I cover the seat belt with a blanket, suitabley confused/stupid people can't work out why they can't get off the stretcher. Another option is this thing called "the police" as we are not allowed to kidnap or restrain people. Bloke on my motor the other day got aggresive so I got shirty back, got my mate to pull over and we dispatched the patient to the pavement. Job done. Saying that, he didn't really need to go to hospital, he was one of those who "knows his rights" and "pay your wages".