A LARGE number of SUVs and pickups have been redesigned to reduce the threat they pose in collisions with smaller cars.

The changes to sport utilities and pickups are being made to prevent them from running over smaller vehicles in a crash. A recent study showed that the modifications, which automakers initially resisted but then agreed to adopt by late 2009, sharply reduced the number of deaths of people in cars struck by these vehicles.

As more Americans buy smaller cars to save money on gas, the danger of collisions between mismatched vehicles is escalating.

“Why should that decision put you in significantly greater jeopardy of being paralyzed or killed when a gigantic SUV slams into you and overwhelms you?” said Byron Bloch, an automotive safety expert who has testified in numerous court cases involving SUV safety.

Automakers agreed in December 2003 to meet the new standards by 2009. Roughly halfway through that period, some companies — Toyota, in particular — have made more progress than others.

The new standards require automakers to lower by half an inch to several inches the height at which their vehicles’ front ends hit other vehicles. Sometimes this is done by adding a hollow steel barbehind the bumper, and sometimes by adjusting the entire frame of the vehicle so that it rides lower to the ground.

Bumpers play little role in crashes at speeds of more than 5 or 10 miles an hour, crumpling almost instantly, so automakers have had to make bigger changes in vehicle designs.

The revamped Toyota RAV4 and Dodge Dakota have lower frames than in past years. Redesigned versions of General Motors' fullsize sport utilities, including the Chevrolet Tahoe and Cadillac Escalade, introduced recently as 2007 models, were lowered and also have so-called compatibility brackets installed on the bottom to prevent them from riding up onto another vehicle. “If you see the new ones versus the old ones, you can tell that they ride a little lower,” said GM spokesman, Alan Adler.

Almost 4 of every 10 sport utilities and pickups built for the 2005 model year did not comply with the new standards, according to the Alliance of Automobile Manufacturers.

Roughly half the light trucks produced by Detroit's carmakers met the new standards in the 2005 model year. But two of the three best-selling sport utilities — the Chevrolet TrailBlazer and some versions of the Ford Escape — did not meet the stan dards. Lower Bumpers, Higher Standards Automakers are voluntarily lowering the bumpers on light trucks, which includes pickups, sport utility vehicles and minivans, to reduce fatalities among occupants of cars hit by these taller vehicles. The industry promises to make all light trucks comply with the new guidelines by late 2009. While all of today’s minivans meet the guidelines, pickups and SUVs are not all yet in full compliance.

The reason for redesign PROBLEM: MISMATCHED BUMPERS When a light truck with a higher bumper hits a car, the car will often go under the truck, leading to more damage to the passenger compartment and higher risk of death for the car’s occupants.

SOLUTION: ALIGNING THE BUMPER ZONES The truck’s lowered bumper and frame allows the force of the impact to be directed to the car’s frame, doing less damage to the passenger compartment of the car and saving lives. Alternately, the existing bumper is augmented so that it is lower to meet the bumper of a car. This does not require a full redesign of the frame, but critics argue that this is at best a Band-Aid solution.

The status of popular models PICKUPS S.U.V.’s Do not meet guidelines Chevy Silverado Chevy 4WD TrailBlazer Dodge Ram 4WD Ford Escape Ford F-150 4WD Ford Freestyle Ford Ranger Hummer H2 GMC Sierra 4WD Mercury Mariner Nissan Titan 4WD Toyota Sequoia Toyota Tundra Meet Guidelines Chevy Avalanche Cadillac Escalade* Chevy Colorado Chevy Equinox Chevy Silverado Chevy HHR 2WD Ford F-150 2WD Chevy Suburban Dodge Dakota Chevy Tahoe* Dodge Ram 2WD Chrysler Pacifica Nissan Frontier Ford Explorer Toyota Tacoma Honda CR-V *2007 model meets guideline NYT