I have a large USA DLC world in 1984 right now, and it has become increasingly glitchy as i add more and more stuff but recently on an oil line my Peter-built 359 got stuck with the back wheels of the trailer off the road right by the oil pickup and the cab seems to have jackknifed with the trailer.
I was trying to insert a screenshot of it but you will have to go to this link to see the picture
You can’t demolition something when one of your own vehicles is on it. You’ll simple get a “vehicle in the way” warning. If reversing it a few times does nothing, you could try to send it back to the depot and hope it responds to that. If not, mess around with the roads around the stop hoping that it will jolt free or go back to an earlier savegame.