Railway traction - Equipment operation and safety

Train operations are part of the railway system (see [D 5 510, § 1] ). It is governed by rules and procedures designed to ensure customer satisfaction in complete safety, within an economically viable system.

From the very beginnings of the railroads, safety was a major concern. This concern grew stronger as performance increased in terms of the loads hauled and the speeds achieved. It's obvious that the kinetic energy acquired during the movement of a heavy convoy brings into play the fundamental parameter of its stopping distance (see [D 5 525, § 3.1] ). What's more, the configuration of a network is, in most cases, complex, with intersecting routes or routes running in both directions. All these parameters call not only for very precise programming, but also for permanent traffic monitoring, capable of coping with the hazards and degraded situations that can arise at any time.

The central player in train operations is man, whether on the ground or at the controls of the train. At the heart of the operation lies this permanent dialogue between the "mobile" and the "ground". To enable this dialogue, a "coded" visual language has been set up in the form of "signals" marking out the railway line. The spirit of this dialogue is based on "passive" and "absolute" obedience, eliminating all improvisation. But human beings have their limits, not least their physiological ones, so failure is always a possibility. At this point, automation comes into play to help, control and even monitor human activity. This is the reason for the tremendous development of safety systems, which have taken over all train-related functions, right up to the "autopilot" systems widely used in urban transport systems such as the metro.

Mechanical, electromechanical and electronic technologies, and nowadays IT, form the basis of all operational safety functions.

The aim of this dossier is to describe the architecture of the main railway safety systems, their components and current applications. Of course, it would be impossible to describe all the systems in service; an encyclopedia would not suffice. We will highlight the essential features and describe their evolution.

We deal with the particular aspect of operating electrified lines in terms of regulating the power supply, which is just as vital as operating conventional lines.

Passengers on a train or metro may not realize the complexity of the "safety web" that constantly ensures the smooth running of their journey or daily commute. This "web" is constantly evolving,...