Bumpers on 2009 models of the Honda Accord, Hyundai Sonata, Mazda 6, and Nissan Maxima performed better than their 2007 predecessors in low-speed crash tests conducted by the Insurance Institute for Highway Safety (IIHS). Bumpers on the 2009 Chevrolet Malibu and 2010 Ford Fusion did worse than earlier models.

None of the six popular midsize sedans earns the top rating of good in a recent series of tests designed to assess and compare how well bumpers resist damage in everyday fender-benders. The Mazda 6 improves to acceptable from marginal, with an average repair cost of less than $900 after four tests at 3 and 6 mph. The Accord and Sonata improve to marginal from poor. The Fusion slips to poor from marginal, and the Maxima and Malibu remain poor.

"Consumers buy midsize cars for practical reasons. There's nothing practical about a $1,000-plus repair bill after a minor bump in commuter traffic," says Joe Nolan, IIHS senior vice president.

This is the second group of vehicles the Institute has evaluated under a new bumper ratings protocol based on repair costs averaged and weighted to reflect real-world damage patterns and insurance claims frequency. The IIHS rates bumpers good, acceptable, marginal, or poor based on performance in 4 tests — front and rear full-width impacts at 6 mph and front and rear corner impacts at 3 mph. Each vehicle is run into a steel barrier designed to mimic the design of a car bumper, with the barrier's plastic absorber and flexible cover simulating typical cars' energy absorbers and plastic bumper covers. These tests are designed to drive bumper improvements that lead to better damage resistance in a range of real-world crashes.

Weaker bumpers mean bigger repair bills

Ford and General Motors made design changes that increased repair costs for the 2010 Fusion and 2009 Malibu over repair estimates for 2007 models.

"Ford fit the Fusion's front and rear with weaker bumper beams, and this had a big effect on the test performance," Nolan explains. The difference is easy to see in the 6 mph full rear test, which simulates a common parking mishap like backing into another vehicle. The Fusion's bumper buckled, which caused it to underride the test barrier, resulting in twice as much damage as the 2007 model in the rear test. In the full front test, the Fusion had $2,529 in damage, more than any other vehicle.

GM raised the Malibu's rear bumper so it's higher than on the earlier model, but it's still the lowest among recently tested bumpers. In the full rear test, the bumper underrode the barrier, resulting in almost $3,500 in damage, the highest among the midsize cars evaluated. GM lowered the front bumper, which didn't help in the full front test. Damage totaled $2,092, partly because the Malibu's front grille overlays the center of the bumper. The result is that the grille, Chevy emblem, and decorative chromed plastic trim get hit before the bumper does in this test.

"Essentially you have to go through them to get to the bumper," Nolan says. "Replacing just the front grille and emblem cost more than $625."

Ford and GM, along with other automakers who sell the same vehicles in both the U.S. and Canadian markets, no longer have to meet a tougher Canadian bumper standard. The Canadian government last year weakened bumper rules to match U.S. regulations, which require only minimal protection. The previous Canadian standard required bumpers to prevent damage to vehicle safety equipment such as headlights in 5 mph impacts. Under the new rules, full front and rear tests are run at 2.5 mph and corner tests are run at 1.5 mph.

To read the entire IIHS news release, click here.