An alternative tactic to deal with the contingency of driver absenteeism

On any given workday, unexpected absence of drivers calls for emergency operational tactics to ensure completion of planned deliveries of merchandise to customers. A typical tactic in the workforce scheduling literature is to rely exclusively on a pool of workers who were not scheduled for work; that is, full-time off-duty drivers and part-time drivers. Concerns about the expense of maintaining a staff of part-timers prompt consideration of alternative tactics. This study proposes one such alternative. It minimizes the part-time pool by reassigning routes among drivers who show for work. In multi-route vehicle routing problems, the prospect of this alternative arises because cost-minimizing patterns of travel distances across routes often allow one driver to do extra work by handling more than one route (subject to time-window and workload constraints). By considering costs such as overtime rates when drivers perform extra (emergency) driving duties and the cost to maintain part-time staff, this study tests the efficacy of the aforementioned alternative. Its efficacy is confirmed by the fact that it is less costly than the typical tactic: while the typical tactic adds just over 22% to driver payroll, the proposed alternative adds a noticeably smaller cost of just under 15%.