The present invention relates to a method and apparatus for determining the order of wagons in a train. The invention configures a plurality of wagons of a train to sense at least one environmental condition that the wagons are respectively exposed to when the train is moving. The invention configures the wagons to generate a corresponding announcement message in response to a change in state of the environmental condition. The invention configures the first wagon of the train to listen for the announcement message generated by any of the plurality of wagons. The invention configures the first wagon to compute a sequence of the announcement messages from an order in which the wagons have been heard.