A train detection system for detecting a train unit that includes a first transponder interrogator configured to generate one or more request signals for transmission, by a first antenna above a first track location, toward a first fixed transponder at the first track location; a second transponder interrogator configured to generate one or more request signals for transmission, by a second antenna above a second track location, toward a second fixed transponder at the second track location; and a controller communicably connected with the first and second transponder interrogators and configured to verify operation of the train detection system based on receipt of one or more message signals responsive to transmission of the one or more request signals from the first and second transponder interrogators.