Bill Simpson, who is pretty much a self taught genius and has done much of the invention on racing safety equipment, has come out with a helmet that should help a lot:
The problem with the helmets is that they are too good.
Modern helmets (and steroids) have enabled increased velocity collisions, because they hurt less on impact. Unfortunately, the force of such collisions has increased to the point that they are not safer, but more dangerous.
Back to leather helmets. Either the death rate would increase greatly, or the velocity of head/neck collisions would decrease.