I was pretty busy mixing concrete with a gas powered mixer, backing away from mixer with a loader full of concrete, I turned about quickly to check the path behind me. When I turned back to facing forward, my forward/reverse foot controls had gone limp, inoperative. I was on a slight grade that led to a steeper bank, then woods. , the tractor started rolling backward. I fumbled with the foot controls, not believing they'd gone limp. The tractor rolled backward over the bank before I could even think to hit the brakes. I guess I should have thought BRAKES! first, but you know, I hardly ever use the brakes on a hydro tractor. It all happened pretty quick. Long story short, I got to the brakes, just before crashing into the woods, and lucky did not flip the tractor. When I had turned to check behind the tractor, my elbow, with heavy coat on, flipped the range shifter to neutral, but I did not know it. I notice now that range shifter sits up pretty tall on the seat. It's an easy thing to inadvertently shift that to neutral. Be careful out there guys. **** happens.