Breakthrou Breakthroughs in Japanese Railways

Breakthroughs in Japanese Railways 2 Learning from Past Railway Accidents—Progress of Train Control Masayuki Matsumoto

To solve this drawback, a new ATS-P Introduction Overview system was brought into service. With ATS-P, the train speed is constantly The earliest railways had no signal Figure 1 shows the progress of train checked against a speed pattern to bring systems, so station employees had to use control systems. Since it was quickly the train to a halt at a stop signal. The hand gestures to train drivers indicating realized that directing trains using signals ATS-P sends digital data about the distance whether to stop or go on. Even so, there (hand, semaphore, lamp, etc.) alone could to stop signals by transponder to on-board were still many train collisions because not stop train accidents, cab warning equipment which checks the train speed drivers missed or ignored the hand signals devices indicating to the train driver that pattern against a reference model and due to human error. The race was on to the train was approaching a stop signal automatically applies the train brakes if develop fool-proof signalling system that soon came into common use but even so, the train speed exceeds the pattern. Since could prevent train accidents. However, train accidents ascribable to driver the system reduces the number of braking it was more like an arms race because as oversight occurred from time to time. To stages, train headways can be shortened soon as a new system was introduced to solve this problem, automatic train stop to improve train operation efficiency. prevent one type of accident, another (ATS) systems—which took the driver However, on high-speed sections with accident caused by another type of error partly out of the equation by adding the trains operating at very short headways, required yet another new system. This ability to stop the train automatically— failure to respond to any signal aspect for race has culminated in today’s almost were added to the cab warning system. any reason can lead to a very serious accident-proof train-control systems, but In this design, the ATS halts the train by collision within seconds. Therefore, even so, new train control systems are still automatically applying the service brakes another system that continuously displays being developed with the focus on if the driver overlooks or disregards a permitted speeds on an in-cab monitor improving operation efficiency and warning signal in the cab. But there was and automatically applies the service passenger services quality. one clear drawback, once the driver brakes was needed. Today, this is called This article describes the development acknowledges the in-cab warning (usually automatic train control (ATC); it was g and improvement of train control by pressing a confirm button), the introduced first in late 1960s on the systems to prevent train accidents, with automatic stop system is overridden and Tokaido Shinkansen where trains were a focus on the train operation mode and the train can proceed, so if the driver running faster than 200 km/h because related technologies. confirms the warning by mistake, a drivers could not safely recognize hs collision can still occur. trackside signal aspects and could not respond quickly enough even when they saw the signals. Figure 1 Progress of Train Control Systems Some time slightly before the debut of ATC

1950 1960 1970 1980 1990 2000 on the Tokaido Shinkansen, the Hibiya

ATS subway line in Tokyo introduced a Cab warning device ATC trackside signal-based ATC system—the Type-A cab warning ATS-A ATS-SN result of R&D into automatic train device ATS-ST Type-B cab warning operation—to improve train safety and device ATS-B ATS-SW operational efficiency. Then an in-cab Type-C cab warning ATS-S device signal-based ATC system to prevent driver Frequency- shift type Transponder-type ATS-P mistakes was put into service on the ATS-P ATS-Ps Nagoya subway. This was soon followed by an installation on the Joban Line of ATC Japanese National Railways (JNR) to D-ATC support through operation with the DS-ATC Chiyoda subway line. KS-ATC ATC is a continuous control system that ATC-NS has improved the safety of train operation ATACS much more than ATS, which is an intermittent control system. This is largely

