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Toronto subway The Toronto subway is a rapid transit system serving Toronto and the neighbouring city of Vaughan in Ontario, Canada, operated by the Toronto Transit Commission (TTC). It is a multimodal transport, multimodal rail network consisting of three Pa ...
uses a variety of
signalling systems Railway signalling (), also called railroad signaling (), 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 enormou ...
on its lines, consisting of a combination of fixed
block signalling Signalling block systems enable the safe and efficient operation of railways by preventing collisions between trains. The basic principle is that a track is broken up into a series of sections or "blocks". Only one train may occupy a block at a ...
and
moving block In railway signalling, a moving block is a signalling block system where the blocks are defined in real time by computers as safe zones around each train. This requires both knowledge of the exact location and speed of all trains at any given ti ...
signalling technologies. The oldest signalling system is known as
automatic block signalling Automatic block signaling (ABS), spelled automatic block signalling or called track circuit block (TCB ) in the UK, is a railroad communications system that consists of a series of signals that divide a railway line into a series of sections, ...
and was designed for the system's heavy rail lines:
Line 1 Yonge–University Line 1 Yonge–University is a rapid transit line on the Toronto subway. It serves Toronto and the neighbouring city of Vaughan in Ontario, Canada. It is operated by the Toronto Transit Commission, has 38 stations and is in length, making it th ...
,
Line 2 Bloor–Danforth Line 2 Bloor–Danforth is a subway line in the Toronto subway system, operated by the Toronto Transit Commission (TTC). It has 31 stations and is in length. It opened on February 26, 1966, and extensions at both ends were completed in 1968 a ...
and
Line 4 Sheppard Line 4 Sheppard is the newest and shortest subway line of the Toronto subway system, operated by the Toronto Transit Commission (TTC). It opened on November 22, 2002, and has five stations along of track, which is built without any open sectio ...
. Since 2022, Line 1 had been fully converted to
automatic train control 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 do ...
(ATC). The remaining lines use ATC:
Line 3 Scarborough Line 3 Scarborough (originally known as the Scarborough RT or SRT) is a light rapid transit line that is part of the Toronto subway system in Toronto, Ontario, Canada. The line runs entirely within the suburban district of Scarborough, encompas ...
uses an early form of ATC known as transmission-based train control (TBTC), while Line 1 along with
Line 5 Eglinton Line 5 Eglinton (also known as the Eglinton Crosstown or the Crosstown) is a light rail line that is under construction in Toronto, Ontario, Canada. Owned by Metrolinx and operated by the Toronto Transit Commission (TTC), the line will be part ...
, a light-rail line under construction, use a modern form of ATC called
communications-based train control Communications-based train control (CBTC) is a railway signaling system that uses telecommunications between the train and track equipment for traffic management and infrastructure control. CBTC allows a train's position to be known more accurat ...
(CBTC).


Transmission-based train control (Line 3)

