A position determining system for a vehicle on a guideway which includes an on-board controller configured to determine a position of the vehicle on the guideway. The position determining system further includes a transmitter/detector array configured to emit an interrogation signal and to receive reflection signals based on the emitted interrogation signal. The transmitter/detector array includes a first antenna and a second antenna, the second antenna spaced from the first antenna in a direction of travel of the vehicle. The position determining system further includes a transponder identification database configured to store transponder information. The on-board controller is configured to determine the position of the vehicle along the guideway based on a modulated reflection signal received by the transmitter/detector array and a first non-modulated reflection signal received by the transmitter/detector array.