A Procedure for Network-Wide Road Safety Assessment in Italy

The European Directive 1936/2019 has innovated the road safety management process, through the introduction of the network wide road safety assessment (NWA) approach, based upon the measurement of in-built safety performance combined with accident data. In order to promote the uniform application of the directive in the EU countries, specific guidelines were published in January 2023 which, however, highlighted limitations in terms of results, due to the need to provide valid segmentation criteria together with performance indicators. For this reason, ANSFISA, the Italian National Agency for safety of railway, road and motorway infrastructures, started a technical discussion with the main Italian road managers aimed at defining a methodology based on a set of indicators for evaluating road network safety on a performance basis. In particular, the identification of the indicators and the proposed methodology is based upon the combination of the “reactive approach” with the “proactive approach” (as defined by the EU guidelines) according to the following steps: segmentation deducted by the performance homogeneity of the network elements; application of the empirical Bayes (EB) method to estimate the expected number of crashes correcting for the regression-to-mean bias based on safety performance functions calibrated on the Italian network; identification of an integrated set of indicators for the proactive evaluation of in-built safety performance, also through explicit evaluation of traffic volumes; comparison of the results of the reactive approach and the proactive approach; and introduction of a new methodology for combining results. The resulting model is presented in this paper, with a report about the results of the first experiences developed along some segments of the Italian road network.