Line 3 Scarborough Line 3 Scarborough (originally known as the Scarborough RT or SRT) is a light rapid transit line that is part of the Toronto subway system in Toronto, Ontario, Canada. The line runs entirely within the suburban district of Scarborough, encompas ...
uses
SelTrac SelTrac is a digital railway signalling technology used to automatically control the movements of rail vehicles. It was the first fully automatic moving-block signalling system to be commercially implemented. What is now branded as SelTrac wa ...
IS, a transmission-based train control system originally developed by
Alcatel-Lucent Alcatel–Lucent S.A. () was a French–American global telecommunications equipment company, headquartered in Boulogne-Billancourt, France. It was formed in 2006 by the merger of France-based Alcatel and U.S.-based Lucent, the latter being a su ...
(now part of
Thales Group Thales Group () is a French multinational company that designs, develops and manufactures electrical systems as well as devices and equipment for the aerospace, defence, transportation and security sectors. The company is headquartered in Paris' ...
) as part of the
Intermediate Capacity Transit System Innovia Metro is an automated rapid transit system manufactured by Alstom. Innovia Metro systems run on conventional metal rails and pull power from a third rail, but are powered by a linear induction motor that provides traction by pulling on ...
(ICTS) technology employed by Line 3, which is identical to that of Vancouver's SkyTrain and the
Detroit People Mover The Detroit People Mover (DPM) is a elevated automated people mover system in Detroit, Michigan, United States. The system operates in a one-way loop on a single track encircling downtown Detroit, using Intermediate Capacity Transit System lin ...
. The system is designed to allow Line 3 trains to be driverless; however, due to safety concerns, an operator is stationed at the front of each train in a cab equipped with a display of signal indications; there are no track-side signals. To control train operation, each two-car
married-pair A twin unit or twinset is a set of two railroad cars or locomotives which are permanently coupled and treated as if they were a single unit. A twinset of cars or coaches can also be called a twin car. In US passenger railroad parlance, twin u ...
has multiple on-board computers communicating with a central computer at
Kennedy station Kennedy is both a terminal and interchange station on Line 2 Bloor–Danforth and Line 3 Scarborough of the Toronto subway system. Opened in 1980, it is located east of the Kennedy Road and Eglinton Avenue intersection. With the adjacent Kenn ...
. Transit Control at the
Hillcrest Complex Hillcrest Complex is the Toronto Transit Commission's largest facility and is responsible for most of the maintenance work on the system's surface vehicles, including heavy overhauls, repairs and repainting. It is located adjacent to the intersec ...
has a terminal connected to the Kennedy station computer.


Communications-based train control (Lines 1 and 5)

The TTC used "Urbalis 400", a
communications-based train control Communications-based train control (CBTC) is a railway signaling system that uses telecommunications between the train and track equipment for traffic management and infrastructure control. CBTC allows a train's position to be known more accurat ...
system made by
Alstom Alstom SA is a French multinational rolling stock manufacturer operating worldwide in rail transport markets, active in the fields of passenger transportation, signalling, and locomotives, with products including the AGV, TGV, Eurostar, Avelia ...
, on
Line 1 Yonge–University Line 1 Yonge–University is a rapid transit line on the Toronto subway. It serves Toronto and the neighbouring city of Vaughan in Ontario, Canada. It is operated by the Toronto Transit Commission, has 38 stations and is in length, making it th ...
. It is engaged in a phased implementation of CBTC to replace the fixed-block signal system on the entire line. CBTC first went live on Line 1 in December 2017 on the newly inaugurated extension between
Vaughan Metropolitan Centre station Vaughan Metropolitan Centre (also known as Vaughan, Vaughan Metro Centre or VMC) is a rapid transit station in Vaughan, Ontario, Canada. Opened on December 17, 2017, it is the north terminus of the western section of the Toronto subway's Line 1 Y ...
and
Sheppard West station Sheppard West (formerly Downsview) is a List of Toronto subway stations, subway station on Line 1 Yonge–University in Toronto, Ontario, Canada. The station, which is located at the southeast corner of Sheppard Avenue, Sheppard Avenue West–Al ...
. Since then, CBTC has been extended as far as
Eglinton station Eglinton is a subway station on Line 1 Yonge–University of the Toronto subway. Located on Eglinton Avenue, it is central to the Yonge–Eglinton neighbourhood in Midtown Toronto. Eglinton station is the seventh busiest station of the Toronto T ...
. Effective September 24, 2022, Line 1 had been fully converted to
automatic train control 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 do ...
(ATC). CBTC requires a set of equipment on trains and at trackside to gather and transmit data to central computers, and to receive instructions back for train operation. ATC beacons and axle counters sit at track level to detect the passage of a train with the axle counters backing up the beacons. The track-level beacons transmit signals to onboard controllers installed on each train. Onboard roof antennas (Data Communications System antennas) transmit information such as speed and location from the controllers to Trackside Radio Equipment which relays the data to central computers and to the TTC's Transit Control Centre. The central computers send speed and braking instructions back to the train, whereby the central computers are effectively directing each train. With computers operating the train, trains can operate safely on closer headways than with the fixed block system. CBTC allows more frequent service and increased line capacity. With the old fixed block signal system, the TTC can schedule 25.5 trains per hour on Line 1, occasionally operating up to 29 per hour. With CBTC, the TTC can operate 30 to 32 trains per hour with a more consistent frequency. However, this goal depends on how well the TTC can manage dwell time in stations, crew changeovers and turnaround at terminals. The grade-separated section of
Line 5 Eglinton Line 5 Eglinton (also known as the Eglinton Crosstown or the Crosstown) is a light rail line that is under construction in Toronto, Ontario, Canada. Owned by Metrolinx and operated by the Toronto Transit Commission (TTC), the line will be part ...
, between
Mount Dennis station Mount Dennis is an intermodal transit terminal under construction in Toronto, Ontario, Canada. Located east of the intersection of Eglinton Avenue and Weston Road in the Mount Dennis neighbourhood in the district of York, the station will be th ...
and
Science Centre station Science Centre is an underground light rail transit (LRT) station and mobility hub under construction on Line 5 Eglinton, a new line that is part of the Toronto subway system. It will be located in the Flemingdon Park neighbourhood at the inte ...
, will also use CBTC. Unlike on Line 1, the system on Line 5 will be supplied by
Bombardier Transportation Bombardier Transportation was a Canadian-German rolling stock and rail transport manufacturer, headquartered in Berlin, Germany. It was one of the world's largest companies in the rail vehicle and equipment manufacturing and servicing industry ...
using its Cityflo 650 technology.


