Communications-based train control explained

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 accurately than with traditional signaling systems. This makes railway traffic management safer and more efficient. Rapid transit system (and other railway systems) are able to reduce headways while maintaining or even improving safety.

A CBTC system is a "continuous, automatic train control system utilizing high-resolution train location determination, independent from track circuits; continuous, high-capacity, bidirectional train-to-wayside data communications; and trainborne and wayside processors capable of implementing automatic train protection (ATP) functions, as well as optional automatic train operation (ATO) and automatic train supervision (ATS) functions," as defined in the IEEE 1474 standard.[1]

Background and origin

The main objective of CBTC is to increase track capacity by reducing the time interval (headway) between trains.

Traditional signalling systems detect trains in discrete sections of the track called 'blocks', each protected by signals that prevent a train entering an occupied block. Since every block is a fixed section of track, these systems are referred to as fixed block systems.

In a moving block CBTC system the protected section for each train is a "block" that moves with and trails behind it, and provides continuous communication of the train's exact position via radio, inductive loop, etc.[2]

As a result, Bombardier opened the world's first radio-based CBTC system at San Francisco airport's automated people mover (APM) in February 2003.[3] A few months later, in June 2003, Alstom introduced the railway application of its radio technology on the Singapore North East Line. CBTC has its origins in the loop-based systems developed by Alcatel SEL (now Thales) for the Bombardier Automated Rapid Transit (ART) systems in Canada during the mid-1980s.

These systems, which were also referred to as transmission-based train control (TBTC), made use of inductive loop transmission techniques for track to train communication, introducing an alternative to track circuit based communication. This technology, operating in the 30–60 kHz frequency range to communicate trains and wayside equipment, was widely adopted by the metro operators in spite of some electromagnetic compatibility (EMC) issues, as well as other installation and maintenance concerns (see SelTrac for further information regarding Transmission-Based-Train-Control).

As with new application of any technology, some problems arose at the beginning mainly due to compatibility and interoperability aspects.[4] [5] However, there have been relevant improvements since then, and currently the reliability of the radio-based communication systems has grown significantly.

Moreover, it is important to highlight that not all the systems using radio communication technology are considered to be CBTC systems. So, for clarity and to keep in line with the state-of-the-art solutions for operator's requirements, this article only covers the latest moving block principle based (either true moving block or virtual block, so not dependent on track-based detection of the trains) CBTC solutions that make use of the radio communications.

Main features

CBTC and moving block

CBTC systems are modern railway signaling systems that can mainly be used in urban railway lines (either light or heavy) and APMs, although it could also be deployed on commuter lines. For main lines, a similar system might be the European Railway Traffic Management System ERTMS Level 3 (not yet fully defined).In the modern CBTC systems the trains continuously calculate and communicate their status via radio to the wayside equipment distributed along the line. This status includes, among other parameters, the exact position, speed, travel direction and braking distance.

This information allows calculation of the area potentially occupied by the train on the track. It also enables the wayside equipment to define the points on the line that must never be passed by the other trains on the same track. These points are communicated to make the trains automatically and continuously adjust their speed while maintaining the safety and comfort (jerk) requirements. So, the trains continuously receive information regarding the distance to the preceding train and are then able to adjust their safety distance accordingly.

From the signalling system perspective, the first figure shows the total occupancy of the leading train by including the whole blocks which the train is located on. This is due to the fact that it is impossible for the system to know exactly where the train actually is within these blocks. Therefore, the fixed block system only allows the following train to move up to the last unoccupied block's border.

In a moving block system as shown in the second figure, the train position and its braking curve is continuously calculated by the trains, and then communicated via radio to the wayside equipment. Thus, the wayside equipment is able to establish protected areas, each one called Limit of Movement Authority (LMA), up to the nearest obstacle (in the figure the tail of the train in front). Movement Authority (MA) is the permission for a train to move to a specific location within the constraints of the infrastructure and with supervision of speed.[6]

End of Authority is the location to which the train is permitted to proceed and where target speed is equal to zero. End of Movement is the location to which the train is permitted to proceed according to an MA. When transmitting an MA, it is the end of the last section given in the MA.

It is important to mention that the occupancy calculated in these systems must include a safety margin for location uncertainty (in yellow in the figure) added to the length of the train. Both of them form what is usually called 'Footprint'. This safety margin depends on the accuracy of the odometry system in the train.

