<p>The railway signalling system is a key player in controlling train traffic, with the purpose of guaranteeing safety while respecting transport demand. For rail vehicles, visual-based driving is unfeasible, and thus, railway signalling systems have been developed as answers to this issue. Moreover, the increasing demand for railway traffic requires improved signalling system performances. Recent developments have led to the theoretical definition of the Moving Block signalling system as an approach to overcome the limitations of the Fixed Block system, currently adopted in many applications worldwide. This paper focuses on the development of a modular time-based simulation tool for Fixed Block and Moving Block railway signalling systems. The simulator incorporates all main elements for the assessment of signalling system’s performances, including the model of the Radio Block Centre, used for the communication among the trains, the On-Board Unit, which generates the reference speed profile, the vehicle longitudinal dynamics, and the speed control algorithm, emulating a human driver’s behaviour. Different operational conditions have been considered to show the capabilities of the simulator, which may represent a first step towards the reduction of on-site testing of railway signalling systems.</p>