Fixed block signalling (Lines 2, and 4)

, fixed block signalling is used on Line 2 Bloor–Danforth and Line 4 Sheppard, and was used on Line 1 Yonge–University until September 24, 2022. It uses wayside signals to give instructions to train operators, which may be automatic block signals or interlocking signals. This system, also called the NX/UR system of signalling, is also used on the
New York City Subway The New York City Subway is a rapid transit system owned by the government of New York City and leased to the New York City Transit Authority, an affiliate agency of the state-run Metropolitan Transportation Authority (MTA). Opened on October 2 ...
, the
Chicago "L" The Chicago "L" (short for "elevated") is the rapid transit system serving the city of Chicago and some of its surrounding suburbs in the U.S. state of Illinois. Operated by the Chicago Transit Authority (CTA), it is the fourth-largest rapid tr ...
, and the
MBTA subway The Massachusetts Bay Transportation Authority (MBTA) operates rapid transit (heavy rail), light rail, and bus rapid transit services in the Boston metropolitan area, collectively referred to as the rapid transit, subway, or the T system. The c ...
in Boston.


Overview

With fixed block signalling, the line is subdivided into blocks – a section of track that can be occupied by a train. Each block is protected by a signal at the start of the block that train operators must obey, with the signal aspects indicating whether it is safe for a train to proceed into the next block. These signals are connected to a trip arm that has the ability to stop a train if it violates a signal (runs a red light), by triggering an emergency brake application. This safety method is identical to that of the New York City Subway system. If a train is occupying a block, the two or more signals behind the train will be red, with the trip arms in the danger position so that another train cannot proceed into the area. The distance between signals (and number of signals that are red when a particular block is occupied) is set in accordance with the stopping distance required by the trains. If a train violates a signal, the trip arm would trigger an emergency brake application to stop it before it reaches the train ahead. In other words, for a particular signal to clear, the system requires two or more full blocks ahead of that signal must be unoccupied. This requirement reduces the number of trains that can operate on the line compared to using automatic train control. Grade timing, a method of speed control, is integrated with the signalling system. Station timing signals, which allows trains to safely run closer together at slower speeds (such as near station stops), are also present. Headway control, a method of evening out the spacing between trains, is active at certain stations with interlocking (or home) signals. Such a signal turns red as a train passes it, and will remain red for a variable amount of time. This time depends on the distance between the last train that passed the signal, and the train that comes after the next train. This system is computerized, and can accurately calculate the relative distances between trains. If the next train is closer to the train before than the train after, then the signal will hold the train at the station. If the next train is closer to the train after it than the train before it, then the signal will clear. There are several limitations to this signalling system that can result in "signal problems" and "signal delays". One of the most common problems is ''track down''. A track down occurs when a block gets a false reading and places signals into the danger position even when there is no train occupying the block. This can occur if debris interrupts the block by grounding out the
track circuit A track circuit is an electrical device used to prove the absence of a train on rail tracks to signallers and control relevant signals. An alternative to track circuits are axle counters. Principles and operation The basic principle behind t ...
mimicking the electric circuit caused by an actual train in the area. When a signal fails to clear, depending on the area, there are three different ways to rectify the situation. At some signals, transit control can perform a "call-on" where an orange aspect blinks and the trip arm is released even when the aspect displayed is red. The second option is a "key-by". Some signals have a plunger that the operator can stop, reach out the window, operate the plunger dropping the trip arm and then operate the train to a less restrictive signal. Where neither of these options exist, the only way to get past a defective signal is to "trip through". The operator at slow speed must trip the signal (which in turn trips the train and places it into emergency). The crew must then reset the emergency valve (by going out the front door of the train) before proceeding.


