The government and the Insurance Institute for Highway Safety are going to make it tougher for vehicles to receive top grades on their respective safety tests.

The Insurance Institute, a safety-research arm of the insurance industry, says that starting with 2010 models, it won't grant its "top safety pick" award to any vehicle that doesn't earn a "good" rating on its new test of roof strength. Separately, the National Highway Traffic Safety Administration is preparing a more-rigorous crash-testing system for 2011 models starting early next year. The NHTSA's new safety rating system will include a tough new side-impact test, which involves smashing vehicles into a pole, and a new overall safety-rating score.

The bottom line: Fewer vehicles are likely to get five-star ratings in the NHTSA's one-to-five-star scoring system, and fewer vehicles are going to get the Insurance Institute's top safety pick award, representatives of the NHTSA and IIHS say. In 2009, a record 84 vehicles earned the IIHS's top endorsement.

This could be confusing for consumers, and present both engineering and communications challenges to car makers. Cars and trucks may get lower scores and fewer stamps of approval, but they won't suddenly be less safe. Instead, the pressure will be on manufacturers to take vehicles to a higher level of safety.

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