OMEGA, The Int. II of Mgmt Sci., Vol. 5, No. 2, 1977.Pergamon Press. Printed in Great Britain Optimal Design of a Post Office KR BALACHANDRAN University of Kentucky, Lexington, USA (Received May 1976; in revisedform September 1976) A mathematical model which describes the postal operations is discussed in this paper. This paper is confined to the problems which arise within a post office in mail sorting and classifying operations. IN A post office, two objectives of fundamental importance in the processing and distribution of mail are decreasing costs and avoiding mail delays. It is sometimes possible to reduce both delay and costs by introducing new mail flow designs but, eventually, these goals can be achieved only at the expense of each other. Oliver and Samuel [1] have dealt with reducing delay subject to total cost. This paper deals with designing the post office to minimize total costs subject to restrictions on delay. MAIL FLOW IN A TYPICAL POST OFFICE The flow of two main forms of mail (letter mail and parcels) in a Post Office is described in this section. The less important forms of mall are not considered here beyond the initial culling stage where they are separated from the letter mail. This paper is written with a view toward future modeling of major postal operations, with a view to minimize total cost or mail delay; consequently, flow descriptions of less important forms of mail are omitted. Parcelflow Parcels are deposited into the post office by post office trucks and private company trucks who bring their parcels directly to the main post office. In- coming and outgoing parcels follow different routes. Air parcels and special handling parcels come in a separate package and are processed separately. The outgoing parcels, after they are delivered by truck, are stored on conveyors. Parcels are allowed to flow in small quantities for primary sorting, and conveyors o~A 512-F 185