ARLINGTON, VA - Bumpers are the first line of defense against costly damage in everyday low-speed crashes. Bumpers on cars are designed to match up with each other in collisions, but federal regulations exempt SUVs from the same rules. According to the Insurance Institute for Highway Safety, new crash tests demonstrate the results: SUV bumpers that don't line up with those on cars can lead to huge repair bills in what should be minor collisions in stop-and-go traffic.

"SUVs and cars share the road," said Joe Nolan, IIHS chief administrative officer. "The problem is they don't share the same bumper rules, and consumers end up paying the price."

A federal standard requires that all cars have bumpers that protect within a zone of 16 to 20 inches from the ground. This means car bumpers line up reasonably well and are more likely to engage during low-speed collisions to absorb energy and prevent damage.

"No bumper requirements apply to SUVs, pickups or minivans, so when these vehicles have bumpers they often are flimsier and higher off the ground than bumpers on cars," the IIHS said. Plus, SUVs and pickups may not have bumpers at all.

In fender-benders with SUVs, cars often end up with excessive damage to hoods, engine cooling systems, fenders, bumper covers and safety equipment such as lights. SUVs don't always come out unscathed either, often needing extensive work, IIHS said.

The IIHS conducted 10 mph front-into-rear crash tests involving seven pairs of 2010-11 models, each composed of a small car and small SUV from the same automaker.

"We picked vehicles from the same manufacturer because we think automakers should at the least pay attention to bumper compatibility across their own fleets," Nolan said. "The results show that many don't."

In the tests, an SUV going 10 mph struck the back of its paired car, which was stopped. Then the configuration was reversed, with the car striking the back of its paired SUV. Results of these low-speed impacts varied widely, from a total of $850 damage to one vehicle to $6,015 damage to another. In some cases, the crash damage included major leaks from broken radiators and cooling fans. If these collisions had happened in the real world, the motorists wouldn't have been able to drive away. If they did, their vehicles could overheat, and the engines could be ruined, IIHS said.

If bumpers don't match up, they'll bypass each other when vehicles collide, and the resulting crash energy will crumple the vehicle body. 

Here are the IIHS test results: 

DAMAGE REPAIR COSTS IN 10 MPH FRONT-INTO-REAR CRASH TESTS

SUV INTO CAR

SUV damage

Car damage

Total damage

Honda CR-V into Honda Civic

$1,721

$1,274

$2,995

Toyota RAV4 into Toyota Corolla

$1,434

$2,327

$3,761

Hyundai Tucson into Kia Forte

$850

$3,223

$4,073

Volkswagen Tiguan into Volkswagen Golf

$2,329

$2,058

$4,387

Jeep Patriot into Dodge Caliber

$1,415

$3,095

$4,510

Ford Escape into Ford Focus

$1,470

$3,386

$4,856

Nissan Rogue into Nissan Sentra

$2,884

$4,560

$7,444

CAR INTO SUV

Car damage

SUV damage

Total damage

Kia Forte into Hyundai Tucson

$1,510

$2,091

$3,601

Dodge Caliber into Jeep Patriot

$2,559

$1,338

$3,897

Honda Civic into Honda CR-V

$4,921

$1,053

$5,974

Volkswagen Golf into Volkswagen Tiguan

$4,555

$1,872

$6,427

Nissan Sentra into Nissan Rogue

$5,114

$1,428

$6,542

Ford Focus into Ford Escape

$5,203

$2,208

$7,411

Toyota Corolla into Toyota RAV4

$3,852

$6,015

$9,867

Note: The Ford Escape and Focus, Hyundai Tucson, and Volkswagen Golf and Tiguan are 2011 models. All other cars and SUVs are 2010s. Repair costs reflect November 2010 parts and labor prices.