This poses more questions than it answers... How would you be run over by the BACK wheels of a truck going 45 mph? It seems like a next to impossible thing to be able to not be hit by the truck, but get under it as it passes so that you are ran over by the back wheels? I can't imagine a reliable way to even do that.
Meanwhile... funny thing... a slow heavy truck is more apt to kill you than a fast moving truck. You'll get hurt to be sure, but the faster the truck moves the less of its weight bears down on you as it goes over you. You actually have a better chance of dying by a truck backing slowly over you.
But man, if you pull this off, it is probably going to really hurt. I wouldn't want to try.