The determination of the economic location of sub-stations in electric railways

The method of attacking the problem of the location of substations in electric railways is governed by the physical layout of the road. The problem involved in the case of networks serving a limited territory, such as urban or suburban lines, may be solved from a study of the magnitude of the various relatively fixed load-centers which are created by the configuration of the lines; and the sub-stations may be placed at the different centroids of the system. In the case of long single roads connecting distant communities, such as interurban and trunk lines, there is presented the study of more or less uniformly loaded stretches, in which there are no distinct centers of load, except those that result from the characteristics of the line profile or the traffic movement. The latter problem is more susceptible to mathematical treatment, so that the contents of this paper will be confined to the consideration of interurban and trunk line projects, or, in other words, to relatively long roads.