STRATEGIC FREIGHT NETWORK PLANNING MODELS. IN: HANDBOOK OF TRANSPORT MODELLING

In this paper the important topic of mathematical models for strategic freight-network planning is focused on. Such models are not meant for use in managing the moment-to-moment or even day-to-day operations of freight companies or freight infrastructure. Rather, such models are employed primarily to forecast, months or years into the future, freight traffic over specific network links and routes and through specific network nodes and terminals. The fundamental decision variables of these models are expressed as flows (volumes per unit time) and are entirely continuous in nature. The time frame is that of month or years. The perspective is generally that of a multimodal partial equilibrium of the transport market, with alternatives being evaluated according to the comparative statistics paradigm. The discussion is restricted primarily to those models that have been commercially available and are well documented in the open literature. In strategic freight network modeling, traffic forecasts are not made by statistical inference or econometric methods; neither is discrete-event simulation typically used. Instead, network models expressed in a closed mathematical form as optimization and game theoretic problems are the usual formalism. Furthermore, these models, because of their large size and complexity, are solved numerically using adaptations of powerful algorithms developed for non-linear mathematical programming and non-cooperative mathematical games. Because strategic freight-network models are primarily concerned with the freight-transport market, the have historically been viewed as distinct from computable general equilibrium (CGE) models, which determine prices and consumption and production activities for the entire economy.