"Equipped with passenger-side air bag"--that ringing phrase, now nearly ubiquitous in U.S. car ads, may not be as desirable as it sounds. Although air bags have saved hundreds of lives, according to the U.S. National Highway Traffic Safety Administration they have also been implicated in the deaths of 21 children, including six infants who were properly strapped into rear-facing child seats. Because the bags are designed with adults in mind, a bag bursting out at a force of up to 320 km/h can slam a child in the head rather than the chest and cause severe injury.

The Big Three U.S. auto makers are trying to figure out how to make air bags safer for children. Ford, for example, received dispensation from the NHTSA to offer a special switch in its 1996 Ranger and 1997 F-150 pickups that will allow the driver to turn off the passenger-seat air bag. But leaving this safety decision up to a possibly forgetful grown-up has others worried. Though the risk is serious for all children under 12, Chrysler has been working with a maker of infant car seats on a design that keeps rear-facing seats from being thrown backward when an air bag deploys. General Motors, too, has focused on car seats and last week announced a $10.6 million advertising campaign to educate the public about proper car-seat installation.

Eventually, auto experts say, cars will come equipped with an air bag that switches off automatically if no one is occupying the passenger seat, or adjusts to match the height of the seat's occupant. Until then, NHTSA spokesman Tim Hurd advises, "The safest place for the child is in the back seat, all buckled up." As all too many parents know, however, an antsy little passenger can take the driver's eyes off the road--posing a whole new sort of safety problem.