Block signals

Block signals are the most commonly used signals on the Toronto subway. They are used to keep trains properly spaced, and are controlled automatically by the trains themselves based on their distance relative to other trains, as determined by signal block occupancy. The following block signals are used by the TTC. File:TTC-signal-block-green.svg, Proceed File:TTC-signal-block-yellow.svg, Proceed with caution, the next signal is currently red File:TTC-signal-block-red.svg, Stop. Passing this signal trips the
train stop Part of a railway signalling system, a train stop, trip stop or tripcock (sometimes called a tripper) is a train protection device that automatically stops a train if it attempts to pass a signal when the signal aspect and operating rules proh ...
. File:TTC-signal-block-yellow-lunar.svg, Entering timed block, the next signal is red ''only'' due to grade timing File:TTC-signal-block-red-lunar.svg, Timed block, timer has not yet run out (red light flashes when timer is about to run out); next block is timed as well as lunar aspect is indicated (in this example this signal would only clear to yellow)


Grade timing (GT)

Grade timing (GT) is used to protect sections where a sharp turn requires a speed limit or where a downhill section would cause a train to accelerate to an unsafe speed if the driver were unwary. When entering a signal block which is subject to GT, one of two things controls the signal: the distance to the train ahead, or grade timing. If the current state of the signal is due to proximity of the train ahead, it behaves as a standard block signal. However, once the train ahead has travelled far enough for this signal to clear, the aspect does not immediately change but remains at red. When a train enters the block before the GT signal, a timer is started and the red aspect at the GT signal starts flashing. Once this timer reaches a predetermined time, the signal then clears as normal and the trip arm is lowered. If the train is travelling too fast, it will reach the GT signal before the timer expires and the trip arm will force the train to stop. The signal at the start of block before a GT signal has an additional white light (termed "lunar aspect" by the TTC) below the other aspects, which illuminates when the following GT signal is at red ''only'' due to grade timing. Where there are several consecutive GT signals, a lunar aspect will be present on the signal at the start of each timing block. A flashing red without the lunar aspect (not included in the images above) would be used for the signal at the end of the last block of a GT section. In addition to lunar white signals, grade timed sections are sometimes indicated by a sign with the letters "GT", or simply "T", in white.


Station timing (ST)

Station timing is used to reduce the separation distance between trains that are operating at slower speeds. It is typically used in and around station platforms, allowing a second train to safely move closer to an already-occupied platform than would otherwise be possible. As with GT signals, a timer is started when a train enters the block preceding the ST signal. If the timer expires before the train reaches the ST signal (i.e. the train is travelling slower than a defined speed), the number of blocks ahead of the ST signal that need to be unoccupied for the signal to clear is reduced. This reflects the shorter braking distance of a train travelling slower than the maximum permitted speed.


