"This paper proposes a UML based approach for the modeling and the verification of Railway signalling Systems specifications. Particularly, we consider the European Rail Traffic Management System (ERTMS) and the European Train Control System (ETCS) specifications. First, the architecture of ERTMS/ETCS is described. The validation and verification procedure is also introduced. Then, class, sequences and use case diagrams related to the technical specifications of ERTMS/ETCS are presented. Finally, a case study from the technical specification of ERTMS/ETCS which represents the operation of "Establishing a communication session" between ERTMS/ETCS On-board equipment and RBC (Radio Block Center) to initiate a communication session is proposed."