Radio Electronic Token Block
Encyclopedia
Railway signalling
Railway signalling is a system used to control railway traffic safely, essentially to prevent trains from colliding. Being guided by fixed rails, trains are uniquely susceptible to collision; furthermore, trains cannot stop quickly, and frequently operate at speeds that do not enable them to stop...
used in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
. It is a development of the physical token system
Token (railway signalling)
In railway signalling, a token is a physical object which a locomotive driver is required to have or see before entering onto a particular section of single track. The token is clearly endorsed with the name of the section it belongs to...
for controlling traffic on single lines
Single track (rail)
A single track railway is where trains in both directions share the same track. Single track is normally used on lesser used rail lines, often branch lines, where the traffic density is not high enough to justify the cost of building double tracks....
.
How it works
On arrival at a "token exchange point", the driverRailroad engineer
A railroad engineer, locomotive engineer, train operator, train driver or engine driver is a person who drives a train on a railroad...
reports his/her position to the signaller
Signalman (rail)
A signalman or signaller is an employee of a railway transport network who operates the points and signals from a signal box in order to control the movement of trains.- History :...
by radio and requests the "token" for the next section of line ahead. If the signaller is in a position to do so, he/she will issue the electronic token applicable to the section ahead. Simultaneously, the driver must operate a button on apparatus in the cab to receive the token. The token is then transmitted to the train by radio. The Solid State Interlocking
Solid State Interlocking
Solid State Interlocking is the brand name of the first generation processor-based interlocking developed in the 1980s by British Rail's Research Division, GEC-General Signal and Westinghouse Signals Ltd in the UK.- Interlocking hardware :...
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 him/herself releases it. After receiving the 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 distant board on the approach has a single permanent AWS inductor
Automatic Warning System
The Automatic Warning System is a form of limited cab signalling and train protection system introduced in 1956 in the United Kingdom to help train drivers observe and obey signals. It was based on a 1930 system developed by Alfred Ernest Hudd and marketed as the "Strowger-Hudd" system...
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
Interlocking
In railway signalling, an interlocking is an arrangement of signal apparatus that prevents conflicting movements through an arrangement of tracks such as junctions or crossings. The signalling appliances and tracks are sometimes collectively referred to as an interlocking plant...
, 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 simple nature of the lineside infrastructure in RETB areas ended with the installation of the Train Protection & Warning System.
History
The genesis of the system was on the Far North LineFar North Line
The Far North Line is a rural railway line entirely within the Highland area of Scotland, extending from Inverness to Thurso and Wick.- Route :...
, a long, remote single-track line between Inverness
Inverness
Inverness is a city in the Scottish Highlands. It is the administrative centre for the Highland council area, and is regarded as the capital of the Highlands of Scotland...
, Wick
Wick, Highland
Wick is an estuary town and a royal burgh in the north of the Highland council area of Scotland. Historically, it is one of two burghs within the county of Caithness, of which Wick was the county town. The town straddles the River Wick and extends along both sides of Wick Bay...
and Thurso
Thurso
-Facilities:Offices of the Highland Council are located in the town, as is the main campus of North Highland College, formerly Thurso College. This is one of several partner colleges which constitute the UHI Millennium Institute, and offers several certificate, diploma and degree courses from...
in Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
. This line was controlled by traditional electric token instruments at each station, but in January 1978 the signal telegraph
Electrical telegraph
An electrical telegraph is a telegraph that uses electrical signals, usually conveyed via telecommunication lines or radio. The electromagnetic telegraph is a device for human-to-human transmission of coded text messages....
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 box
Signal box
On a rail transport system, signalling control is the process by which control is exercised over train movements by way of railway signals and block systems to ensure that trains operate safely, over the correct route and to the proper timetable...
es to the cabs of trains. The line selected for the trial was another remote and lightly used Scottish line: the old Highland Railway
Highland Railway
The Highland Railway was one of the smaller British railways before the Railways Act 1921; it operated north of Perth railway station in Scotland and served the farthest north of Britain...
route from Dingwall
Dingwall
Dingwall is a town and former royal burgh in the Highland council area of Scotland. It has a population of 5,026. It was formerly an east-coast harbor but now lies inland. Dingwall Castle was once the biggest castle north of Stirling. On the town's present-day outskirts lies Tulloch Castle, parts...
westwards to Kyle of Lochalsh
Kyle of Lochalsh
Kyle of Lochalsh is a village on the northwest coast of Scotland, 63 miles west of Inverness. It is located at the entrance to Loch Alsh, opposite the village of Kyleakin on the Isle of Skye...
