Most light trucks fail to protect passengers adequately in a rear-end collision, according to a study released today by the Insurance Institute for Highway Safety, the Detroit Free Press reports. The designs of seats and head restraints in 21 current SUV, pickup and minivan models are rated “good” for protecting people in rear impacts, and 12 were rated "acceptable." But those in 54 other models are rated “marginal” or “poor.” The ratings on 87 current models are based on geometric measurements of head restraints and simulated crashes that assess how well people of different sizes would be protected from neck injury or whiplash in a typical rear crash. According to the Free Press, among the best performers are the seat and head restraint combinations in SUVs made by Subaru and Volvo and new designs from Acura, Ford, Honda and Hyundai. Three minivan models from Hyundai and Ford earn good ratings. The redesigned Toyota Tundra is the only pickup evaluated that had seat and head restraints rated "good."