Citation

Tingvall C. J. Traffic Med. 1982; 10(3): 41-47.

Copyright

(Copyright © 1982, International Association for Accident and Traffic Medicine)

DOI

unavailable

PMID

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Abstract

In this paper a theory formed by John Adams is discussed. By a graphical comparison of accident statistics from 18 countries, John Adams has come to the conclusion that one can doubt the effects of seat belt legislation on fatally injured car occupants. John Adams' hypothesis is that if a driver puts his seat belt on, he will use the reduced injury-risk for taking more risks when driving. This can be done by, e.g., driving faster. It has been shown in several investigations that the use of seat belts protects people from injuries. For fatal injuries the reduction factor is 40-60% and for serious non-fatal injuries 65-70%. The fact that the seat-belt use protects from injuries was well known, at least among the Swedish public, long before the seat belt act came into force in 1975. This knowledge, paired with the fact that most cars sold in Sweden from the year models 1960-1965 were equipped with seat belts in the front-seats, led to the circumstance that seat-belt use in Sweden was surprisingly high long before 1975. Seat belt use, however, was not equal in all areas and for all individuals. Factors influencing seat-belt use were (and still are in some respects) speed, type of car, age, sex and accident proneness. By dividing the car-occupant population into 3 groups, belted before and after the enforcement of the law (A), unbelted before and belted after the enforcement of the law (B) and unbelted both before and after the enforcement of the law (C), we can better understand how the different factors mentioned above have influenced the outcome of seat-belt legislation. The C-group, in rural areas, probably not exceeding 15%, is a high-risk group with a higher-than-average proportion of drunken drivers and young male drivers. The B-group differs from the A-group especially when it comes to accident severity and injury risk. From different studies we can say that the B-group translated to the population of killed drivers is smaller than can be assumed from observational studies of seat-belt use of drivers. By a multifactor discussion, we can come to the conclusion that the room for reducing especially the number of fatally-injured car occupants is limited and that the outcome of seat-belt legislation well fits into what can be expected. As far as can be seen, there is no room for explanations such as the theory of John Adams, which implies that the B-group has increased its injury risk (when the belt-use effect is omitted) when starting to use seat belts. The corollaries of Adam's hypothesis are also examined, showing that there is no indication found that there is an increased accident or injury risk (when the belt-use effect is omitted) due to seat-belt use. An unsolved problem is how to convince the group of car occupants still not wearing seat belts to protect themselves from injuries. This is especially important, as this group belongs to a high-risk population. By including all occupants in cars possible to protect by existing restraint systems (seat belts, child seats) we calculate that approximately only 60% of the injury-reducing potential afforded by restraint systems are used.