Well, let me tell you. It happened to me with my 78 Dodge Diplomat. I almost won the Darwin Award that year.
It happens. A family friend was nearly killed by her Lincoln when she got out to get something out of her other car, and when she closed the door, it went into reverse, and ran over her leg. Her leg got hung up somehow under the car, and she spent an hour, face down in the snow, yelling for help before someone heard her. She doesn't have a very strong voice anyway, and with the snow, and her being face down, nobody heard her. The mailman finally heard her and called 911. Her leg had been crushed and for some time, the doctors weren't sure they could save her leg. She threw a clot and almost died. She made a good recovery, but she will always have a limp.