Alright. Not an open road accident, but definitely fscking funnier than yours. Had the '77 Sierra in the back yard attached via some seriously hardcore chain to a 50 foot tall, very thin tree. We were trying to bring it down, but didn't want to leave a stump. So we grabbed some shovels and dug out around the stump and cut the roots. Kept trying to pull it down with the truck as we cut off the roots. Anyway, I got out of the truck and went back to help hack away at a few more. I left it in neutral to keep tension on the lines. Cut a few roots and start walking back to the truck.
I noticed the lines go slack next to me and my brother yells "GET OUT OF THE WAY!" and the truck starts rolling. The tree comes down on the top of the closed tailgate and makes a massive dent, and the truck keeps rolling out from under the tree only to roll straight into another one.
Why did the tree fall? My idiot brother hit it with a hammer, which was apparently enough to throw it off balance.