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By Jim Kerr

Did you know that the best safety feature on your vehicle was introduced to the market in 1959 by Nils Bohlin, a Volvo engineer? Or that it has been a standard feature on passenger cars since the late 1960s? And that 92.5 per cent of Canadians use it on a regular basis?

If you guessed this feature is your vehicle’s three-point seat belt, give yourself a pat on the back. It is estimated that this simple device may have saved over a million lives since the 1960s. But though a simple design, there are more to modern three-point seatbelts than meets the eye.

When you click the buckle in place on your seatbelt, it does more than just rest across your lap. Many newer vehicle seatbelts for the front seats, and rear seats in some vehicles, are equipped with pre-tensioners. The most common type of pre-tensioner uses an explosive charge that is activated by the airbag system on your vehicle when it senses a crash. The explosive charge is contained in a cylinder and pushes a piston that is connected by a cable to the seat belt. When the pre-tensioner goes off, the seatbelt is rapidly pulled tight around the occupant and holds them back against the seat cushion.

The second type of pre-tensioner is mechanical. Although it performs the same functions, this type can be reused several times. Mercedes-Benz uses this type in some of their vehicles with their Pre-Safe system that automatically tightens the seatbelt in near crash or accident avoidance situations and releases it again if no collision occurs.

Now, with you held firmly in the seat, the seatbelt is ready to let you slowly ride down the collision. When your vehicle stops suddenly during a collision, the forces on your body are tremendous and serious injuries could result. To prevent this, the seatbelts allow your body to decelerate at a slower rate by extending their length slightly as the force on the belts increases.

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