Crash tests of side impact air bags show they can help prevent serious head injuries, even in collisions between passenger cars and high-riding light trucks, insurance industry researchers report, according to Associated Press (AP). In its first such tests, the Insurance Institute for Highway Safety rammed a pickup truck travelling at 32 mph into the side of a Volvo S80 going 16 mph and found the car's side air bags protected the crash dummy's head against what could have been a fatal head injury.

The Volvo S80 comes with, as standard equipment, an inflatable curtain air bag that unfurls from the roof along the door to protect the head.

In a crash test without the air bag, the heads of the driver and rear passenger dummies were hit by the hood of the pickup truck. The force was high enough to kill the passenger, while the driver dummy's head barely escaped severe impact, according to the institute.

In a test with the head protection air bag, the curtain acted as a cushion between the dummies' heads and the hood. Instruments on the dummy heads recorded a low impact.

Nearly 10,000 people were killed last year in side-impact crashes, federal accident data show, and about half involved head injuries.

Adrian Lund, the institute's vice president for research, told AP that the test demonstrates that lives could be saved, especially in crashes involving light trucks. Pickups, vans and sport utility vehicles are more likely to kill passenger car occupants in crashes because of their height, Lund said.

''These tests reflect the way that people are getting injured in real-world crashes,'' he said. ''It's very difficult to prevent these injuries without side impact air bags.''

The institute also conducted a ''car-into-pole'' test, running the S80 and a BMW X5 sideways at 18 mph into a rigid pole. Again, the force measured on the dummies' heads was low.

The BMW X5 has a long tubular bag that inflates from the roof but does not extend so far down the window as the S80's bag. Other side air bags available in 2001 models deploy from the seat to inflate forward and upward.

The federal government requires front air bags on all vehicles and has standards for testing them. The government does do vehicle-to-vehicle crash testing for side air bags, which are standard or optional on more than 80 2001 vehicles, according to the institute.

As an option, side air bags can cost several hundred dollars.

At least 158 deaths since 1990 are blamed on front air bags, but at least 5,000 lives have been saved. The National Highway Traffic Safety Administration has investigated 50 crashes with side air bag deployments and found no fatalities attributed to the safety devices.

Federal authorities told AP that their testing shows side air bags could kill or seriously injure young children, especially those sleeping or leaning against a door when the bag inflates.

The auto industry has committed to voluntary testing for all side air bags, starting with the 2004 model year. The tests will measure the impact on dummies representing 3- and 6-year-old children and small adults, AP says.