Letter to the Editor—Optimal Container Inventory for a Two-Gateway System

The optimal size of the container inventory for a two-gateway system is determined. A rule is found, according to which containers are acquired until the last container produces savings just greater than the costs incurred due to empty trips. The actual size of the optimal inventory depends on container costs, the costs of shipping full and empty containers, the cost of shipping mail uncontainerized, and the probability distribution of the volume in each direction. Numerical results are given for two parcel-post systems.