WHIPS boosts neck injury research
WHIPS boosts neck injury research
Safety research at Volvo Cars never stands still. Lotta Jakobsson was recently conferred with her PhD in traffic safety engineering and has over ten years of research experience in the field. Her early research contributed to the development of the WHIPS seat. Now, with a wider knowledge of the factors which cause neck injury in rear-end impacts, she has developed a method of providing car occupants with better protection against this type of injury in frontal and side impacts.
It is a familiar fact that increased knowledge usually produces more new questions. And that it also induces greater humility. Lotta Jakobsson is an example of this. A graduate mechanical engineer practising as a biomechanical engineer, she has worked for Volvo Cars since 1989, and has been carrying out research in traffic safety engineering at Chalmers University of Technology, Göteborg (CTH) since 1999. Now a doctor in her field, she is one of Sweden’s leading experts in the area.
Despite this, she emphasises that ‘whiplash’ is a difficult concept, that neck injuries are incredibly complex, and that we know all too little about what happens the neck in an accident and what really causes injury to it. In the course of many years of collaboration with the neck injury group at the Traffic Injury Register Office at Östra Sjukhuset (one of Göteborg’s major hospitals), she has acquired even greater knowledge – and has had to ask herself even more questions.
Many affected
“Neck injuries are difficult because we do not know how they occur or what their nature is,” says Lotta Jakobsson. “Furthermore, the pain can spread due to the incorrect use of other muscles, with the result that the sufferer then begins to experience pain in other muscle groups.”
She emphasises that she is an engineer, and that it is for physicians to determine what has been injured and what is causing the neck pain.
“However, I have to understand as much as possible about how we function,” she says. “Added to that, we use results from real-life accidents, backed by computer simulations and crash tests carried out in our own Safety Centre.”
As the most common type of traffic injury, neck injuries affect an estimated 25,000 people per year in Sweden alone. Of , about 1,500 suffer disability.
Within the EU, the corresponding number of injured people is probably in the region of a million, with over 50,000 suffering long-term effects. Every year!
In the USA, the National Highway Traffic Safety Administration (NHTSA) estimates that over 270,000 Americans suffer whiplash injuries every year and that the social cost is of the order of USD1.75 billion – for injuries regarded as relatively minor!
Importance of psycho-social factors
Psycho-social factors have been shown to play a very significant role in the recovery of neck injury patients, and in whether or not they develop long-term problems. Much research remains to be done in this area, with the particular aim of ensuring that sufferers receive high-quality rehabilitation and recover a positive attitude to life.
Lotta Jakobsson’s research during the first half of the 1990s contributed to the development of the WHIPS seat, which was first introduced in the Volvo S80 in 1998. All Volvo models have been equipped with this feature since 2000.
“Our statistics for rear-end impacts are now so good that we know its protective effect,” comments Lotta. “Compared with our earlier seats – which were already among the best – WHIPS reduces the risk of initial injury by 33% and the risk of long-term effects by 53%.”
Tall women most at risk
Her research has revealed that a woman is exposed to a higher risk of neck injury than a man in a rear-end impact. Tall people are more at risk than short people, and this difference is also greater in the case of women. In frontal impacts, the risk to light people is greater than to their heavier counterparts.
“The manner in which a subject is seated at the instant of impact has a major bearing in a rear-end impact. If the person’s head is straight, he or she is looking ahead and is leaning against the head restraint, the effect of the impact will not be that great – and the risk of injury will be small,” explains Lotta. “However, if the person is leaning forward, or if the head is turned to the side, the risk of injury will be much greater. ‘Panic tensing’ of the muscles can also increase the risk. You might think that rally drivers should suffer neck injuries, but they probably learn to tense their neck muscles in an ideal manner.”
Lotta always has a skeleton, or at least a spinal column, close to hand. Not in a cupboard, but preferably in her hands as she discusses her subject. Since the human head is fairly heavy – just over 4 kg – it can impose high stresses on the neck in the event of an accident. The head is thrown forward and backward during the accident sequence, stretching the tendons, muscles and ligaments between the vertebrae.
“We don’t actually know the site in which injury occurs, but it is probable that there are several,” believes Lotta Jakobsson. “Although this makes our task more difficult, we try consistently to reduce the extremes of movement.”
Seat must absorb energy
She compares the front and rear seats in a car. Research has shown that the rear-seat occupants are not as prone to injury in a rear-end impact as their front-seat counterparts. The structure in the rear is ‘deader’ and the degree of rebound less. In the front seat, on the other hand, the actual seat frame in contact with the back is more springy and generates rebound. The seat absorbs some, but not all, of the energy. The seat padding is very important in terms of the support it gives the body – even support is good.
When the WHIPS seat operates, the backrest is first ‘shifted’ back slightly relative to the seat cushion and is then tilted backward in a controlled manner, depending on the subject’s weight and the force of the impact, providing the occupant with a responsive movement.
“By the time we developed WHIPS, we had already worked out how to design the seat through interviews with injury sufferers, studies of crashed cars, our own crash tests and simulations,” says Lotta Jakobsson. “At that time, there were no crash dummies with spinal columns and we realised that this was essential.”
Even a dummy needs a backbone
She tells us that her Volvo colleague, Clas Jernström, developed a mathematical dummy with a spinal column. This enabled many solutions to be verified and helped to make WHIPS a highly effective system from the very outset.
This was followed, about a year later, by the BioRID dummy, which was developed as a joint project by Volvo, Saab, Autoliv and CTH. BioRID is now used by many carmakers and by various research institutions, and is likely to become a ‘rating dummy’ in future test programmes, including EuroNCAP.
Thus, the research efforts of Lotta and her colleagues have progressed and given rise to further developments. Although WHIPS has been thoroughly evaluated, refinement of the system is naturally ongoing.
Lotta’s focus is now on the development of protection against neck injury in frontal and side impacts.
“Most neck injuries actually occur in crashes and impacts of these types,” she stresses. “In my doctoral thesis, I proposed a method of developing protective systems for situations in which the injury mechanism is unknown.”
Next challenge beckons
“My thesis shows that the method we used really works. Our research can never be an exact science, but is more of an ‘engineering’ nature,” remarks Lotta Jakobsson. “We have done the jigsaw – and got it right – and our approach has been proved correct. “We have closed a circle,” she says with some pride.
Using the same three guidelines which formed the basis for developing WHIPS, Dr. Jakobsson is now turning her attention to developing means of protecting vehicle occupants in frontal and side impacts. This involves three aspects:
- Reducing acceleration stress
- Minimising relative movement of the spine
- Reducing rebound
“We have identified the problem areas and we have a great deal of information in our Volvo database. Our work to date has laid the foundations. Both the seat and the method for providing protecting people in rear-enders have been developed. Now, we have to decide what we want to do,” says Lotta Jakobsson. “We know where we are going – we only have to decide how!”
Captures
Lotta Jakobsson recently took her PhD in traffic safety engineering.
Lotta Jakobsson’s research contributed to the development of WHIPS. The system protects 33% of car occupants from initial neck injury and 53% from long-term neck injury in a rear-end impact.
A typical pattern of movement in a frontal impact.Illustration. The relationship between height and the risk of neck injury is clear from the charts. Tall women are exposed to the greatest risk, whereas the increase in risk with height among men is not as pronounced.
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