European railway systems are in a constant technological progression combined with an international interoperability and standardization. This need gave birth to the European Rail Traffic Management System (ERTMS) with the goal to provide the basic framework to the interoperable rail signaling and train control. The analysis, verification and validation of such specifications are naturally crucial. These studies are done on models that are more or less formal. The presented work has chosen Colored Petri Nets (CPN) for the system modeling and analysis. CPN allow not only the modeling of the overall system structure but also its possible evolution in time. It is in this context, that they are applied in this paper to express both: 1. the ERTMS operational procedures as well as 2. the on-board and trackside component communication. The main goal of this work is to test the feasibility of the construction of the complete specification model using a unique modeling approach and to prepare the model for a further in-depth analysis for safety and/or performance proprieties.