[emj]

The greatest share of accidents are because of infrastructure, so put all your effort into getting better road for foot and cycle traffic, it's more effective to prevent accidents than injuries.

I've never hurt my head while on a bike, yet the first thing you hear when I've been in a crash is: "Did you have a helmet?". Statistically helmets help in rare but severe cases, compared to a seat belts and airbags that helps against almost all injuries in cars from mild to serious..