Can anyone 'splain to me why seat belts seem to be so prone to jamming on impact?
If I were to design a seat belt buckle, I would make sure that it would still operate after being subject to a load equal to the breaking strength of the webbing, no?
This goes back to research do in the 1960's and 1970's by the Department of Transport (D.o.T.) in the UK. They were trying to establish why so many car accidents where fatal.
One of the things that came out of those tests was the very poor design of the seat belt's. The seat belt is intended to keep the driver/passenger in the seat, which under most circumstances is the safest place for them.
They discovered that the actual locking mechanism's failed under peak loads. That meant that the belt would effectivly break. With fatal consiquences.
They redesigned and tested various designs before settling on the current design. If the current lock fails, the parts in the lock itself fail in such fashion as to jam the lock closed. Thus preventing the occupant being throw from the seat.
Ofcourse the downside of that you very occasionally get a situation in which some one is then trapped in the seat.
It should be understood by anyone reading this that not using a seatbelt or using a design that does not jam closed WILL BE FATAL in a crash.