CBTC systems based on moving block allows the reduction of the safety distance between two consecutive trains. This distance is varying according to the continuous updates of the train location and speed, maintaining the safety requirements. This results in a reduced headway between consecutive trains and an increased transport capacity.

Grades of automation

Modern CBTC systems allow different levels of automation or Grades of Automation (GoA), as defined and classified in the IEC 62290–1.[7] In fact, CBTC is not a synonym for "driverless" or "automated trains" although it is considered as a basic enabler technology for this purpose.

There are four grades of automation available:

Main applications

CBTC systems allow optimal use of the railway infrastructure as well as achieving maximum capacity and minimum headway between operating trains, while maintaining the safety requirements. These systems are suitable for the new highly demanding urban lines, but also to be overlaid on existing lines in order to improve their performance.[8]

Of course, in the case of upgrading existing lines the design, installation, test and commissioning stages are much more critical. This is mainly due to the challenge of deploying the overlying system without disrupting the revenue service.[9]

Main benefits

The evolution of the technology and the experience gained in operation over the last 30 years means that modern CBTC systems are more reliable and less prone to failure than older train control systems. CBTC systems normally have less wayside equipment and their diagnostic and monitoring tools have been improved, which makes them easier to implement and, more importantly, easier to maintain.[10]

CBTC technology is evolving, making use of the latest techniques and components to offer more compact systems and simpler architectures. For instance, with the advent of modern electronics it has been possible to build in redundancy so that single failures do not adversely impact operational availability.

Moreover, these systems offer complete flexibility in terms of operational schedules or timetables, enabling urban rail operators to respond to the specific traffic demand more swiftly and efficiently and to solve traffic congestion problems. In fact, automatic operation systems have the potential to significantly reduce the headway and improve the traffic capacity compared to manual driving systems.[11] [12]

Finally, it is important to mention that the CBTC systems have proven to be more energy efficient than traditional manually driven systems. The use of new functionalities, such as automatic driving strategies or a better adaptation of the transport offer to the actual demand, allows significant energy savings reducing the power consumption.

Risks

The primary risk of an electronic train control system is that if the communications link between any of the trains is disrupted then all or part of the system might have to enter a failsafe state until the problem is remedied. Depending on the severity of the communication loss, this state can range from vehicles temporarily reducing speed, coming to a halt or operating in a degraded mode until communications are re-established. If communication outage is permanent some sort of contingency operation must be implemented which may consist of manual operation using absolute block or, in the worst case, the substitution of an alternative form of transportation.[13]

As a result, high availability of CBTC systems is crucial for proper operation, especially if such systems are used to increase transport capacity and reduce headway. System redundancy and recovery mechanisms must then be thoroughly checked to achieve a high robustness in operation.With the increased availability of the CBTC system, there is also a need for extensive training and periodical refresh of system operators on the recovery procedures. In fact, one of the major system hazards in CBTC systems is the probability of human error and improper application of recovery procedures if the system becomes unavailable.

Communications failures can result from equipment malfunction, electromagnetic interference, weak signal strength or saturation of the communications medium.[14] In this case, an interruption can result in a service brake or emergency brake application as real time situational awareness is a critical safety requirement for CBTC and if these interruptions are frequent enough it could seriously impact service. This is the reason why, historically, CBTC systems first implemented radio communication systems in 2003, when the required technology was mature enough for critical applications.

In systems with poor line of sight or spectrum/bandwidth limitations a larger than anticipated number of transponders may be required to enhance the service. This is usually more of an issue with applying CBTC to existing transit systems in tunnels that were not designed from the outset to support it. An alternate method to improve system availability in tunnels is the use of leaky feeder cable that, while having higher initial costs (material + installation) achieves a more reliable radio link.

With the emerging services over open ISM radio bands (i.e. 2.4 GHz and 5.8 GHz) and the potential disruption over critical CBTC services, there is an increasing pressure in the international community (ref. report 676 of UITP organization, Reservation of a Frequency Spectrum for Critical Safety Applications dedicated to Urban Rail Systems) to reserve a frequency band specifically for radio-based urban rail systems. Such decision would help standardize CBTC systems across the market (a growing demand from most operators) and ensure availability for those critical systems.

