Models for urban freight distribution design

Starting from this state-of-the-art, the paper proposes models for urban freight distribution design and refers to models that aim at simulating the relevant aspects of a transportation system under the assumption that supply and activity systems are exogenously given. These models can be used as “design tools” by simulating the main effects of exogenously specified projects, verifying their technical compatibility and evaluating their “convenience”. This approach is known in literature as “what if”. On the other hand, design models provide “what to” indications, i.e., how to alter supply in order to optimize given objectives while satisfying given constraints. Clearly, in order to identify solutions for the design problem, it is necessary to evaluate the system responses (freight demand, freight flows and performances) to the possible actions; therefore the simulation model is a component of the design model. The cost of the generalization given by this class of models is not only the simplification of the real design problem (e.g. it is not possible consider the interaction among the different stakeholders involved in the urban freight transport), but also the simplification of the simulation models, now sub-models of a wider model. However, the most methods are limited to a small scale simplified problems.