It is striking to see the common as

It is striking to see the common aspects in all definitions: the use of more than one transportation mode. Of course, the devil is in the details and some definitions put more emphasis on certain aspects of the transportation process. Synchromodal emphasizes the (real-time) flexibility aspect, intermodal focuses on the same loading unit, and co-modal adds resource utilization. Note, however, that the basic definition of multimodal transportation does not exclude any of the other definitions. In our view, the definition of multimodal transportation is still valid and should be used rather than developing new definitions and/or new words. Multimodal is the broadest definition and includes the other notions. Additionally, the relevant Operations Research (OR) literature does not provide any additional explanations on the characteristics and (conceptual) formulations. Our review reveals that in the literature, multimodal and intermodal are used interchangeable. No OR literature is found where co-modal or synchromodal is used. In what follows, we use multimodal consistently.

The structure of our paper is similar to the previous review papers and is based on the decision horizon of the planning problems: strategic, tactical, and operational planning. In Section 2, we cover the recent literature on strategic planning problems. Section 3 presents the recent developments on tactical planning problems and Section 4 gives an overview on recent papers about operational planning problems. Finally, in Section 5 we provide overall conclusions and a fundamental prospective for future research. In total, we reviewed 78 papers, of which 28 papers are on strategic planning, 37 papers on tactical planning, and 13 papers on operational planning problems. We approached the different papers by looking at their motivations, the characteristics of the different encountered problems, and their respective solution methods. Every section then was built around more or less the same structure: (1) a description of the conceptual and mathematical models (2) the solution methods used and (3) the opportunities for future research based on the identified gaps