86 Railway & Transport Review 43/44 • March 2006 because ATC assures safe train operation wireless train control system (ATACS) set at right angles to the line (unseen from even if the driver misreads a traffic signal. using digital radio, computer and the train) to indicate danger, and parallel In ATC, the trackside equipment transmits information technologies (IT) that adopts to the line to indicate safe. This device an ATC signal matching the control train a new framework for trackside and on- evolved into the three-aspect semaphore speed to the track circuit and the on-board board equipment functions. signal, indicating danger, caution, and safe equipment receiving the ATC signal by setting a rectangular board at various displays the signal on the monitor and Railways and Signals angles. The semaphore signal soon slows the train according to the signal. —Human Errors became widespread in Japan. However, ATC is relatively old technology Various other safety devices were invented that was developed during the early stages In 1804, the Cornishman Richard in quick succession, including equipment of the Tokaido Shinkansen and has Trevithick built the first steam locomotive preventing entry of more than one train problem, including inability to cope with to run on rails, marking the start of into a tunnel at one time, the fixed block increasing numbers of trains. railways. In 1814, the English engineer for preventing train collisions, and the The ideal train control system would George Stephenson built an improved track circuit for detecting trains. All determine the distance to the position steam locomotive and spent a great deal contributed to much-enhanced train where the train must stop—the only of effort constructing a 40-km line from safety and many present signal systems are information needed to prevent a collision Stockton to Darlington. The line was still based on the core concepts of those with the ahead train—and stop the train finally completed in 1825 with the 19th century technologies. there safely. In this case, the basic successful operation of Locomotion When Japan’s first railway opened required system information is the current hauling freight trains. The world’s first between Shimbashi and Yokohama, 16 exact train position and exact position commercial passenger railway was semaphore signals of two types were where the train must stop. opened in 1830 between Liverpool and installed: station semaphores (one pole Reconsideration of the purpose of Manchester. A signal system was with two arms), and distant semaphores conventional train control systems led to introduced years later to passenger lines (one pole with one arm), each with three new decisions on the basic functions of a to secure safe train operation and handled aspects. The arm face was red and the new train control system where the increasing traffic volumes. back was white. An upright aspect (with trackside equipment transmits the position Japan’s first 29-km government railway white lamp at night) indicated safe, a 45° where the train must stop to the on-board opened between Shimbashi and downward tilt (with green lamp at night) equipment, which determines the current Yokohama in 1872. It was soon followed indicated caution, and a horizontal position of the train and calculates the by rapid expansion throughout the position (with red lamp at night) distance to the stop position. The system country— despite some local indicated danger. applies the train brakes as necessary at opposition—and railways played a curves and on down grades. These are leading role in the government’s ‘rich Operations mistakes and the operation principles of the newly country, strong arms’ policy. accidents developed digital ATC (D-ATC). The world’s first railway accident occurred Existing train control systems have been Early railway signals at Parkside Station in England in in long use and boast high degrees of In the first days, a man on horseback rode September 1830 when a Member of safety. At the same time, they have in front of the train waving a flag to warn Parliament who had helped establish the contributed to better track utilization. people that the train was approaching. As railway company was hit by a train as he However, some of the technologies, such speeds increased along with more trespassed on the track. Many accidents as detection of train position using track junctions, a guard was stationed at each occurred in following years. In Japan, the circuits and transmission of data to the on- critical point to ensure safety using three first railway accident was a derailment board equipment via the rail, are very old. hand gestures: danger (both hands raised and overturned train caused by some There has been recent remarkable above head); caution (one arm raised problems with a turnout in the Shimbashi progress in mobile communications and above head); and safe (one arm stretched Station yard on 11 September 1874. In computer technologies which can be used out sideways). Some time later, a those days, train operation were for train control systems to reduce the permanent signal consisting of an upright controlled by telegraph communications amount of ground equipment and cut pole, crosspiece and lamps was installed between stationmasters. After a head-on costs. Therefore, we are developing a new at each critical point. The crosspiece was collision caused by one train departing

