In 1958, Sweden's Saab became the first car-maker to include seat belts as standard equipment in its cars.

The first belts were elementary contraptions which had to be manually adjusted, like aircraft seat belts. Locking mechanisms were introduced over the years. They minimised forward movement when jerked.

In the 1980s, seat belts with pretensioners arrived. In the event of a collision, sensors at the front of the car would trigger small explosive devices that tightened the seat belt, strapping the occupant in more tightly.

These pretensioners have since been replaced by electronic alternatives that do the same. They can be programmed to tighten when the car "senses" a crash is imminent. For instance, if emergency braking is applied or if roadholding is compromised.

Mercedes-Benz is the first to offer this pre-emptive feature in its cars.

What's next? Car-makers are now working on four-point seat belts, which go over the wearer's shoulders like haversack straps.

These are supposed to be better than the current three-point belts because they further restrict body movement in a crash. The force of the restraint is also spread more evenly.

This article was first published in The Sunday Times on May 4, 2008.