We investigate substitution-based equipment balancing for a package express carrier operating multiple equipment types in its service network. The weekly schedule of movements used to transport packages through the service network leads to changes in equipment inventory at the facilities in the network. We seek to reduce this change, i.e., the equipment imbalance associated with the schedule of movements, by substituting the equipment types initially assigned to the movements. We conduct a complexity analysis of the underlying optimization problems, i.e., minimizing network imbalance and minimizing the number of substitutions required to achieve the minimum network imbalance. Furthermore, we perform a computational study using real-world instances to analyze the performance of an integer programming based solution approach and assess the benefits of substitution-based equipment balancing.
Y. Yang, Y. Ridouane, N. Boland, A. Erera, M. Savelsbergh, Substitution-based Equipment Balancing in Service Networks with Multiple Equipment Types", 2020.