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before the stationmaster gave the equipment, was tested at Yurakucho Accident at Rokken Station and departure signal, the staff-and-ticket block Station in January 1933. However, there cab warning system system, which permits only one train in were also plans to increase capacity by Rear-end train collisions were common one-track section, was introduced earlier quadrupling this section, so the ATS after the war, especially on electrified than planned. In another accident, a train project was abandoned. sections. The April 1947 collision ran from a side track onto the main track Following this, the government railways between commuter trains near Tabata of a single-track section to collide with tested a cab signal system on the Kikuna– Station on the Tohoku Line caused 118 another train. This accident led to the Kozukue section of the casualties. Many of those accidents were development of the safety siding system, and the Hodogaya–Totsuka sections of the ascribed to stop-signal violations by which derails an over-running train rather Tokaido Line. In February 1937, a simpler careless or overstrained crews. Clearly, than let it trespass onto the main track—a cab warning system was tested on the development of a cab warning system was system that is still used today. After Tokamachi Line. It issued a warning to an urgent priority. Around 1950, studies another head-on collision between the train crew when the home or distance were started on devices for preventing opposite trains in a single-track section signal could hardly be seen in heavy fog rear-end collisions on electrified sections. was caused by the illegal issuance of a or snow. The study showed a cab warning system tablet, the block equipment was modified When a 3-minute headway was planned would be effective for preventing rear-end to prevent tampering. for the Kanmon Tunnel (opened June collisions on commuter sections As described, each of the many railway 1942), a combination of a closing-in characterized by short block lengths and accidents in the 19th and early 20th system and ATS system was tested on the high-density operations. century was followed by an improvement Shonan section of the Tokaido Line in July Therefore, the newly formed JNR to the signal system. Nevertheless, railway 1940. After good results, in December developed a cab warning system using accidents still occurred from time-to-time. 1942, it was decided to introduce the current in the track circuit at commercial combined system on the Tokaido, Sanyo, frequency. A relay circuit is connected to Evolution from Cab and Kagoshima lines as well as several the sending end of a conventional track Warning to ATS-P electric railways in Tokyo and Osaka. circuit. When the relay detects that a train However, after most of the ground is approaching the braking point side of a Early cab warning devices equipment and scores of on-board units stop signal, the current from the track The 1920s to 1940s in Japan saw testing had been installed, they were destroyed circuit is interrupted, issuing a warning to and development of cab warning devices by air raids and the project did not come train crew. Consequently, when the track that eventually evolved into ATC devices. to fruition. circuit becomes ‘no current,’ the main In 1921, the magnetic induction type ATS In January 1947, testing of the same relay of the on-board equipment opens (using permanent magnets on sleepers) magnetic-induction type intermittent cab and a warning is issued to the crew. The developed in the United States was tested warning system tested in 1937 was system was called the continuous on the Shinagawa–Shiodome section of resumed at Minakami Station on the Joetsu induction Type-B cab warning system the Tokaido Line. Some time later, Line. The on-board equipment was using vacuum tubes. It was put into use similar ATS tests were made on the composed of a pickup coil excited by a in December 1954 on the electrified Tsukaguchi–Kanzaki (now Amagasaki) DC power supply and a main relay sections of the and Keihin section of the Amagasaki Line belonging connected in series with the pickup coil Tohoku Line. to Hankyu Railway, and the Kikuna– and operating at all times. The trackside About 2 years later on 15 October 1956, Kozukue section of the government equipment was a coil called an inductor. a collision between trains at Rokken railway’s Yokohama Line. Around 1930, The pickup coil and inductor were Station on the Sangu Line killed 42 to meet the need for higher-density train arranged so that they coupled outside the passengers and injured 94. The accident operations, the government railways track gauge. When the pickup coil occurred because the driver of the down considered operating trains at a headway coupled while the inductor coil was open, train misunderstood that his train, which of 90 s on the Tabata–Tamachi section the main relay tripped, issuing a warning had already passed Rokken Station—the shared by the Keihin Line and the to the driver. However, MacArthur’s station where it passed the up train—had Yamanote Line. To that end, the trip arm General Headquarters (GHQ) rejected a been changed from Matsuzaka Station to type ATS, which mechanically transmits request for permission to continue Rokken Station and entered the safety the signal aspect to the on-board construction and work had to stop. siding where it collided with the up train.

