In a perfectly elastic collision between rigid bodies, any impact forces acting on the cars would have to also be transferred to the driver in both instances, b

In a perfectly elastic collision between rigid bodies, any impact forces acting on the cars would have to also be transferred to the driver in both instances, but cars are neither perfectly elastic, nor do they behave like rigid bodies in a collision. > EDIT2 (because I can't reply): the force acting on the driver will be the sum of the force of Car B acting on Car A opposing the force of Car A acting on Car B plus the force of Car B acting on Car A. There are 2 forces in each direction of travel that are exerted by the cars. The force felt by the driver is the sum of these 2 forces, exerted by the dashboard on the driver's face. If the car hits a brick wall, the only force opposing the direction of travel of the car is the force of the wall acting on the car, which opposes the force of the car acting on the wall. As such the force felt by the driver of the dashboard acting on their face is halved. If this was how it worked, crumple zones would do nothing. Next you're going to model the airbag as a rigid body too? Ouch.