“Crash” is about the strange lure of the auto collision, provoking as it does the human fascination with death and the tendency to eroticize danger. Most motorists will slow down to stare at the scene of a collision; they may feel their pulses quickening and become aware of the fragility of their own bodies. The characters of “Crash” carry this awareness a step further, cherishing and nurturing it. For them, a car collision is a sexual turn-on, and a jolting life force they come to crave.