Speed Distribution and Traffic Safety Measures

It is well known that speed is a crucial road safety factor. Many implemented safety measures aim to induce road users to reduce their speed and comply with speed limits. With respect to the change in the mean speed, the impacts on road safety in terms of number of accidents and the number of injured and killed people are well known. For example, this relationship is described by the Power model [ELV 04, NIL 04], which is often used to estimate the traffic safety effects of speed changes. However, it is not certain that only the mean speed is affected by particular traffic safety measures measures such as the 85th percentile, standard deviation of speed and shape of the speed distribution can also be affected. 

Traffic Safety, First Edition. Edited by George Yannis and Simon Cohen. ISTE Ltd 2016. Published by ISTE Ltd and John Wiley Sons, Inc. 

This study investigates and compares the changes in speed distribution and estimated accident risk for three traffic safety measures, namely  

This study seeks a better understanding of the relationship between traffic safety measures and speed distribution, to obtain a better basis for planning and evaluating 

Speed limit changes and speed enforcement are two available measures to reduce the speed of the road users. Here, decreased speed limits on roads with and without speed cameras and the introduction of new speed cameras are examined. 

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Figures 11.1, 11.2 and 11.3 show the speed distributions before and after the following three traffic safety measures ...

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