The changes include using female test dummies as well as male ones in crashes to show the effect on smaller bodies. A new test will simulate the effect of hitting a tree, and other frontal tests are being added.

The new tests will be introduced in 2010 along with a new safety rating that will combine results from frontal, side and rollover tests.

"Knowing how many horses a car engine has is important, but knowing how safe a car is before you even step into a dealership ought to be essential," Peters said. "We want to make sure consumers can easily take safety into consideration when choosing a new vehicle, along with price, fuel efficiency, size and the color they like best."

Peters said that under the new regulations buyers will also be told whether new crash-prevention electronics such as systems that warn when a vehicle is drifting from its lane are optional or standard equipment.