The Senior Transportation Problem

The senior transportation problem (STP) is an optimization problem in which a fixed fleet of volunteer-operated, heterogeneous vehicles from multiple depots must satisfy as many elderly door-to-door transportation requests as possible within a fixed time horizon. All requests consist of a oneto-one pickup and delivery with time windows. Moreover, as the clients are seniors, a maximum ride time is enforced to minimize user discomfort and inconvenience. The problem is similar to the classical dial-a-ride Problem (DARP) or the pickup and delivery problem with time windows (PDPTW). However, due to the limited resources, not all requests can be met within the time horizon and, therefore, the problem is to select a subset of requests such that the total weight of all served requests is maximized. Additionally, all drivers operate on a volunteer basis, thus aspects such as multi-depots, heterogeneous vehicles, and time windows on vehicles also need to be considered. This document formally defines the STP and presents related work and a mixed integer programming formulation for the STP.