Two-thirds rule (railway safety)

Last updated

The two-thirds rule is railway safety rule originating from the Southern Region of British Railways. The two-third rule requires that the speed of a freight train is limited to no more than two-thirds of the speed limit for a passenger electric multiple unit (EMU). [1]

For safety reasons, speed limits are imposed on trains running on a railway line. Many factors can affect the speed limit of a particular line including the state of the track, the curvature of the track, the number of stations, the individual features of stations or junctions and the stopping distances of trains running on that track. During the existence of the BR Southern Region, EMUs used on these lines were generally capable of slowing down much more quickly than the freight trains that shared these tracks. The Southern Region introduced the "two-thirds rule" as a safety and performance measure in response to this discrepancy.

On the modern British railway network, this rule was included in the Railway Group Standards (RGS) GK/RT0034 and then persisted in to the GK/RT0075 Requirements for Minimum Signalling Braking and Deceleration Distances. A study concluded in 2014 proposed that a strategy be introduced to replace the two-thirds rule due to increased performance of modern freight locomotives, [2] however the rule persists on many parts of the railway in southern England. [3]

See also

Related Research Articles

<span class="mw-page-title-main">Multiple unit</span> Self-propelled train

A multiple-unit train or simply multiple unit (MU) is a self-propelled train composed of one or more carriages joined together, which when coupled to another multiple unit can be controlled by a single driver, with multiple-unit train control.

<span class="mw-page-title-main">Railway signalling</span> The principle of signals used to control railway traffic

Railway signalling (BE), also called railroad signaling (AE), is a system used to control the movement of railway traffic. Trains move on fixed rails, making them uniquely susceptible to collision. This susceptibility is exacerbated by the enormous weight and inertia of a train, which makes it difficult to quickly stop when encountering an obstacle. In the UK, the Regulation of Railways Act 1889 introduced a series of requirements on matters such as the implementation of interlocked block signalling and other safety measures as a direct result of the Armagh rail disaster in that year.

<span class="mw-page-title-main">Brake van</span>

Brake van and guard's van are terms used mainly in the UK, Ireland, Australia and India for a railway vehicle equipped with a hand brake which can be applied by the guard. The equivalent North American term is caboose, but a British brake van and a caboose are very different in appearance, because the former usually has only four wheels, while the latter usually has bogies. German railways employed Brakeman's cabins combined into other cars.

The Train Protection & Warning System (TPWS) is a train protection system used throughout the British passenger main-line railway network, and in Victoria, Australia.

<span class="mw-page-title-main">British Rail Class 73</span> British electro-diesel locomotive

The British Rail Class 73 is a British electro-diesel locomotive. The type is unusual in that it can operate from the Southern Region's 650/750 V DC third-rail or an on-board diesel engine to allow it to operate on non-electrified routes. This makes it very versatile, although the diesel engine produces less power than is available from the third-rail supply so the locomotives are rarely operated outside of the former Southern Region of British Rail. Following the withdrawal and scrapping of the more powerful Class 74 electro-diesels in 1977, the Class 73 was unique on the British railway network until the introduction of the Class 88 electro-diesels in 2017. Ten locomotives have been scrapped.

<span class="mw-page-title-main">Signal passed at danger</span> Train passing stop signal without authority

A signal passed at danger (SPAD), known in the United States as a stop signal overrun and in Canada as passing a stop signal, is an event on a railway where a train passes a stop signal without authority. In the United States and Canada, this may be known colloquially as running a red, though this idiom principally refers to automobiles passing red traffic signals.

<span class="mw-page-title-main">Automatic Warning System</span>

The Automatic Warning System (AWS) provides a train driver with an audible indication of whether the next signal they are approaching is clear or at caution. Depending on the upcoming signal state, the AWS will either produce a 'horn' sound, or a 'bell' sound. If the train driver fails to acknowledge a warning indication, an emergency brake application is initiated by the AWS. However if the driver correctly acknowledges the warning indication by pressing an acknowledgement button, then a visual 'sunflower' is displayed to the driver, as a reminder of the warning.

<span class="mw-page-title-main">Nuneaton rail crash</span> British rail disaster

The Nuneaton rail crash occurred on 6 June 1975, on the West Coast Main Line just south of Nuneaton railway station in Warwickshire, England, United Kingdom.

<span class="mw-page-title-main">Automatic train control</span> Class of train protection systems for railways

Automatic train control (ATC) is a general class of train protection systems for railways that involves a speed control mechanism in response to external inputs. For example, a system could effect an emergency brake application if the driver does not react to a signal at danger. ATC systems tend to integrate various cab signalling technologies and they use more granular deceleration patterns in lieu of the rigid stops encountered with the older automatic train stop (ATS) technology. ATC can also be used with automatic train operation (ATO) and is usually considered to be the safety-critical part of a railway system.