As a CBTC system is required to have high availability and particularly, allow for a graceful degradation, a secondary method of signaling might be provided to ensure some level of non-degraded service upon partial or complete CBTC unavailability.[15] This is particularly relevant for brownfield implementations (lines with an already existing signalling system) where the infrastructure design cannot be controlled and coexistence with legacy systems is required, at least, temporarily.[16]

For example, the BMT Canarsie Line in New York City was outfitted with a backup automatic block signaling system capable of supporting 12 trains per hour (tph), compared with the 26 tph of the CBTC system. Although this is a rather common architecture for resignalling projects, it can negate some of the cost savings of CBTC if applied to new lines. This is still a key point in the CBTC development (and is still being discussed), since some providers and operators argue that a fully redundant architecture of the CBTC system may however achieve high availability values by itself.[16]

In principle, CBTC systems may be designed with centralized supervision systems in order to improve maintainability and reduce installation costs. If so, there is an increased risk of a single point of failure that could disrupt service over an entire system or line. Fixed block systems usually work with distributed logic that are normally more resistant to such outages. Therefore, a careful analysis of the benefits and risks of a given CBTC architecture (centralized vs. distributed) must be done during system design.

When CBTC is applied to systems that previously ran under complete human control with operators working on sight it may actually result in a reduction in capacity (albeit with an increase in safety). This is because CBTC operates with less positional certainty than human sight and also with greater margins for error as worst-case train parameters are applied for the design (e.g. guaranteed emergency brake rate vs. nominal brake rate). For instance, CBTC introduction in Philly's Center City trolley tunnel resulted initially in a marked increase in travel time and corresponding decrease in capacity when compared with the unprotected manual driving. This was the offset to finally eradicate vehicle collisions which on-sight driving cannot avoid and showcases the usual conflicts between operation and safety.

Architecture

The typical architecture of a modern CBTC system comprises the following main subsystems:

  1. Wayside equipment, which includes the interlocking and the subsystems controlling every zone in the line or network (typically containing the wayside ATP and ATO functionalities). Depending on the suppliers, the architectures may be centralized or distributed. The control of the system is performed from a central command ATS, though local control subsystems may be also included as a fallback.
  2. CBTC onboard equipment, including ATP and ATO subsystems in the vehicles.
  3. Train to wayside communication subsystem, currently based on radio links.

Thus, although a CBTC architecture is always depending on the supplier and its technical approach, the following logical components may be found generally in a typical CBTC architecture:

Projects

CBTC technology has been (and is being) successfully implemented for a variety of applications as shown in the figure below (mid 2011). They range from some implementations with short track, limited numbers of vehicles and few operating modes (such as the airport APMs in San Francisco or Washington), to complex overlays on existing railway networks carrying more than a million passengers each day and with more than 100 trains (such as lines 1 and 6 in Madrid Metro, line 3 in Shenzhen Metro, some lines in Paris Metro, New York City Subway and Beijing Subway, or the Sub-Surface network in London Underground).[17]


Despite the difficulty, the table below tries to summarize and reference the main radio-based CBTC systems deployed around the world as well as those ongoing projects being developed. Besides, the table distinguishes between the implementations performed over existing and operative systems (brownfield) and those undertaken on completely new lines (Greenfield).

