In 2006, Dr Ian Walker, a University of Bath psychologist, did some seminal research into bicycle safety.
The power of perception
He modified his bike with proximity sensors to see how much distance motorists gave him while overtaking. Motorists gave him less distance while wearing a helmet than when he didn’t wear a helmet.
This suggests that wearing a helmet is MORE dangerous than not wearing one, since the likelihood of a collision is greater. Furthermore, he decided to wear a wig to see whether motorists gave him more distance if they perceived him as female. And it actually worked, which suggests that cyclists are safer if they wear wigs than helmets.
This shows just how powerful perception can be when designing. In this case a functional product (the helmet) is arguably a poorer solution than a purely perception based solution (the wig).