The trade-offs between economic and environmental sustainability of the transition towards clean-fuel vehicles in Local Public Transport

Starting from the 21th UN Climate Change Conference of Parties (COP21), hosted in Paris in 2015, world leaders committed to step up the efforts to contrast the impacts of climate change and to invest resources consistently with a pathway towards low greenhouse gas emissions and climate-resilient development. Particularly in the transport sector, several strategies have been adopted to assure a smooth transition to achieve the goal of decarbonised transport, and to promote the use of clean fuel vehicles. To this aim, national and local government have introduced scrappage incentives of old (diesel and petrol) vehicles for clean (electric or hybrid) new ones, and have constrained public funds for the renewal of local public transport (LPT) fleet to the acquisition of electric and/or hybrid buses. In some Countries, internal combustion engine vehicles are going to be banned starting from 2030. Such policies need to be carefully assessed and duly planned, in order to govern an effective transition without undesirable indirect counter-effects. For instance, incentives should be distributed according to the market conditions: there are cases, for instance, where there is no need of incentives for new vehicles but rather for developing the charging infrastructure, or cases in which electric engines are not suitable due to the climate (temperature) and the orography (slope) of the territory, as well as the itinerary characteristics of the bus lines (e.g. length). In this paper we analyse the case of a LPT agency of the provinces of Como, Lecco and Varese (North Italy), with the aim of identifying what are the most suitable fleet size and vehicles typologies in the mid-term scenario (2030) - with an outlook to 2040 -, and how to achieve it. The study area includes both urban and ex-urban services, with 190 lines and 860 operating buses. The average age of the fleet is about 10 years old and the buses are almost all equipped with diesel engines. The methodology is articulated in three steps. We firstly carried out a focus group including LPT operators, vehicles manufacturers and the energy providers, to investigate about their mid-term plans and views. It emerged, for instance, that full electric vehicles would be suitable mainly for urban services, where the route length and line frequency are adaptable to the battery duration. At the same time, they see a likely transition from diesel to natural gas power train for ex-urban lines. Based on the outcomes of the focus group we set-up three different scenarios (i.e. conservative, business-as-usual and disruptive) both for the urban cases and the ex-urban cases. In the disruptive case, we have also identified suitable pathways for the transition, i.e. possible intermediate scenarios at year 2025, based on the current characteristics of the fleet (age and capacity), and the future plans to upgrade both the service and the level of service. In the third step a multi-criteria analysis of the (intermediate and final) scenarios is carried out including the investment and the operating costs of different vehicles typologies and the related recharging infrastructure, as well as the energetic and environmental (CO2 emission) impacts. The results showed that in the disruptive scenario the operating, maintenance and investment costs are 15-20% higher than in the conservative scenario. However, such higher financial costs translate into lower energy costs and less pollutants emissions