The Post Office lines network is divided into three separate but related categories for planning and other uses. These categories are: the main network, connecting main switching units; the junction, connecting local to trunk and local exchanges; and the subscribers distribution network. Detailed national plans for the first two categories for up to five years ahead are produced annually and published as a demand forecast known as the annual schedule of circuit estimates (ASCE). The money spent on these two networks is in the order of £60M per annum, and consequently improvements in planning or utilization can realize quite considerable savings in terms of capital demands and capital servicing. In addition to considering cost, manual systems require large amounts of staff time to maintain and prepare the detailed plans. With the increasing complexity and size of the networks there is a need to reduce the time scales between publication of the forecast demand and the production of the planning requirements and to make the most effective use of the networks. The paper presented at a one-day Symposium on Networks, organized by the Computer-Aided Design specialist group of the British Computer Society and held on the 18th March 1974.