Crashes speed, role

The role of speeding as a direct crash cause was probably first analyzed in a detailed and comprehensive manner by Treat et al (1977). In this study, described in detail in Chapter 17, a representative sample of more than 2,000 police-reported crashes was analyzed by crash investigators at the crash sites, and 420 of them were further analyzed by multidisciplinary teams. A cause was defined as an event or action whose absence would have prevented the crash, all other things being equal. Furthermore, a human cause was cited if the causal behavior was a deviation from the normal or expected behavior of the average driver. Thus, speed would not be cited in a crash of a speeding vehicle imless the speed deviated from the speed expected at that site under the conditions that prevailed and the crash would not have occurred had the speed been as expected. With this approach to causation, the study estimated excessive speed to be a definite cause in 7-8 percent of the crashes and a probable cause in an additional 13-16 percent of the crashes. 

Further analyses on U.S. and European data have all confirmed the very strong associations between speed and injury severity. Bowie and Waltz (1994) analyzed U.S. national data and showed that while speed is cited as a crash cause in 10.2 percent of property-damage-only crashes, and in 14.6 percent of crashes with minor (non-incapacitating) injuries, it is cited in 34.2 percent of all fatal crashes. More objective analyses that do not rely on possibly-biased clinical assessments of the role of speed have also demonstrated the relationship in a much more direct manner, as discussed below. 

So what is the role of the driver and other occupants in mitigating the consequences of a crash Actually their role is quite crucial. First, they must take advantage of the best restraint systems that will keep them in their seats when a crash occurs. Second, the driver must compensate for these benefits by engaging in high risk behaviors that can increase the likelihood of a crash, or the impact speed if a crash occurs. If we now recall the risk homeostasis hypothesis (see Chapter 3), this means that drivers must be convinced not to increase their speed because their car can help them survive high speed crashes that were unsurvivable 30 years ago. Unfortunately not everyone takes advantage of the belts, and some occupants who do, still don t get all the expected benefits. Who these drivers and occupants are, why they behave this way and what can we do about it is the focus of this chapter. 

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