RESEARCH A CAR Get invoice and market prices, specs, reviews and photos • Sport • Sedans • SUVs • Luxury Pick Category Minivans Sedans SUVs Coupes/Hatchbacks Sport Convertibles Wagons Crossover Exotic Luxury Pickups Check latest incentives GET A QUOTE Pick Make Pick Model RESEARCH A USED CAR Get used car pricing, reviews, ratings, and more. Pick Year Pick Make Research used cars

NEW YORK (CNN/Money) - Headrests in most minivans don't provide enough protection in the case of a rear-end crash, according to an insurance industry auto group.

Headrests protect occupants' heads from snapping back in the event the vehicle is hit from behind. Poorly designed headrests can allow neck injuries in rear-end collisions.

The Insurance Institute for Highway Safety, which conducts its own crash tests separate from government tests, said Sunday that only Ford Freestar and its twin, the Mercury Monterey, received "Good" ratings for their headrests. Headrests in the Honda Odyssey are rated "Marginal" overall, according to the group. Some of the headrests in Dodge Grand Caravan/Chrysler Town & Country models are rated "Acceptable."

Tthe Institute gave "Poor" ratings to the headrests in four General Motors models -- the Chevrolet Uplander, the Buick Terazza, the Pontiac Montana SV6 and Saturn Relay.

It also gave "Poor" ratings to Chevrolet Astro, GMC Safari, neither of which are in production any longer, as well as the Mazda MPV, and Nissan Quest. In addition, some seats in the Grand Caravan and Toyota Sienna were called "Poor" because the headrests could not be positioned to protect tall people. Because of that, the IIHS did not even perform crash tests on those models.

"It's disappointing that so many minivan seats are rated poor for rear impact protection," said Institute chief operating officer Adrian Lund in a prepared statement. "Drivers of minivans spend a lot of time on urban and suburban roads where rear-end collisions are common in stop-and-go traffic. Moms often are behind the wheel, and women are more vulnerable to whiplash injuries so they especially need good seats and head restraints."

Whiplash and other neck injuries aren't life-threatening, but they can be painful and debilitating, according to the Institute, which estimates that serious injuries from rear-end accidents result in 2 million insurance claims each year, which cost at least $8.5 billion.

Toyota said in a statement, "during extensive internal testing, the head restraint system employed in Toyota, Scion, and Lexus passenger cars and light trucks has performed well.

DaimlerChrysler released a statement saying, "Chrysler Group considers a variety of test results as well as other safety information as part of its effort to continuously improve the crash-worthiness of its vehicles."

GM questioned the validity of the IIHS test.

"The intent of the IIHS test is to evaluate the risk of whiplash, but the mechanisms of whiplash injury are still not proven or understood," GM said in a statement, "and the criteria (used in the IIHS test) are not validated with real-world injury studies.

Honda told the Long Island, N.Y.-based newspaper Newsday that the institute has ranked the Odyssey a "best pick" for the van's frontal crash protection and said, "We feel it is important that any safety test be considered in the context of a vehicle's overall safety performance."

"Beginning with the 2005 model, the Quest has front seat active head restraints which help reduce whiplash injuries in real-world crashes," NIssan said in a statement regarding the tests. "Nissan has received and will study the results from the Insurance Institute of Highway Safety and will continue to evaluate ways to satisfy our customers."

The Kia Sedona has been redesigned for the 2006 model year but isn't yet available for tests, the Institute reported.

For more on autos and automakers, click here.