This deliverable gives an outline of the process of prioritising road safety measures. It should be used by policy makers to understand how they can use the SafetyCube Decision Support System (DSS) to choose between different countermeasures.
Candidates for countermeasures are mostly selected on the basis of crash analysis (either microscopic or macroscopic) or departing from specific risk factors. Both approaches are supported in the SafetyCube DSS. The number of casualties a countermeasure can save depends on the target group -- the number of cases on which the measure can possibly have an effect -- and the percentage reduction within that group. This can be expressed as CMF or as relative risk. If the measure is not implemented / used everywhere it also depends on the degree of usage, the penetration rate.
Three analyses of a countermeasure’s economic efficiency are investigated: Cost- effectiveness analysis, cost utility analysis, and cost benefit analysis. It is concluded that cost-benefit analysis fits the purpose of prioritising between alternative countermeasures best. It allows the joint evaluation of measures’ effectiveness in reducing crashes of different severity. Moreover, it provides information on the socio-economic return of countermeasures, and in principle allows to include side effects into the analysis. Although, the valuation of possible side effects of road safety measures was beyond the scope of SafetyCube, the presentation in terms of cost-benefit ratios allows for the post hoc inclusion of other impacts.
To help decision makers prioritize between different measures, the Decision Support System provides a calculator for Economic Efficiency Evaluations (E3). This E3 calculator combines input on the measures with input on the cost of crashes and calculates different indicators of economic efficiency. One of the major criticisms on cost-benefit analysis is that the outcomes are highly dependent on the costs that are assumed for crashes. SafetyCube has therefore dedicated large efforts to collecting, analysing, and harmonising the crash-cost estimates from European countries, also providing a set of European standard values, which was used for all SafetyCube example analyses.
DSS users can use the E3 calculator to conduct their own analysis. They can choose to depart from a SafetyCube example analysis in which they change values according to their own situation. To determine the crash costs, they can select the target-country of their analysis and choose between the country’s own reported values or a set of harmonised values for the target country. Users can also include side-effects if they have an estimate of their costs / benefits. A quick guide how to use the E3 calculator is included, describing the input necessary from the user as well as the input and calculations provided by SafetyCube. Conducting a sensitivity analysis is shown exemplary in the SafetyCube examples and is advised for users who conduct their own analysis.
The output of the E3 calculator consists of criteria of cost-effectiveness (the costs per prevented crash or casualty) and cost-benefit indicators. The benefit-cost ratio (benefits / costs) favours measures with the best value for money even if their actual benefits are relatively small, because they are implemented at a small scale. The net-present value (benefits – costs) favours measures with large benefits (even if they come at a relatively large cost). The break-even cost is the maximal cost for a countermeasure to still be economically efficient. It is relevant when the analysis is done without precise information on the cost of the countermeasure.
It is acknowledged, that data are not always available to perform a full-scale cost-benefit analysis including all aspects that are relevant for the choice between alternative measures. Multicriteria decision analysis denotes a group of systematic tools for decision making that allow taking several criteria into account – even if no monetary valuation (or other quantitative estimates) exist for them. Often these analyses involve the stakeholders in parts of the analysis process and also give information on how preferable different alternative measures are for each of them. The output of the Road Safety Decision Support System and the E3 calculator can be used in a multicriteria analysis as one of the indicators under consideration.
The DSS gives the end-user the building blocks for developing a road safety program. It is based on a taxonomy of risk factors and measures, it makes the user aware of different options to treat a problem, it indicates how well each approach has been found to work, and it contrasts the costs of each measure with its estimated effectiveness.
