A bilevel optimization approach of energy transition in freight transport: SOS1 method and application to the Ecuadorian case

In this work, we propose a new model to evaluate the impact of potential governmental policy as a green transition to decarbonise road freight transport. Contrary to the classical literature on the topic, our approach employs a bilevel structure optimization scheme. More precisely, a single-leader-multi-follower (SLMF) model is developed, where the state represents the leader and the freight companies act as the followers. A carbon tax is the selected public policy to foster the shift to less polluting freight technologies. The model responds to an exogenously determined demand that must be satisfied by a fleet that remains constant in size through time. The aim is thus to determine to what extent the tax policy will generate an evolution of the fleets of the different companies towards greener vehicles. An additional scientific contribution of the paper is that the SLMF model is solved thanks to a new numerical approach based on the so-called SOS1 technique. The implementation is applied in the case of the Ecuadorian freight transport and the results highlight an interesting evolution of the fleets.