Head restraints in some minivans inadequately protect people against neck injuries in rear-end crashes, the US insurance industry said on Sunday, according to The Associated Press (AP), which noted that several automakers took issue with the latest test results.

Earning poor overall ratings were seven models subjected to a simulated crash: versions of the 2004-2006 model years of the Dodge Grand Caravan and its corporate twin, the Chrysler Town & Country; a version of the 2005-2006 Toyota Sienna; and four General Motors minivans from the 2005-2006 model years – the Chevrolet Uplander, Buick Terraza, Pontiac Montana SV6 and Saturn Relay, AP said.

The 2004-2006 Ford Freestar and Mercury Monterey received the highest rating, or good, from the Insurance Institute for Highway Safety, the report said. An edition of the Dodge Grand Caravan and Chrysler Town & Country with adjustable lumbar and head restraints got the second-highest rating, or acceptable. The 2005-06 Honda Odyssey received the second-lowest, or marginal.

“It’s disappointing that so many minivan seats are rated poor for rear impact protection,” Adrian Lund, the institute’s chief operating officer, told the Associated Press. “Drivers of minivans spend a lot of time on urban and suburban roads where rear-end collisions are common in stop-and-go traffic.”

AP noted that the minivans were tested on a crash simulation sled which replicates the forces in a stationary vehicle that is struck in the rear by a similar vehicle at 20 mph. Vehicles got a higher rating if the head restraint contacted the dummy’s head quickly and the forces on the dummy’s neck and the acceleration of the torso were low.

However, DaimlerChrysler spokesman Max Gates told the news agency the Grand Caravan and Town & Country are “two of the safest vehicles on the road” and pointed to their top marks in the government’s frontal and side impact crash tests.

“No single test, including the new rear impact test developed by the Insurance Institute for Highway Safety, can determine a vehicle’s overall safety performance,” Gates reportedly said.

Toyota spokeswoman, Allison Takahashi told AP Toyota conducts extensive internal testing of the head restraint system. She said Toyota’s seats incorporate a system that is designed to help reduce neck injuries in rear-end collisions.

“The protection provided by Toyota’s seating systems has always been among the best in the world,” she reportedly said.

GM spokesman Alan Adler told the news agency the automaker’s head restraints are engineered to offer high levels of safety. He said the institute’s test is “extremely sensitive to variation and can result in different ratings in the same vehicle, such as when one has leather-covered seats and the other has cloth-covered seats.”

Models that received poor or marginal scores for the restraint design were given poor overall marks because they could not be positioned to protect many motorists, the institute said, according to AP.

Lund reportedly said many mothers frequently drive minivans, and women tend to be more vulnerable to whiplash injuries, which account for about two million insurance claims annually.