to drive, and practical experience would be even better. When people try cycling, they nearly always say it changes the way they treat other road users when they get back in their cars.”