To model the multimodal transport network, it is helpful to take an abstract view at first step. The multimodal
network can be viewed from many aspects. From a physical point of view, it can be classified into road, rail, water
and air. On the other hand, from a functional point of view, it can be classified into private modes (e.g. foot, bike
and car) and public modes (e.g. bus, train, tram, metro). An advantage of the functional view is that it highlights the
service provision to a traveler. Private networks offer continues service at any time associated with both physical
nodes and physical links. On the other hand, public transport networks offer discrete services according to time
tables whereby physical nodes (e.g. stops, stations) are visible while physical links are usually invisible. Therefore,
the functional view is suitable for modeling the multimodal transport network.