Representation of the Freight Transport System

The authors seek to identify, by means of a systemic analysis of freight transport, the agents that are directly involved in freight transport, their options, their decision-making modes and their interactions. The authors have identified a set of decisions that play a fundamental role in the formation of freight transport and are suitable for explicit representation in a spatialized supply-demand model. This representation therefore forms a potential structure for building a realistic freight transport model. A particular point of interest in this representation lies in the fact that it allows the authors to distinguish clearly phenomena that do not appear spontaneously in databases collected in the traditional manner. The authors distinguish the supply flows, (or production-consumption flow), the freight flows, shipments and traffic. In static models, only flows and traffic are systematically informed and explicitly taken into account at present. This involuntary pooling of shipments and this lack of distinction between logistics related imperatives for shippers on one hand, linked to their chosen method for delivering their products to their customers, and the logistics-related imperatives for carriers on the other hand, linked to the way in which their assigned transport operations are performed using the resources available to them to the best advantage, most probably introduces a degree of bias in these models, or means that these specific problems need to be handled in a rudimentary manner. This paper does not highlight all the complex phenomena implicated in the operation of the freight transport system. Most particularly, relations between companies are not accounted for explicitly; they are either overlooked or handled by ad hoc hypotheses. The way in which the different types and different sizes of carriers form their partnerships, the specific role of logistics service providers, the types of agreements set up between shippers and carriers, are all points that do indeed play a significant role in freight transport operations.