Sorry, testing-type folks, but the impact against say the solid concrete of a curb, sidewalk, or trail is going to be worse than the sproingy sheet metal of a car hood... unless that car is you know, moving at 30mph and hits the cyclist. Which is of course what usually happens. I cannot see how you could design a helmet to be safer by firing it downward at a 45º angle at a car hood.

You wanna improve my safety? Teach people how to drive.