Low emission zone and mobility behavior: Ex-ante evaluation of vehicle pollutant emissions

Exposure of the population living in urban areas to an increasing level of air pollution has led local authorities to implement vehicle access restrictions to limit the circulation of pollutant vehicles and foster sustainable travel habits. With these aims, Low Emission Zones (LEZs) have been introduced in several European cities. Many previous works have evaluated the impacts of such regulation; however, they adopted pre-defined assumptions about new travels to access the regulated area and neglected potential behavioral changes induced by the measure. The aim of this paper is to quantify the effects of a LEZ on vehicle pollutant emissions, considering potential short-term variations of travel habits after its introduction (i.e., vehicle replacement, modal shift and destination change), and the associated uncertainty. The study area was the Municipality of Padova (Italy), where a LEZ is likely to be enforced. A holistic evaluation framework was applied combining a behavioral model and a traffic simulation model, calibrated using responses from a mobility survey administered to local stakeholders and traffic counts. The results highlighted the measure could contribute to induce fleet renewal and modal shift toward sustainable transportation means, that could be furtherly fostered by increasing the awareness of the benefits of the LEZ. Furthermore, the outcomes confirmed that the intervention could significantly reduce vehicle pollutant emissions within the area. Nevertheless, a spillover effect could occur outside the LEZ, due to the long detours that travelers deciding to avoid entering the zone have to perform.