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Radio Electronic Token Block is a system of railway signalling used in the United Kingdom. It is a development of the physical token system for controlling traffic on single lines. The system is slightly similar to North American Direct Traffic Control, which unlike RETB does not have a cab display unit.
On arrival at a "token exchange point", the driver reports their position to the signaller by radio and requests the "token" for the next section of line ahead. If the signaller is in a position to do so, they will issue the electronic token applicable to the section ahead. Simultaneously, the driver must operate a button on an apparatus in the cab to receive the token. The token is then transmitted to the train by radio. The Solid State Interlocking controlling the system prevents the issue of any token permitting conflicting movements.
In the same way as with the traditional system, when a physical token with the name of the section engraved on it would be carried in the cab, the electronic token is received and displayed by name on the train equipment. This token is the authority to occupy the single line, and it cannot be removed from the train until the driver themself releases it. After confirming they have received the correct token, the driver is then given verbal permission to pass the "Stop Board" and enter that section; the stop board is used instead of signals and therefore needs no electrical supply. The fixed distance board on the approach has a single permanent AWS inductor which gives a warning in the cab regardless of the signal box instruction and has to be cancelled when passed.
Points at the entrance to a crossing loop are spring-loaded for the correct track for facing movements, and are pushed across by the wheels for trailing movements; they too require no power or interlocking, other than for points heating purposes. In the facing direction, a 'points indicator' is provided to indicate to the driver that the points are correctly set. The points indicator is in the form of a yellow light, lit only while the points are electrically detected in the required position. The whole line can be operated by just one or two signallers and needs very little infrastructure other than the track itself, making it a very cost-effective method.
The simplicity of the lineside infrastructure in RETB areas was reduced by the installation of the Train Protection & Warning System. A train stop loop is provided at each stop board, and is normally activated (so that any train attempting to pass it will be immediately brought to a halt). When the signaller issues a token for a train to enter a section, the TPWS loop at the appropriate board is deactivated, so allowing the train to proceed. Indication of the state of the TPWS is provided by a blue light mounted below the stop board. This shows a steady blue light when the TPWS is activated, and a flashing blue light when it is deactivated.
The genesis of the system was on the Far North Line, a long, remote single-track line between Inverness, Wick and Thurso in Scotland. This line was controlled by traditional electric token instruments at each station, but in January 1978 the signal telegraph pole route was brought down by bad weather over more than forty miles of track. The simplest, cheapest and quickest way of restoring the links between the instruments was found to be by radio: each machine was fitted with an external controller containing a unique microprocessor code so that the effect of a dedicated link to the machine at the other end of its section was maintained. The manual issue of the tokens continued as before.
With the feasibility of using radio to effect the interlocking of single line token instruments demonstrated, and the additional benefit of voice communication between the signaller and the drivers noted, it was but a short step of invention to moving the instruments from staffed signal boxes to the cabs of trains. The line selected for the trial was another remote and lightly used Scottish line: the old Highland Railway route from Dingwall westwards to Kyle of Lochalsh. The contract was placed with Westinghouse of Chippenham, Wiltshire, and the system was brought into use on 28 October 1984, with the control equipment situated at Dingwall. [1] Over the next four years, control was transferred to Inverness and the Wick and Thurso line was included in the scheme.
A new control centre was brought into use at Banavie for the West Highland Line from Helensburgh Upper to Fort William and Mallaig, and from Crianlarich to Oban. The system was also used on two other British rural lines: the East Suffolk Line, where the control centre was at Saxmundham, and the Cambrian Line from Shrewsbury to Aberystwyth and Pwllheli, where the control centre was at Machynlleth.
RETB is being gradually replaced with the new European in-cab signalling system, ERTMS. [2] The Cambrian line was due to be changed over to the new system by spring 2010 but was delayed, being commissioned on 11 March 2011. [3] The East Suffolk Line's system underwent life extension works in 2006, but was converted to conventional Track Circuit Block with axle counters in connection with increasing the service frequency to a point where the RETB could not have handled it. RETB was phased out on the East Suffolk Line after the last Ipswich-Lowestoft service arrived at Oulton Broad South on Friday 19 October 2012.
From 2014, RETB Next Generation was developed and installed.
Due to the loss of the Band III Sub Band 2 radio frequencies used by the NRN radio system from the digital TV spectrum reallocation the need arose for a system to replace RETB on two lines in Scotland - the West Highland Line and the Far North Line. The rugged terrain and light line traffic made it cost-prohibitive to install GSM-R for these areas and so a new radio system, with new base station and on-train equipment, was developed. This allows RETB to continue to operate on Band III Sub Band 1. RETB NG. [4]
A number of upgrades to RETB NG have been integrated since the system was renewed, to secure its future as an effective signalling and train control system for remote and rural lines around the world. These include improved train positioning technologies that allow train protection without the need for external lineside infrastructure. A 'Request to Stop' system has been installed on the Far North Line. [5]
A railway signal is a visual display device that conveys instructions or provides warning of instructions regarding the driver’s authority to proceed. The driver interprets the signal's indication and acts accordingly. Typically, a signal might inform the driver of the speed at which the train may safely proceed or it may instruct the driver to stop.
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.
In railway signalling, a token is a physical object which a train driver is required to have or see before entering onto a particular section of single track. The token is clearly endorsed with the names of the section to which it belongs. A token system is more commonly used for single lines because of the greater risk of collision in the event of a mistake being made by a signaller or traincrew, than on double lines.
The Train Protection & Warning System (TPWS) is a train protection system used throughout the British passenger main-line railway network, and in Victoria, Australia.
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The Cambrian Line, sometimes split into the Cambrian Main Line and Cambrian Coast Line for its branches, is a railway line that runs from Shrewsbury, England, westwards to Aberystwyth and Pwllheli in Wales. Passenger train services are operated by Transport for Wales Rail between the western terminals of Pwllheli, in Gwynedd, and Aberystwyth, in Ceredigion, and the eastern terminal at Shrewsbury, Shropshire, as part of the Wales & Borders franchise. The railway line is widely regarded as scenic, as it passes through the Cambrian Mountains in central Wales, and along the coast of Cardigan Bay in Snowdonia National Park.
The European Train Control System (ETCS) is a train protection system designed to replace the many incompatible systems used by European railways, and railways outside of Europe. ETCS is the signalling and control component of the European Rail Traffic Management System (ERTMS).
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.
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The European Rail Traffic Management System (ERTMS) is the system of standards for management and interoperation of signalling for railways by the European Union (EU). It is conducted by the European Union Agency for Railways (ERA) and is the organisational umbrella for the separately managed parts of
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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.
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The European Rail Traffic Management System (ERTMS) is an initiative backed by the European Union to enhance cross-border interoperability and the procurement of signalling equipment by creating a single Europe-wide standard for train control and command systems.
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