[kbui]

Visualize the problem this way. Imagine 2 exactly the same vehicle hitting perfectly head-on. The middle plane where the 2 cars meet will be the symmetry plane. Then all the mass of each car from the symmetry plane all the way to the back of each vehicle will have a velocity of 120mph at impact. The crushing of the each vehicle will start at the symmetry plane and progress toward the back of each vehicle. This happens because the mass at the front of the each car slowed down first and the back of each car keeps on coming. The progression of the crushing is slowing each car until all the mass of each vehicle is completely slowed down and rebound. Neither car's front end will pass thru this symmetry plane. Hence it's equivalent to each car is hitting a rigid/fixed plane at 120mph. All cars can only be designed for survivable accidents. Most will have their front end completely crushed at about 30-40mph into a rigid/stone wall. When you double or triple the speed, your kinetic energy is increased by a factor of 4 to 9. There is not much hope unless you have a full hi-strength steel cage or a tank. Even if you can design a structure to withstand that kind of crash, I am not so sure the occupant can survive from the head deceleration alone.