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Collision odds favor light trucks

In this corner, weighing in at 3,326 pounds: the Ford Taurus, America's best-selling car. In that corner, weighing in at as much as 5,174 pounds: the Ford Expedition, one of the most popular among the fast-growing category known as light trucks that includes sport utility vehicles, pickup trucks and minivans.

Such mismatches, even more striking with sports vehicle behemoths like the Chevrolet Suburban that weighs up to 6,750 pounds, are becoming far more common on America's roads. The consequences can be deadly.

More Americans now die in crashes involving a car and a light truck than in crashes involving two cars, federal accident statistics show. And that is true even though light trucks still make up just a third of all vehicles on the roads and are involved in fewer crashes than cars.

What is more, of the 5,426 people killed in collisions between cars and light trucks in 1995, the most recent year for which statistics are available, only 20 percent were in the light trucks; 80 percent were in the cars. (The number killed in collisions between cars in 1995 was 4,271.)

The gap in weight between light trucks and cars has widened considerably in recent years. For the first time since the government began keeping reliable records in 1984, the average light truck outweighed the average car by at least half a ton, or 1,000 pounds, in the 1995 and 1996 model years, the most recent for which figures are available.

Yet most cars are designed to meet federal crash standards that test the ability to withstand a collision with a similarly shaped vehicle within 500 pounds of its own weight.

The main criticism of light trucks has long been their poor fuel economy, with the largest models getting less than 15 miles a gallon in city driving. But now federal and non-government experts also are concerned about the safety question.

The National Highway Traffic Safety Administration will issue several reports within a few days looking at the links between safety and vehicle weight. The Insurance Institute for Highway Safety, the large research group backed by insurers seeking to reduce the cost of accident claims, also plans a study later this year on accidents involving light trucks, said Brian O'Neill, the group's president.

Safety engineers at federal agencies, automakers and advocacy groups all agree that collisions between vehicles of mismatched weights tend to be the deadliest. In an accident, the sheer bulk of a light truck "will provide some benefits to its occupants, in effect, by penalizing the occupants of smaller vehicles," O'Neill said.

Safety experts at most private groups make the further claim, contested by automakers, that the design of light trucks makes them an even greater threat to cars than their weight would suggest.

For example, even though fewer than a quarter of all buyers of sport utility vehicle use them for off-road driving, most models are designed with very high ground clearances to allow travel over rocky, rutted roads without leaving a trail of parts from the undercarriage.

Because the bumpers and frames of many bigger light trucks are higher off the road than the bumpers and the strongest sections of most cars, the light trucks tend to hit cars in structurally weak places, said Robert Knoll, the director of automobile testing for Consumer Reports magazine.

"In many cases, it would go over the bumper and into parts of the vehicle that aren't designed to take the impact," Knoll said. As one example, the nine-seat Ford Expedition has a bumper that reaches 31 inches off the ground, whereas the Taurus' is 21 inches.

Almost all light trucks are made by separately assembling the body and a stiff steel-framed underbody, and then lowering the body onto the frame and welding it.

Cars used to be built this way, but these days almost all cars are so-called unibody designs in which a lightweight steel shell is welded together and then filled with seats, a dashboard and other equipment. When the steel beams that form a light truck's rectangular underbody encounter the thinner steel lattice of an automobile's shell, they tend to inflict a lot of damage, said Gerald Donaldson, the senior research director at Advocates for Highway and Auto Safety, an advocacy group in Washington.

Safety engineers at automakers acknowledge that the greater weight of sport utility vehicles and other light trucks gives them an advantage in crashes, but contend that the designs are not a problem.

The two steel beams that run the length of the underbody of Ford's light trucks, for example, have a wavy pattern near the front that is designed to let them compress in an accident, reducing the odds that they will punch through the other vehicle, said Charles Christopher, a Ford safety engineer.

"It's not just a big dagger sticking out there; it's designed to collapse," Christopher said.

A draft of one report being prepared by the National Highway Traffic Safety Administration shows that federal investigators are worried because sport utility vehicles, pickup trucks and minivans are not only becoming more common but are also becoming larger and heavier.

"Continued growth in the number and weight of light trucks, unless offset by safety improvements, is likely to increase the hazard in collisions between the trucks and smaller road users," said the draft, which has been circulated for peer review by safety experts at other Federal agencies.

Groups like Advocates for Highway and Auto Safety favor two big design changes to reduce the risks that light trucks pose: requiring all vehicles to have bumpers of the same height and replacing the steel beams in light-truck frames with lighter, steel-lattice "unibody" designs. But neither change is likely soon.

Automakers say that a reduction in traffic accidents is better accomplished by cracking down on drunken drivers, encouraging seat belt use and fixing potholes.

The overall safety record of pickup trucks, sport utility vehicles and minivans is mixed. Because their centers of gravity are higher, the tallest of these are more likely to roll over, particularly during tight high-speed turns.

While occupants of light trucks tend to fare better than car occupants in multiple-vehicle accidents, their fatality rates are higher in single-vehicle accidents, according to the Insurance Institute for Highway Safety.