NEW DELHI (Metro Rail News): Automatic train control (ATC) is a broad category of railway train protection systems that incorporates a speed control mechanism in response to external inputs. For example, if the driver does not respond to a danger signal, the system may apply the emergency brakes. ATC systems typically incorporate multiple cab signalling mechanisms and use more granular deceleration patterns rather than the rigid and stiff stops witnessed with former automatic train stop (ATS) technology. ATC, which can also be utilised with automatic train operation (ATO), is typically regarded as the most crucial safety component of a railway system.
Over time, there have been various alternative ‘automatic train control’ safety systems. The Great Western Railway developed the first experimental machinery on the Henley branch line in January 1906, although it is now been designated as an automated warning system (AWS) because the driver retained full control of braking. The word is notably common and prevalent in Japan, where ATC is used as a replacement for ATS on all Shinkansen (bullet train) lines and several conventional rail lines.
Analogue ATC
ATC-1, ATC-2, ATC-3 (WS-ATC), ATC-4 (CS-ATC), ATC-5, ATC-6, ATC-9, ATC-10 (New CS-ATC), ATC-L are the various types of Analogue ATC mostly used on high-speed metro lines.
Digital ATC
The digital ATC system detects the presence of a train in the section using track circuits and then transmits digital data from wayside equipment to the train on the track circuit numbers, the number of clear sections (track circuits) to the next train ahead, and the platform that the train will arrive at. The received data is compared to track circuit number information kept in the train’s onboard memory, and the distance to the next train ahead is calculated. Data about track grades and speed limits across curves and points are also saved in the onboard memory. All of the aforementioned data is used by ATC to make decisions and make judgements about managing the service brakes and stopping the train.
The running pattern defines the braking curve to stop the train before it enters the next track section occupied by another train in a digital ATC system. When the train approaches the braking pattern, an alarm rings, and the brakes are applied if the braking pattern is exceeded. The brakes are applied mildly at first to improve ride comfort, then more forcefully until the desired deceleration is achieved. When the train speed reduces to a predefined speed below the speed limit, the brakes are applied more lightly. By controlling the braking force in this manner, the train can decelerate in accordance with the braking pattern while maintaining riding comfort.
There is also an emergency braking pattern outside of the standard braking pattern, and the ATC system deploys the emergency brakes if the train speed exceeds this emergency braking pattern. There are several advantages to using a digital ATC system:
The use of one-step brake control allows for high-density operations because there is no idle running time owing to operating delay between brake releases at the intermediate speed restriction stage.
Trains can operate at their maximum speed without having to begin early deceleration because braking patterns for any type of rolling stock can be developed based on data from wayside equipment indicating the distance to the next train ahead. This allows for the combined running of express, local, and goods trains on the same track at maximum possible speed.
When running faster trains in the future, there is no need to replace the wayside ATC equipment.
To date, the following digital ATC systems are used:
D-ATC: Some East Japan Railway Company (JR East) lines use it on non-high-speed routes. The abbreviation stands for Digital ATC. The key difference between this and prior analogue ATC technology is the transition from ground-based control to train-based control, which allows braking to reflect each train’s ability while also enhancing comfort and safety. Its ability to enhance speeds and provide denser timetables is vital for Japan’s congested railways. D-ATC is utilised with the Taiwan High Speed Rail’s THSR 700T, which debuted in early January 2007.
DS-ATC: Implemented on JR East’s Shinkansen routes. Digital communication and control for Shinkansen-ATC. The Thoku Shinkansen, Hokkaido Shinkansen, Joetsu Shinkansen, and Hokuriku Shinkansen all use it.
RS-ATC: As a fallback level from DS-ATC, it is used on the Tohoku, Hokkaido, Hokuriku, and Jetsu Shinkansen. In essence, RS-ATC is similar to GSM-R in that radio signals are used to manage train speed limits, as opposed to trackside beacons and/or transponders on other types of ATC.
ATC-NS: ATC-NS (ATC-New System) is a digital ATC system based on DS-ATC that has been used on the Tkaid Shinkansen since 2006. The Taiwan High Speed Railway and the San’y Shinkansen both use it.
