New, tougher insurance crash test gives passing grade to just three of 11 luxury sedans

One of the auto industry's unspoken secrets is that the chief driver of crash safety improvements over the past decade wasn't rules from any government agency, but the Insurance Institute for Highway Safety. By combining industry-backed research with marketing that made a "Top Safety Pick" award essential, the IIHS can force automakers to make improvements they otherwise might not. Today, IIHS announced a new, tougher front crash test that only three of 11 luxury sedans passed -- and that at least one automaker complains goes too far.

The IIHS crash tests have long been more severe than those used by the National Highway Traffic Safety Administration. NHTSA's crash tests slam vehicles into a rigid barrier at 35 mph; the IIHS had run vehicles at 40 mph into a softer wall that only strikes the driver's side. It's rare for a new model to get less than three out of five stars in NHTSA tests, and most get good marks on IIHS crashes. The IIHS also requires protection against whiplash in rear crashes as part of its "Top Safety Pick" -- because such injuries were a major cost to insurers.

But more than 10,000 people a year still die on U.S. roads from head-on crashes. Based on its analysis of data and crash reports, the IIHS found that a quarter of front-end crashes with injuries or deaths involved vehicles hitting poles, trees and other thin objects. The new IIHS test known as a "small overlap crash" mimics that type of accident by ramming cars at 40 mph into a five-foot-tall barrier that strikes a quarter of the vehicle's width on the driver's side -- a test not required by any U.S. or European safety agency.

The IIHS ran its crash test on 11 luxury sedans, the type of cars most likely to have a full raft of safety features. Of the group, only three -- the Acura TL, the Volvo S60 and the Infiniti G Series -- earned "good" or "acceptable" scores. The Acura TSX, BMW 3 series, Lincoln MKZ and Volkswagen CC scored a "marginal" rating, while the Mercedes-Benz C-Class, Lexus IS 250/350, Audi A4 and Lexus ES 350 got a "poor" grade. The institute reported many safety failures during the tests: side airbags misfiring, legs of crash test dummies being caught in wreckage, seat belts allowing too much slack and in the case of the Volkswagen CC, a door coming off.

"These are severe crashes, and our new test reflects that," said Adrian Lund, head of the IIHS. "Most automakers design their vehicles to ace our moderate overlap frontal test and NHTSA's full-width frontal test, but the problem of small overlap crashes hasn't been addressed. We hope our new rating program will change that."

For now, the "Top Safety Pick" awards won't include results from the new test in 2013, but the IIHS says that will change the following year. And while the U.S. government would have to consider automakers' objections or complaints before changing its tests, the IIHS does not.

Mercedes-Benz said in a statement that the IIHS test replicates an "unusually severe and correspondingly uncommon accident scenario" that didn't reflect the real world. Yet Mercedes also said it would make changes to the C-Class to improve its rankings -- as most automakers will do, despite the engineering challenges that could require heavier cars even as fuel economy rules press for lighter vehicles. When it comes to crash safety, there's lots of debate, but only one set of hands on the wheel.