Good question, I'm kinda wondering the same thing. Is cutting the seatbelt a common occurance? I would hope the seatbelt buckle would operate flawlessly after a high stress situation. Maybe they don't release while under load? I don't know. I wonder if the airline style seatbelts, with the lever instead of the button, are more reliable after an impact. Seems like a lot of the racing belts are like that, rather than the button type that you find in cars.