List

Location/SystemLinesSupplierSolutionCommissioningkmNo. of trainsType of FieldGrade of AutomationNotes
Greenfield UTO With train attendants who monitor door status, and drive trains in the event of a disruption.
Greenfield UTO
SelTrac Greenfield UTO
SelTrac Greenfield DTO with train attendants (Train captains) who drive trains in the event of a disruption.
CITYFLO 650 Greenfield UTO
CITYFLO 650 Brownfield UTO
Urbalis 300 Greenfield UTO with train attendants (Train captains) who drive trains in the event of a disruption.
SelTrac 2020 (Tuen Ma Line Phase 1)2021 (Tuen Ma Line and former West Rail Line)Greenfield (Tai Wai to Hung Hom section only)Brownfield (other sections)STO Existing sections were upgraded from SelTrac IS
SelTrac Greenfield UTO
SelTrac Greenfield STO
Greenfield UTO
SelTrac Greenfield UTO
Urbalis 300 Greenfield UTO
CITYFLO 650 Greenfield UTO
, CITYFLO 650 Brownfield STO
CITYFLO 650 Brownfield UTO
Silom Line, Sukhumvit Line (North section) CITYFLO 450 Brownfield (original line)
Greenfield (Taksin extension)
STO with train attendants who drive trains in the event of a disruption. These train attendants are on standby in the train.
, Greenfield UTO
SelTrac Greenfield STO
Trainguard MT CBTC 69[18] Brownfield STO
SelTrac Greenfield and Brownfield STO
Urbalis 300 Greenfield UTO with train attendants (Rovers) who drive trains in the event of a disruption. These train attendants are also on standby between Botanic Gardens and Caldecott stations.
Greenfield and Brownfield UTO
SelTrac Greenfield UTO
SelTrac Greenfield STO
SPARCS Greenfield ATO
CITYFLO 650 Greenfield DTO
SelTrac Greenfield DTO
Urbalis Greenfield and Brownfield UTO CBTC operates in Lines 1 and 2 and it is being installed in Line 3
Trainguard MT CBTC data-sort-value="9999"Greenfield UTO First UTO line in Latin America
SelTrac Brownfield STO
CITYFLO 650 Brownfield UTO
Urbalis Brownfield STO
CITYFLO 650 STO
CBTC Greenfield STO
SelTrac Greenfield UTO
Sukhumvit Line (East section) CITYFLO 450 Brownfield (original line)
Greenfield (On Nut extension)
STO with train attendants who drive trains in the event of a disruption. These train attendants are on standby in the train.
SelTrac Greenfield UTO
Sirius data-sort-value="0" style="text-align:center;" ? Brownfield STO
Trainguard MT CBTC Brownfield DTO
Sacramento APM CITYFLO 650 Greenfield UTO
CITYFLO 650 STO
Urbalis 888 data-sort-value="2011" Greenfield STO
CBTC Greenfield STO
CBTC data-sort-value="2011"Greenfield STO
UTO
Trainguard MT CBTC Greenfield STO
Trainguard MT CBTC data-sort-value="2012"Greenfield STO
Urbalis 888 Greenfield ATO
SelTrac Greenfield
M5BombardierCityFLO 650Phase 1: 2017Phase 2: 2018GreenfieldUTO
Ankara MetroM1Ansaldo STSCBTCBrownfieldSTO
M2Ansaldo STSCBTCGreenfieldSTO
M3Ansaldo STSCBTCGreenfieldSTO
M4Ansaldo STSCBTCGreenfieldSTO
Urbalis Greenfield STO
Trainguard MT CBTC Brownfield DTO
Various Greenfield A test track was retrofitted in 2012; the line's other tracks will be retrofitted by the early 2020s.
CITYFLO 650 Greenfield UTO
KAFD Monorail CITYFLO 650 Greenfield UTO
Urbalis 2012 20.4 ? Brownfield ATO (GoA 3)
Sirius Brownfield UTO
STO
STO
Sirius data-sort-value="0"Brownfield
Urbalis 888 Greenfield ATO
, Urbalis Greenfield ATO
Ansaldo STS / Siemens Inside RATP's
Ouragan project
data-sort-value="2013"Brownfield STO
SelTrac Brownfield STO
Urbalis 400 76.78 65[19] Brownfield (Finch to Sheppard West)
Greenfield (Sheppard West to Vaughan)
STO CBTC active between Vaughan Metropolitan Centre and Eglinton stations as of October 2021.[20] The entire line is scheduled to be fully upgraded by 2022.[21] [22]
Urbalis 888 Greenfield STO
Sirius Greenfield UTO with train attendants who drive trains in the event of a disruption.
Trainguard MT CBTC data-sort-value="2014" style="text-align:center;" 2013 (M2)
2014 (M4)
Line M2: STO