<span class="mw-page-title-main">Train event recorder</span> Train electronic recording device

A train event recorder – also called On-Train Monitoring Recorder (OTMR), On-Train Data Recorder (OTDR), Event Recorder System (ERS), Event Recorder Unit (ERU), or Juridical Recording Unit (JRU) – is a device that records data about the operation of train controls, the performance of the train in response to those controls, and the operation of associated control systems. It is similar in purpose to the flight data recorder or black box used on aircraft.

<span class="mw-page-title-main">UK railway signalling</span> Rail traffic control systems used in the United Kingdom

The railway signalling system used across the majority of the United Kingdom rail network uses lineside signals to control the movement and speed of trains.

<span class="mw-page-title-main">British electric multiple units</span> Trains without locomotives, in the European country

An electric multiple unit (EMU) is an electric train capable of operating in multiple with other EMUs that does not have a separate locomotive, typically passenger trains with accommodation in every vehicle and a driving position at each end. The term can also be used to describe a train such as the Advanced Passenger Train that was a permanent formation with a non-driving power car. As of December 2010 two-thirds of the passenger carriages in Britain are formed in EMUs.

<span class="mw-page-title-main">Transmission Voie-Machine</span> Railway cab signaling technology used on high-speed rail

Transmission Voie-Machine is a form of in-cab signalling originally deployed in France and is mainly used on high-speed railway lines. TVM-300 was the first version, followed by TVM-430.

Standards for North American railroad signaling in the United States are issued by the Association of American Railroads (AAR), which is a trade association of the railroads of Canada, the US, and Mexico. Their system is loosely based on practices developed in the United Kingdom during the early years of railway development. However, North American practice diverged from that of the United Kingdom due to different operating conditions and economic factors between the two regions. In Canada, the Canadian Rail Operating Rules (CROR) are approved by the Minister of Transport under the authority of the Railway Safety Act. Each railway company or transit authority in Canada issues its own CROR rulebook with special instructions peculiar to each individual property. Among the distinctions are:

<span class="mw-page-title-main">Detonator (railway)</span> Signaling system for trains

A railway detonator is a coin-sized device that is used as a loud warning signal to train drivers. It is placed on the top of the rail, usually secured with two lead straps, one on each side. When the wheel of the train passes over, it explodes, emitting a loud bang. It was invented in 1841 by English inventor Edward Alfred Cowper.

<span class="mw-page-title-main">Route availability</span> System for grading the railway network of Great Britain

Route Availability (RA) is the system by which the permanent way and supporting works of the railway network of Great Britain are graded. All routes are allocated an RA number between 1 and 10.

Headway is the distance or duration between vehicles in a transit system measured in space or time. The minimum headway is the shortest such distance or time achievable by a system without a reduction in the speed of vehicles. The precise definition varies depending on the application, but it is most commonly measured as the distance from the tip of one vehicle to the tip of the next one behind it. It can be expressed as the distance between vehicles, or as time it will take for the trailing vehicle to cover that distance. A "shorter" headway signifies closer spacing between the vehicles. Airplanes operate with headways measured in hours or days, freight trains and commuter rail systems might have headways measured in parts of an hour, metro and light rail systems operate with headways on the order of 90 seconds to 20 minutes, and vehicles on a freeway can have as little as 2 seconds headway between them.

British Rail Telecommunications was created in 1992 by British Rail (BR). It was the largest private telecoms network in Britain, consisting of 17,000 route kilometres of fibre optic and copper cable which connected every major city and town in the country and provided links to continental Europe through the Channel Tunnel.

Route knowledge is one of the core skills together with train handling and a full understanding of railway rules, which the operating crew must possess in order to be able to operate a train safely.

Automatic Train Protection (ATP) was a method of beacon based railway cab signalling developed by British Rail. The system never progressed beyond the pilot schemes installed on the Great Western Main Line between London Paddington and Bristol Temple Meads, and the Chiltern Main Line from London Marylebone to High Wycombe and Aylesbury.

References

  1. "Provision of Permissible Speed Signs". www.railsigns.uk. SDL. Retrieved 17 January 2021.
  2. "Review of the braking tables in RGS GK/RT0075 Lineside Signal Spacing and Speed Signage (T999)". www.rssb.co.uk. Rail Safety and Standards Board . Retrieved 17 January 2021.
  3. "GK/GN0675 Iss 4 - Guidance on Lineside Signal Spacing and Speed Signage". www.rssb.co.uk. Rail Safety and Standards Board . Retrieved 17 January 2021.