Automotive air bags not just a bag of hot air

By Barry Lake

ASKING if air bags in cars are good or bad for your health is a bit like asking the same question of polyunsaturated fats.

They can be good and they can be bad... depending on how -- and if -- you use them.

It's preferable to ensure your car is well serviced and fitted with a good set of tires, then drive carefully, and stay alert.

The chances are you won't crash and you will never need to "test drive" your air bag.

But like insurance, it is good to have the air bags "just in case".

Forced to make a choice, I would opt for a good-handling car, ABS brakes, and a good set of tires rather than an air bag. It is far better to avoid the crash in the first place.

Air bags were primarily invented for Americans who insisted on driving without seat belts. And the bags have done a reasonably good job in protecting people in uncomplicated front and rear collisions.

Overall, seat belts are better than bags. Combine the two, and you have a very safe situation. The seat belt does most of the work while the air bag ensures you don't smash your face and head on the steering wheel or, in the case of front seat passengers, on the dash panel.

Don't kid yourself, though. An air bag is not a big puffy pillow that will catch you in its soft embrace.

When an air bag comes out of the steering wheel center or from the dash panel on the passenger's side at several hundreds of kilometers an hour, it does so with an almighty explosion that would wake the dead.

It has to inflate within milliseconds to be of any use, and the "catching" is done as the bag deflates -- also very rapidly.

The pace and violence of the bag's sudden inflation means there is an element of danger involved. There are still problems with drivers who sit close to the steering wheel, and for children who might be sitting too far forward in the front passenger seat.

There are also dangers for people wearing glasses, or who are smoking or have a pen in their mouth. But these risks have always existed, with or without belts or air bags.

In the U.S., air bags are designed to save occupants who are unrestrained by a seat belt. In such a case, the air bag has to inflate even more rapidly in order to be fully inflated by the time the passenger is flung violently against it. Therefore, all of the above dangers are magnified.

But law or not, if you are wearing a seat belt you will be far better off. In accidents the belts alone are sufficient. Seat belts are designed to stretch progressively in an accident so that the occupant stops less violently than did the car itself.

Because of this, the occupant approaches the steering wheel or dash panel at a much lower speed. This enables the car's designers to provide air bags that do not activate at all in accidents at low speed, and which -- when needed -- inflate more slowly and less violently than the American variety.

Air bags in the U.S. are designed to operate after vehicle impact speeds as low as 12kmh. In most other countries it requires a speed of more than double that to activate the air bags.

This means a huge saving in repair costs after accidents at low speed because the bags, steering wheel center and dash panel do not need to be replaced.

But motorists still need to think about safety. A modern car with a strong occupant capsule surrounded by impact-absorbing front and rear "crumple zones" and side-impact protection, combined with seat belts and air bags, will help lower the risk of death or serious injury in a crash.

Accidents occur unexpectedly, so stay alert behind the wheel. With both hands on the steering wheel at all times you are better able to steer around a potential crash situation.

It also ensures that, should a crash occur, you are seated in a position in which both the seat belt and air bag will be able to protect you.

So don't rest your elbows on the steering wheel center, drive with a pen in your mouth, drink from a bottle, or -- as a passenger -- ride with your feet planted firmly on the dash panel containing an air bag.

So, belt-up, bag-up, and above all, drive safely.