BOSTON — Sport-utility vehicles - the current object of Americans' love affair with the highway - have become the object of a growing controversy over vehicle safety.
So-called light trucks - pickups, sport "utes," and minivans - now account for 34 percent of the vehicles on US roads, and they pose new risks for the smaller cars that make up the bulk of traffic.
The trucks sit higher off the ground and have a stiffer construction to minimize damage for those rare excursions off-road.
So when they run into conventional cars, their frames don't flex as much and inflict more damage on the cars. In a frontal collisions, they also hit cars above the bumper and can ride up over a car's hood.
Compounding the problem: Trucks weigh more. When heavier vehicles hit lighter ones, they always inflict more damage than they sustain.
Two new research efforts are designed to study how to reduce light trucks' "hostility" in collisions with cars.
This month, the National Highway Traffic Safety Administration (NHTSA) began a new kind of crash test to confirm statistical evidence: running sport-utility vehicles into the sides of Honda Accords to see how the cars and trucks can be modified to reduce the deadliest crashes.
And the Society of Automotive Engineers has proposed for the first time to cross-reference two existing databases to show which car models are related to what injuries in crashes. This information could allow automakers to combine the best designs of the safest cars.
Light trucks have always been more damaging than cars, says Brian O'Neill, president of the Insurance Institute for Highway Safety (IIHS). But their numbers were small until sport utes became trendy. Last year, almost 50 percent of new vehicle registrations in the US were classified as light trucks: pickups, SUVs, minivans.
And the trend is toward bigger - and heavier - sport-utility vehicles (SUVs) such as Ford's giant Expedition, back-ordered at many dealers.
Incompatible with today's cars?
All these trucks increase what the IIHS calls "crash incompatibility" on American roadways, and some insurers have raised premiums on SUVs. Analysts expect more to follow. Two of the nation's largest insurers, Farmers and Progressive, have raised liability premiums for SUVs. Farmers, whose increase affected only two states, has partially offset that with reduced rates for collision and personal injury coverage.
Experts peg much of the trend toward greater crash incompatibility to a collision of economics and demographics.
High gasoline prices in the 1970s drove Americans out of their gas-guzzling giants and into smaller cars. They burned less gas but crumpled more easily. Government fuel-economy standards forever sealed the demise big cars.
Fast forward to the mid-1980s - falling gas prices, more-efficient vehicle engines, and the burgeoning love affair with SUVs. And the trucks aren't subject to cars' tight fuel-economy regulations.
The core problem, say experts, is that while SUVs grow more numerous, and bigger, those smaller cars still crowd the roadways. And while yesterday's car buyers were primarily young yuppies looking for bargains, today's SUV buyers are yuppies well along the road to affluence.
The giant Ford Expedition - about $35,000 - measures almost exactly the same length, width, and interior height as a 1956 Ford Woody station wagon. But its four-wheel-drive system makes it taller, and modern safety and luxury features make it much heavier - 5,100 pounds.
And Ford plans the biggest SUV ever in 1999: a 10,000-pound behemoth based on the company's new, heavy-duty pickups.
The most popular SUVs weigh between 4,000 and 5,500 pounds. A mid-size import weighs about 3,000 pounds.
Sport-utility vehicles do offer better protection to their own occupants and other cars than do pickups and full-size cargo vans, says Julie Rochman, spokeswoman for the Highway Loss Data Institute. And they offer their occupants better protection in two-vehicle crashes than cars, vans, or pickups, though they have a higher rate of fatal single-vehicle accidents, especially rollovers.
There is growing controversy in the fact that vehicles classified by the government as trucks - including pickups, vans, sport utes, and minivans - are exempt from many passenger-car safety standards, including bumper height from the ground.
That standard was passed in 1974 to ensure crash compatibility between cars in an era when trucks sprinkled the highways sparsely.
Many critics have called for trucks to come under the same safety, fuel-consumption, and pollution standards as cars. And manufacturers have responded by voluntarily installing required passenger-car safety features on minivans and sport utes.
But while such measures help protect SUV and minivan occupants, they do nothing for occupants of other cars.
Even so, says the insurance institute's O'Neill, trucks are not the biggest concern of car drivers. "Most fatal accidents involve two cars, not a car and a truck."
That's why IIHS says the most important first step is improving crash safety in cars. "If you're in a small car, everything you come upon is bigger," says O'Neill.
And consumers who buy small cars don't always have a choice, economically, Ms. Rochman notes. So improving the safety of small cars is the most effective way to protect those people.
But solutions exist to make SUVs safer for cars as well.
Mercedes-Benz claims to have eliminated most of the accident hostility of its new M-class sport-ute by lowering its frame and "softening" its "crumple zones." But the M-class retains the usual high SUV ground clearance, despite its lower frame.
Crumple zones are what engineers call the front and rear portions of a car where no one sits, such as the hood and trunk. They are designed to crush to absorb the impact of a crash and prevent the passenger compartment from collapsing around the occupants.
In a crash, crumple zones reduce the impact on passengers, which is key to reducing injuries. While most of today's trucks and virtually all cars are designed with crumple zones, those in most cars are more effective because they're newer designs, O'Neill says. Minivans and SUVs are redesigned much less frequently - as seldom as once every 20 years, compared with three- to five-year product cycles for most cars.
"It's important to focus now," O'Neill says, "because all the public attention gives us an opportunity to make sure [vehicle incompatibility] doesn't become a bigger problem."
* Comments to firstname.lastname@example.org