KS-ATC: Since 2004, it has been used on the Kyushu Shinkansen. Kyushu Shinkansen-ATC is an abbreviation for Kyushu Shinkansen-ATC.
ATACS
ATACS is a CBTC-style moving block ATC system designed by RTRI and first installed by JR East on the Senseki Line in 2011, followed by the Saiky Line in 2017, the Koumi Line in 2020, and the Jban Line local tracks in 2021. It is regarded as Japan’s equivalent to ETCS Level 3.
The ATC system in various metro and rail systems:
Japan: The Automatic Train Control (ATC) system was developed in Japan for high-speed trains such as the Shinkansen, which run at such a pace that the driver has almost no time to perceive and acknowledge trackside signs. Despite the fact that the ATC system delivers AF signals, including information regarding the speed limit for each track section along the track circuit. When these signals are received on board, the train’s current speed is compared to the speed limit, and if the train is travelling too fast, the brakes are immediately applied. As soon as the train slows below the speed limit, the brakes are released. This technology provides a higher level of safety by preventing collisions caused by driver error, hence it has been placed on heavily used lines such as Tokyo’s Yamanote Line and some underground lines.
Although the ATC automatically applies the brakes when the train exceeds the speed limit, it cannot adjust the motor power or train stop position when approaching stations. However, the automatic train operation (ATO) system can handle station departure, speed between stations, and stop position in stations automatically. Some subways have it installed. However, ATC has three drawbacks. First, the idle running time between releasing the brakes at one speed limit and applying the brakes at the next slower speed limit prevents the headway from being extended. Second, the brakes are deployed as the train reaches top speed, resulting in a less comfortable ride. Third, if the operator wishes to run faster trains on the line, all essential roadside and on-board equipment must first be replaced.
Denmark: Denmark’s system of ATC (officially designated ZUB 123) is different from that of its neighbours. From 1978 until 1987, the Swedish ATC system was trialled in Denmark, and a new Siemens-designed ATC system was implemented between 1986 and 1988. As a consequence of the Sorø railway accident, which occurred in April 1988, the new system was progressively installed on all Danish main lines from the early 1990s onwards. However, all systems are now been gradually replaced by the modern and worldwide CBTC signalling standard as of 2023.
Norway: Bane NOR, the Norwegian government’s railway infrastructure organisation, uses the Swedish ATC system. Trains, in general, can cross the border without being properly modified. However, unlike in Sweden, the ATC system used in Norway distinguishes between partial ATC, which ensures that a train stops whenever a red signal is passed, and full ATC (FATC), which ensures that a train does not exceed its maximum allowed speed limit in addition to preventing overshooting red signals. In Norway, a railway line can have either DATC or FATC installed, but not both at the same time. ATC was initially tested in Norway in 1979, four years after the Tretten train tragedy, which was triggered by a signal passed at risk (SPAD). Between 1983 and 1994, DATC was first deployed on the segment Oslo S – Dombs – Trondheim – Grong, and FATC was first implemented on the Ofoten Line in 1993. FATC has been used on the high-speed Gardermoen Line since its inception in 1998. Following the tragic disaster in 2000, the Rros Line’s development of DATC was accelerated and intensified, and it became operational in 2001.
Sweden: ATC development in Sweden began in the 1960s (ATC-1) and was formally implemented in the early 1980s alongside high-speed trains (ATC-2/Ansaldo L10000). However, as ATC-2 is generally incompatible with ERTMS/ETCS (as is the case with the Bothnia Line, Sweden’s first railway line to use ERTMS/ETCS), and with Trafikverket’s ambition of eventually replacing ATC-2 with ERTMS/ETCS over the next few decades, a Special Transmission Module (STM) has been developed to automatically switch between ATC-2 and ERTMS/ETCS.
The United Kingdom: The Great Western Railway in the United Kingdom developed a technology known as ‘automatic train control’ in 1906. GWR ATC is referred to as an automatic warning system (AWS) in modern context and terminology. This was an intermittent train protection system that relied on an electrically energised (or de-energised) rail that ran between and above the running rails. This rail was called as an ATC ramp because it sloped at each end and made contact with a shoe on the underside of the passing locomotive. The ramps were available at distant signals. However, a version of the design intended for use at stop signs was never realised.
