I’ve seen this research before, but according to this article you are less likely to get hit by a car if you aren’t wearing a helmet.
Apparently drivers are much more cautious around commuters that don’t have a helmet on because they perceive them as more vulnerable. This makes sense to a certain degree, and according to Ian Walker’s research, 23% more drivers came within a meter (3.3ft) of him when he had a helmet on as opposed to riding without.
Assuming this is true… what’s the better decision? Leave the helmet at home to decrease your chance of getting hit by a car? Or wear it and increase your chance of living once it happens?