Vehicle to Vehicle Collisions

I want to tweak/improve the vehicle to vehicle collisions for my game. When a vehicle hits a building the behavior looks correct. However if a fast moving vehicle hits a slower moving vehicle. The slow moving vehicle doesn't speed up at all and the fast vehicle will flip over when it shouldn't.

I traced through the code and looks like in the rigid class,the function resolvecollision() does the work. This function is called whether the vehicle hits a brick wall or a car. I though about making a special case for vehicle to vehicle collisions. Has anybody else tried this or improved this problem?

Brian