Safety Tips

Pain in the Neck
New Head Restraints Can Help Prevent Whiplash
By Tara Baukus Mello
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It was years ago, but the memory of the day pops into my mind every time I glimpse someone in my rearview mirror following a little too closely.

I was on the way home from work and traveling through an intersection when the traffic in front of me stopped. I stopped, too, but the woman behind me didn't. I watched in my mirror as her front grille got closer and closer to me without slowing.

The crash happened so fast that I barely remember it. What I remember vividly are the aches that had settled in by the time I awoke the next morning. If you've ever been in a car accident then it's more than likely you know the feeling of waking up the next day with that nagging soreness in your neck. That pain, known as whiplash, is the most common type of injury after a rear-end crash.

While whiplash may be common, it is an injury that can be far less severe and sometimes prevented entirely depending on the type of headrest you have and if it is adjusted properly. Indeed, the term "headrest" is really quite misleading. This fixture in your automobile is not for resting your head. Its true purpose is to protect your head from thrusting too far backward in a rear-end collision — in other words, it's there to reduce whiplash. In fact, safety experts and automakers call these fixtures by their proper term — head restraint.

The Insurance Institute for Highway Safety (IIHS), one of two groups in the United States that provide consumers with crash test ratings, began studying the effectiveness of head restraints in 1995. At that time, just five vehicles were designated with a "Good" rating (the Institute's highest score) for their head restraints. The Institute used a "static" test, essentially a series of measurements of a crash test dummy's head in relation to the head restraint — what the Institute calls "head restraint geometry."

Since then head restraints have improved dramatically. In the IIHS' study of 2004 model-year vehicles, 80 percent of vehicles had "Good" or "Acceptable" ratings for their head restraints, among the highest the Institute gives. But the IIHS developed a "dynamic" test, implemented that same year, in which the seat and a crash test dummy are actually propelled forward on a sled to simulate a crash. The same vehicles that scored well in the static test did not perform well in the dynamic test. In fact, 53 cars the Institute tested recently in the dynamic test were rated "Poor" (the Institute's lowest score), and many of them are some of the best-selling vehicles on the market. (For a complete list of head restraint ratings by model, visit the IIHS Web site at www.hwysafety.org.)

Only a handful of vehicles received the Institute's highest rating, including all models of Volvos and the Saab 9-3, although each automaker takes an entirely different approach to this safety feature. "The designs are different, but the result is the same," says Adrian Lund, chief operating officer at the IIHS. "Both Volvo and Saab have found a way to reduce the differential motion of an occupant's head and torso that causes neck injury in rear crashes. This is what we want every automaker to do."

Testing: New vs. Old
The IIHS began assessing head restraints over a decade ago, but at that time it looked solely at the geometry of the restraint based on how close the restraint was to the back of the head of an average-sized man. While it published ratings for 1995 model-year vehicles, it also recognized that simply having "good" geometry wasn't enough to protect occupants from whiplash injuries. Other important factors included the construction and the relative stiffness of the seatback. While the Institute recognized the limitations in its assessment, it was the one that made the most sense at the time. Very few vehicles had head restraints with sufficiently good geometry for them to be considered for a dynamic test.

Even if the geometry of the head restraints had been better back then, the IIHS was at a loss to conduct a dynamic test because of the lack of a dummy that could reproduce the effects of a human during a rear crash. "We needed a dummy that would be able to measure what happens to a person's neck and spine in this type of crash," explains Lund. At the time, the only crash test dummies available had rigid spines and necks that weren't designed to simulate humanlike responses during a rear crash.

It wasn't until another crash test dummy, called BioRID, was developed that a dynamic test of head restraints could be considered. Once the testing methods were refined, the Institute began using the dynamic test in combination with the static test ratings to produce more advanced ratings for head restraints. In order for a vehicle to be put in the dynamic test, the head restraint geometry is first assessed and rated on the Institute's system of Poor, Marginal, Acceptable or Good. It must receive either an "Acceptable" or a "Good" rating in order to move on to the dynamic test. If it moves on to the dynamic test, the seat and a BioRID dummy are then placed on a Hyge sled and are propelled forward. The goal is to simulate the effects of being in a stationary vehicle when it is rear-ended at 20 miles per hour by another vehicle of the same weight.

How Pass Becomes Fail
As the IIHS suspected from its initial tests back in 1995, head restraints that have acceptable geometry are not guaranteed to be top performers in the dynamic test. In fact, of the vehicles tested recently, five that were rated "Good" and 10 that were rated "Acceptable" in their geometry performed poorly in the dynamic test. "Those failed because the head restraint doesn't meet the head quickly enough — either because the seatback deforms and bends back too far or because it is too stiff and therefore pushes too hard," says Lund.

With some vehicles, there were small differences between the seats used on specific models that affected the test results. For example, when the 2004-2005 Volkswagen New Beetle had seats equipped with both adjustable lumbar support and active head restraints, it received a "Good" rating. Take away the lumbar support, however, and the New Beetle received only an "Acceptable" rating.

"While we've seen a lot of improvement in the geometry of the head restraints, in many cases automakers need to make further improvements to their seats and head restraints in order for them to really protect in rear crashes," says Lund.

