The design of a service network is a complex planning problem involving interrelated and interdependent choices that can be classified in three planing steps: strategic, tactical and operational planning. Tactical planning step addresses medium term planning decisions, mostly related to the design of the service network: selection of the services to perform, schedules and routing of freight.
Service network design problems have mainly been studied under the assumption that all the necessary information needed to make decisions are available and completely known before the design decisions are made.
Instead, it is an inherently stochastic problem, involving making choices in a highly uncertain environment. Demands, costs, profits,travel time, service time and, sometimes, customers' locations are examples of needed and uncertain parameters in a tactical planning problem.
Service network design problems under uncertainty have already been treated [add references] in the literature. However, few contributions dealing with design of services and stochastic time have appeared. In many real-life applications, however, a considerable degree of variability in travel times could be observed, and thus a static and deterministic travel time assumption does not represent an accurate and realistic approximation of actual travel time. Instead, variability on time can lead to important changes, mostly related to the planned schedules.
Our research focuses on stochastic travel time. In particular, on a scheduled service network design problem with unexpected stochastic travel time variations
