well said jake - the rii can shut a truck off, but it doesn't stop the truck instantly. if you get a truck moving 60mph and the driver is knocked out, the truck could easily coast the length of 2 football fields before it rolls to a stop.
Hm I remember when I worked a grocery store there were these "locks" on the carts and once they went over this wire it would activate the lock thus locking the wheel on the cart making it immobile. I wonder if there wasnt a system that could be used like this on a monster truck. Maybe it could lock the brakes when the rii is hit. Not only could it kill the engine but also stop the truck.