[amit_m]

No, the helmet is not supposed to split in half. It is supposed to crush, absorbing the impact's energy.

And you would most likely not suffer serious question injury from such a fall. The horizontal speed is not so important if you hit your head on a flat surface. The vertical speed is essentially the same as if you've fainted standing still.

[Lewton]

by curb he probably meant the edge of the curb in which case the helmet splitting in half makes sense, and also that probably would have done quite a bit of damage without a helmet