Interlocking signals

Interlocking signals are typically used in interlockings, which are any areas where train movements may conflict with each other. They are controlled by either human operators or a computer, not automatically by the movement of trains. Interlocking signals also tell train operators which way
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are set. The following interlocking signals are used on the TTC. File:TTC-signal-interlocking-green-green.svg, Proceed, points set to straight File:TTC-signal-interlocking-yellow-green.svg, Proceed with caution, points set to straight, next signal is currently red File:TTC-signal-interlocking-yellow-yellow.svg, Proceed with caution, points set to diverge. File:TTC-signal-interlocking-red-red.svg, Stop and stay File:TTC-signal-interlocking-red-red-callon.svg, Call on (train has been given permission to pass red signal) File:TTC-signal-interlocking-yellow-green-lunar.svg, Entering timed block, points set to straight, next signal is red ''only'' due to grade timing File:TTC-signal-interlocking-yellow-yellow-lunar.svg, Entering timed block, points set to diverge File:TTC-signal-interlocking-red-red-lunar.svg, Timed block, timer has not yet run out (top red light flashes when timer is about to run out); next block is timed as well as lunar aspect is indicated (in this example this signal would only clear to yellow over green) Interlocking signals can also include grade timing and station timing, which functions in the same way as for block signals. For GT interlocking signals, only the top red aspect will flash while the timer is running, the bottom red aspect remains constantly lit.


Signal numbers

All signals have an alpha-numeric number that relates to their location within the subway system. The number is assigned using the Chain system of measurement, whereby a signal's number is assigned based on the nearest chain measure. Each line or portion of a line has an assigned letter, and that precedes the number ascertained by the Chain measure. Signals that are on a northbound portion of track use the nearest even valued chain measure, where signals on a southbound portion of track use the nearest odd valued chain measure.


Temporary signals

In work zones, staff place yellow beacons on the track bed between the rails to inform train operators that a "slow order" is in effect; the first beacon is usually accompanied with a speed restriction sign indicating the speed limit for the affected area. A green beacon indicates the end of a work zone and allows operators to resume normal operation. In outdoor sections, yellow and green flags are also used for the same purpose. A flashing blue light at track level indicates workers may be present, subway operators are required to sound their horn, and follow the signals of track workers when approaching and passing them.


See also

*
1995 Russell Hill subway accident The 1995 Russell Hill subway accident was a deadly train crash that occurred in Toronto, Ontario, Canada, on Line 1 Yonge–University of the Toronto subway on August 11, 1995. Three people were killed and 30 were taken to hospital with injuries ...
* New York City Subway signaling *
Railway signalling Railway signalling (), also called railroad signaling (), 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 enormou ...


References


External links


SIGNALS: Questions and Answers about the Signals in use by the Toronto Transit Commission
(PDF Format). ''Transit Toronto''.
TTC's Signal System Explained
on
YouTube YouTube is a global online video platform, online video sharing and social media, social media platform headquartered in San Bruno, California. It was launched on February 14, 2005, by Steve Chen, Chad Hurley, and Jawed Karim. It is owned by ...
, published by the TTC on March 5, 2014
How the Toronto (TTC) Subway Train Signal System Works
on
YouTube YouTube is a global online video platform, online video sharing and social media, social media platform headquartered in San Bruno, California. It was launched on February 14, 2005, by Steve Chen, Chad Hurley, and Jawed Karim. It is owned by ...
, published by T2P Films on June 23, 2014 * This article explains the old block signal system and the new communications-based train control (CBTC) to be implemented on Line 1 between 2017 and 2019. *, published by ''
The Globe and Mail ''The Globe and Mail'' is a Canadian newspaper printed in five cities in western and central Canada. With a weekly readership of approximately 2 million in 2015, it is Canada's most widely read newspaper on weekdays and Saturdays, although it ...
'' on June 7, 2017 {{TTC Toronto rapid transit Railway signaling in Canada Train protection systems