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Understanding Side Air Bags

Understanding Side Air Bags

By Jeff Youngs,
Since there are currently no federal requirements for side air bags in vehicles (as there are with front air bags), the federal government leaves it up to automotive manufacturers to decide whether to offer them and how much to charge for them. Automakers also determine what type of air bags to use, which models to offer them in, where to locate them within the vehicle, and which seating positions they will protect. While there is general agreement that side air bags are a viable safety technology, the absence of federal oversight for side air bags means that all automakers are not working from a single consistent standard for design and performance.

Side air bags can protect the head, the chest, or both, depending on the design. The Web site for the National Highway Traffic Safety Administration (NHTSA, provides a complete list of automakers that offer side air bags, along with details on the various types offered.

Protecting the head
Air bags that protect the head use a curtain or tubular design. Both designs typically deploy from the roofline in a downward motion, covering the majority of the window, and sometimes the entire window. They offer head protection only to occupants who are tall enough so that their heads would impact the window in a crash, and only to those seated adjacent to where the air bag deploys (not those seated in the middle). While vehicles with head protection air bags always provide protection for at least the front-seat passengers, they do not always cover second- and/or third-row passengers. To learn more about air bags that protect during rollovers, read "New Safety Technology: Rollover Air Bags."

Protecting the chest
To protect the chest and rib cage, some automakers offer a second air bag (often called a torso air bag) that deploys from either the door panel or the side of the seat. Chest-protecting air bags are less common than head-protecting air bags, and they are usually installed to protect front seat occupants. Torso protection for rear-seat passengers is currently offered only by a few automakers.
Some automakers use a "combination" air bag to protect both the head and the chest with a single dual-chamber air bag that deploys from the door or the side of the seat. This type of air bag is most common on convertible models, since there is no permanent roof to install a head curtain-style air bag.

Are they safe?
While NHTSA does not currently have any safety requirements for side air bags, it has publicly stated that these air bags should not cause harm to occupants, regardless of their age, size or seating position, and whether or not they are properly restrained with a seat belt.

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 for side air bags. Collectively, these groups have created a series of tests that each participating automaker has agreed to perform to ensure that its side air bags meet acceptable standards.

There are 15 different tests that cover every type of air bag in every possible location within a vehicle. Tests are conducted with "dummies" that represent the average 3-year-old and 6-year-old child, as well as a small adult woman. The logic is that if an air bag is safe enough for a child or small adult woman, it is also safe for larger adults.

Automakers try to account for real-world situations by conducting tests with the dummies in various positions in which they are not properly restrained, such as sitting sideways on the seat leaning against the door, lying down on the seat with their head on the armrest, and leaning on the door and window as if asleep.

There are many different applications of side air bags in use today because the technology is evolving so rapidly. As a result, more vehicles are likely to be equipped with side air bags in the near future, and those designs are likely to evolve to offer protection for a wider range of occupants.
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