How to estimate the social cost of transport? An Italian case study?

The valuation of the social cost of transport is an important issue of transport research. Social cost analyses have been performed for a variety of reasons and to support a wide range of policy positions but there is not much agreement on the best method to use to evaluate it in the most accurate way. This paper is focused on the application of two different methodologies, the contingent valuation (CV) and the stated choices (SC), comparing them in order to understand if there are some differences in their estimates and which is the technique most reliable and accurate. The application of these two different methods is based on the data collected during a survey carried out in the town of Alessandria, a medium size city in the north-west of Italy, about 100 km from Torino. The survey has concerned a sample of 690 units and has been focused on the understanding of the whole cost of the town’s mobility as perceived by its inhabitants. The results of the study show that there is a great difference between the estimates of the social cost of transport using the two methodologies: the CV method tends to underestimate the value of the social cost while the SC method is likely to be more accurate. Further research efforts should be mainly aimed at understanding how to build up a reliable instrument for the evaluation of the social cost of transport in term of both survey design and estimation technique. Another important topic should be aimed at carrying out comparisons between estimations obtained using datasets from cities having similar characteristics.