We present a system, CREWS_NS, that is used in the long-term scheduling of drivers and guards of the Dutch Railways. CREWS_NS schedules the work of about 5,000 people. CREWS_NS is built on top of CREWS, a scheduling tool for speeding the development of scheduling applications. CREWS heavily relies on the use of AI techniques and has been built in the perspective of a "white box" system, in the sense that the planner can perceive what is going on, can interact with the system by proposing alternatives or querying decisions, and can adapt the behaviour of the system to changing circumstances. Scheduling can be done in automatic, semi-automatic or manual mode.