An apparatus for determining the direction of travel of an electrically driven model train through a model railroad track layout having track segments with rails of opposite polarity is disclosed. A diode and transistor are operatively coupled to at least one rail of a powered track segment, such that passage of an electrically driven model train over the powered track segment in a first direction enables a flow of electrical current through the transistor to a signal or control circuit, while passage of the electrically driven model train over the powered track segment in a second direction does not. The polarity of the rails is determined by a circuit driven by a control circuit attached to an adjacent track segment.