Air bags have been with us quite a long time now and they continue to proliferate – especially in upscale vehicles where safety is often a major sales point.

I get lots of letters from readers who are puzzled by the air bag options now available and are not sure exactly what they’re getting for their money. Basically, the more you pay for a vehicle, the more air bags you’re likely to get, but that may not always be the case.

One automaker may decide that its best course is to offer extra air bags as an option, while another may see more sales opportunities for their new product by including extra air bags as standard. It’s sometimes a complex process and not easy to figure out. Automakers go to great lengths to pack in the maximum number of features the sticker price will allow, but some companies have different priorities than others.

As most experienced motorists know by now, the first air bags were fitted to the driver's side only and were of a simpler and less sophisticated design than they are now. While legislators moved to make air bags mandatory once the technology was available for automakers to economically include them, some manufacturers edged ahead of the legislation and began adding air bags in different locations around the vehicle. Initially, passenger side air bags were either an option, or an addition you'd only find on upscale vehicles. For a long time now, though, just about all vehicles have offered dual air bags up front.

Initially, all air bags deployed at the same rate of speed, regardless of the severity of the impact. This led to some tragic accidents, many of them involving low-speed collisions and front seat passengers who were not sitting correctly in their seats. A couple of family members of mine were injured in a rear-ender by the air bags in a situation which the seat belts could easily have taken care of.

It's always worth remembering that the main impetus for air bags originally came from the fact that Americans would not wear seat belts and insurance companies there wanted automakers to offer some kind of supplementary restraint. Canadians, incidentally, have been very reliable seat belt wearers from "day one" and the figures for usage in this country have always been impressively high.

All new vehicles now have "second-generation" air bags which deploy at different rates according to the severity of the impact. A low-speed impact only brings a mild response from the bag system, while a high-speed crash will see the bag deploy at full speed and pressure. Since the adoption of second-generation systems, injuries from air bags seem to have diminished considerably and it's a long time since I actually heard of one involving any serious injury.

As soon as dual air bags became common up front, safety-oriented automakers began fitting side bags to further protect the front seat occupants. These bags deploy from behind the door trim, or sometimes from the sides of the seats themselves. They are very effective in protecting people from side impacts, but concentrate their protective powers on the lumbar region or rib cage. Not long after front side bags became popular, upscale automakers started fitting side air bags in the rear compartment of the vehicle to protect people seated in the back. In case you're counting, we're now up to six air bags per car, standard or optional, depending on which model you choose.

Of course, the most vulnerable part of the body in a side impact is the head and the next step was to develop an air bag system that would take care of such eventualities. The result was the "curtain" air bags that have popped up on all kinds of vehicles, mainly in the prestige segment. Curtain air bags deploy along the entire length of the passenger compartment and protect the heads of all occupants who are seated in "outside" locations. The passenger who sits in the middle of the rear seat has always presented a challenge to automotive safety people, though all kinds of techniques have been experimented with. Side curtain air bags might be the most sought-after units yet because we all dread the idea of someone running a light and "T-boning" us in an intersection.

Air bags, incidentally, are triggered according to impact by technically complex sensors around the vehicle and deployed using a mild explosive device. They inflate in milliseconds and can certainly be lifesavers in any kind of severe accident situation.

Automotive safety engineers are always working on new ways to ensure passenger safety, but motorists should remember that defensive driving is the best way to avoid accidents. Also, seat belts are still the first line of defence and are the safety features most likely to save you from serious injury in a collision - especially the pre-tensioner units that "cinch up" at the first stage of an accident.

As far as air bag options go, the best advice I can offer is to take whatever's on offer, even if it means skimping on luxury extras on the vehicle. On average, it's unlikely that you'll ever see an air bag deploy, but if you do, it could be the one item of automotive technology that could sake your life and those of your passengers.

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