. The contract was placed with Westinghouse
Westinghouse Rail Systems
Westinghouse Rail Systems Ltd is a British supplier of railway signalling and control equipment to the rail industry worldwide. Its head office is in Chippenham, Wiltshire, where it manufactures a variety of mechanical and electrical/electronic railway signalling equipment...
of Chippenham, Wiltshire, and the system was brought into use on 28 October 1984, with the control equipment situated at Dingwall. 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
Banavie
Banavie is a small settlement near Fort William in the Highland Council Area of Scotland. One of the closest villages to Ben Nevis, it is about 4 km north east of Fort William town centre, next to Caol and Corpach.It has been suggested that Banavie is one of the possible birth places of Saint...
for the West Highland Line
West Highland Line
The West Highland Line is considered the most scenic railway line in Britain, linking the ports of Mallaig and Oban on the west coast of Scotland to Glasgow. The line was voted the top rail journey in the world by readers of independent travel magazine Wanderlust in 2009, ahead of the iconic...
from Helensburgh Upper
Helensburgh Upper railway station
Helensburgh Upper railway station serves the town of Helensburgh, Scotland, on the north shore of the Firth of Clyde to the west of Glasgow. It is located in a residential area uphill from the town centre and is by far the smaller of the town's two stations....
to Fort William
Fort William, Scotland
Fort William is the second largest settlement in the highlands of Scotland and the largest town: only the city of Inverness is larger.Fort William is a major tourist centre with Glen Coe just to the south, Aonach Mòr to the north and Glenfinnan to the west, on the Road to the Isles...
and Mallaig
Mallaig
Mallaig ; is a port in Lochaber, on the west coast of the Highlands of Scotland. The local railway station, Mallaig, is the terminus of the West Highland railway line , completed in 1901, and the town is linked to Fort William by the A830 road – the "Road to the Isles".The village of Mallaig...
, and from Crianlarich
Crianlarich
Crianlarich is a village in the Stirling district and registration county of Perthshire, Scotland, about six miles north-east of the head of Loch Lomond...
to Oban
Oban
Oban Oban Oban ( is a resort town within the Argyll and Bute council area of Scotland. It has a total resident population of 8,120. Despite its small size, it is the largest town between Helensburgh and Fort William and during the tourist season the town can be crowded by up to 25,000 people. Oban...
. The system is also used on two other British rural lines: the East Suffolk Line
East Suffolk Line
The East Suffolk Line is an un-electrified secondary railway line running between Ipswich and Lowestoft in Suffolk, England. The traffic along the route consists of passenger services operated by National Express East Anglia, while nuclear flask trains for the Sizewell nuclear power stations are...
, where the control centre is at Saxmundham
Saxmundham
Saxmundham is a small market town in Suffolk, England. It is set in the valley of the River Fromus, a tributary of the River Alde, approximately northeast of Ipswich and west of the coast at Sizewell. The town is bypassed by the A12 and is served by Saxmundham railway station on the East Suffolk...
, and the Cambrian Line
Cambrian Line
The Cambrian Line is a railway from Shrewsbury to Welshpool, Aberystwyth and Pwllheli. The railway runs first through the central part of Wales and then along the coast of Cardigan Bay....
from Shrewsbury
Shrewsbury
Shrewsbury is the county town of Shropshire, in the West Midlands region of England. Lying on the River Severn, it is a civil parish home to some 70,000 inhabitants, and is the primary settlement and headquarters of Shropshire Council...
to Aberystwyth
Aberystwyth
Aberystwyth is a historic market town, administrative centre and holiday resort within Ceredigion, Wales. Often colloquially known as Aber, it is located at the confluence of the rivers Ystwyth and Rheidol....
and Pwllheli
Pwllheli
Pwllheli is a community and the main market town of the Llŷn Peninsula in Gwynedd, north-western Wales. It has a population of 3,861, of which a large proportion, 81 per cent, are Welsh speaking. Pwllheli is the place where Plaid Cymru was founded. It is the birthplace of Albert Evans-Jones -...
.
The future
RETB is now regarded by the rail industry as a redundant technology and is being gradually replaced with the new European in-cab signalling system, ERTMS. The Cambrian lineCambrian Line
The Cambrian Line is a railway from Shrewsbury to Welshpool, Aberystwyth and Pwllheli. The railway runs first through the central part of Wales and then along the coast of Cardigan Bay....
was due to be changed over to the new system by Spring 2010 but was delayed, being commissioned on 11 March 2011. The East Suffolk Line underwent life extension works in 2006 however the RETB system is due for replacement by 2011. Another reason for the replacement of the system is due to the radio frequency licence expiring.
External links
- Modernisation of the Cambrian Lines; includes discussion on a practical application of RETB.
- Details of RETB controlled from Inverness
- Details of RETB controlled from Banavie 'South'
- Details of RETB controlled from Banavie 'North'