“Car Tonnage” as a Parameter for Calculating the Impact of Vehicles on Urban Sustainability and for Supporting Space Retrofitting Policies

In the last century, cities evolved adapting their structure to vehicular traffic and this condition determined that a significant share of the urban surface has been devoted to host infrastructures such roads and parking lots for cars. Such design is a major obsta-cle to the transformation of the urban fabric into more resilient forms capable to cope with climate conditions that are more extreme than in the past in term of both high temperatures and precipitation intensity. Decreasing the share of impervious surfaces and reconverting them into green areas is the objective of many administrations that introduced a mix of disincentives (reduced number of parking lots, accession fees, lim-ited accessibility to specific zones) and incentives (more reliable public transportation, support of active mobility) to decrease the overall vehicular traffic. These measures can be effective but often miss to target preferentially those vehicles that are the most inconvenient in terms of encumbrance, and danger, because particularly heavy and bulky. Here a proposal is presented that identifies the “car tonnage” as the parameter to refer to for a selective disincentive policy. Car tonnage has been conceived as an in-dex incorporating weight and volume of the vehicles and should be treated inde-pendently with respect to the motorization type. The idea is discussed for its environ-mental, but also social and economic implications.