Dynamic window reduction for the multiple depot vehicle scheduling problem with time windows

We consider a widespread branch-and-price approach to solve the multiple depot vehicle scheduling problem with time windows. We describe a dynamic time window reduction technique to speed up this approach. The time windows are transferred from nodes to arcs in order to take advantage of dual information and to tighten as much as possible the time variable domains. The performance of the proposed technique is evaluated through computational experiments on randomly generated instances involving several depots and up to 900 tasks.