"Though much safer than they were a few years ago, mini-cars as a group do a comparatively poor job of protecting people in crashes, simply because they're smaller and lighter," Adrian Lund, IIHS president, said in a statement.

In a match-up between the Honda Accord and Fit, the Accord "held up well," but the Fit was "less than good" with a high risk of leg injury.

In the Mercedes C class vs. the Smart Fortwo test, the Smart "went airborne and turned around 450 degrees" when it hit the C class. The injuries in the Smart were judged to be "poor" with the likelihood of injury to head and legs. The C class "held up well" with injury likelihood in the "good" range.

The description of potential injury in the Yaris appeared to be close to cataclysmic. The car's door was torn away, driver's seat tipped forward and the steering wheel "moved excessively." The test dummy's head struck the car's steering wheel through the airbags, earning a poor rating for head protection. There were also extensive indications of neck and leg injuries. The Camry was rated acceptable.

All three mini-cars earned a "poor" rating in the car-to-car test.

Statistically, even though the mini-cars' safety has improved, minis that were one-to-three years old had a death rate of 35 per million for single-vehicle crashes in 2007, compared to 11 per million for very large cars, the IIHS said.

The IIHS said fuel efficiency standards can be improved without sacrificing safety with mini-cars through better use of technology and reduction of the speed limit, which both reduces gas consumption and decreases accidents.

Automakers should be forced to use "engine-enhancing technology to improve fuel efficiency instead of to boost performance," said the IIHS in its report. Not only would cars be more fuel efficient, but the less powerful cars would be safer to drive.