Line M4: UTO

Urbalis Greenfield STO
SelTrac Brownfield DTO
Trainguard MT CBTC data-sort-value="0"Greenfield and Brownfield STO[23]
Hong Kong MTR SelTrac Brownfield UTO
SelTrac Greenfield UTO
King Abdulaziz APM CITYFLO 650 Greenfield UTO
SelTrac Brownfield STO
Thales[24] SelTrac data-sort-value="9999"Greenfield DTO
SafeNet CBTC Greenfield STO
CITYFLO 650 Greenfield UTO
Nanjing Airport Rail Link SelTrac Greenfield STO
SelTrac Greenfield UTO
Urbalis 888 Greenfield ATO
Urbalis Greenfield ATO
CITYFLO 650 Greenfield UTO
SelTrac Greenfield
Trainguard MT CBTC data-sort-value="2014"Greenfield STO
Urbalis Greenfield and Brownfield STO
Urbalis 888 data-sort-value="2015" Brownfield and Greenfield STO and DTO
Sukhumvit Line (East section) CITYFLO 450 Greenfield STO Samrong extension installation.
L4, L7 Urbalis Greenfield ATO
Line 7, Line 9 CITYFLO 650
Trainguard MT CBTC data-sort-value="2015"Greenfield
CITYFLO 650 Brownfield & Greenfield UTO
Urbalis 888 data-sort-value="2015" Greenfield UTO and STO
Taipei Metro CBTC Greenfield UTO
Urbalis Greenfield STO
Philadelphia SEPTASEPTA Routes 101 and 102CBTCSTO
Greenfield STO with train attendants who drive trains in the event of a disruption. These train attendants are on standby in the train.
Trainguard MT CBTC ? ?
Trainguard MT CBTC TBD TBD
Urbalis 400 Greenfield UTO
L1, L2, L3 SelTrac Greenfield STO
L1 Urbalis 400 Greenfield ATO
SelTrac 46[25] Brownfield and Greenfield STO
SelTrac Brownfield UTO
SelTrac Brownfield UTO
Urbalis Greenfield and Brownfield DTO
SelTrac Brownfield UTO
Trainguard MT CBTC Greenfield STO
Greenfield UTO
Delhi MetroLIne-8Nippon SignalSPARCS2017 (Temp. Driver on Board)2021 (Full ATO Operations)GreenfieldUTO
Urbalis Brownfield UTO
L1 Urbalis Greenfield ATO
Siemens/Thales Trainguard MT CBTC data-sort-value="2017" [26] [27] 309 Brownfield ATO Train conductors will be located aboard the train because other parts of the routes using the Queens Boulevard Line will not be equipped with CBTC.
SelTrac 15.4 15 Greenfield UTO
CBTC Brownfield STO->UTO
Urbalis Greenfield UTO
SelTrac Brownfield UTO[28] with train attendants (Train Captains) who drive trains in the event of a disruption. These train attendants are on standby in the train.
Sukhumvit Line (East section) CITYFLO 450 Greenfield STO Samut Prakarn extension installation.
SelTrac Brownfield (original line)
Greenfield
(Tuas West Extension only)
UTO with train attendants who drive trains in the event of a disruption. These train attendants are on standby in the train.
All lines Trainguard MT CBTC Brownfield STO
L1 SelTrac Greenfield ATO
Siemens/Thales Trainguard MT CBTC data-sort-value="2018" [29] Brownfield ATO Train conductors will be located aboard the train because other parts of the routes using the Eighth Avenue Line will not be equipped with CBTC.
Ottawa Light Rail SelTrac Greenfield STO
All lines Trainguard MT CBTC Brownfield ATO
Trainguard MT CBTC Greenfield UTO
L4, L5 and L6 Urbalis Greenfield ATO
Sosawonsi Co. (Gyeonggi-do) Trainguard MT CBTC ATO
Trainguard MT CBTC Brownfield & Greenfield STO with train attendants who drive trains in the event of a disruption.
Sukhumvit Line (North section) CITYFLO 450 Greenfield STO Phaholyothin extension installation.
TBD TBD TBD
Trainguard MT CBTC greenfield STO
SPARCS Greenfield UTO
SPARCS Greenfield STO
Urbalis Greenfield ATO
SelTrac 21.7 22 Greenfield UTO
Urbalis 400 Brownfield UTO
Urbalis 400 Greenfield UTO
CITYFLO 650 Greenfield UTO
Trainguard MT CBTC Greenfield UTO
Trainguard MT CBTC Brownfield STO
Bucharest MetroLine M5AlstomUrbalis 40020206.913STOTo be fully operational after the delivery of the 13 Alstom Metropolis BM4 trains.
CBTC Brownfield STO
CITYFLO 650 Greenfield UTO
Trainguard MT CBTC Brownfield STO
CITYFLO 650 Greenfield UTO
SelTrac Brownfield STO
CBTC Greenfield STO
SelTrac Greenfield UTO under construction
Brownfield STO CBTC only available between West Footscray and Clayton stations
SPARCS Greenfield UTO under construction
Tokyo Metro Marunouchi Line[30] ? data-sort-value="9999" style="text-align:center;" 2023 Brownfield ?
? ? data-sort-value="9999"Brownfield ?
SeoulSillim Line
? ? data-sort-value="9999"? Brownfield ?
SelTrac Brownfield UTO
Guangzhou Metro Trainguard MT CBTC data-sort-value="9999" style="text-align:center;" ? ?
SelTrac Greenfield DTO
Marmaray Lines Commuter Lines Sirius data-sort-value="9999" style="text-align:center;" ? ? Greenfield STO
Jōban Line[31] SelTrac data-sort-value="9999" Brownfield STO The plan was abandoned because of its technical and cost problems; the control system was replaced by ATACS.[32]
Advanced SelTrac 2025-2029 Brownfield STO & DTO
IND Crosstown Line[33] SelTrac 309 Brownfield STO
Ahmedabad MEGA Nippon Signal SPARCS ? ? ?
LahoreOrange LineAlstom- CascoUrabliss88820202727 (CRRC)GreenfieldATO

