A method for determining the composition of a train including a plurality of vehicles grouped as successive units (10A, 10B, 10C) connected to each other, among which a head unit and a tail unit, the train including: - a safety management device (24A, 24B, 24C) per unit (10A, 10B, 10C), each device (24A, 24B, 24C) having two identifiers which are specific to it, - a coupling communication link (12, 14; 80, 81) for each pair of adjacent units, each coupling communication link (12, 14; 80, 81) only connecting two devices (24A, 24B, 24C) of adjacent units, - a general network connecting all the devices (24A, 24B, 24C) to each other, the method comprising an initial step for transmitting with each device (24A, 24B, 24C), over the general network, a non-secured broadcast message including its two identifiers, and a step for receiving, with each device (24A, 24B, 24C), messages including the identifiers of the other devices (24A, 24B, 24C), the method being characterised in that it comprises the following steps: - transmitting over the general network and over each coupling communication link (12, 14; 80, 81), with at least one device (24A, 24B, 24C) a secured message to one of the devices (24A, 24B, 24C) adjacent to said device (24A, 24B, 24C), the message including one of the identifiers of said device (24A, 24B, 24C), - transmitting over the general network, with each device (24A, 24B, 24C) having received an identifier of another device (24A, 24B, 24C) connected through a coupling communication link (12, 14; 80, 81), at least one restoration message including the two identifiers of said device as well as the received identifier, - receiving, with each device (24A, 24B, 24C), transmitted restoration messages, and - determining, with at least one device (24A, 24B, 24C), the composition of the train, said determination step consisting in the application of a predetermined algorithm within said device (24A, 24B, 24C). - a safety management device (24A, 24B, 24C) per unit (10A, 10B, 10C), each device (24A, 24B, 24C) having two identifiers which are specific to it, - a coupling communication link (12, 14; 80, 81) for each pair of adjacent units, each coupling communication link (12, 14; 80, 81) only connecting two devices (24A, 24B, 24C) of adjacent units, - a general network connecting all the devices (24A, 24B, 24C) to each other, - transmitting over the general network and over each coupling communication link (12, 14; 80, 81), with at least one device (24A, 24B, 24C) a secured message to one of the devices (24A, 24B, 24C) adjacent to said device (24A, 24B, 24C), the message including one of the identifiers of said device (24A, 24B, 24C), - transmitting over the general network, with each device (24A, 24B, 24C) having received an identifier of another device (24A, 24B, 24C) connected through a coupling communication link (12, 14; 80, 81), at least one restoration message including the two identifiers of said device as well as the received identifier, - receiving, with each device (24A, 24B, 24C), transmitted restoration messages, and - determining, with at least one device (24A, 24B, 24C), the composition of the train, said determination step consisting in the application of a predetermined algorithm within said device (24A, 24B, 24C).