This thesis presents the design and implementation of a simulation model of a Train External Access Door within a digital twin environment, developed in TrainLab . The work focuses on the AS300 project, aiming to reproduce the functional behavior of the external door system to support testing and validation activities in a safe and efficient virtual setting. A key motivation behind the study lies in the comparison between traditional text-based programming approaches and block-based modeling within the ControlBuild environment. In conventional workflows, door system functionalities are implemented with text-based languages, offering precision, scalability, and strong integration into industrial development pipelines. This approach supports robust debugging and comprehensive documentation, making it highly suitable for complex railway automation.