Professor Jonathan Bard and PhD student Yutian Yang received the Best Application Paper Award for their article “Internal Mail Transport at Processing and Distribution Centers” published in IISE Transactions on Design and Manufacturing. The award was given out at the annual Institute of Industrial & Systems Engineering conference in Orlando, FL in May.

The work described in the paper concerns the routing of mail in U.S. Postal Service regional facilities. Throughout the day, large volumes of partially processed mail must be transferred between workstations in accordance with narrow time windows and a variety of operational constraints. To facilitate management supervision, it was first necessary to cluster the pickup and delivery points into zones forming subnetworks with restrictions on boundary crossing. Given these zones, the objectives were to find the minimum the number of vehicles required to satisfy all demand requests, and then to minimize the total distance traveled.

Solutions take the form of an invariant assignment of vehicles to zones and a routing plan for each 8-hour shift of the day. The clustering was performed with a greedy randomized adaptive search procedure, and two heuristics were developed to find solutions to the VRP, which proved intractable for realistic instances. An extensive analysis was undertaken to evaluate the relative performance of the two heuristics and to better understand how solution quality is affected by changes in parameter values, including sub-problem size, vehicle speed, number of zones, and time window length. The computational study was carried out using data provided by the Chicago USPS facility.