Most bulldozer drivers assume that you step out of the way, not into the way. Human wheel chock does not work for cars, why would it work for bulldozers?
I recall reading the story from one of her comrades. They were playing 'chicken'. They would jump on the dirt rolling up in front of the blade, then jump off again.
Po, po, little Rachel wasn't very good at jumping off.
That is truely insane!