Maybe a bit off topic, but I watched "The Bus Movie" on Youtube last night that someone else posted up.
They say that the rear engine was inherently unsafe in head on crashes, as the weight of the engine/gearbox was behind driver, whilst with a front engined car the forward stopping forces of the engine are not transferred through the cabin, but direct into the wall, which I sort of understand. (the bus body will be prone to crumpling, whereas in a front engined vehicle everything behind the engine wouldn't crumple)
They go on to say this is somewhat mitigated by buses being so much higher, but I suppose that only helps if you hit a car. (and lift your feet up quick!)
Cheerful subject - sorry !