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In some areas, notably the United States , these laws are controversial. Their effect is open to differing interpretations, and claims of lives saved by such laws are disputed. Disputing the efficacy of seat belt legislation is not the same as disputing the efficacy of seat belts themselves. Nor is it necessary to believe that the proposed mechanisms offsetting the efficacy of seat belts will necessarily eliminate all the benefit; the offsetting effects could be greater than, equal to or less than the protective effect of seat belts. PREDICTED EFFECTS The move towards seat belt legislation started in Australia in the late 1960s, although it was echoed elsewhere. It was influenced primarily by doctors working in emergency medicine, who noted that seat belt wearers were less likely to be seriously injured in collisions. Hospital based Case-control studies of crash victims supported the empirical observation that those wearing seat belts were less likely to be killed or seriously injured than those not wearing them. Based on this type of study, predictions such as 45% reductions in fatal injury and 50% reductions in moderate-to-critical injury were made. Experiments using both Crash Test Dummies and actual human Cadaver s also indicated that wearing seat belts should lead to reduced risk of death and injury in certain types of car crash. As a result of such predictions the use of seat belts by vehicle occupants was made compulsory in Victoria, Australia in 1970, followed by the rest of Australia and other countries during the 1970s and 1980s. Predicted savings of lives in the thousands or (in the case of the USA) tens of thousands have been the standard currency of seat belt legislation proponents. MEASURED EFFECTS Initial reports from Australia indicated that the laws had indeed been effective: a rising trend in fatalities pre-1970 had been arrested and reversed, and this was attributed to the effect of seat belt legislation. But this did not met with universal acceptance: introduction of early seat belt laws coincided with the world Oil Crisis , and it was evident that road casualties had dropped in all countries, not just those with seat belt laws (an identical reversal of trend is visible in the UK at the same time although British seat belt legislation was not introduced until a decade later). Claims of lives saved based on extrapolation of trends pre-law would therefore be skewed by the effect of the oil crisis, which resulted in all countries in reduced miles travelled and reductions in speeds. When a seat belt law was proposed in the UK, similar claims for potential lives and injuries saved were advanced. William Rogers , secretary of state for transport, stated that: 'On the best available evidence of accidents in this country - evidence which has not been seriously contested - compulsion could save up to 1000 lives and 10,000 injuries a year'. Professor John Adams of University College London was sceptical of such claims and set out to analyse the effect of seat belt laws as then in force and assess how well they matched predictions. His findings were published in 1981 (and can be found in the Society Of Automotive Engineers transactions of that year: {Link without Title} . His conclusion was that in the eighteen countries surveyed, accounting for approximately 80% of the world's motoring, those countries with seat belt laws had fared no better, and in some cases (e.g. Sweden , Ireland and New Zealand ) significantly ''worse'' than those without. In particular, those outside cars (pedestrians and cyclists) had experienced significant increases in fatalities involving cars. In response the UK's Department of Transport commissioned a study on the effects of seat belt laws in Sweden , West Germany , Denmark , Spain , Belgium , Finland , the Netherlands and Norway . This study, known as ''"the Isles report"'' after its author, used the United Kingdom and Italy as controls for no-law countries compared casualty trends for both those inside and outside cars between law and no-law states. The report predicted that, based on the experiences of the eight countries studied, a UK seat belt law would be followed by a 2.3% ''increase'' in fatalities among car occupants. In order to explain this disparity, Adams advanced the hypothesis that ''Protecting car occupants from the consequences of bad driving encourages bad driving''. Subsequent analysis has suggested that a number of mechanisms are in play:
There is evidence to support the risk compensation theory. In one experiment, two groups of drivers (habitual wearers and habitual non-wearers) were asked to drive a test track under the guise of testing different seat belt materials for comfort. It was observed that the habitually unbelted drivers consistently drove faster and cornered faster when wearing seat belts. Similar effects have been observed in respect of other interventions such as Anti-lock Brakes . Non-vehicle occupants From the very beginning in Australia, and subsequently New Zealand, there had been indications that seat belt laws might produce increases in deaths and injury among those outside cars such as motorcyclists, cyclists and pedestrians. The author of the Isles report was alarmed to find that in Europe the predominant effect of seat belt legislation was of increased numbers of injuries to non-car users. The author predicted that in the UK, deaths to other road users would rise by approximately 150 per year in the event of compulsory seat belt wearing legislation. In terms of injuries to other road users the prediction was for a 11% increase in pedestrian injuries with injuries to other road users climbing by 12 to 13% (numerically 7,000 and 36,000 respectively). The British Law The Isles report was never published (some say it was suppressed as it did not back the pre-existing position of Government and the Department), and is known mainly because it was leaked to '' The Spectator '' magazine some time after the law was passed. A law was passed which at the same time introduced evidential breath testing. The year of the law saw increases in deaths to pedestrians of 135 per year and of deaths to cyclists of 40 per year, a 75 year high and somewhat in excess of Isles' predictions. There was a reduction in driver fatalities and an increase in fatalities of rear passnegers (not covered by the law). A subsequent study of 19,000 cyclist and 72,000 pedestrian casualties seen at the time suggests that seat belt wearing drivers were 11-13% more likely to injure pedestrians and 7-8% more likely to injure cyclists. Analysis of fatality figures before and after the law shows:
