The majority of all whiplash injuries occur at benign velocity changes – below 25 kilometres an hour. Even though women are at much greater risk, whiplash protection systems are primarily adapted to men.
"I hope that my research will lead to improved whiplash protection for both women and men when they are hit from behind in a collision. From a national economics perspective, it would be advantageous to adapt car protection systems to suit women as well," says Anna Carlsson, who recently defended her thesis at Chalmers.
Women's bodies move faster in a collision
In order to produce a model for a female crash test dummy, Anna Carlsson tested women getting hit at very low speeds and acceleration in order to assess how an average-sized woman's body moves when hit from behind in a collision.
The researchers then developed a computational model of a female crash test dummy, which they named Evarid (RID = Rear Impact Dummy). The model is now available for purchase. On the basis of the mathematics model, the researchers produced a prototype for a crash test dummy with female proportions.
The dummy was then subjected to eight crash tests in regular car seats. The results were compared to a male dummy. When hit from behind, the female crash test dummy demonstrated generally higher acceleration and quicker motion than the male dummy. Car seat backs do not yield backwards to the same extent when a woman is hit, which means women experience an earlier and more powerful forward rebound.
The average sized female rear impact prototype dummy, Biorid50F. Credit: Dr Steffan Datentechnik
The neck has a slight curvature when we sit in a normal position. When hit from behind, however, the body is pushed forward by the backrest while the head lags behind, resulting in the neck becoming s-shaped before the head and neck subsequently rotate backwards. The next motion is the body being propelled forward into the seatbelt. This entire course of events takes about half a second. Good whiplash protection reduces injuries, but statistics indicate that the current protection in general is 30 percent more effective for men than for women.
Crash test dummy development has reduced injuries
"If we can lower the forward acceleration for both women and men during collisions, we can also significantly lower the risk of injury. One way of doing this is to manufacture a seat that yields backwards in a collision. Another way is to allow the upholstery padding to absorb the energy, meaning the seat frame does not move," says Anna Carlsson.
Volvo and Saab have been exceptionally good at producing whiplash protection. Anna Carlsson believes their success is due to Biorid, which is the male crash test dummy they developed at the end of the 1990s in cooperation with Autoliv and Chalmers. The Biorid crash test dummy is currently used all over the world and the risk of injury has been reduced by around 50 percent in the best car seats.
"Injuries can be further reduced by producing a female size dummy and by adapting car protection systems", says Anna Carlsson.
She hopes that she will be able to continue developing the female crash test dummy, which at this stage is still a prototype. She would also like to develop biomechanical limit values for women since the existing ones are adapted to men.
"Since the research indicates that women generally run a higher risk of sustaining injuries during car accidents, we need to separate the statistics and injury criteria for men and women."
The study was partly performed within the EU project Adseat
Caption, top image: The average sized male and female rear impact dummy models, Biorid and Evarid. Credit: Fred Chang, Humanetics
More information about whiplash injuries
Whiplash injury resulting from vehicle impacts is of worldwide concern. From a societal perspective these injuries are costly since they are frequent and can lead to long-lasting pain and disability. In Europe, the annual cost of whiplash injuries has been estimated to 10 billion Euros (Richter et al. 2000). In Japan, 547,654 traffic related injuries were registered during 1996, in which 44 percent of the victims suffered neck injury (Watanabe et al. 2000). In the USA, the number of whiplash injuries each year has been estimated to 800,000. Of these whiplash injuries, 270,000 were resulting from rear impacts with an annual cost of $2.7 billion (NHTSA 2004).
For more information please contact:
Anna K. Carlsson, Department of Applied Mechanics/Safer, Chalmers University of Technology, firstname.lastname@example.org
, +46 31-772 36 50 or +46 705-94 36 50