Airbag Technology

Since Ralph Nader's seminal book "Unsafe at Any Speed" came out over 40 years ago, seat belts, padded dashboards, collapsible steering columns, improved bumpers and other safety features have become standard fare on cars and trucks. After seat belts, the most significant advance in automobile safety has been the airbag.

Airbags are gas-inflated cushions that rapidly discharge from compartments hidden in steering columns, dashboards, roof rails, doors and seats, hyper-inflating to protect a vehicle's safety-belted adult driver and passengers.

Driver and front-passenger airbags have been required in cars by the federal government since the 1998 model year (since 1999 for light trucks). Mercedes-Benz first put airbags in all its models in 1986.

By the National Highway Traffic Safety Administration's own estimates, airbags saved nearly 3,000 lives last year, bringing their total to 28,000 lives saved by airbags through the end of 2008. NHTSA calculates that using a seat belt and having an airbag reduces the risk of death by 61 percent. Simply put, this combination is the most basic and effective safety precaution available.

In recent years, an armada of airbags has been added to cars and trucks. Some rides, such as the BMW M3, now possess as many as eight of the nylon inflatables.

Side-impact airbags, which Volvo debuted in the mid-1990s, are one of these bonus bladders. Variations shield the pelvis, chest and head and can deploy from the door, seat or roof of a vehicle. Side curtain-type airbags protect the head and, in some models, remain inflated for up to five seconds during rollovers. BMW was an early curtain pioneer.

Side airbags not only help passengers in more rollover-prone sport utility vehicles, but they also protect occupants of smaller cars from these same light trucks.

The Insurance Institute for Highway Safety is a nonprofit trade group that crash tests vehicles and conducts related research. The organization's chief operating officer, Adrian Lund, says of SUVs, "When these things hit you on the side if you're in a car, basically their hood is right at your head."

Side airbags can provide a cushion between bodies and intruding SUVs. "We've seen about a 45 percent reduction in fatal injuries for vehicles that are equipped with side airbags," Lund says.

NHTSA is working on upgrading side-impact safety standards for all passenger vehicles. Starting Sept 1, 2009, the agency will phase in new side-impact standards that will require side airbags as standard equipment.

Other airbag innovations continue apace. General Motors was the first to introduce dual-depth passenger-side airbag. These bags inflate to different girths, depending on variables such as seat position, the severity of the crash and whether the seat belt is clasped or not.

Dual-stage airbags, present on several new Volvo models, work slightly differently. With this technology, a sensor measures the severity of a crash and seat-belt usage to adapt airbag inflation speeds; a severe crash results in a full, rapid deployment, while a fender-bender triggers a slower, 70-percent inflation.

BMW has also been at the forefront of advanced airbag technology. Its 7 Series was an early adopter of knee airbags, which protect the legs and help the driver avoid sliding down and forward during a crash.