Notes and references

Further reading

Notes and References

  1. 1474.1–1999 – IEEE Standard for Communications-Based Train Control (CBTC) Performance and Functional Requirements.https://ieeexplore.ieee.org/document/815310 (Accessed at January 14, 2019).
  2. Digital radio shows great potential for Rail http://findarticles.com/p/articles/mi_m0BQQ/is_5_41/ai_80931845/ Bruno Gillaumin, International Railway Journal, May 2001. Retrieved by findarticles.com in June 2011.
  3. March 29, 2018 . Bombardier Marks 15th Anniversary of Its World-First Radio-Based, Driverless Rail Control System . Bombardier Transportation . MarketWired . January 22, 2019 . https://web.archive.org/web/20190122095005/http://www.marketwired.com/press-release/bombardier-marks-15th-anniversary-its-world-first-radio-based-driverless-rail-control-tsx-bbd.a-2246505.htm . January 22, 2019.
  4. CBTC Projects. http://www.tsd.org/cbtc/projects/index.htm www.tsd.org/cbtc/projects, 2005. Accessed June 2011.
  5. CBTC radios: What to do? Which way to go? http://www.tsd.org/papers/CBTCRadios.pdf Tom Sullivan, 2005. www.tsd.org. Accessed May 2011.
  6. Book: Subset-023. "ERTMS/ETCS-Glossary of Terms and Abbreviations". ERTMS USERS GROUP. 2014. 2018-12-21. https://web.archive.org/web/20181221134721/https://www.era.europa.eu/node/641/210_en. 2018-12-21. dead.
  7. IEC 62290-1, Railway applications – Urban guided transport management and command/control systems – Part 1: System principles and fundamental concepts.http://webstore.iec.ch/webstore/webstore.nsf/ArtNum_PK/36384?OpenDocument IEC, 2006. Accessed February 2014
  8. CITYFLO 650 Metro de Madrid, Solving the capacity challenge.http://Bombardier.com/files/en/supporting_docs/RCS_Case_Study_Metro_Madrid_en.pdf Bombardier Transportation Rail Control Solutions, 2010. Accessed June 2011
  9. Madrid's silent revolution.http://goliath.ecnext.com/coms2/gi_0199-12316026/Madrid-s-silent-revolution-the.html in International Railway Journal, Keith Barrow, 2010. Accessed through goliath.ecnext.com in June 2011
  10. Semi-automatic, driverless, and unattended operation of trains.http://www.irse-itc.net/index.php?option=com_content&view=article&id=85:semi-automatic-driverless-and-unattended-operation-of-trains&catid=36:published-itc-publications&Itemid=29 IRSE-ITC, 2010. Accessed through www.irse-itc.net in June 2011
  11. CBTC: más trenes en hora punta.http://www.madrid.org/cs/Satellite?c=CM_InfPractica_FA&cid=1142612783785&idTema=1142598699551&language=es&pagename=ComunidadMadrid%2FEstructura&perfil=1273044216036&pid=1273078188154 Comunidad de Madrid, www.madrig.org, 2010. Accessed June 2011
  12. How CBTC can Increase capacity – communications-based train control. http://findarticles.com/p/articles/mi_m1215/is_4_202/ai_75214234/?tag=mantle_skin;content William J. Moore, Railway Age, 2001. Accessed through findarticles.com in June 2011
  13. ETRMS Level 3 Risks and Benefits to UK Railways, pg 19 https://web.archive.org/web/20110204131707/http://www.trl.co.uk/downloads/general/20100929_ERTMS_Level_3_Final_Report.pdf Transport Research Laboratory. Accessed December 2011
  14. ETRMS Level 3 Risks and Benefits to UK Railways, Table 5 https://web.archive.org/web/20110204131707/http://www.trl.co.uk/downloads/general/20100929_ERTMS_Level_3_Final_Report.pdf Transport Research Laboratory. Accessed December 2011
