The Chevrolet Volt and Nissan Leaf have earned the highest safety ratings in the first-ever U.S. crash test evaluations of plug-in electric cars, the Insurance Institute for Highway Safety said Monday.

The Volt and Leaf earn the top rating of good for front, side, rear, and rollover crash protection. With standard electronic stability control, they qualify as winners of Top Safety Pick, the Institute's award for state-of-the-art crash protection.

The ratings help consumers pick vehicles that offer a higher level of protection than federal safety standards require, it said.

What powers the wheels is different, but the level of safety for the Volt and Leaf is as high as any of our other top crash test performers, says Joe Nolan, the Institute's chief administrative officer.

Nissan has a long standing commitment to safety and innovation, said Brian Carolin, senior vice president, sales and marketing, Nissan North America, Inc. The award confirms that the commitment to passenger safety continues with the 100 percent electric Nissan LEAF.

The Volt and Leaf are classified as small cars, with their overall length, width, and passenger capacity in line with their peers. But their hefty battery packs put their curb weights closer to midsize and larger cars. The Leaf weighs about 3,370 pounds and the Volt about 3,760 pounds. This compares to about 3,200 pounds for Nissan's Altima, a midsize car, and about 3,580 pounds for Chevrolet's Impala, a large family car. Larger, heavier vehicles generally do a better job of protecting people in serious crashes than smaller, lighter ones because both size and weight influence crash-worthiness.

The Institute awarded the first Top Safety Pick to 2006 models with good ratings for front and side protection and acceptable for rear protection.