Speed and crashes

As evidenced by the tremendous power of nuclear bombs, nuclear reactions involve quite a lot of energy. In the laboratory, researchers fabricate nuclides with the aid of special, high-energy equipment such as reactors in which nuclear reactions can take place, or particle accelerators in which particles such as protons are accelerated to high speed and crash into one another, or some other target. For example, in 2006, researchers at the Joint Institute for Nuclear Research in the Russian Federation and the Lawrence Livermore National Laboratory in California synthesized isotopes of element 118 for the first time. To make the new isotope, researchers smashed calcium atoms into a target made of californium (which has an atomic number of 98). These new isotopes decayed quickly. (Element 118 and other recently discovered elements have not yet been named.)... 

A number of studies have investigated the relationship between absolute driving speed and crash rate (Aarts and van Schagen, 2006). Irrespective of the research method used, almost all studies find that the relationship between speed and crash rate is best expressed as a power function the risk of a crash increases exponentially when speed increases and vice versa (see Figure 22.3). 

FIGU RE 22.3 Diagram of the power function of the relationship between speed and crash rate. 

Speeding is logically related to mobility and subjectively related - for many people at least - to pleasure. Unlike the dangers of drinking and driving and the benefits of belts, about which there is a near-consensus, people s perceptions of the relationship between speed and crashes... 

To evaluate the validity of this axiom we resort to empirical research that attempts to evaluate the causal relationship between speed and crashes. Three problems come up in attempting to do this. First, in referring to speed as a predictor variable and crashes as a predicted variable, we assume that speed is the independent variable of interest and that safety is the dependent variable of interest, in the sense that the former affects the latter, and is not just correlated with it. Optimally, to demonstrate that speed is the independent variable behind changes in crashes, it should be under the experimenter s control. But it rarely is. For crashes to be a true dependent variable, a causal relationship has to exist, and it can never be unequivocally justified. Second, both crashes and speed can be defined in many ways. For example we can study the effects of mean traffic speed, individuals speed, variability in traffic speed, or... 

There are at least three theoretical approaches or models of driver behavior that can and have been used to account for the relationship between speed and crashes. Each model views the driver and the fraffic environment from a different perspective, and each leads to somewhat different conclusions — all of which have received some empirical support. Two of the models — ftie information processing and the risk homeostasis - have been described in some detail in... 

Solomon s data in Figure 8-6b. A detailed discussion about the relationship between road type, speed, and crashes is available in Shinar (1998). 

The controversy and most of the research about the relationship between speed and crashes has evolved around three questions what is the relationship between the absolute speed of a vehicle and its crash likelihood What is the relationship between the deviation of a vehicle speed from the prevailing traffic speed and its crash likelihood What is the relationship between the physical severity of impact in a crash and the injury severity of the occupants ... 

Shinar, D. (1998). Speed and Crashes a Controversial Topic and an Elusive Relationship. In Managing Speed a Review of Current Practice for Setting and Enforcing Speed Limits. National Research Coimcil, Transportation Research Board Special Report 254. National Academy Press, Washington, D.C. 

Table 18-8. The effects of increases in enforcement (in multiples relative to baseline) on speeding and crashes (from Bjomskau and Elvik, 1992, with permission from Elsevier).

SHI 98] Shinar D., Speed and crashes A controversial topic and an elusive relationship . Appendix B in Managing speed Review of current practice for setting and enforcing speed limits. Special report no. 254, Transportation Research Board, Washington, DC, 1998. 

Hauer, E. Speed and crash risk An opinion. 2004, RACV, Melbourne, Austraha. 

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