A multi-modal supply-demand equilibrium model for predicting intercity freight flows

In this paper a new approach to intercity freight transportation system modeling is developed. Modeling formulation considers supply-demand equilibrium, where the demand side represents the behavior of shippers (cargo owners) and the supply side represents the behavior of carriers (transportation operators). Shippers decisions considered include choice of destination, mode, carrier for pure modes and transfer point for combined modes. Carriers take routing decisions over a multi-modal, multi-product and multi-operator network. A new mathematical formulation, not known before, is proposed to find consistent equilibrium solutions for modal O-D shipments, network flows and levels of service. Necessary conditions are deduced to show that the solutions obtained, from the mathematical formulations proposed, satisfy the behavioral principles assumed in each case. It is shown that special rationality conditions are required, with respect to fares charged and network routing decisions, to obtain consistent supply-demand equilibrium solutions. Sufficient conditions for the existence and uniqueness of solutions to diagonalized versions of the mathematical problem formulated are deduced. Finally, a general solution approach is proposed and an application example is developed to illustrate the characteristics of the model and solution algorithm.

Effect of advanced traveler information systems and road pricing in a network with non-recurrent congestion

The effect of the application of advanced transport information system (ATIS) and road pricing is studied in a transportation system under non-recurrent congestion. A stochastic network deterministic user equilibrium model (SNDUE) with elastic demand is formulated and used to evaluate the welfare and private impacts of different market penetrations of ATIS, together with road pricing for a simple network. Both marginal first-best road pricing and a second-best fixed road pricing are considered. The incentives of private users to use ATIS are analyzed and the characteristics of optimum tolls as a function of ATIS market penetration are shown. We conclude that ATIS is an efficient and necessary tool to reduce the effects of non-recurrent incidents in a transportation network, especially when non-recurrent congestion causes a significant deterioration of operational conditions of the network. If the impact of non-recurrent incidents on free flow costs is small or is reduced only to congestion effects, the use of road pricing would be more efficient. Social benefits obtained when jointly implementing ATIS and road pricing are practically the same whether first-best or second-best road pricing is used. Considering the private costs perceived by the network users, and the benefits experienced by equipped users, the maximum level of market penetration achieved could be limited because private benefits disappear after certain market penetration is obtained.Advanced transport information system Road pricing Optimum tolls Non-recurrent congestion ATIS market penetration