  15. ETRMS Level 3 Risks and Benefits to UK Railways, pg 18 https://web.archive.org/web/20110204131707/http://www.trl.co.uk/downloads/general/20100929_ERTMS_Level_3_Final_Report.pdf Transport Research Laboratory. Accessed December 2011
  16. CBTC World Congress Presentations, Stockholm, November 2011 https://web.archive.org/web/20120303131523/http://www.cbtcworldcongress.com/presentations Global Transport Forum. Accessed December 2011
  17. Bombardier to Deliver Major London Underground Signalling.http://www.bombardier.com/en/transportation/media-centre/press-releases/details?docID=0901260d80181411 Press release, Bombardier Transportation Media Center, 2011. Accessed June 2011
  18. This is the number of four-car train sets available. The BMT Canarsie Line runs trains with eight cars.
  19. Web site: Service Summary. Toronto Transit Commission.
  20. 1444431122998431746 . TTCStuart . This weekend's scheduled #TTC subway closure is now over and full service has resumed. Crews have completed the work on this phase of the new Automatic Train Control signaling system on Line 1. ATC now operating Vaughan MC to Eglinton. . Stuart Green . 2021-10-02.
  21. Web site: New signal system is three years behind schedule and $98M over budget: report. Fox. Chris. 2019-04-05. CP24. en. 2019-04-10.
  22. Web site: Modernizing the signal system: 2017 subway closures. January 18, 2017. Toronto Transit Commission. January 23, 2017. [video position 1:56]Trains will be able to operate as frequently as every 1 minute and 55 seconds instead of the current limit of two and a half minutes. [2:19]When installation is completed along the entire line in 2019, it will allow for as much as 25% more capacity. [2:33]ATC will come online on all of Line 1 in phases by the end of 2019 starting with the portion of Line 1 between Spadina and Wilson stations and with the Line 1 extension into York Region that opens at the end of this year..
  23. Helsinki Metro automation ambitions are scaled back. Urban Rail News Railway Gazette International 2012
  24. Web site: Thales awarded signalling contract for new Salvador metro . Thales Group . 2014-03-24 . 2019-05-09.
  25. This is the number of eleven-car train sets available. The IRT Flushing Line runs trains with eleven cars, though they are not all linked together; they are arranged in five- and six-car sets.
  26. Work being done in phases; the main phase between 50th Street and Kew Gardens–Union Turnpike stations was completed in 2022
  27. Includes a 1.48 km "express bypass" where non-stopping express trains take a different route than stopping local trains.
  28. News: Cheng. Kenneth. 2017-04-12. Full-day signalling tests on North-South Line to start on Sunday. TODAY Online. en. 2022-05-22.
  29. Work being done in phases; the first phase is between 59th and High Street stations.
  30. https://news.mynavi.jp/article/20180222-587991/ 三菱電機、東京メトロ丸ノ内線に列車制御システム向け無線装置を納入
  31. Web site: JR East selects Thales to design first Japanese CBTC . Briginshaw . David . January 8, 2014 . hollandco.com . Holland . January 9, 2014.
  32. Web site: https://www.nikkan.co.jp/articles/view/00446042 . ja:首都圏のICT列車制御、JR東が海外方式導入を断念-国産「ΑTΑCS」推進. 12 January 2018. Nikkan Kogyo Shimbun . ja.
  33. Web site: Artymiuk . Simon . MTA awards Crosstown Line CBTC contract to Thales and TCE . International Railway Journal . March 7, 2023 . August 4, 2024.