How to select the most appropriate measures for a particular road safety problem? : providing a methodolody. In order to tackle a certain traffic safety problem, one can often choose out of a set of different traffic safety measures. The choice for a suitable traffic safety measure is not an easy task. This report describes a methodology that can be used to choose the best measure, i.e. the measure that can reach the highest effects with the lowest costs. The report consists of two parts: The first part describes how the amenability to treatment of traffic safety problems can be studied. Two dimensions can be balanced against each other: the magnitude of the problem and the public support to solve the problem (Elvik, 2008). The magnitude of the problem can be expressed by the population attributable risk, which refers to the contribution a factor makes to the total number of cases (i.e. all crashes) (Elvik, 2008). The magnitude of a problem needs to be balanced against the public support to solve the problem. In order to quantify the public support, one can use questionnaires, telephone surveys, discussion groups, experimental sessions, etc. The application of this method on the three most important causes of severe injuries (speeding, drunk driving and not wearing a seatbelt) shows that speeding leads to the highest number of fatal crashes, but the public support to tackle the problem is the lowest. The public support to tackle the problem of drunk driving is the highest, whereas the magnitude of the problem is half as high as the magnitude of speeding. Once the decision is taken to tackle a certain traffic safety problem, one need to decide which traffic safety measure will be implemented to reduce or to solve this problem. Often different measures are available and the selection of this measure is not an easy task. Therefore the second part of this report describes a methodology that can be used when a traffic safety measure needs to be selected. Three dimensions should be taken into account: 1) The effectiveness of the measure; 2) The public support to introduce the measure; 3) Costs of the measure (Elvik, 2008). An analysis of the different possible traffic safety measures on each of these three dimensions and the balance against each other can help policymakers to make an objective and well-founded choice to select the best measure. In this decision the analytic hierarchic process can be used, which consists of three steps. During the first step each of the three dimensions receive a weight, which indicates the importance of each of the dimensions against the other dimensions. The policy makers need to decide which weight every dimension receives. This can be the result of a political or social discussion. In a second step one need to get a view on the score of every possible measures on each of the three dimensions. In order to know the effectiveness, public support and costs of the different traffic safety measures, one can apply a study or one can search through the literature for existing studies. Next, the different measures need to be compared pair wise per dimension. This eventually will lead to a classification of the measures for each of the dimensions, through which the measure with the highest effectiveness, the highest public support and the lowest costs receive the highest score. In a third step the results of step 1 and step 2 need to be combined. This means that the score for each measure per dimension needs to be multiplied with the weight that is given to each of the dimensions. The traffic safety measure with the highest score in a certain scenario, is the best measure for that scenario. As an example this method was applied on the most frequently implemented traffic safety measures in Flanders, and traffic safety measures that will gain popularity in the near future. (Author/publisher)
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