A fixed-point model and solution algorithms for simulating urban freight distribution in a multimodal context

Urban road networks are generally shared by cars, buses and freight vehicles whose travel times are reciprocally affected (the crossed congestion phenomenon). Hence, simulating performances of urban road networks requires the development of a multimodal assignment model that takes into account the effects of reciprocal influences among vehicles on user travel choices. In this paper, we extend the model proposed in a previous paper (D'Acierno L., Montella B. and Gallo M., 2002, Multimodal assignment to congested networks: fixed-point models and algorithms. Proceedings of the European Transport Conference 2002, Cambridge, United Kingdom) to the case of urban freight distribution simulation, considering crossed congestion among all considered transportation systems. The proposed model is tested on a real dimension network, adopting three algorithmic approaches (external, internal and hyper-network) for its solution and comparing their performances in terms of computing times and result reliability. Finally, we discuss the effects of crossed congestion on freight path choices and the influences of freight vehicle presence on (road and transit) user choices.