That explains the behavior of all the drivers as I cycle to work. They are all moral philosophers and believe that by killing me they provide donor organs to save 6 others. Maybe I need a cycling top that says "I don't carry a donor card"
I remember watching a documentary where they found that drivers are much more likely to cut off cyclists wearing helmets than those without helmets. They also measured things like average distance between car and bike when passing. If people see you not wearing a helmet they assume that you are unsafe and will stay further away from you.
He also discovered that drivers gave a female cyclist much more space - although since he did the experiment himself in a blonde wig he did consider that perhaps they just give unconvincing transvestites more room !