EXPRESS: Mixed Appointment Scheduling: Managing Routine and Same-Day Appointments for Outpatient Clinics

This paper introduces a novel scheduling approach for managing a mix of routine and same-day appointments in an outpatient clinic. While the well-known carve-out scheduling (COS) policy reserves the provider capacity for same-day patients, its use of dedicated slots for each patient class may increase the risk of system underutilization or overload and long patient wait times. We propose the mixed appointment scheduling (MAS) policy, which allows routine and same-day patients to share common appointment slots, and investigate its performance relative to COS. By formulating a new model to determine the optimal scheduling decisions under the MAS policy, we demonstrate that the problem’s objective function (the total daily cost) is no longer multimodular in the presence of priority service discipline and demand uncertainty. We develop efficient methods to identify optimal scheduling policies and show that MAS reduces system costs, improves utilization, and decreases delays, particularly when same-day demand is moderate relative to clinic capacity.