You need to make a few versions of the car, and every time it hits an object, replace the car model with a more crashed one.
If you build your own custom car from primitives, you can use the
vertex gizmo to make the crashed versions of the car.
You can put all the car models inside a group or a transparent cube, and use the visible parameter to display/hide the relevant car model according to the crash level.
You can also check the
car speed before replacing the car model with something more crashed.
Regards,
Cyebrix3D team