The higher the speed is, there is an increased risk of being involved in a car accident. Different studies have come up with quite different levels of increased risk when driving faster than the average speed and there is still considerable uncertainty of what the individual risk curve actually looks like. There is no overall increased risk if you drive slower than the average speed on the road. These are some of the results of a study made at VTI which describes the state of knowledge in terms of speed distribution and traffic safety. Real changes in the speed distribution and estimated accident risk for three different traffic safety measures are studied. The aim is to gain a better understanding of the relation between speed distribution and traffic safety and thereby obtain a better basis in efforts to plan and evaluate different road safety measures. The study consists of three parts. First, a literature review on models for the relationship between speed and accident risk. In the second study, the effects on the speed distribution of various traffic safety measures are studied. The third study compares different models that estimate accident risk. (Author/publisher) This report may be accessed by Internet users at http://www.vti.se/en/publications/traffic-safety-and-speed-dispersion/
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