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Better adjustment of head rests is necessary

The danger of whiplash injuries due to a rear collision can be reduced when head rests are positioned correctly. Therefore it is crucial that head rests in passenger cars are set correctly. SWOV has carried out a field survey (R-95-19) to find out how much people know about whiplash and head rests, and how head rests are positioned in passenger cars. Another study concerned the technical aspects of head rests. Measurements of new cars were performed at car dealers and surveys were carried out in public parking areas. This field study was supplemented by a technical study (R-95-30).

At present, head rests in cars are not (yet) compulsory in the Netherlands. If they are fitted - as is virtually always the case - a Dutch law called the new vehicle regulation states that they should comply with an (obsolete) EC guideline. At present, partly at the insistence of the Netherlands, an adaptation to the guideline is being prepared in a European context, where the requirement concerning the minimal height of head rests will become markedly stricter.

Studies

Surveys and measurements were used to gather information. The measurements were made in large car parks outside shopping centres and roadside restaurants, amongst others. The cars investigated had just come out of road traffic.

The following criteria were applied to determine the correct positioning of head rests:

Eighty percent of the male front-seat occupants proved to have their head rests set too low. On this point the percentage of women at fault proved to be lower (48 percent) due to their average height. For 28 percent of front-seat occupants, the horizontal distance between head and head rest was incorrect. This was mainly due to the back rest of the seat being positioned incorrectly.

 

Knowledge

Passenger car occupants proved to have an imperfect understanding of the correct positioning of head rests. This fact can be pointed to as the main cause of the frequent incorrect positioning. Their understanding of the function of the head rest, and the phenomenon of whiplash, can be viewed as adequate.

 

Proper adjustment not always possible

It has been shown that it is not possible to raise the head rests sufficiently in many cars. If all front passengers were to adjust their head rest to the highest position, this would still not be sufficient in 46% of the cases. This is an obvious point of attention for the industry as improper adjustment of head rests increases the chance of whiplash injury due to a rear collision.

SWOV Research Activities 5 - March 1996

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