So, Walker attached ultrasonic sensors to his bike and rode around Bath, allowing 2,300 vehicles to overtake him while he was either helmeted or naked-headed. In the process, he was actually contacted by a truck and a bus, both while helmeted—though, miraculously, he did not fall off his bike either time.

The extra leeway granted to him when he pretended to be a woman, he explains, could result from several factors, including drivers' perceptions that members of the fairer sex are less capable riders, more frail or just less frequent bikers than men. (Scientific American)