Towards a More Sustainable Use of the Portuguese Road Network: The A25 and IP5 Case Study

The transport sector is an energy-intensive industry whose main purpose is to promote the mobility of people and goods. As such, a more rational use of the existing road infrastructures is unquestionably a way to reduce the environmental impact of this sector and to mitigate the depletion of energy resources. Some factors, however, may negatively affect the user’s decision on which route to take, from an energy sustainability perspective. In this context, the introduction of tolls on modern highways can have the perverse effect of diverting some traffic to other routes that often do not favor the energy sustainability of the transport system. This work addresses this issue and is based on a Portuguese case study, aiming to compare the relative merits of two parallel routes, the A25 and the IP5, as to energy consumption, GHG emissions, and travel times. These roads cross the district of Viseu. The A25 is a modern 2 × 2 lane highway, with tolls, while the other is 2-lane toll-free road with severe slopes. These indicators were evaluated through a physics-based approach, considering detailed vehicle specifications and reported traffic volumes, supported by literature. The results show that for equal travel times the A25 is more environmentally friendly, for all vehicle classes, in terms of energy consumption and GHG emissions. However, the IP5 is more attractive from an economic point of view, except for heavy traffic.