What are the effects of muscle and fat mass on survivability?
For car crashes, it's a mixed bag:


Better
Better
Worse
Worse


Basically, it looks like, if wearing a seat belt, slightly overweight is more likely to survive a car crash, but if no seat belts are worn they are at a disadvantage; the very obese are always more likely to die, however.  Also, some of this was found only for males, not females.