What about the impact on a driver or passenger who survives a fatal crash?

You could have a manor of all sorts of injuries. From neck trauma to fractured vertebrae. The thing you would most have to worry about would be internal damage to your organs. If your organs are injured you could die from internal hemorrhaging due to ruptures or tears in the organs. You could also die from the bile that is released by your pancreas if it is ruptured, as well as your feces if your bowles are damaged from the car accident.