Short sea shipping (SSS) is a concept that refers to short-range maritime transport. SSS has been the subject of detailed analysis and debate in international Transport Policy due to its capacity to articulate intermodal chains for domestic traffic in place of trucking. Due to the fact that SSS was widely assumed as the most sustainable transport option to decongest roads, European Transport Policy has supported the intermodal alternative though the Motorways of the Sea (MoS) initiative. The MoS concept includes not only seaborne transport, but also all the necessary services for modal shift in order to provide “door-to-door transport.” Even though international interest in SSS is mainly based on sustainability, recent reports have highlighted environmental under-regulation regarding trucking. This fact, along with the drawbacks of the pollutant abatement systems, constitutes a significant challenge for it to remain a preferable alternative in transport policies.