In a post in Straight Dope Message Board, run over and run under are used in car accident context, but I can't differentiate them. In my understanding, in both cases the victim is hit directly by the vehicle's front, no wheel runs over the body. I cannot google out an example of run under in the context of car accident (only thrown under the bus, but this is irrelevant).
So what is the difference between run over and run under?
When hit by a car, the vast majority of people are not run over; they are run under. The lower legs break, sending them into the air. They usually strike the hood of the car, often with the back of the head impacting the windshield, "starring" the windshield, possibly leaving a few hairs in the glass. They then go over the top of the car. They are still alive, although with broken legs, and maybe with head pain from the nonfatal windshield impact. They die when they hit the ground. They die from head injury.
A person hit by a bus would actually be run over. There would be two separate sets of injury. The first would be when the kinetic energy of the bus struck the pedestrian. Mass times velocity squared. This is the closest approximation to the ground that your example offers. The likelihood is that they would incur lots of fractures, but not be killed by simple impact. If they were killed, the injury I have seen most often, in my autopsies as a medical examiner, is rib fractures, with the free ends of the ribs bending inward at the moment of impact, to perforate heart and lungs. This is a vanishingly rare injury in fatal falls.
By the way, what is go over the top of the car?