A system mounted on a train , the system comprising an onboard control device , a train control on-board radio station , a public-radio-network on-board radio station and a train-information management device ; the on-board control device being configured to obtain the train position on the basis of the running distance of the train , and to transmit, to a train-presence management device , train position information from the train control on-board radio station connected to the on-board control device via a train control radio base station , a base device , and a train control dedicated network ; the train-information management device being configured to obtain the position of the train independently from the on-board control device , and to connect itself to the train control dedicated network and the train-presence management device via the public-radio-network on-board radio station , a public-radio-network base station , a public radio network , and a ground router , and then to transmit train position information to the train-presence management device , the train-information management device comprising: an intra-block position calculator configured to convert information on a kilometrage that indicates a position of the train into information on a block number and an intra-block position of a plurality of blocks into which a route of the train is divided and that are used when a train position is specified by a train radio system; and a communication device configured to communicate the information on the block number and the intra-block position to the train-presence management device on the ground side via the public-radio-network on-board radio station and over the public radio network . the on-board control device being configured to obtain the train position on the basis of the running distance of the train , and to transmit, to a train-presence management device , train position information from the train control on-board radio station connected to the on-board control device via a train control radio base station , a base device , and a train control dedicated network ; the train-information management device being configured to obtain the position of the train independently from the on-board control device , and to connect itself to the train control dedicated network and the train-presence management device via the public-radio-network on-board radio station , a public-radio-network base station , a public radio network , and a ground router , and then to transmit train position information to the train-presence management device , the train-information management device comprising: an intra-block position calculator configured to convert information on a kilometrage that indicates a position of the train into information on a block number and an intra-block position of a plurality of blocks into which a route of the train is divided and that are used when a train position is specified by a train radio system; and a communication device configured to communicate the information on the block number and the intra-block position to the train-presence management device on the ground side via the public-radio-network on-board radio station and over the public radio network . an intra-block position calculator configured to convert information on a kilometrage that indicates a position of the train into information on a block number and an intra-block position of a plurality of blocks into which a route of the train is divided and that are used when a train position is specified by a train radio system; and a communication device configured to communicate the information on the block number and the intra-block position to the train-presence management device on the ground side via the public-radio-network on-board radio station and over the public radio network . <EOS>