Energy conservation in subway systems by controlled acceleration and deceleration

Abstract

The 1975 electric bill for propulsion in the New York City subway system was close to 90 million dollars. This paper addresses the question of how a subway motorman should run his train in order to minimize this energy consumption. It is shown that using maximum acceleration followed at the appropriate time by coasting, and then braking at the maximum acceptable rate, gives a particularly low energy consumption for typical subway trains (although slightly different velocity profiles can be better under appropriate circumstances). This velocity profile is relatively easy to implement, and has now been proved effective in experimental tests. As a result of recommendations reported here, the New York City Transit Authority ran idealized tests of the profile, followed by recently completed tests in revenue service which demonstrated an 18.4 per cent decrease in energy consumption using a daily weighted increase of 4.25 per cent in trip time. This paper also evaluates the energy saved using an alternative method involving equipment modification for field shunting in the series mode.