The designs of seats and head restraints in 21 current SUV, pickup, and minivan models are rated good for protecting people in rear impacts, but those in 54 other models are rated marginal or poor. Another 12 are rated acceptable. The latest evaluations of occupant protection in rear-end collisions by the Insurance Institute for Highway Safety (the Institute) found that the seat/head restraints in more than half of light truck and minivan models fall short of state-of-the-art protection from neck injury or whiplash.

The ratings of good, acceptable, marginal, or poor for 87 current models are 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.

Among the best performers are the seat/head restraint combinations in 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,” says 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.

Keeping heads and torsos together

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.

The key to reducing whiplash injury risk is to keep the head and torso moving together. 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.