Using the hand brake
Join Date: Jul 2002
Pre tensioner seat belts are pyrotechnical (small explosive thingie), they fire in case of an accident and tension the seat belt so you don't fly away. Just like Nicola wrote.
The usually come with a torsion limiter mounted inside the seat belt reel, so you don't get squized too much. It is also called load limiter.
It was standard on my Peugeot 206 GTi, don't know about Alfa (havent read the whole manual yet).