When you're shopping a family car, you probably use the frontal crash test ratings to help determine whether a vehicle will protect your family. It's actually side-impact collisions that pose the greatest risk of injury to occupants. This is because the "crush zone" — the space between the outer edge of the vehicle and the passenger compartment — is so much smaller on the side than on the front or rear of a vehicle. In response, most automakers have been outfitting their vehicles with side airbags designed to protect passengers' heads and chests.
"As vehicles have improved in how they protect occupants in frontal crashes, the relative importance of protecting people in side-impact crashes has increased," says Adrian Lund, chief operating officer for the Insurance Institute for Highway Safety (IIHS). In newer model cars in collisions with other vehicles, there's now a higher proportion of deaths in side-impact crashes than in frontal ones." In 2007, 8,225 people died in side-impact crashes, accounting for 28 percent of all vehicle crash fatalities.
We're going to explain the basics of side airbags, so that you'll at least understand the differences between the various types when it comes time to equip your family car.
Protecting the Head
Side airbags can protect the head, the chest or both, depending on their design. Safercar.gov is a good place to start your research, as it provides a complete list of automakers that offer side airbags along with details on the various types.
Airbags that protect the head only use a curtain or tubular design. Volvo was the first to offer head-protecting curtains, starting in the 1999 Volvo S80. Both designs typically deploy from the roofline in a downward motion, covering the majority of the windows, sometimes all of them. They offer head protection only to occupants who are tall enough that their heads would impact the window in a crash. Further, they only protect occupants seated in the outboard positions adjacent to where the airbag deploys.
May Not Help Kids
Vehicles with head protection airbags always cover at least the front-seat passengers, but they do not always cover second- or third-row passengers.
Even if a head curtain airbag covers the rear seats where children are most likely sitting, it won't necessarily offer them any protection. "Most children are too short to receive any protection from a curtain-type side airbag," says Russ Rader, IIHS spokesperson.
"At the Chrysler Group [which includes the Chrysler, Dodge and Jeep brands], we design our curtain-style airbags to provide protection for the 5th-percentile female dummy," Scott Redman, manager of safety planning and policy, told us. The 5th-percentile female dummy is 5 feet tall and weighs 100 pounds.
Some automakers use what's called a "combination" airbag to protect both the head and chest with a single dual-chamber airbag that deploys from the door or the side of the seat. Ford uses this type of airbag in most of its cars, although it uses the curtain-style airbags for head protection in its SUVs.
Other automakers use combination airbags exclusively for convertible models, since there is no permanent headliner to use for a head curtain design.
What Happens in a Rollover
An added benefit of some head protection airbags is that they help reduce injury and the potential for ejection during a rollover accident. Airbags that have a rollover feature differ from the standard type in two ways. First, the airbag stays inflated longer to compensate for the extended time period in this type of accident, and second, a sensor assesses when a vehicle is about to roll over even if no collision is involved.
"A typical side-impact crash takes about 60 milliseconds from start to finish, while a rollover collision can last multiple seconds," explains Jim Khoury, manager of advanced safety technology engineering at General Motors.
GM's curtain-style airbags with rollover protection retain about 80 percent of their inflation for about 5 seconds — about three consecutive rolls of a vehicle. These airbags are slightly larger than GM's non-rollover curtain design and they cover the entire window, which helps to decrease the chances of an occupant being ejected from the vehicle. "Of course, being properly restrained by wearing your seatbelt or being in the appropriate child restraint is the first and best line of defense for reducing injury in a crash," Khoury notes.
Protecting the Chest
To protect the chest and rib cage area, some automakers offer a second airbag, usually called a torso airbag, that deploys from either the door panel or the side of the seat. Volvo was also the first to offer chest protection, with its Side Impact Protection System (SIPS), introduced in 1994.
Fewer automakers offer chest-protecting airbags, and they are usually installed only in the front seat. Torso protection for rear-seat passengers is currently offered only by European automakers, among them Audi, BMW, Mercedes-Benz and Volkswagen.
Mercedes-Benz feels so strongly about the benefits of side airbags that they are standard for both front and rear passengers in most of its vehicles. "Rear-seat torso-type airbags are designed to protect the chest area of adult occupants, but they do have the potential to offer some protection to children, because they are usually at a height that would be roughly equivalent to a child's head or shoulders," says the IIHS' Rader.
While there are voluntary testing standards that most automakers use to ensure their airbags will not cause significant injury to a child, some automakers that offer torso-type airbags for rear passengers take added precautions.
"Even with the extensive testing, we know that not all consumers, primarily those with young children, are comfortable with having those types of airbags in the car, so we've made the decision to offer them only as an option," says Steve Keyes, a spokesperson for Volkswagen and Audi.
BMW also believes rear-seat torso airbags should remain optional, but in addition, it ships all vehicles equipped with these airbags to the dealer with rear-seat torso airbags deactivated — even if the vehicle is a special order for a buyer who has requested these airbags. The customer then has to ask an authorized retailer to activate the airbags, a process performed free of charge at the dealership. Once activated, the airbags can be deactivated at any time, at the consumers' request. A sticker located on the inside of both rear doors indicates whether the airbags are active or not, should a future owner not be aware of a prior owner's decision.
"We want owners to make a conscious decision to have these airbags activated or deactivated," says William Scully, BMW spokesperson. "We simply don't want any concerned parents to worry about this."
Are They Safe?
NHTSA has publicly stated that these airbags should not cause harm to occupants, regardless of their age, size and seating position — regardless of whether they are properly restrained.
In 1999, NHTSA asked the Alliance of Automobile Manufacturers and the Association of International Automobile Manufacturers, which together represent 19 automakers and numerous suppliers, to develop voluntary standards. The IIHS' Lund heads up the Technical Working Group (TWG) formed by crash safety and biomechanics experts from all the companies in response to NHTSA's request. The TWG created a series of tests that each participating automaker has agreed to perform to ensure its side airbags meet acceptable standards.
There are 15 different tests that cover every type of airbag in every possible location within a vehicle. Tests are conducted with dummies that represent the average-size 3-year-old and 6-year-old child, as well as the 5th-percentile female dummy. The thinking is that if an airbag will not harm a child or small adult female, it's also safe for larger adults.
"Airbag technology is evolving very rapidly, which is why we have so many different applications of the technology in use today," says Phil Haseltine, president of the Automotive Coalition for Traffic Safety. "In the future, we'll probably see more airbags in vehicles rather than fewer, because there are so many potential benefits from airbags during side impacts and rollovers."
