Here's a subject close to my heart: cycling. Not least because I'm a keen cyclist myself but also because cycling is good in so many different ways - but I'm not going to bang on about that now. This study, however, has some counter-intuitive findings (the best kind!) about helmet wearing that seems to suggest cars pass closer if you've got a lid on. Also, and in stark contrast to conventional wisdom among experienced cyclists, riding further away from the curb does not cause road users to leave more space when over-taking.

Here's the suggested explanation for the 'helmet-effect':

"Research suggests drivers tend to believe helmeted cyclists are more serious and less likely to make unexpected moves; the helmet effect seen here is likely a behavioural manifestation of this belief."

And on the riding position:

"The riding-position effect suggests drivers simply do not change their overtaking paths very much as a function of where a rider is: if a cyclist rides further into the road, they will on average be closer to passing vehicles as a result. However, there are also plenty of reasons why riders should not just stick to the road edge, e.g., debris, car doors, and drivers' attention patterns at junctions."

Oh, and when the experimenter wore a wig, it seemed to have a repellent effect on other road users. That, I'm less surprised about.

Walker (In press) Drivers overtaking bicyclists: Objective data on the effects of riding position, helmet use, vehicle type and apparent gender. (Press Release | Overview of results [PDF])
Cognitive Daily asks whether this research might hold good in the US