Proposed federal standards aiming to protect passengers during side vehicle crashes are increasing the interest in side air bags - and renewing questions on material selection and styling.
The Department of Transportation's National Highway Traffic Safety Administration on May 12 proposed new tests focused on protection for a passenger's head in a side crash. Existing impact tests measure the impact on the torso and pelvis - allowing carmakers to put the emphasis on safety beams within car doors.
``We expect that this rigorous requirement will spur the introduction of a comprehensive array of technologies for side-impact protection,'' NHTSA administrator Jeffrey Runge said in a news release.
The proposal does not specify how carmakers would meet the new standards, but they probably would rely on some kind of curtain side air bag covering the window area. The agency said the improvement could save as many as 1,000 lives annually if the rule is phased in after 2005.
Side air bags are available as an option on a variety of vehicles, but typically are not standard equipment.
Automakers have been cautious, trying to make certain the systems will work properly, said Tom Brown, product engineering manager for side-impact products with Troy, Mich.-based Delphi Corp.'s electronics and safety division.
Side air bags - typically tucked into the roof rail under plastic trim or within a car seat - must react in as little as 20 milliseconds, compared with 50-60 milliseconds for front air bags. Systems aimed at providing protection during a rollover also must remain inflated for longer, he said.
Air bags created for sport utility vehicles also are far larger, some stretching the entire length of the interior.
``It's a little different with a side impact than frontal,'' Brown said.
But some questions popping up now about side air bags are similar to those related to the early passenger-side air bags in instrument panels.
As with those air bags, carmakers and their suppliers must find trim materials to cover the bags that can withstand the temperatures and pressures when the systems are triggered.
``It's almost déjÃ vu to the early 1990s with the passenger-side air bags,'' Brown said. ``We've got the same kinds of questions for the trim for side impact now that we had then.''
A standard PVC cover skin would be less expensive but, like the skin on an instrument panel, probably would require a visible seam for an air-bag release, he said.
That would leave designers forced to decide if they should style that seam into the trim or seek out alternative materials, such as a thermoplastic polyolefin, that would allow for an invisible seam.
``This is really the next generation for air bags,'' Brown said.