> The damage isn't the same because car/car has twice the crumple zone. More of the energy will be dissipated through elastic deformation, so the deceleration w

> The damage isn't the same because car/car has twice the crumple zone. More of the energy will be dissipated through elastic deformation, so the deceleration will be slightly gentler. Is it though? Genuinely wondering if I'm missing something in my ponderings... I would assume that a collision between two identical cars traveling at the same velocity would each decelerate to zero within the distance of one crumple zone. ie due to the other one also decelerating the same way. Assuming that they don't end up in some sort of intermingled mashup (spherical cows and all that) which is maybe what you're describing? And that a car at the same speed hitting a practically immovable object would also decelerate the same amount in the same single crumple zone distance. Anyway as an irrelevant aside, hitting a brick wall isn't the same as hitting an immovable object - a car will mostly go right through a fairly standard unreinforced brick wall. Which unless a brick coming through the windscreen hits you directly, is probably going to be a lot safer than the deceleration of hitting an oncoming car or immovable object.