DETROIT -- Automakers are failing to equip most car models sold in the United States with seats and head restraints that provide good protection against neck injuries in rear-end crashes, according to a new insurance industry study.
The study, released on Sunday by the Insurance Institute for Highway Safety, said only eight of 73 seat and head restraint combinations it tested got a "good" rating for whiplash prevention, while 16 others were rated "acceptable."
Nineteen earned only "marginal" ratings and 30 got "poor."
Among the seat-head restraint systems that were tested, good ratings were earned by Volvo's S40, S60 and S80 cars and Saab's 9-2X and 9-3 models. The Swedish automakers, long known for putting a premium on safety, are owned by Ford Motor Co. and General Motors, respectively.
The Jaguar S-Type, Subaru Impreza and some of Volkswagen AG's New Beetle cars also earned top scores.
In the rear impact tests, which simulate a stationary car being struck by a vehicle of the same weight at 20 miles per hour, the seat-head restraint on Toyota Motor Corp.'s 2004 model Corolla also rated good. But the Corolla's overall rating dropped to "acceptable" because of the head restraint's poor positioning.
Cars that earned poor overall ratings ran across all segments from the 2005 model Corolla and the Toyota Camry -- America's best-selling car -- to the Cadillac CTS and BMW 3 series.
"It's obvious that some automakers are doing a better job than others of designing seats and head restraints to protect their customers' necks in rear crashes," Adrian Lund, the Insurance Institute's chief operating officer, said in a statement.
He added that many car models still have "poor or marginal geometry," meaning head restraints that are not closely enough positioned behind an occupant's head.
The Insurance Institute said 24 seats, two-thirds of them in GM cars, were not tested at all because of "inadequate head restraint geometry."
Neck injuries in rear-end crashes are rarely life-threatening, especially when they occur at low to moderate speeds. But the Insurance Institute said they cost at least $7 billion in U.S. insurance claims per year.