88 Japan Railway & Transport Review 43/44 • March 2006 Figure 2 Operating Principle of Cab Warning System

Relay Red Since many of the victims were school frequency-shift type, and the On-board lamp equipment students on a trip, the accident was a great absorption type. shock to Japanese society. In the The former type consists of a ground- 105 kHz accident’s wake, JNR decided to adopt a based resonance circuit and an on- L1 L2 Trackside coil new cab warning system that gave an board special feedback oscillation Signal S aspect C audible stop signal to the driver. At the circuit. It utilizes the phenomenon in 130 kHz same time, JNR pressed ahead with which the normal oscillation frequency automation of signal devices and use of (105 kHz) changes to the resonance coloured lamps for signalling. frequency (130 kHz) of the trackside train brakes automatically unless the The Type-B cab signal system developed coil when the pickup coil couples with driver pressed the confirm button within for electrified sections with a fixed braking the trackside coil as the ground circuit 3.5 s after the warning. The other had distance is unsuitable for sections serving is short-circuited or opened. train identification and speed check trains with different braking distances. As The latter type uses the same trackside coil functions; both were tested on the JNR a result, JNR studied two new types of cab as the frequency-shift type, but is based Chuo Line in March 1959 with good signal systems: the Code Type using on the principle that the oscillation stops results (Table 1). In particular, the several different code currents obtained when the trackside coil couples with the operation principle of the latter prototype by turning an AC current off and on, and pickup coil. Prototype systems were was applied to the design of an ATS for the Track Circuit Type, passing a frequency subjected to various tests and the implementing through services on the of about 1 kHz to the track circuit. frequency shift type was found to be Keihin Electric Express Line, Tokyo Metro Eventually, the latter type was adopted due superior in terms of stability, sensitivity Asakusa Line and the Keisei Line. It to its advantages. This device was called characteristics, etc. This system was became the prototype of the later so- the Type-A cab warning device in which called the Type-C cab warning system and called ATS-1. a 1300-Hz AM waveform is superimposed it was adopted in August 1957. From early on the track circuit at commercial 1958, about 1100 trackside coils and Mikawashima disaster and ATS frequency to issue a stop-signal warning about 450 pickup coils were installed over In January 1960, a train with the Type-A to the train crew. Since transistor a total track length of 957 km on the cab warning system collided with the reliability was still poor, vacuum tubes Hokuriku, Shin’etsu, Uetsu, and Ou lines, preceding train near Yurakucho Station. were used for the circuits (Fig. 2). The but because there were some instability After this accident, the need to add an system was introduced on the 689-km problems only thoroughly checked steam ATS capability to the cab warning system section between Tokyo and Himeji and locomotives were operated between was discussed and 18 plans were studied entered operation in July 1960. Maibara and Aomori in June 1961. as the result. In 1961, four promising On the other hand, JNR developed a In 1958, two different prototypes of the types were prototyped for performance system using the change in magnetic flux Type-B cab warning system with added and endurance tests. They were the PM that occurs when a ground-based inductor ATS capability were tested. One was a type using permanent magnets installed couples with the on-board pickup coil. prototype of the ATS-B put into practical on the ground; the loop type using a loop There are two system types: the use later. It had a function to apply the coil; the frequency-shift type using the

Table 1 Types of Cab Warning Systems

Type-A Type-C Type-B Type C-2 Type C-2 Type Track circuit Code Type C-1 (frequency shift) (absorption) ApplicationImportant trunk lines Electrified sections Quasi-trunk lines Signal current passed to track circuit, from When arrival of train Trackside coil On-board equipment On-board which modulated signal current at braking point exciter current frequency changed equipment transmitted to on-board equipment detected by relay, switched on and off by resonance with oscillating energy Operating Amplitude Code generated by track circuit current to transmit warning trackside coil absorbed by principle modulation of turning on and off interrupted for signal to on-board trackside coil 1300-Hz 1300-Hz specified time to equipment fundamental wave fundamental wave transmit warning signal to on-board equipment

