Lunchlezing ORTEC

Departure Time Optimization in Vehicle Routing

Optimizing departure times in vehicle routes is a crucial step in developing good vehicle route schedules. In practice, restrictions such as time-dependency resulting from traffic congestion, driving and working time legislation, and multiple time windows make departure time optimization a challenging scheduling problem. On top of that, vehicle routes are often interdependent, due to, e.g., trailer swaps between truck/driver combinations. This increases the complexity of the problem, since optimizing the departure time of a single route may disrupt the schedules of dependent routes. In this talk, we illustrate these challenges through several examples from practice. An important observation hereby is that departure time optimization is not only done to reduce costs by better utilization of resources, but is also required to find feasible schedules with respect to driving and working time legislation. Finally, practice does not allow complete freedom in planning waiting times or breaks in vehicle route schedules whenever it improves the overall cost. For example, planning early breaks to consume some inevitable waiting time is only accepted in practice if a reasonable amount of time has passed since the previous break. These limitations should also be considered in solution methods for the departure time optimization problem.