I got really confused with the motorbike restrains on Velocity at Flamingo Land - I thought they were going to send the train out without fastening me in, as I couldn't figure out how to do it. Turns out that it was actually just a really slow dispatch (a usual at that park).
Also, at the opposite end of the scale, I went on an enterprise, then thought my car's seatbelt had been broken, so I went to the next carriage, and that one didn't have one either. Obviously now I know you don't even need restraints!