Crash test is pain in the neck for car makers

NEW YORK (CNNMoney.com) -- Some car companies - even those that have "Top Safety Pick Awards" from the Insurance Institute for Highway Safety - say its rear impact protection test doesn't reflect reality, and that its methods force auto makers into a one-size-fits-all solution.

The institute's rear impact test, which was developed in conjunction with auto safety groups around the world, is supposed to show how well a car protects you from whiplash in case of a rear collision.

While whiplash may not seem like much, it's a big deal if you suffer from it - the pain is severe and can last for weeks or months. And it's a really big deal if you're running an insurance company. Whiplash claims cost them $8.5 billion every year, according to the Insurance Institute for Highway Safety.

Two years ago, the institute begin giving out "Top Safety Pick" awards for car, SUV and van models that get its top rating of "Good" for front side and rear impact protection. Winning car companies even get an actual trophy.

But getting a top grade for front and side impact protection, where poor performance means an increased likelihood of death, isn't enough to win the prize. Autos have to protect against whiplash too.

Cars that have earned the institute's "Top Safety Pick" award include the 2008 Ford (Charts, Fortune 500) Taurus, the Volvo C70 convertible and Hyundai Entourage minivan.

But some cars that get top "Good" ratings for both front and side impact crash ratings, including the BMW 3-series and the Toyota Camry and Avalon, still get "Poor" ratings for rear impact protection.

The Insurance Institute's rear impact safety test has two parts. The first simply measures the seat to determine the relationship between the seat back and head restraint, which is commonly known as a headrest.

Only seats with a headrest that's located and shaped to prevent the head from moving back in a crash even get to go on to the actual "impact" test. If not, the seat automatically gets a "Poor" or "Marginal" rating.

Seats that get an "Acceptable" or "Good" rating - the institute's two best ratings - are then mounted on a moving platform, and a crash test dummy is seatbelted in pace. A puff of compressed air sends the sled forward in a sudden movement to mimic the impact of a car traveling at 20 miles per hour.

Automakers object to these tests for two reasons. The first is that the Institute crash-tests seats once using a single average-sized crash test dummy. Car companies say they test their seats using dummies of various sizes.

"General Motors designs its head restraints to meet a variety of driver sizes rather than focusing on a single set of metrics," GM (Charts, Fortune 500) said in a statement regarding recent rear impact tests on SUVs, trucks and vans. "Head restraints are part of the integrated approach to occupant protection in all GM vehicles."

The Institute counters that, in real life, people rarely adjust their head restraints, usually leaving them in the lowest position no matter how tall they are. In an impact test, however, the institute does move the headrest to the proper height for the dummy. At worst, said Institute president Adrian Lund, it still replicates a situation that's probably safer for occupants than real life.

Some car companies object to the fact that the "impact" test is conducted using a sled rather than a real car being hit by another real car.

"Impact absorbing structures on Toyota vehicles play a major role in helping to effectively absorb impact energy in the event of a front, side or rear collision," said Toyota (Charts) in a statement. "When performing the rear crash dynamic test, the IIHS procedure does not take the whole vehicle into account."

Crashing real cars is expensive, though, and the Institute wrecks many real cars for front and side impact crash tests. In the rear impact protection test, said Lund, the jet of air that briefly rockets the sled forward is precisely programmed, from the rate of acceleration to the way the sled stops, to emulate the movement of a vehicle's passenger compartment during a 20 mile-per-hour rear hit.

In the end, the Institute insists, its rear impact test is just as good as crashing real cars, which shows in reduced whiplash claims for occupants with "Good" seats.

"Of all the safety devices in our vehicle," said Russ Rader, a spokesman for the Insurance Institute, "you are more likely to need a good head restraint than an airbag"