A dial-a-ride problem for client transportation in a health-care organization

We propose a double request dial-a-ride model with soft time windows and its application to the CAB Health and Recovery Services, Inc., a non-profit organization in the Boston Metropolitan area for the purpose of addressing the CAB clients' transportation needs. The objective of the proposed model is to minimize a convex combination of total vehicle transportation costs and total clients' inconvenience time. The latter consists of excess riding time, early/late delivery time before service and late pickup time after service. The proposed model was used to compare the benefits of coordination and central dispatching over the current system under which individual centers of the organization schedule their own clients' appointments and route their own vehicles.