Even though their vehicles will meet 1997 federal side-impact standards, General Motors Corp. and Ford Motor Co. are moving aggressively forward with plans to install side air bags for the '97 model year and beyond.

Surprisingly, Chrysler Corp.--the first automaker to equip its entire model lineup with front air bags--is taking a wait-and-see stance on active flank protection systems.

The federal regulation states that vehicle occupants may experience no more than 85 gs (in 4-doors) or 90 gs (in 2-doors) in the chest area, and no more than 130 pelvic gs when a 3,000-lb. (1,360-kg) object strikes the side of the vehicle at 33.5 mph (54 kph). This can be accomplished with structural improvements or side air bags.

Each of the Big Three says 100% of its '97 vehicles affected by the regulation will meet federal standards via modifications such as additional structure around the door ring and more cross-car beams.

But Ford and Miles Inc.'s Polymers Div. developed another solution for the Ford Contour/Mercury Mystique and Windstar minivan: an energy-absorbing door trim featuring foam between the interior door panel and the inner part of the door's exterior.

GM is jumping on the side air bag bandwagon started by the Volvo 850 in 1995 and the Volvo 950 in '96 by equipping its '97 Cadillac DeVille and Catera models with seat-mounted bags for front-seat passengers. Ford says it's still on schedule to introduce combination head-torso side air bags for front-seat passengers on its full range of cars and light trucks in Europe and North America in two or three years.

Chrysler is being more cautious. "We're studying what's going on in the industry, but haven't made a determination," says Ron Zarowitz, Chrysler's manager of vehicle safety and regulatory affairs. "We're continuing to study data--important data on real-world benefit."

Mr. Zarowitz admits that the recent wave of negative publicity concerning risks associated with air bag deployment has the No.3 automaker a bit gun shy. "We're considering all the pluses and the minuses. Nobody wants surprises," he says.

Some industry insiders think Chrysler's approach may be a mistake considering the marketing advantage side air bags could present. A recent survey by the Automotive occupant Restraints Council indicates that 84% of motorists think that having side air bag protection is either somewhat important or extremely important.

"We feel that there is a societal benefit and have analysis that shows (side air bags) are an improvement over the federal side-impact standard," says Mick Scherba, GM's director of occupant restraint systems.

Most early side bag systems, including Volvo's (supplied by Lear Corp.), Cadillac's and Ford's early efforts protect the torso only. Federal data show that side-impact head injuries result in more than 15,000 fatal or serious injuries a year.

Ford's two- or three-year plan involves a combination head-torso bag. And GM says it is quickly migrating to a bag that also protects the head.

"Side air bags are a relatively immature technology and will continue to evolve," says Mr. Scherba, adding that beyond refining the technological aspects of side bags, they eventually will extend to reach the rear seats as well. In fact, Takata Inc. says it has a contract to supply rear-seat side air bags for a '97 European model.

Despite Chrysler's resistance at this juncture, most folks in the industry are bullish about the future of side air bags. "People are going to be aggressive if they can see a marketing advantage," says Larry DeBow, development engineer at DuPont Automotive.

Lear Chairman Kenneth L. Way says he expects side air bags to reach at least 60%--and could hit 100%--of market penetration by around 2000. John A. Janitz, executive vice president for TRW's occupant Restraint Systems Group, is less optimistic; he predicts 30% penetration by 2000. At the same time, he says TRW is working on side air bag programs for 55 different vehicles.

Although Ford's side air bag program is moving ahead, Bob Hultman, Ford's chief side-impact research engineer, says side bags raise some questions. "You don't want the bags to induce injuries and you want them to be effective for all size occupants with no seat-belt interference," he says. "And you have to be careful about the noise being so close to the occupant's head."

Because side bags aren't regulated by the government, the industry has an opportunity to refine the technology and tailor the systems for specific vehicles.

"We have the ability to optimize the aggressiveness of the deployment," says Mr. Scherba. "Front air bags have to have a certain aggressiveness because they have to be able to stop a 165-lb. (75 kg) unbelted man."

The additional air bag protection may be what the U.S. industry needs for its world cars to meet European side impact standards, which differ significantly from those in the U.S. Dummies used in the U.S., for example, measure acceleration, while the more advanced European test subjects measure deflection and compression. "A bag might make it easier to pass both tests," Mr. Hultman says.

Mr. Hultman says the harmonization of international standards is important because "we're wasting resources on two different designs, and the customer is paying for it and not getting any additional benefit." He adds that it's going to take time to get all the sides to agree.