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However, since ATS-S had already become widespread and the Type-A system employing vacuum tubes had a short life, the Type-A system was retired in 1970. A study on modification of the Type-B cab warning system into an ATS was started in 1963. While the trackside equipment was kept unchanged, the method of handling the warning by the crew and the connection of the warning system with the brake system were modified and a new receiver using transistors in place of vacuum tubes was developed. The introduction of the new ATS was started Scene of Mikawashima disaster (JNR CPH) in September 1964.

change in coupling resonance frequency four cars. This disaster prompted the Accidents at Hirano and Nishi of the trackside coil and pickup coil; and decision to introduce a new ATS, Akashi Stations and ATS-P the oscillation-stop type using the combining a cab warning system and ATS. After a derailment at Hirano Station on phenomenon in which the impedance of As a result, the frequency-shift type ATS the Kansai Line in December 1973, it the pickup coil changes and the was introduced on all JNR lines by April was decided to add a speed check oscillation stops when the pickup coil 1966. It was called the Type-S cab ability to ATS-S because of the couples with the trackside coil. The PM warning system (ATS-S). Trackside coils following three problems. type malfunctioned frequently and could were installed at about 43,300 points on • No ability to check train speed hardly secure the required S/N ratio while the ground and pickup coils were installed • After train driver confirmed warning the oscillation-stop type had practical on about 13,000 carriages. within 5 s, subsequent safe operation problems (difficulty in securing trackside As shown in Figure 3, the ATS-S system dependent entirely on him. coil resonance frequency appropriate to warns the driver of red signals and stops • Ground equipment transmitted pickup coil oscillation frequency). the train automatically if the driver fails information to on-board equipment Therefore, only the frequency-shift type to apply the brakes properly. When the only when train at some specified and loop type were subjected to long- train approaches a stop signal, the system point ahead of stop signal. term tests with the former on the Shin’etsu warns the driver by a bell, chime and red and Joban Lines, and the latter on the lamp, prompting the driver to confirm the In addition, since the warning point was Hachiko Line. signal. If the driver does not confirm the set at a point where even a train with As tests continued, the worst railway signal within 5 s, the system automatically brakes with the poorest performance accident in JNR’s history occurred in 1962 applies the emergency brakes to stop the could stop before the stop signal, the at Mikawashima Station, killing 160 train. As long as the driver confirms the warning was issued even to trains with passengers and injuring 296. A down signal properly, he can continue operating good brake performance. Therefore, the freight train in the Mikawashima Station the train himself. However, if the driver warning did not always indicate a critical yard on the Joban Line, entered the safety makes a mistake in the confirmation condition. And because warnings were siding when the driver missed the stop procedure, it can lead to an accident. This issued too frequently the effect was less signal. The locomotive and one freight is a weak point of ATS-S. than initially expected. wagon derailed, blocking the main track On the other hand, a detailed study of To solve these problems, it was necessary of the down line. A following down train ATS-A, which is a modified version of the to transmit the signal aspect and distance hit the freight train and derailed blocking Type-A cab warning system, was carried to the signal to the on-board equipment, the main up line. Six minutes later, an up out. As a result, a system that makes good meaning an increased volume of passenger train collided with the use of the advantage of continuous information transmitted to the on-board previously derailed cars, derailing its first control was put into use in July 1965. equipment. Therefore, considering

90 Japan Railway & Transport Review 43/44 • March 2006 Figure 3 ATS-S Operating Principle Figure 4 ATS-P Operating Principle

Brake pattern 5 seconds

Service brake

Train Train speed 1708 32 kHz 3000 32 kHz FSK speed Emergency brake FSK 64 Kbps 64 Kbps

