SUVs That Best Withstand a Rear-end Collision

On the road yesterday, I sat at a red light, and watched, sickened, as the SUV behind me was rear-ended... pushing his bulky vehicle eerily close to my coupe. Luckily, he'd left plenty of space between our two vehicles, and I was fortunate enough to escape scratch-free.

He, however, likely suffered a nasty case of whiplash.

Noting the number of rear crashes in SUVs, pickups and minivans, the Insurance Institute for Highway Safety (IIHS) recently rated the seat design and head restraints in the fore-mentioned vehicles in the event of a rear collission. What they found was 21 current SUVs, pickups and minivans that were "good" for protecting passengers — and 54 models that were rated "marginal" or "poor." Another 12 made it to the non-celebratory median of "acceptable."

The bottom line: Seat and head restraints in over half of light truck and minivan models fall short of state-of-the-art protection from neck injury or whiplash.

The ratings of all 87 current models (by IIHS) were based on geometric measurements of head restraints and simulated crashes that together assess how well people of different sizes would be protected in a typical rear crash. A dummy specially designed to assess rear-end crash protection, BioRID, was used to measure the forces on the neck during the simulated crashes. Researchers also measure how hard the seatback pushes on the dummy's back and how quickly the head restraint supports the head.

Among the best performers of the test were SUVs made by Subaru and Volvo and new designs from Acura, Ford, Honda, and Hyundai. Seat/head restraints in 3 minivan models from Hyundai and Ford earn good ratings. The redesigned Toyota Tundra is the only pickup model evaluated with seat/head restraints rated good for rear crash protection.

"In stop and go commuter traffic, you're more likely to get in a rear-end collision than any other crash type," said David Zuby, senior vice president of the Institute's Vehicle Research Center. "It's not a major feat of engineering to design seats and head restraints that afford good protection in these common crashes."

Rear-end collisions are frequent, and neck injuries are the most common injuries reported in auto crashes. They account for 2 million insurance claims each year, costing at least $8.5 billion. Such injuries aren't life-threatening, but they can be painful and debilitating, making proper head and neck protection especially crucial for drivers.

In fact, good seat/head restraint designs keep people's heads and torsos moving together:  When a vehicle is struck in the rear and driven forward, its seats accelerate occupants' torsos forward. Unsupported, an occupant's head will lag behind this forward torso movement, and the differential motion causes the neck to bend and stretch. The higher the torso acceleration, the more sudden the motion, the higher the forces on the neck, and the more likely a neck injury is to occur. To accomplish this, the geometry of a head restraint has to be adequate — high enough to be near the back of the head. Then the seat structure and stiffness characteristics must be designed to work in concert with the head restraint to support an occupant's neck and head, accelerating them with the torso as the vehicle is pushed forward.

"The reason may be that automakers have updated or introduced many new SUVs since 2006, but minivans and pickups are being updated more slowly," Zuby said.

In the latest tests seat/head restraints in the Mitsubishi Outlander improved to good from the previous design that was rated acceptable. Those in the Acura MDX, Honda CR-V, Honda Element, Hyundai Santa Fe and Kia Sorento improved from their previous ratings of poor to good. Those in the Honda Pilot and Mercedes M class improved from marginal to good. The seat/head restraints in the Toyota Tundra pickup improved to good from acceptable.

In contrast, some manufacturers have introduced new models with subpar seat designs. The ones in the BMW X5, Dodge Nitro, and Suzuki XL7 are rated poor. Those in the new Mazda CX-7 and CX-9 are rated marginal. (The "poor" rated models didn't even make it to the testing stage because they can't be positioned to protect taller people). Among these lowest rated seats are those in the Cadillac SRX SUV, Nissan Quest minivan and Ford Ranger pickup.

Fear not. Safety ratings and government rules are driving the changes. Some manufacturers are making changes to the seat/head restraint designs in their vehicles to earn the Institute's TOP SAFETY PICK award. Other improvements are being spurred by changes to federal safety rules. Front-seat head restraints will have to extend higher and fit closer to the backs of people's heads under a rule issued by the National Highway Traffic Safety Administration in 2004. Manufacturers must start to fit better front-seat head restraints in 80 percent of their models beginning in September 2009. Front-seat head restraints in all new vehicles made after September 2010 must comply.

(Source: IIHS)