Signalling block system

Safeworking is the application by railways of sets of rules and physical equipment so as to avoid collisions between trains. It may or may not involve the use of signals. Safeworking is used to control trains between stations and yards, and not normally within them. Different methods of safeworking are required for single track, where a danger exists of both head-on and rear-end collision, and double track where the main danger is rear-end collision.

Safeworking is an Australian term for what is known in the UK as method of working and in the U.S. as method of operation.

The objective of this article is to describe the various methods of safeworking used around the world. For the purposes of this article a station is any place on a railway where the rules of the railway allow two trains to pass, while a dispatcher is an official whose role is to control the movement of trains across the railway. Dispatcher is a common term in the United States, the British equivalent is train controller.

Safeworking and standard time

Prior to the introduction of the railways, every town kept its own time, based on the observation of the noonday sun. Thus the time in two towns only a few miles apart would be slightly different. There was no need for standardised time, as there was no way for people to communicate instantly across any distance, and no need to synchronize their actions.

The railway changed that. Timetables could not be written allowing for changes in time between every town. Nor could train crews be expected to adjust their timepieces continuously as the journey progressed. Thus the arrival of the railway brought about the need for standard time, and the concept of time zones. A standard time across a railway, or at least a division of a railway was essential for the safeworking of trains.

Methods of safeworking

One Engine in Steam

The rules of the railway only allow one engine to operate at one time, making any collision a physical impossibility. This method is only feasible on short railways with minimal traffic.

Strict timetable operation

Trains operate according to a strict timetable, that is cannot leave a station until an appointed time and until any other trains they were to meet at that station have arrived. Rarely used as a method of safeworking, as if one train is delayed, all trains it is scheduled to meet are delayed. This can quickly lead to all trains on the railway being affected.

Timetable and Train Order

The most popular method of safeworking on single lines in the United States up until the 1950s. While trains operate by timetable, a dispatcher can amend the schedule of trains by train order. The dispatcher can also alter the stations at which trains are to meet, add extra trains and annul timetabled trains as required.

Train orders are communicated by the dispatcher to station staff by telegraph, or later telephone. They are then written out on a form, and passed to the appropriate train crews. Two types of train order are normally recognised. The first are minor orders that do not affect the safety of trains, and these may be passed to the train crew without the train having to stop to receive them. The second are regarded more seriously, and trains must stop so the appropriate crew members can read them and sign for them as read. A signal is usually provided at stations so as to communicate to passing trains that there is an order for them.

Complexity is often added with the concept of superior and inferior trains. Trains may be regarded as superior or inferior by way of class or direction. Thus a passenger train may be placed in a superior train class to a freight train, while eastbound trains may be regarded as superior to westbound trains of the same class, for instance. Considerable judgment is required of train crews to maintain a timetable, comply with train orders, and at the same time avoid delaying any superior train.

Staff sections

See Token (railway signalling).

Miniature Electric Staff

See Token (railway signalling).

Staff and Ticket

See Token (railway signalling).

Telegraph Block

Used on multiple track sections whereby the passage of trains from one point to the next was controlled by instruments connected by telegraph wires. Used extensively in Australia.