Controlled Speed: According to a 2004 report from the World Health Organisation a total of 22% of all injury mortality worldwide were from road traffic injuries in 2002 and without increased efforts and new initiatives casualty rates would increase by 65% between 2000 and 2020. The report identified that the speed of vehicles was at the core of the problem and said that speed limits should be set appropriately for the road function and design along with physical measures related to the road and the vehicle and effective enforcement by the police. Road incidents are said to be the leading cause of deaths among children 10 – 19 years of age (260,000 children die a year, 10 million are injured). They are also occasionally set to reduce vehicle emissions or fuel use. Maximum speed limits place an upper limit on speed choice and if obeyed can reduce the differences in vehicle speeds by drivers using the same road at the same time. Traffic engineers observe that the likelihood of a crash happening is significantly higher if vehicles are traveling at speeds faster or slower than the mean speed of traffic; when severity is taken into account the risk is lowest for those traveling at or below the median speed and increases exponentially for motorists driving faster. It is desirable to attempt to reduce the speed of road vehicles in some circumstances because the kinetic energy involved in a motor vehicle collision is proportional to the square of the speed at impact. The probability of a fatality is, for typical collision speeds, empirically correlated to the fourth power of the speed difference (depending on the type of collision, not necessarily the same as travel speed) at impact, rising much faster than kinetic energy. The 2009 technical report An Analysis of Speeding-Related Crashes:Definitions and the Effects of Road Environments by the National Highway Traffic Safety Administration showed that about 55 percent of all speeding-related crashes in fatal crashes had exceeding posted speed limits among their crash factors, and 45 percent had driving too fast for conditions among their crash factors. However, the authors of the report did not attempt to determine whether the factors were actually a crash cause, contributor, or an unrelated factor.
Posted on: Sat, 26 Oct 2013 03:10:33 +0000
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