Well I say stationary, I guess it’s almost stationary. I was driving through a town and managed to get my truck wedged between a car and a house, it wouldn’t budge when I was hammering reverse and forward was the house wall. I was being chased by zombies and as they came close to come and bang on my truck, my attempts at reversing would occasionally bump the speed to -1 despite not moving anywhere and the adjacent zombies would spontaneously explode as if they were run over at full force. I guess they die if they collide with the car and the speed is anything other than 0, but this seems not as intended? I think damage at low speeds probably needs to be nerfed.
PS I managed to wriggle my truck free and get out of dodge before I was dragged from it and nommed in case anyone wondered.