One wonders whether there is a place for "Active Crumple Zones"? Instead of a car having to weigh more that the opposition, it carries an explosive charge in it's nose, which is used to provide a burst of forward momentum to the leading edge of the car during a crash, preventing it from being forced back into the passenger compartment. One can imagine refinements, such as inertial sensing and a feedback loop to control the size of the discharge, so the "virtual" weight of the light vehicle matches the vehicle that it is colliding with.

Count this as idle speculation rather then a serious proposal! Mind you, if a bike was equipped with such a system a 4WD owner would get a big surprise when they ran into a cyclist and got like-for-like.

Edit: I guess I'm really describing Reactive Armour for everyday vehicles.