GM’s Hummer H3, on the other hand, had one of the poorest showings. The Murano was the best overall performer in front, side, and rear-crash tests. Bob Yakushi, Director of Product Safety for Nissan North America Inc., credits the use of high-strength steel in the vehicle’s architecture for its outstanding performance.

The Jeep Liberty, Jeep Wrangler four-door, and Kia Sorento, all 2008 models, were the worst performers in side-crash tests. The Liberty, also sold as the Dodge Nitro, and Wrangler earned the second-lowest rating (marginal) for protection in side crashes. The Sorento earned the lowest.

The Mazda CX-7 and CX-9, as well as the Mitsubishi Endeavor, would have been Top Safety Picks if they had offered better protection against neck injury in rear-end crashes. The seat/ head-restraint combinations in both Mazdas were rated marginal for rear-crash protection and the Endeavor’s was rated poor.

“You don’t know what kind of crash you’re going to get into, so you want a vehicle that affords the best protection in the most common kinds of crashes,” says Institute senior vice president Joe Nolan.

Head protection is important in a side crash, but so is protecting the chest and abdomen. Manufacturers can do this by putting additional padding in the doors or including side air bags that deploy from the side of the seat. Some of the SUVs that were tested have standard curtain air bags but lack separate ones to protect the torso. Curtain air bags in the H3, Liberty, and Sorento provided good head protection, but all three were downgraded because forces on the crash-test dummy’s metal rib cage indicated possible rib fractures and internal-organ injuries in real-world crashes of that severity.

“People often think they’re safer in an SUV, but many cars perform much better in our side test than some SUVs,” says Nolan.

Most vehicles tested by the Institute earn the top rating for frontal crash protection. But the Hummer H3 received an “acceptable” rating. The H3 is one of only two midsize SUVs that didn’t earn a “good” rating in recent frontal tests by the Institute. The other is the Chevrolet TrailBlazer. The H3 also got an “acceptable” rating in the side-crash test and a rating of poor in the rear-crash test.

In the H3’s frontal-offset crash test, sensors on the dummy’s lower right leg recorded forces that suggested a likelihood of injury. Meanwhile, forces on the dummy’s head and chest were low, and the H3’s structure held up well.

“Acceptable isn’t a bad rating,” Nolan explains. “It’s just not the best protection available. Considering the Hummer’s acceptable side rating and poor rating in the rear test, this SUV hasn’t been designed with the state-of-the- art crash protection of many of its competitors.”

According to a GM spokesman, “The Hummer H3 meets or exceeds all federal crash-safety standards. The Insurance Institute tests represent one measurement of crash performance.” He also said the company designs its headrests to suit a variety of driver sizes, rather than the average-size man used in the institute’s tests.

The institute’s frontal crashworthiness evaluations are based on results of 40-mph frontal offset crash tests. And overall evaluations stem from measurements of intrusion into the occupant compartment, injury measures recorded on a Hybrid III dummy in the driver seat, and analysis of slow-motion film to assess effectiveness of the restraints.

Side evaluations are based on a crash test in which the side of the vehicle is struck by a barrier moving at 31 mph. The barrier simulates the front end of a pickup or SUV. Measurements on a dummy in the driver seat and another in the seat behind the driver determine the likelihood of serious injury to various parts of the body in a similar real-world crash. Engineers measure the amount of B-pillar intrusion into the occupant compartment to determine the vehicle’s structural integrity.

Rear-crash protection is rated according to a two-step procedure starting with head-restraint geometry — the height of the restraint, and distance from the head of an average-size man. Seats are also tested using a dummy to measures forces on the neck. The test simulates a rear-end collision at 20 mph.