Canada: The Toronto Transit Commission began implementing ATC on Line 1 Yonge-University in 2017, at a cost of $562.3 million. With the contract awarded to Alstom in 2009, the TTC is now able to shorten the headway between trains on Line 1 during rush hours and increase the number of trains operating on Line 1. ATC was implemented in stages, commencing with a test between Dupont and Yorkdale stations in November 2017. It was first introduced permanently in December, 2017, with the opening of the Toronto-York Spadina subway line between Vaughan and Sheppard West stations. The technology was installed on the remaining sections of the line during weekend closures and at night when the subway remained closed. The project had delays, with schedules for the complete conversion of Line 1 being pushed back several times until 2022. The Finch station’s ATC upgrade was completed in September 2022.
Converting Line 1 to ATC necessitated the construction of 2,000 beacons, 256 signals, and over one million feet of wire. ATC is also scheduled to be deployed on the soon-to-be-opened Line 5 Eglinton line; however, unlike Line 1, the system on Line 5 will be provided by Bombardier Transportation and will use its Cityflo 650 technology. The TTC intends to convert Line 2 Bloor-Danforth and Line 4 Sheppard to ATC in the future, subject to budget availability and the ability to replace non-ATC compatible trains on Line 2 with trains that are, with a completion date of 2030.
The United States: In the United States, ATC systems are nearly commonly integrated with existing continuous cab signalling systems. The ATC is supported by electronics in the locomotive that apply some type of speed control based on cab signalling system inputs. An overspeed alarm sounds in the cab if the train speed exceeds the maximum speed allowed for that section of track. If the engineer fails to lower speed and/or apply a brake to reduce speed, a penalty brake application is automatically applied. Due to the sensitive handling, delicate manoeuvring and control concerns with North American freight trains, ATC is almost exclusively deployed in passenger locomotives in both intercity and commuter service, with freight trains using cab signals without speed control. Some high-volume passenger railroads, such as Amtrak, Metro North, and the Long Island Rail Road, require freight trains that run on all or part of their networks to use speed control.
While cab signalling and speed control technology have been around since the 1920s, ATC deployment became a concern after a series of major incidents several decades later. After a pair of fatal accidents caused by ignored signals, the Long Island Rail Road introduced its Automatic Speed Control system within its cab-signalled region in the 1950s. Following the Newark Bay Lift Bridge disaster, New Jersey mandated the use of speed control on all major passenger rail operators inside the state. While speed control has been implemented on many passenger lines in the United States, it is usually voluntary on the part of the railways that own the lines.
India: The Delhi Metro Rail Corporation (DMRC) introduced the country’s first Train Control and Supervision System. It is the nation’s first in-house designed Train Control and Supervision System. It is a computer-based system that manages and supervises train operations, including basic functions such as commencing, accelerating and stopping. The DMRC and Bharat Electronics Limited (BEL) collaborated to build the i-ATS as part of the Government of India’s ‘Make in India’ and ‘AatmaNirbhar Bharat’ Metro Rail Transit System projects. The system has been developed to reduce and lower the metro’s reliance on foreign vendors for metro operations. With this accomplishment, the country has taken a significant step towards developing an indigenously developed CBTC (Communication-Based Train Control)-based signalling system for the Metro line.
The i-ATS technology has been designed to be adaptable enough to interact with the systems of other signalling vendors with little modifications. Because the ATS is an integral component of the CBTC signalling system, the invention of i-ATS is a big step forward in the CBTC (Communication Based Train Control) signalling system for metro railways. With the introduction of i-ATS, India became the sixth country after France, Germany, Japan, Canada, and China to have its own ATS products. Additionally, Indian Railways has created its own automatic train protection system known as ‘Kavach’ to improve the safety of moving trains.
The Research Design and Standards Organisation (RDSO) developed Kavach in collaboration with three Indian manufacturers. When a loco pilot jumps a signal (Signal Passed at Danger – SPAD), which is one of the primary reasons of train collisions, the ‘Kavach’ system alerts. When it detects another train on the same line within a certain distance, the system can immediately inform the loco pilot, take control of the brakes and bring the train to a halt. The Kavach system has been developed to assist loco pilots not just in avoiding signal passing at risk and over-speeding, but also in train operation during bad weather such as dense fog. As a result, Kavach is expected to improve the safety and efficiency of train operations.
