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S. Muralidhar

UNTIL the arrival of global car manufacturers to Indian shores, one of the most neglected areas was passenger protection (occupant safety). Now, technology in the form of safety restraint systems (SRSs), such as seat belts, crumple zones, impact protection beams and airbags, are available to car users. Some are standard features even in low-end, entry-level cars such as the Maruti 800. Yet, car owners in India do not actively participate in promoting safety while driving, for themselves or for others.

One of the most effective occupant protection devices in a car is the seat belt. Of all the SRSs in a car, active or non-active, the seat belt saves more lives than all the others put together. The importance of the seat belt cannot be overemphasised. It is statistically proven that wearing the seat belt doubles the chances of survival for the user in the event of a collision.

But despite the odds being loaded in favour of wearing the seat belt, compliance in India is almost non-existent. In many countries wearing the seat belt is mandated by law, not just for front passengersbut also for those in the rear. In India, with the launch of more powerful vehicles and high-speed highway travel now becoming possible, the law for enforcing seat belt use is just about getting activated.

Technology that touches our lives

Today's three-point emergency locking retractor (ELR) seat belt is a technological marvel vis-à-vis the relatively primitive belt across the driver's lap — the only safety device available even in racing cars of the 1930s and the 1940s.

Though a number of drivers still loathe wearing it, seat belt in the modern automobile is extremely comfortable and offers far more protection compared to its predecessors.

The nondescript looks of seat belts belie the kind of cutting-edge technology that go into making it work so effectively.

During a collision at high speeds, the seat belt prevents the user from crashing onto the car's steering wheel and dashboard or from being flung out of the windscreen. These can cause serious injuries to the head or chest of the driver.

To prevent such a crashing forward of the driver, the seat belt is made of special material that can take the tremendous force of a collision and at the same time cause minimal injury by the tightening of the belt against the driver's body. The seat belt works along with other safety features such as the airbag, crumple zones and anti-submarining seats to prevent the driver from crashing forward. However, the protection provided by the other safety features, including the airbag, will not be effective unless the seat belt is worn.

The sum of its parts

Seat belt webbing is one of the most complex and specially developed methods of weaving polyester fibre in such a way as to give it the ability to withstand the pressure of a collision and at the same time stretch only to that extent to accommodate and cushion the driver's forward motion.

The automobile industry continues to try out new materials that will be better than the current synthetic fibres used for seat belt webbing.

The modern day ELR seat belt's impact on the user is lessened by the fact that it passes across two of the strongest areas of the human body — the ribcage and the pelvic region. This is another reason why car seat belts should ideally come with height adjustments on the B-pillar, so that the user can change the position to get a best fit across his/her chest.

Modern seat belt systems also come with a set of assisting equipment that improves the belt's performance. These include ELRs, pretensioners and load limiters.

The typical seat belt system's webbing end is attached to a locking retractor mechanism, which is basically a spring-loaded spool that locks up and prevents the seat belt from loosening in the event of a collision. Most of the ELRs today's cars are triggered into locking position by the sudden movement of the seat belt, which is usually caused by a collision or sudden deceleration of the car. That is why even if you manually attempt yanking the seat belt swiftly across it tends to lock up, while a gradual pull will unwind the belt easily from the retractor's spool.

In some of the newer and more advanced seat belt systems, in addition to the ELR, another piece of equipment called the pretensioner pulls in the seat belt not just to prevent any slack during an accident, but also to ensure that the driver is forced into a safer posture to withstand the collision. In cars with airbags, the pretensioner is connected to the same central processor that controls the SRS airbags.

One other mechanism that some new seat belt systems use is the load limiter, which helps in reducing the risk of injury caused by the seat belt itself. In the event of a high-speed impact, the pressure of the driver's body against the belt can vary based on his built and weight. Load limiters allow the seat belt to adjust and provide a little more slack to prevent a heavier driver from getting injured by excessive seat belt rigidity.

Buckle up

A good seat belt dramatically improves the driver's chances of surviving a crash. But regular maintenance of seat belts is essential for their optimal performance. Look for signs of wear and tear. These may include a cut (abrasions can even be caused by objects in the driver's shirt pocket), excessive pilling or fraying, difficulty in locking the belt clip onto the clamp on the floor of the car and excessive slackening of the belt.

Wearing the seat belt should become a habit. Even low speed city travel can cause injury. Seat belts are not infallible, especially in high-speed collisions, but they would still halve the car driver's risk. That is reason enough why everyone should wear the belt.

So, remember to buckle up every time you take the car out. It is a matter of life and death.

Belt evolution

HERE are the milestones in the development of passenger seat belts.

1930-1950: Use of lap belts in automobiles make a beginning around the world. US laws make it mandatory for race drivers to wear lap belts.

1956: Two-point car seat belts are offered as optional accessory by a few European and American car manufacturers.

The Swedish car manufacturer Volvo (now part of Ford) becomes the first company to try out the two-point across the chest, diagonal belt instead of the across the lap type.

1958: Nils Bohlin, an engineer and designer with Volvo, patents the three-point safety seat belt. This early version consisted of two separate belts, one across the lap and another across the chest.

1959: Volvo, which went on to become the pioneer in improving safety standards for car occupants, becomes the first company to make the three-point belt as standard fitment for the front passengers.

1967-1968: Volvo introduces the three-point belt as standard for rear passengers.

It also introduces emergency locking retractors (ELRs) as standard fitment for front passenger seat belts, and thus was born the three-point, ELR safety seat belt.

1969-1970: More countries, such as Sweden, Australia and Japan, join the list of those mandating three-point belts a standard fitment in the front and rear seats of passenger cars.

Mercedes Benz introduces the three-point seat belt for the first time for rear passengers.

1970-1975: ELR seat belts find greater acceptance and become part of standard fitment in the cars of manufacturers such as Mercedes Benz, Ford and Volvo.

Volvo introduces the adjustable B-pillar anchor point for the driver's seat belt for affording a better fit for users.

1975-1979: New Zealand, West Germany and France join list of countries mandating seat belt use.

1980: Mercedes Benz is the first company to provide a driver's side airbag and pre-tensioners on all three-point seat belts.

1981 onwards: Seat belt use is mandated in more countries and finds increased acceptance as a life-saving, occupant protection system. Seat belt use also extends to other forms of passenger transport such as buses and trucks.

Future: New technologies and new materials will further improve safety for passengers by making seat belts more flexible and more responsive in the event of an accident, thereby reducing the risk of injuries caused by the belt itself.

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