Block System

The Block System

The Block System, quite simply, stops trains bumping into each other.

It is the method by which signalmen communicate with each other to manage the location of trains. The main system used is called the Absolute Block system, the basic principle of which is that there is only one train on any section of line at any one time. Such sections of line are separated by, and protected by, signals. Communication is by single-stroke bell signals supported by indications on devices known as Block Instruments.

The railways of Britain were required to operate passenger trains under the Absolute Block system, although the detail of the method of working varied a little between each company. Even after British Railways was formed in 1948, a few differences continued – it wasn’t until 1960 that the Rules and Regulations were officially harmonised and even then the Southern and Western Regions retained certain differences. There were further significant revisions as time passed.

A more modern (and simpler) system is known as Track Circuit Block, where the position of trains is detected continuously by electrical circuits in the rails. Signals on this system often work automatically. But there are still many places where the lines are not track-circuited throughout, so the Absolute Block system still has to be used.

Single Lines were worked by a different method, using Staffs or Tokens to give a driver permission to enter a single-line section.

To describe all of the different companies’ practices would be a mammoth and confusing task  so for consistency in the section the British Railways 1960 regulations  are referred to here unless otherwise stated.

Principles of Block Working

Bell Signals

  1. Bell signals in use in 1960
  2. Pre-1960 bell signal variations

Absolute Block

  1. The basic principles
  2. Keeping the trains apart
  3. Fouling the clearing point
  4. Working at junctions
  5. The Warning Arrangement (Regulation 5)
  6. Distant signals and short sections
  7. Different types of train
  8. Shunting
  9. Alarms and excursions
  10. Closing the box

In the flesh – photographs of Block Instruments

Railway Company designs

  1. Cheshire Lines Committee
  2. Glasgow & South Western
  3. Great Northern
  4. Great Western
  5. Lancashire & Yorkshire
  6. London & North Eastern
  7. London & North Western
  8. Midland
  9. South Eastern
  10. Southern Railway
  11. British Railways (Scottish Region)

Contractors’ designs

  1. Spagnolletti
  2. Sykes & Co
  3. Tyer & Co

Other systems

  1. Single Line Staffs
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