Making cars safer

As I mentioned in Car Clinic a few weeks ago, passive safety equipment, especially airbag technology, has reached new levels of sophistication in recent years.

Let's look briefly at the history and current state of passive car safety.

Attempts to make cars safer for the occupants in the event of an accident started with the introduction of seat belts and padded dashboards in the 1950s.

From simple, two-point designs, seat belts have evolved to the now widely adopted three-point, inertia-reel designs.

Later seat belts were fitted for rear-seat passengers - studies found that unbelted rear passengers increased the mortality rate of belted front seat occupants nearly five-fold.

The latest generation of seat belts incorporate the following refinements:

Some device is provided which reduces the shock load of the belt on an occupant during an accident by allowing the belt to extend slightly as the force on it increases.

Pretensioners are used to tighten the seat belts if signals received from sensors indicate to the on-board computer that an accident may be imminent.

This prevents the occupants from jerking forward, or sliding under a loosely worn belt in a crash.

Mercedes' Pre-Safe system, launched on the S-class in 2002 and now into its second upgrade, was a milestone in the development of this technology.

It's a comprehensive and integrated system which literally endows the car with its own reflexes. The system continuously communicates with the electronic stability programme, brake assist programme, and airbag controls.

Which brings us to airbags. First used in the late 1980s, airbags have now spread to entry-level cars. Along the way they have evolved and improved considerably.

The first airbags were designed to protect an unbelted 75kg person in a 60km/h frontal crash.

Unfortunately, the force needed to achieve this could injure smaller adults and children, so second-generation, depowered airbags appeared around 1998.

Even with these there is some risk of injury to eyeglass wearers, small children in the front seat, and short drivers who must sit closer than 250mm from the steering wheel.

Statistically speaking, however, there is no doubt the airbags do far more good than harm in an accident. What started as driver-side front airbags only, has proliferated into many types of devices: passenger-side front bags, side-impact, curtain-type, knee and chest airbags, even rear-seat side-impact bags.

"Smart" airbags have appeared which take into account numerous factors - weight, height, belt use, and so on, all determined by sensors - to compute the appropriate type of deployment.

Research continues unabated to produce safer, better and smarter airbags. Now, if only we could find a way to produce safer, better, more considerate drivers.