Kavach trials were undertaken on the South Central Railway’s Lingampally-Vikarabad-Wadi and Vikarabad-Bidar sections, covering a distance of 250 km. Three vendors have been recognised and approved for additional developmental orders on the Indian Railways network following satisfactory trials. The total amount spent on the development of Kavach is Rs 16.88 crore. Kavach has been planned to be installed on the New Delhi-Howrah and New Delhi-Mumbai sections, with a completion deadline of March 2024. The initial implementation’s experience will be used to guide future expansion.
Conclusion
Thousands of people use railways to travel from city to city, across huge landscapes with abundant countryside. Nowadays, railway operators are collaborating with technology to realise intelligent railway operations, allowing them to do more than just monitor rolling stock status and passenger and equipment safety. Transport operators dedicate a significant amount of time and effort to examine and analyse potential hazards in order to proactively schedule preventive maintenance in terms of railway safety, cost, and operational efficiency. In recent times, the majority of these are handled by an automatic train control (ATC) system. It needs to be emphasised that an automated train control (ATC) system integrates all important and non-vital operations that ensure train safety. It is divided into three subsystems, which include onboard and off-board equipment:
- Automatic Train Supervision (ATS)
- Automatic Train Operation (ATO)
- Automatic Train Protection (ATP)
Together with a full interlocking system, these sub-systems accomplish the following functions:
- Signalling
- Automatic train protection
- Traffic management
Automatic train control encompasses automatic train operation functions as well. This comprises a number of rail components that must work in conjunction with and in close proximity to automatic train control systems. The Auxiliary Power System, Train Status, Railway Track Status, and Wayside Signal Status are all important components of on-train safety monitoring system coverage. On-train management systems must have the following secure and fault-resistant capabilities to achieve any time, all year round, rolling stock, wayside, signal, power, obstacle detection, monitoring, and data collection.
Sensing: Enables and allows real-time rolling stock motoring of pantographs, bogies, train axles, wheels, and important equipment on the wayside, such as signals and the tracks. For diagnostics and prognostics, acquires and collects data on distances, speeds, inclinations, curvatures, and horizontal/vertical parameters.
Diagnostics: To achieve 24/7 rolling stock monitoring, the onboard subsystem must have both measurement and diagnostic capabilities, as well as dependable connectivity to transmit diagnostic results to the cloud or data centre for synchronisation with trackside diagnostic devices.
AI scalability: As railway transportation trends towards autonomous operations, systems require extremely reliable automation solutions. Advanced wireless technologies transfer on-train data, pictures, images and video to control centres for real-time analysis by high-end AI capable of making quick decisions and taking action.
Wireless Expandability: The system may figure out potentially abnormal instances where some maintenance may be required, and engineers can know the specific place where tracks need to be repaired through the use of on-train technologies to monitor equipment status and track location through GPS. This is where high-speed, low-latency wireless networking comes into play. Additionally, the various other on-train solutions for secured railway transportation are as under:
Railway Power Supply Monitoring: This is accomplished using a pantograph monitoring system. Data collected from cameras and sensing devices can be collected, analysed, monitored, and stored by a pantograph monitoring system. The data is then graphically shown so that operators can dynamically analyse the health of the equipment and report any irregularities.
On-board Train Safety Protection: For on-board train safety protection assessments, axle box vibration and a train track switching monitoring system are used. Data from axle boxes, locomotive adhesion coefficients, and railway track switching sites are collected, stored, and analysed by an axle box and train track switching monitoring system. The data can be used to generate diagnostic reports in order to keep trains running. The solution eliminates the high expense and risk associated with manual human investigation while also achieving the goal and purpose of predictive maintenance.
Rail Track Monitoring: Intelligent software and hardware solutions collect and analyse data from rail tracks, allowing maintenance teams to troubleshoot, repair, and schedule preventive maintenance. Data can even be utilised to improve driving behaviour, equipment efficacy, and overall railway safety, operations, and scheduling efficiency.
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