DETROIT, Michigan - Most mid-size luxury cars - including the Mercedes-Benz C-Class - have not performed well in a new frontal crash test developed by the US Insurance Institute for Highway Safety.The test was designed to replicate a collision with another car or fixed object such as a a tree with 25% of a car's nose striking at 64km/h. The results don't bode well for non-luxury models, which will be the next to undergo the new test.ANALYSED FRONTAL CRASHESInsurance Institute crash test results are closely watched by the US auto industry and often lead to changes in design or safety features. Good scores are also frequently touted in vehicle advertising.The group said it developed the test after years of analysing actual frontal crashes which kill more than 10 000 people a year in the US.Of the 11 cars tested (each a 2012 model) only the Acura TL, Volvo S60 and Infiniti G earned good or acceptable ratings from the institute, which is funded by insurers.Four cars (Acura TSX, BMW 3 Series, Lincoln MKZ and VW CC) earned marginal ratings. Four more (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 crash.UNCOMMON SCENARIOThe institute said the new test indicated that side air bags designed for 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 (BMW, Mercedes, VW) the seat belts spooled out too much during the crash and the crash-test dummies hit hard surfaces. The VW door was sheared off during the test.Mercedes said it didn't agree with its ranking and pointed out that the C-Class was listed as one of the institute's top safety picks. Mercedes said the crash test mimicked an unusually severe and uncommon scenario.The automkaker said: "As a leader in automotive safety, we have full confidence in the protection the C-Class affords its occupants and less confidence in any test that doesn't reflect that."Toyota, parent of Lexus, accepted the results. The automaker responded: "This new test has raised the bar again and we will respond as we design new vehicles."Toyota also noted that it had more top safety picks, 17, than any other automaker.The institute said it planned to change its criteria for the top safety picks in 2013 to include the new test.