Plaintiffs try to drive General Motors toward auto compatibility.

The drunk-driving accident that killed 18-year-old Dereck Lopez was typical: A large pickup ran through a red light and rammed the teen's car in the side. But in an atypical lawsuit, Lopez's parents are suing the manufacturer of both the truck and the car, General Motors (GM), for building vehicles that are incompatible with each other in crashes. (Lopez v. Quino, No. 17-197104-03 (Tex., Tarrant County Dist. Ct. filed May 29, 2003).)

Because the front of the Chevrolet Silverado pickup was higher than most of the midsize Chevrolet Cavalier's door (which is designed to absorb energy from crashes and thus protect passengers), it also smashed into the driver side window. The car, a 1998 model, had no side air bags; they were not an option when the car was purchased, although other GM cars had them at the time.

Lopez's injuries were mainly on the left side of her head. "She didn't have any neck, torso, or pelvic injuries," said Lee Brown of Dallas, her parents' attorney. "She was a fatality that resulted from no side protection for these incompatibility accidents. Who other than GM knows that their pickup trucks are inflicting the damage that they are? The public documents, GM's documents, are very clear on the risks of these side impacts from pickup trucks hitting passenger cars.... The only way you can safely mitigate that risk is through side air bags."

Auto safety advocates say that vehicle in compatibility is a growing problem in the United States. Light trucks and vans (LTVs, including pickup trucks, vans, and SUVs) now constitute about half of all new car sales, and the average weight of these vehicles has increased faster than that of cars. Analyzing data from 1995 to 2001, National Highway Traffic Safety Administration (NHTSA) researchers determined last year that "a consistent and significant compatibility problem exists in the U.S. fleet. The passenger car occupants incur a disproportionate number of fatalities in LTV-car crashes."

The researchers estimated that side impacts by LTVs into cars are 3.5 times more likely to kill the car drivers than side impacts by another car. They found that these results were related not only to weight disparities between cars and LTVs, but also to structural differences, such as bumper height and vehicle stiffness.

The Lopez lawsuit is unusually strong because the defendant manufactured both vehicles involved in the crash, said Peter O'Neil, a Seattle lawyer who has tried crashworthiness cases brought against automakers.

"I've always thought the cleanest sort of these cases would be against the maker of both cars," he said. "I remember the first time I went to Detroit, I saw a little Saturn at the GM building where they display cars, and they had a giant Suburban aiming straight at the Saturn. It was kind of obvious what would happen to the people in the Saturn.

"For years now, companies like GM and Ford have been selling trucks and SUVs because they are a lot more profitable than passenger cars. So they're not protecting entry-level buyers who are buying cars like the Cavalier."

Arguing that the Cavalier was "defective and unreasonably dangerous for side impacts with pickup trucks," the Lopez complaint notes the car's lack of side air bags to minimize head injury. Including the air bags was a reasonable alternative design, Brown said.

"Did General Motors have a design in production at the time the car was built that ... wouldn't be unreasonable in cost and wouldn't create more dangers for the occupants, so it would not only make [the car] safer in side impacts but also wouldn't cause it to be more dangerous in other crashes?" asked Brown. "Clearly they did: The side curtain, the inflatable tube, and the torso head bag were all in production, all known by GM and the rest of the industry, and all substantial improvements on what they had."

O'Neil said plaintiff lawyers often have difficulty proving that such designs would have helped their clients. For him, this is a classic case of big guy versus little guy.

"Car manufacturers, I think, have a duty to explore those different designs, and they can do it: They've got the machinery, the computers, the vehicles to do it on a crash test pad when they need to," O'Neil said. "But for a plaintiff, running one test is an extraordinarily expensive endeavor. So most people who have been injured in a crash like that don't want to authorize their attorneys to spend $25,000 or $50,000 to test something that may or may not work--whereas the vehicle manufacturers can do it and really have a duty to do it."

In May some auto manufacturers, including GM, Ford, and Daimler Chrysler, voluntarily agreed to increase side-impact protection--most likely with side air bags that provide head cover age--in all new vehicles by 2010. A few days later, NHTSA's administrator introduced proposed regulations that would require such protection.