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Speed and the probability of a collision Kwan, Thomas Yan Wa


Speed related automobile accidents account for about one-third of all vehicle accidents in the United States and in the province of British Columbia. The estimated economic cost of speeding-related vehicle accidents in the US is $27.7 billions USD (1994 dollars). Researchers have different views on the role that speed plays as a causative factor in automobile collisions. The purpose of this research is to develop an equation between speed and the probability of a collision using a risk approach. Risk is defined as the product of the exposure, the probability, and the consequence of an event. By using published data from the province of Saskatchewan, an equation to estimate the probability of a collision as a function of speed is developed. This probability equation is a function of the average vehicle travelling speed raised to an exponent, in which the exponent is also a function of average vehicle speed. From the literature, the consequence of a fatal or serious injury collision is the fourth power function of the collision speed. Thus the equation for fatality risk for an individual travelling on a road is a fairly complex function of the operating speed. Additional analysis of traffic accident and speed data on US rural highways and data for Bangkok urban expressways were used to estimate risk. This research found that not only does speed increase the severity of a collision, but it also increases the probability of a collision.

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