In analysing these results, Adams concludes that there is no evidence of the seat belt law having reduced overall fatality numbers, and that there is evidence of fatalities having migrated from drivers to vulnerable road users. Although the Government argued at the time that the law had saved lives, it has subsequently attributed almost all the benefit for the small reduction in overall driver fatalities to the introduction of evidential breath testing. Seat belt use is a binary: the belt is either worn or not. Belt laws, which tend to lead to substantial changes in wearing rates over very short periods, would, if the predictions of up to 50% reductions in fatalities are correct, be expected to demonstrate large scale Step Change s in fatality figures. No such changes have been observed. Whether seat belts reduce fatalities, it is inescapably true that any reductions fall well below the predicted levels, a fact widely interpreted as supporting risk compensation theory. SUPPORT FOR SEAT BELT LEGISLATION and Air Bag s, according to NHTSA , DOT ]] Other authorities claim that seat belt legislation ''has'' reduced the number of casualties in road accidents. For example, this statistical analysis by the NHTSA claimed that seat belts save over 10,000 lives every year in the US. The FARS further writes: [http://www-fars.nhtsa.dot.gov/new_tips.cfm?stateid=0&year=2001&tipscat=Restraint%20Systems] "Research on the effectiveness of child safety seats has found them to reduce fatal injury by 71 percent for infants (less than 1 year old) and by 54 percent for toddlers (1-4 years old) in passenger cars. {Link without Title} Among passenger vehicle occupants over 4 years old, safety belts saved an estimated 11,889 lives in 2000." However, these figures for lives saved are obtained by extrapolating experimentally derived estimates for seat belt effectiveness to the entire population based on recorded seat belt use and recorded crash rates; this is problematic for the reasons noted above and it is argued that this is an example of Begging The Question : such evidence cannot of itself provide evidence of actual reductions in deaths that might be reasonably attributed to seat belts. In Victoria, Australia use of seat became compulsory in 1970. By 1974 decreases of 37% in deaths and 41% in injuries, including a decrease of 27% in spinal injuries, were observed, compared with extrapolations based on pre-law trends. The Victorian legislation coincided with the Oil-crises of the early 1970s, a time when traffic injuries and deaths fell in most industrialised countries. Adams' analysis shows Victoria's injury trends as being above the average for all industrialised countries. CURRENT POSITION United States Recently there has been a push for seat belt laws in the United States . As elsewhere, this has resulted in controversy. In addition to the above observations in respect of the measured effect of seat belt laws, the debate in the US has highlighted some other comments which received less attention in other countries. One facet of the US case is speculative consideration of effects on car occupants (e.g., the possibility that seat belt use can cause internal, neck and Spinal Injuries as it leaves the head free to move inertially while the rest of the body is restrained), and may trap an occupant in a vehicle. However, proponents of seat belts claim that the benefits in injuries saved far outweigh these risks, and do not credit the idea that they prevent occupants from escaping the car (and also claim that in any case being thrown from the vehicle is much more likely to result in death than being restrained within it). It is valid to consider the issue of rotational injury to the brain, causing Diffuse Axonal Injury , a leading cause of persistent vegetative state, but there is little credible evidence to support the idea that this is positively associated with seat belt use and considerable evidence to support the idea that head injuries are much more likely to happen, and to be severe, in unrestrained drivers. Many US opponents also object on the grounds that seat belt laws infringe on their Civil Liberties . This is accorded much higher priority in the US than in some other countries. Developing countries It might be argued that the risk posed to vulnerable road users is of less importance where walking and cycling are relatively insignificant, as they are in the US. In many developing countries, however, pedestrians, cyclists, rickshaw operators and moped users represent the majority of road users. These countries rarely have the resources to physically separate such road users from car traffic (an idea which is itself arguably inequitable, given that those forced into second-class facilities are not the ones posing the danger). In many such countries non-car occupants also represent the majority of road fatalities. Some believe such countries face a serious moral dilemma about importing "Western", "car-centered", models of "road Safety" such as compulsory seat belt legislation. Dilution of risk compensation effect There is very little literature considering how risk compensation effects, subjective as they must be, change over time. Although there is good evidence that habitually unbelted drivers will take more risks when belted, and that habitually belted drivers will be more cautious when unbelted, by the nature of laws, new drivers will be habituated from the outset. An interesting footote to the debate is analysis by Adams of the relationship between accident records and car ownership, a relationship known as Smeed's Law ( {Link without Title} ). It appears that this empirical rule relating car casualties to the level of car ownership has continued to hold across several decades of safety interventions, including seat belt laws. It may be that modern drivers, habituated from the outset to seat belt use, are also habituated from the outside to greater expectations of car performance: faster cornering, faster acceleration, later braking. Alternatively it may be that improvements are due to the increasing profile of safety interventions as car ownership increases, whatever the country, as road safety professionals prefer. SEAT BELT LEGISLATION AROUND THE WORLD This section gives an overview of the years in which seat belt legislation was introduced in various countries around the world.
SUMMARY Seat belt legislation is an interesting case-study in safety intervention. What appears at face value to be a simple and valid inference, that comparisons between those who do and do not use a safety aid voluntarily can be scaled to predict benefits for an entire population subject to compulsory use of that aid, has been shown to be flawed. The same flawed reasoning has been used to support other interventions such as Bicycle Helmet s, with similarly contradictory results. Whether seat belt laws save lives is still disputed. Arguably any risk compensation effect might be diluted or disappear altogether over time as belt use becomes the norm, and trends in motor casualties are undoubtedly favourable (although some put this down to Smeed's Law ). There is little dissent, though, from the view that any actual savings fall well short of the numbers predicted by simple extrapolation, and it was these predictions which led to the laws being passed. Whether or not laws would have been passed based on much more modest reductions, accompanied by rises in fatalities for vulnerable road users, is debatable. SEE ALSO EXTERNAL LINKS Links to sites/studies that endorse seat belts
Links to sites/studies skeptical/critical of seat belt legislation
REFERENCES AND FURTHER READING
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