I've often thought it would be useful to put a permanent marker of some sort at the spot of every traffic fatality. In the US, people often put crosses up, but

I've often thought it would be useful to put a permanent marker of some sort at the spot of every traffic fatality. In the US, people often put crosses up, but this is haphazard, and of course can't be in the roadway. Maybe a painted gray X or something. The point is that a crap-ton of these would serve as a useful warning to the wise.