Don't wear your helmet!

Bicycle helmets may backfire by encouraging cars to drive closer to the cyclist. Theory: Wearing a helmet makes you look like you know what you're doing, so drivers assume you can operate in tighter space. Evidence: A traffic psychologist rode a sensor-equipped bike around Britain, and when he wore a helmet, cars passed more than three inches closer, on average, than when he didn't. He was also hit by two vehicles while wearing the helmet. Bonus finding: When he dressed as a woman, drivers gave him more than five inches of extra space. Psychologist's interpretation: Helmets protect you in a low-speed tumble but may backfire in serious car traffic. Accident-prevention group's rebuttal: Wear your helmet, and we'll educate drivers to give you more space. (For Human Nature's update on the dangerous distraction of car navigation systems, click here.)
-slate.com