This seems to be a common phenomenon — lots of people report being unable to avert their eyes from a wound or dead body or even the mess after they blow their nose! But is there a single word for it? I found some related terms like "rubbernecking", but that seems to be the act of looking rather than the urge to look (or inability to look away).
One might exhibit morbidity, or possess a morbid curiosity, morbid fixation, or morbid fascination with such things:
morbid, adj.: 1. having or expressing a strong interest in sad or unpleasant things, especially disease or death
Note that morbidity means something quite different in medical jargon.
Consider train wreck
a chaotic or disastrous situation that holds a peculiar fascination for observers