More than half of car seats in the US do a poor job of preventing whiplash injury because of the way they are built, according to tests by the insurance industry -- while a similar study in the UK found that almost two-thirds of car seats left motorists vulnerable to injury.
In the US, General Motors Corp cars were among the worst performers, the Insurance Institute for Highway Safety said in results released on Sunday. Volvo and Saab cars were among the best.
The institute examined 97 seat and headrest combinations found in 88 cars now on the market. It tested 73 of those seats in a 32kph rear-impact crash to see how well they would protect an average-size male dummy.
Eight seats earned the institute's highest rating, including those in the Volvo S40, S60 and S80, the Saab 9-2X and 9-3 and the Jaguar S-type.
Sixteen seats, including those in the Chevrolet Malibu and the Subaru Outback, got the second-highest rating of acceptable; 19 seats, including those in the Ford Focus and the Mini Cooper, earned the third-highest rating of marginal.
The other 30 received the worst rating, poor, indicating the highest likelihood of neck injury in a rear-impact crash. Among those were the seats in the Audi A4 and S4, the BMW 3 Series, the Dodge Neon and the Jaguar X-type.
The institute did not test 24 seats because it determined the headrests were designed in a way that would not protect taller people.
GM said in a statement that it has been following the institute's guidelines for placement of head-rests. It said people come in many sizes and sit in various positions in the vehicle and cautioned against making changes based on one test.
"If the test methods chosen are not reflective of reducing real-world harm, there could be significant potential to cause seat design changes that are directionally wrong," GM said.
"It's obvious that some automakers are doing a better job than others of designing seats and head restraints to protect their custo-mers' necks in rear crashes," said Adrian Lund, the institute's chief operating officer.
In the UK, tests by the Thatcham research center near London showed 60 percent of car seats were inadequate in a rear-end shunt -- the most common accident.
Among the cars given a poor rating were the BMW 3 series, the Jaguar X-type, Honda's CRV and the Toyota Corolla.
As many as 25 models automatically failed the examination because their seat positioning did not provide the minimum protection and they were therefore not tested.
Of the 114 models tested, only 18 were rated as good and 27 were just acceptable. The rest were either marginal or poor.
"These results are very disturbing," said Matthew Avery, head of the test program at Thatcham.
Neck injuries sustained in a rear-end crash rarely are life-threatening, but they happen frequently and can be painful and expensive. Neck injuries cost around US$7 billion in insurance claims each year, the Insurance Institute for Highway Safety said. Whiplash happens when a vehicle is hit from behind and the seat propels forward. If the headrest does not move with the seat, the occupant's neck will bend back and stretch.
On the best-performing cars, the seat was sturdy but had enough cushion so the occupant's body could sink into it, keeping the head closer to the headrest.