Impact of methodological choices on road safety ranking

Abstract

Composite indicators aggregate a lot of information in one index based on which countries are often ranked. However, the position of a country can largely be influenced by the methodological choices made during the composite indicator process. This process consists of several phases such as selecting appropriate indicators, normalising the indicator values, assigning a weight to each indicator and selecting an aggregator. In order to guarantee a robust index considering several possibilities and alternative techniques during each phase, an uncertainty and sensitivity analysis is essential. Researchers, policymakers as well as the community of road users will benefit from such analysis. The most influencing methodological aspects will be indicated for which extra information is most valuable in order to reduce the uncertainty in the end result. Incorporating the necessary uncertainty and sensitivity analysis in the process is an aspect that will enlarge the acceptability of composite indicators. In this research, the road safety ranking of countries based on different weighting and indicator options is studied. The results show that the ranking of countries differs significantly according to the selected weighting method, expert and set of indicators. Of these three factors, the indicator set resulted to be the most influencing factor. Additional research on the selection of appropriate indicators (beside other aspects) will reduce the uncertainty in ranking and help in obtaining a robust road safety index.