their area to a minimum. However, constraints on junction spacing and weighting of links are not possible and solutions for large numbers of points are not unique. In practice, therefore, the mechanical method has proved more workable as, despite its bulky appearance and inconvenient operation, large systems of points can be treated with integral weights assigned to individual links, and very rapid solutions of reasonable accuracy can be obtained. Silk 1965) made extensive use of a 33-point model in a study of optimal road designs for the county of Monmouth. Here, fixed pegs located on a 1/63,360 base board were used to represent settlements within the county, and a system of pulleys and string was employed to structure the network.