Signalling system for a railway network comprising: - a ground architecture comprising a control centre centralizing a supervision system, ICC, an interlocking system, IXL, and a Radio Block Centre, RBC; and, - on-board each train (1, 2) circulating on the railway network, a European Vital Computer, EVC, each EVC being configured to send position reports to the RBC and receive Movement Authority, MA, from the RBC, the ground architecture of the signalling system being compliant with the European Train Control System level 2, the signalling system having fixed sections, the IXL being capable of creating routes, called L2 routes, based on the occupancy state of the sections and the constraint "only one train on a section at a time", characterised in that the signalling system is augmented with a Dynamic Sub-Sectioning - DSS, managed by the RBC, wherein a DSS interface is provided between RBC and IXL, in which: - the IXL is configured to create a route, called L3 route, for a following train, said L3 route comprising a section (A2-B1) which is currently occupied by a leading train, said leading train being equipped with an EVC configured to provide, in the position reports sent, a data relative to the integrity of the leading train, and - the RBC is configured to upgrade the MA of the following train based on the last position report received form the leading train and to send the upgraded MA to the following train, wherein the RBC is configured to manage a separation distance between the leading train and the following train on said section, by calculating a distance between the rear of the leading train and a stop point of the current MA of the following train, and, when said distance is greater than an elementary distance, said elementary distance corresponding to a size of the subsectioning of the considered section as defined by the DSS, by extending the current MA to a distance corresponding to a multiple of said elementary distance such that a possible new end of the MA corresponds to the last dynamic sub-section that is free. - a ground architecture comprising a control centre centralizing a supervision system, ICC, an interlocking system, IXL, and a Radio Block Centre, RBC; and, - on-board each train (1, 2) circulating on the railway network, a European Vital Computer, EVC, each EVC being configured to send position reports to the RBC and receive Movement Authority, MA, from the RBC, - the IXL is configured to create a route, called L3 route, for a following train, said L3 route comprising a section (A2-B1) which is currently occupied by a leading train, said leading train being equipped with an EVC configured to provide, in the position reports sent, a data relative to the integrity of the leading train, and - the RBC is configured to upgrade the MA of the following train based on the last position report received form the leading train and to send the upgraded MA to the following train, wherein the RBC is configured to manage a separation distance between the leading train and the following train on said section, by calculating a distance between the rear of the leading train and a stop point of the current MA of the following train, and, when said distance is greater than an elementary distance, said elementary distance corresponding to a size of the subsectioning of the considered section as defined by the DSS, by extending the current MA to a distance corresponding to a multiple of said elementary distance such that a possible new end of the MA corresponds to the last dynamic sub-section that is free.