Real-World Research
In addition to conducting tests in its research facility, the IIHS also studied the effectiveness of head restraints in real-world crashes using claims data provided by Nationwide, Progressive and State Farm insurance companies. The study assessed the old and new seat/head restraint designs in a variety of vehicles. Automakers took three different approaches to the whiplash problem — improve the geometry of the restraints (so they were closer to the occupants' heads and more centered behind them); design active head restraints (the occupant's torso moves back into the seat while the head restraint simultaneously moves closer to the head); and redesign the seatbacks themselves (the seat moves in order to support the body).

Of all the designs studied, the IIHS determined that the key to reducing whiplash injury is to keep the occupant's head and torso moving together. The results of the data suggested some improvement in injury claims regardless of what type of system was used. One definitive finding was a 43-percent reduction in neck injury claim rates for Saab, General Motors and Nissan models equipped with active head restraints.

Interestingly, the study found that the decrease in neck injury claims in women was far greater than for men. Of the Saabs in the study, for example, there was a 55-percent reduction in claim rates for women, compared with 31 percent for men. This was particularly encouraging to the researchers because women have a much higher occurrence of whiplash injuries in rear-end crashes than men.

"It's a bit of a mystery why we see larger improvements with women than men," says Lund. "One theory is that women's neck muscles are not as strong, so they experience greater injury in the same type of crash. It may also have to do with the fact that women generally weigh less than men, so the acceleration of their bodies in a crash is greater."

The Volvo Approach
Of the vehicles tested in the Institute's first dynamic head restraint tests in 2004, all three Volvo models received the highest ratings. Volvo's head restraint system, called WHIPS (short for Whiplash Protection System), was first introduced in 1999 on the Volvo S80 and currently is standard equipment on all Volvos. The WHIPS system looks at the seat as an entire unit, versus just the head restraint alone. Dr. Lotta Jakobsson, an engineer at Volvo Cars Safety Center, explained how WHIPS works in a rear-end collision this way: "The seatback moves together with the occupant in a way that is similar to catching a ball gently, while the head restraint remains rigid to support the neck."

Volvo seats with WHIPS actually have a piece of metal inside the seat that bends and absorbs energy in a crash, therefore reducing the impact. The effect is that the seat essentially reclines slightly. While the amount of movement in the seatback depends on the force of impact and the weight of the person sitting in the seat, it's not a large movement. "The movement is very small, actually just a few centimeters, but it makes a big difference," says Jakobsson.

Because this metal bar is designed to deform in a crash, it requires repair after a rear-end crash. "It's a relatively small repair both in time and parts required, particularly when there will need to be other repairs to the vehicle after a collision of this type," says Jakobsson.

In Sweden, Volvo has a special team that goes out to study real-world crashes in their vehicles; this team has been assessing neck injuries since the early 1970s. With data from over 30,000 crashes over 30-plus years, it, too, found that women have a higher incidence of neck injuries than men. Unlike other researchers, it does not believe that more women are injured because they are shorter or weigh less than men. "We really aren't sure why, but we think the fact that women generally have a more slender neck and a greater range of movement may be a factor in increased injury," says Jakobsson.

Based on this research, Volvo designed its WHIPS system to work over a large range of body sizes and shapes. With women, it seems to have worked marvelously. In the IIHS study of real-world crashes, it found that the WHIPS system reduced neck injury claims in women by 69 percent when compared with Volvo's previous head restraint design.

The Saab System
The system that Saab uses, called Saab Active Head Restraint or SAHR for short, focuses on the head restraint itself. "During a rear impact, the car is pushed forward and the occupant is pushed backward into the seat. When this happens, a mechanism activates the head restraint pushing it up and forward to minimize the distance between the head and the head restraint," explains Stefan Olsen, a Saab safety engineer. Unlike Volvo's WHIPS system, Saab's mechanism does not require any repair after a collision. It simply resets itself immediately after the crash.

While Saab drivers can adjust their head restraint up and down, this is not the key to why SAHR is effective. In fact, in the IIHS' tests, researchers leave all head restraints in the lowest position because so few people in the United States adjust their head restraints. What makes SAHR effective is purely the internal mechanism that automatically pushes the head restraint up and forward in a crash.

Saab has since developed its second generation of the SAHR system. "The big difference between the two is that the second generation activates quicker — in less than 70 milliseconds," says Olsen. Despite its impressive results in IIHS testing, Saab doesn't see itself anywhere near being done in its research and refinement of head restraints. "We think there is a lot more to learn using the BioRID dummy," says Olsen. "We are really very early in this type of testing."

Seeing Results
Although the National Highway Traffic Safety Administration (NHTSA) does not rate head restraints, the governmental agency sees value in the research conducted by the IIHS and by individual automakers. Acknowledging the role that seat and head restraint design plays in reducing whiplash, it has created a new regulation that will require front-seat head restraints to sit closer to the back of the head and be centered vertically behind it. If head restraints are adjustable, they must lock in place after positioning. These same rules will apply to rear-seat head restraints if they are installed on a vehicle, but it does not require automakers to equip vehicles with head restraints in the rear. The regulation goes into effect on all passenger vehicles that are manufactured from September 1, 2008, onward. It estimates that whiplash injuries will drop by 17,000 when all new vehicles meet the requirement.

"By standardizing the best practices in head restraint performance, we can reduce the most common form of injury in rear-end collisions," says NHTSA chief Dr. Jeffrey Runge. "Many of these injuries are more than just a pain in the neck. They become chronic, painful, debilitating and costly."

See our checklist on how to protect yourself from whiplash in the event of a rear-end crash.