The Signal Box

Photo: Stations Past Website

Signal boxes are shelters or small buildings constructed specifically to house the levers and other control equipment used to safely space, route and locally coordinate railway trains; and to provide signalling staff with a vantage point from which to safely observe and efficiently control nearby trains.

Railways need a signalling system to control the passage of trains so as to prevent accidents occurring. In the early days of railways a timing system was used, trains leaving a station at least ten minutes after the previous train had left and lineside “policemen” could stop a train if it arrived at their position before the ten minutes had elapsed. Problems occurred however when trains broke down after leaving a station or passing a “policeman” and accidents happened. A system of semaphore signals was therefore developed, each signal displaying a simple message, stop or go.

Each station had a signal box which controlled all movements into and out of the station area, before a train can leave one station it has to be accepted by the Signaller at the next station.

Points

Unlike cars, which can follow any suitable road between two places, trains have to follow a set route to their destination and this route is determined by where the rails have been laid. There is however scope for trains to move between different tracks on lines with more than a single track and between the main line and various sidings. Nor can trains stop quickly and in order to prevent accidents the route that they are to follow has to be set before they can leave the station. This is done by the Signaller in the signal box.

Signal boxes on the railway control not only control the signals – which tell the driver when it is safe to go - but also the associated points - and the two have to be interlocked so that it isn't possible for a signal to indicate that a train must go in a certain direction while the points are set for another. If that were to happen accidents could arise.

Signals and points are generally controlled by a system of levers in the signal box, connected to the rails by pre-tensioned wires and rods. Some points are however electrically operated, usually where they are a long way from the signal box and the distance involved would make a mechanical system difficult to operate.

For more information about the principles of signals and signalling, we also reccomend you visit The Signal Box website. Though the website is about British Railways signaling, it was British Railway Engineers who established Australia's railway operations. Aas the applied the same principles of block systems to keep trains apart, signalling, lever frames and track layout when developing Australia's railways, much of the detail described applies to Australia's railways also.

Australian Railway Signalling

Australian railway signalling varies between the states of Australia, because each railway system was established under the different colonial governments with separate legislation. Just as with the notorious variation of Australian rail gauges, there are differing signal systems. The systems in New South Wales generally follow British precedents, although American influence has increased somewhat since the 1990s. Victoria uses American-style speed signalling on its main lines. That can cause confusion where the systems meet.

Australian Towns and Their Railway Stations

Incorporating a beginners guide
to how railways work