Most midsize luxury cars — including the Mercedes-Benz C-Class — performed poorly in a new frontal crash test developed by the Insurance Institute for Highway Safety in the U.S.

The new test is designed to replicate what happens when a car strikes another car or a fixed object like a tree or utility pole. The test strikes 25 per cent of a car's front end into a 1.5-metre rigid barrier at 64 km/hr.

The results don't bode well for non-luxury models, which will be the next to undergo the new test. Insurance Institute crash test results are closely watched by the auto industry and often lead to changes in design or safety features. Good scores are also frequently touted in car ads.

Of the 11 cars tested, only the Acura TL, Volvo S60 and Infiniti G earned good or acceptable ratings from the institute, which is funded by insurers.

Four cars — the Acura TSX, BMW 3 Series, Lincoln MKZ and Volkswagen CC — earned marginal ratings. Four others — the Mercedes C-Class, Lexus IS 250, Audi A4 and Lexus ES 350 — earned poor ratings. Marginal or poor ratings indicate the cars wouldn't protect occupants very well in a real-world crash.

All of the cars tested were from the 2012 model year.

The institute said the new test indicates that side air bags — which are designed for direct impact, T-bone crashes but not for off-centre, frontal ones — may not go off in time or extend far enough to protect occupants. In three cars — the BMW, Mercedes and Volkswagen — the seat belts spooled out too much after the crash, causing the crash-test dummies to strike hard surfaces. The Volkswagen's door was completely sheared off during the test.

Mercedes said it didn't agree with its ranking and pointed out that the C-Class is listed as one of the institute's top safety picks. Mercedes said the crash test mimics an unusually severe and uncommon scenario.

Toyota accepts results

"As a leader in automotive safety, we have full confidence in the protection that the C-Class affords its occupants — and less confidence in any test that doesn't reflect that," Mercedes said in a statement.

Toyota Motor Co., which owns the Lexus brand, accepted the results.

"With this new test, the Institute has raised the bar again and we will respond to this challenge as we design new vehicles," Toyota said.

But Toyota also noted that it has more top safety picks — 17 — than any other automaker.

The Insurance Institute said it plans to change its criteria for the top safety picks next year to incorporate the new test. The group developed the test after years of analyzing real-world frontal crashes, which kill more than 10,000 people annually in the U.S.