NEW YORK (CNN/Money) - The difference in the height of bumpers between cars and sport/utility vehicles is responsible for much higher repair bills, an insurance group study said.

This low-speed crash test between a sedan and an SUV shows damage that can come from uneven bumper height, an insurance group says.

The Insurance Institute for Highway Safety said even low-speed collisions of 10 mph, common in city driving, are seeing increasing repair costs because of the difference in bumper height between the two common vehicle types.

Car bumpers are required by a federal standard to match up reasonably well, said the institute's report. But it said no such requirements apply to SUVs and that some of those popular vehicles don't even have bumpers.

The institute ran low-speed crash tests between cars and trucks from the same manufacturer, such as the Ford Taurus, its midsize sedan, and Explorer, its mid-size SUV. It found 40 percent of those crashes produced damages of $5,000 or greater for the two vehicles.

The most expensive crash was $6,129 when Jeep Grand Cherokee hit a Dodge Stratus, both vehicles from DaimlerChrysler.

Max Gates, safety spokesman for Chrysler Group, said the company is taking steps to address the problem cited by the institute.

He said new Dodge Durango SUV and Dodge Dakota pickup models have bumpers that line up reasonably well with the Dodge Neon compact. Automakers are working together though their trade group and the federal government to address issues of bumper heights, he added.

Gates said he couldn't comment specifically on the institute's crash test cited in the report because Dodge hasn't seen the data. But the cost of repair is not the key issue for automakers in low-impact crash test results.

"Our testing is related to customer safety, not the cosmetics of the damage done," he said.

The Ford crashes were the least costly to repair, with $2,608 when the Taurus hit the Explorer and $1,256 when the Explorer hit the Taurus. But those were the only two collision with less than $4,000 in damages.

"The federal rules should be changed to make SUVs and cars more compatible," Institute chief operating officer Adrian Lund said in a statement Sunday. "The manufacturers already are working on this for high-speed collisions, and they ought to be doing it for low-speed impacts like these tests."

"SUVs can have the same utility they do today and still be equipped with decent bumper systems that extend down to where they match up with those on cars," Lund added. "Until then, motorists who bump into mismatched vehicles, even at very low speeds, will have no choice but to open their wallets."

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The institute said that some SUVs don't even have bumpers, causing expensive repairs even when the two vehicles hit each other.

Its low-speed crash test between two RAV4s -- the compact SUV from Toyota -- produced $4,380 in damage to the striking vehicle and $3,230 to the struck RAV4, which was hit from behind where it did not have a bumper. Instead its spare tire mount hit the front grill of the other vehicle.

"This spare tire was the 'antibumper.' It didn't absorb any energy. It didn't prevent any damage. In fact, it caused most of the damage to both vehicles," said Lund.