Railway Infrastructure - Signalling

Understanding Railways Series:

UK Railway Industry for Dummies, focusing on Rail Infrastructure

Railway Infrastructure - Signalling (this post)

  Signalling for Railways 

Historically, trains were operated by a driver who knew a lot about the train, the route, and even the train itself.  Speed, signalling, and braking distance were controlled by the driver, and they had to manage the train, the driving, and the route information affecting them.  Signalling was used to help the driver determine whether the rail line was clear or approaching, when to slow down, and to provide reminders, thereby allowing the driver to control the train safely by managing multiple factors.

Advancements in technology have built on existing infrastructure and approaches, enabling more trains, safer travel, and better information.  For example, wheel counters allowed signalling to ensure that a train and all its wheels have cleared a section.

Telecommunications allow a central control centre (ROC) to communicate with the drivers.  GSM-R...

The train should run regardless of temporary telecommunications issues or unavailability (assuming it is safe).  The onboard computer on every train can provide the driver with information or act on it, such as automatically stopping the train if a red light is detected while the train is on the section of track the driver is entering.  

ETCS is for modern signalling; the fundamental principle is that all trains, routes and tracks can be managed centrally safely (see SIL4).  Everything on the railway has to be safe.  Super safe, if unsure, stop is the principle.

Common Equipment

Balise

A balise is a device mounted on the track between the two rails that sends messages to a train as it passes overhead, primarily conveying the train's position.

Understanding Railways Series:

UK Railway Industry for Dummies, focusing on Rail Infrastructure

Railway Infrastructure - Signalling (this post)