The role of transport supply in the acceptability of pollution charging extension. The case of Milan

In the beginning of 2008 a pollution charging in the central area of Milan was introduced. It initially had a large impact on traffic volume, but in some years its effect worn off, as the citizen of Milan started to change their cars. This is why in June 2011 Milan citizens were consulted i n a referendum for the extension of this measure to all cars (except the zero emission ones), and the outcome proved that inhabitants of Milan were strongly in favour of this kind of policy. We initially describe and contextualize the Milan experiment within the main European experiences on urban road charging, and revise their main characteristics and results, in order to have a better understanding of the problem of acceptability of this kind of measures. The paper then attempts to study which are the determinants of the highly positive vote in favour of an extension to a road pricing scheme. The starting hypothesis is that variables likely to affect voting behaviour can divided into three groups: (i) ideological orientation, approximated by the voting out comes in the last municipal elections; (ii) economic and environmental variables, such as income, number of inhabitants and quality of life; (iii) distance from the city centre, which is the area where the scheme has been implemented, and public transport provision (i.e. number of transport means and variety in the neighbourhood voters live in). We are mainly interested in this last variable, as we want to assess the relationship between policy acceptability and neighbourhood accessibility, to verify the hypothesis that public transport was essential to the successful implementation of road charging. The results seems in line with these predictions.