New research claims to show that cyclists who wear helmets are more likely to be knocked off their bicycles than those who don't.
The reason? Well motorists believe that helmeted cyclists are more proficient in their riding abilities and therefore more aware of their surroundings and road rules.
Those without a helmet are more likely to be given a wider berth as drivers feel they are more at risk of being caught in an accident.
The research, conducted by Ian Walker a traffic psychologist, who himself has been hit twice whist wearing a helmet, measured the exact distance of passing traffic using a computer and sensor fitted to his bicycle.
Half the time Dr Walker, of the University of Bath, was bare-headed. For the other half he wore a helmet and has the bruises to prove it.
Dr Walker suggests the reason drivers give less room to cyclists wearing helmets is down to how cyclists are perceived as a group.
"This may lead drivers to believe cyclists with helmets are more serious, experienced and predictable than those without."
"The idea helmeted cyclists are more experienced and less likely to do something unexpected would explain why drivers leave less space when passing."
"In reality there is no real reason to believe someone with a helmet is any more experienced than someone without."
To test another theory, Dr Walker wore a long wig to see if there was any difference in passing distance when vehicles thought they were overtaking a female cyclist.
Vehicles gave him an average of 14cm more space when he was wearing the wig. Dr Walker said that this may be because women are seen as less predictable than men on the roads, or because female cyclists are more rare and so are treated with more caution.
Dr Walker said he hoped his research would raise awareness of the dangers facing cyclists on busy roads.