Published online by Cambridge University Press: 03 February 2011
Is a railroad like a toy wind-up set, the locomotive moving endlessly, stupefyingly around a single circle of track? Or, as I believe, is it more like a fancy set, with various sidings, and connecting routes? Professor Weiss assumes that the carrying capacity of a railroad is bounded by its ability to store all its freight cars on the main line. And the view he (somewhat incorrectly) attributes to me—that “for every starting point there are 10 miles of clear road ahead”—is nothing more than the belief that a real railroad is not a simple circle. For railroad sidings do exist for inventorying cars. And connecting railroads that move cars out of a particular system do exist. Economists who contrast the productive capacity of Ford and GM rarely worry about whether a week's production can be stored within the factory. Entrepreneurs envisaged slack variables before they were baptised as such. (If sidings did not exist, or were a significant portion of the cost of one transport system but not another, matters might be quite different.)
1 It should be superfluous to add that my figures relate to ton-miles of freight moved, and not to tonnage over any given mile. This is so because he stipulates a closed loop. Allowing for headway requirements and speed, he then visualizes 66 trains and 120 boats, each set continuously circling for 12 hours, then stopping abruptly. For each hour of service I had estimated 7.0 times as many trains as boats per mile. He assumes 0.5 to 1 because he envisages no railroad sidings, towns, and connecting railroads, with all cars stopping on the main line at once.
2 Somewhat over one third of my estimate for rail costs at potential was for interest on rolling stock.