Resources Requirement and Routing in Courier Service with Cooperative Operations and Transfer Opportunity

The typical courier service involves picking up documents from customer sites and returning them to the mail centre within specified pickup and return time windows, respectively. Two common types of resources (e.g., couriers and vans) are considered here in independent/cooperative operations, with document transfer allowed between resources and the transfer locations to be decided. The heavier resource is capable of carrying documents, as well as limited units of the lighter resource, along its route. This was observed in the actual practice of using a van as a shuttle for transporting couriers, or/and as a single unit performing pickups and deliveries. The option of transporting one resource by another (as well as carrying customer items) has rarely been studied in pickup and delivery problems. Savings in cost and resources are to be examined. This study models such cooperation with document transfer opportunities, and allows multiple routes to be assigned to each unit resource with the objective of minimizing the total cost, comprising the fixed costs of resources and travelling costs. An exact solution method provides benchmarks for performance comparison, while a heuristic is also proposed to solve larger problems.