Integrated Duty Assignment and Crew Rostering

We propose an integrated model for the Duty Assignment and the Crew Rostering problem. Both problems are part of the crew planning process at Netherlands Railways; The Duty Assignment problem consists of finding a `fair' allocation (according to some measure) of the duties among the roster groups. The Crew Rostering problem is well known in literature, and consists of finding good rosters given a set of duties. Our model integrates the above two problems, and hence involves large scale optimization (since all duties have to be assigned simultaneously). Our research evaluates the effectiveness of an integrated approach compared to e.g., a sequential approach. We also propose a second model to counter the problem of weak lower bounds, a problem well known for rostering problems. We show that this new model leads to promising results.