Rail signalling is the digital and physical intelligence that allows trains to run safely, efficiently, and on time. It determines when a train may move, how fast it can travel, and which route it should take. In simple terms: signalling is the system that makes train movement possible,  

A complete signalling system brings together several interdependent layers:

• Onboard systems that calculate safe speed, braking curves and movement authority
• Wayside systems such as interlockings (safe route allocation), train detection, point machines and balises
• Digital communication networks connecting the train and trackside (radio, GSM‑R/FRMCS)
• Control centres supervising operations and optimising traffic flow

This combination forms a complex digital system architecture, merging software engineering, IT hardware, safety‑critical computing, cybersecurity and data management - a reality often invisible to passengers but fundamental to daily railway operations.

Alstom is a leader in signalling

We are both an early adopter and co‑creator of modern signalling standards, having shaped European Rail Traffic Management System (ERTMS) evolutions and delivered complex systems across hundreds of global projects. Its unique strength lies in decades of multi‑domain experience, a strong safety culture, deep engineering methodology, digital leadership, and proven large‑scale deployment capability - making signalling a safer, greener, high‑performance backbone of mobility.