Imminent car crash, should I brake? So I am sitting at traffic lights, stationary, in my car.
A drunk driver has crossed over and is about to hit me head on at 40 mph.
I only have enough time to do one thing, hit the brakes or leave them off. Which should I do to minimise injury to myself? Are they the same?
The case for hitting the brakes is that I am stationary and by hitting the brakes, I will remain as close as possible to stationary as I can be. Thus less has happened to me?
The case for leaving the car free to roll is that, in an ideal world, I would reverse to 40 mph and simply never be hit. Braking is to apply a force in the opposite direction (i.e. forward) while reversing would be to apply a force in the other direction. So leaving the car free to roll is as close to reversing as possible. Thus as close to optimal as possible.
My guess is that it doesn't matter, the maximum force (acceleration) I will feel is going to be the same but perhaps someone has come across this before and can shed more light.
Any ideas appreciated.
 A: 
The case for hitting the brakes is that I am stationary and by hitting the brakes, I will remain as close as possible to stationary as I can be.

This is what you want. The least possible energy transferred into your body.

The case for leaving the car free to roll is that, in an ideal world, I would reverse to 40 mph and simply never be hit. Braking is to apply a force in the opposite direction (i.e. forward) while reversing would be to apply a force in the other direction. So leaving the car free to roll is as close to reversing as possible. Thus as close to optimal as possible.

This is the way to minimize the damage to your car, since it allows some energy to be transferred into moving the car rather than deforming the car. But it's not the best way to minimize damage to the occupant(s).
If you were to put your car into reverse and get out of the way, the acceleration your body experienced would be limited by the ability of the engine to accelerate the car.
If you leave the brakes off and let the other car hit you, you will be accelerated much more rapidly, which is likely to lead to injury (because not all parts of your body will be accelerated equally).