Wayside coil 130 kHz Wayside coil Aspect information Distance information 1700 400 Hz (48 bit) EC FSK, 1200 bps compatibility with existing Type-S full compatibility with actual JNR efficient rail transportation even in systems, JNR started development of a operation conditions. The multi- sections in which trains are new multi-frequency shift-type ATS, frequency shift-type ATS-P described operated densely. allowing a wider range of frequency shift. above had about 10 applicable This new system provided on-board frequencies, which was insufficient for The basic ATS-P operation principle is that equipment with a speed check pattern to the large volume of information required when the signal aspect is stop, the eliminate the need for crew confirmation to implement the function, so it was trackside coil ahead of the signal causes and added the ability to generate a speed decided to develop a transponder-type the on-board equipment to generate a check pattern based on information ATS-P with transponder for exchanging speed check pattern (brake pattern) based supplied by a trackside coil some distance 48-bit data between the trackside and on- on the distance to the signal and train before the signal. The system was tested board equipment, permitting the on- speed (Fig. 4). The service brakes are on a train running between Nara Station board equipment to control the train applied automatically to stop the train and Minatomachi Station on the Kansai speed to the prescribed speed pattern. safely after signal only when the train Line. After satisfactory test results, the In developing the new system, it was speed exceeds the brake pattern. system was installed on the Nara– decided that the train operation should Therefore, the ATS system never Minatomachi section and entered be kept unchanged (the driver would intervenes in train operation as long as operation in May 1980. still operate the train according to the the train speed is within the brake pattern. Nevertheless, on 19 October 1984, the signal aspects), that the new system If the train speed exceeds the brake pattern Fuji limited express sleeper derailed at should be used as a backup facility, and due to driver operation error, the brakes Nishi Akashi Station on San’yo main line, that the new system should have the are applied immediately. Consequently, injuring 32 people. Although the speed following functions: ATS-P has a very sophisticated man- that the train could pass the turnout in the • If the train approaches a stop signal machine interface compared to ATS-S. station yard had been regulated, due to a and the driver fails to apply the brakes Technically, the receiver is a compact, change in course from the main track to correctly, the system automatically reliable simplex system achieved by the sub-track for track maintenance, the applies the emergency brakes to stop stabilized circuit characteristics, use of driver operated the train at the normal the train after the signal. ICs, introduction of a newly developed speed of about 100 km/h, hitting the • Even if the driver starts the train by ceramic filter, compact electromagnetic platform. The accident was due partly to mistake through misreading a signal, relay, and wet reed relay, self-diagnostic the inability of ATS-S to check speed. etc., the system automatically applies functions, logic circuit for troubleshooting, Those days saw massive increases in the the service brakes. etc. The compact trackside coil with number of trains, especially express and • The system maintains the ATS stable and reliable characteristics can be limited expresses, and in train speeds. functions at all times. installed on a wide sleeper. Because more accidents were being • As far as possible, the system offers ATS-P prevents accidents due to signal caused by stop signal violations, it was measures to prevent violation of speed violations and over-speeding at turnouts, realized that ATS functions could not limits at turnouts and curves and curves and down grades. It also speeds completely prevent this kind of accident. violation of shunting signals on the up signal indications for high-deceleration Therefore, there was an urgent necessity main track. trains. The information about whether a to introduce an advanced new ATS with • The system does not interfere with train has high, medium, or low

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deceleration is transmitted from the on- 240 km) of the Tohoku, Chuo, Sobu, required research on AF track circuits and board equipment to the trackside Joban Line, etc., in the Tokyo area; an AF cab warning device in 1955. equipment, so the signal aspect can be expansion continued and also introduced The Tokaido Shinkansen was a remarkable changed as required. The train number the system on the innovation in railway signalling. and some other information can also be and . Today, some 1500 Although introduction of electronic transmitted to the trackside equipment. km in the Tokyo Metropolitan area are signalling typified by ATC and CTC Consequently, ATS-P has a wider protected by ATS-P. underlies the shinkansen system, the application scope, such as constant concept of ATC with cab signalling dates warning time control of level crossings ATS-S Improvements back to 1938 when the first ‘bullet train’ based on train control and train speed and Although the newly developed ATS-P project was planned. Technically, the passenger broadcasts. system was introduced on major trunk kilocycle track circuit (introduced on the lines, other sections still used ATS-S, so Hokuriku Line in 1957) and the Type-A Accident at Higashi Nakano and the new companies in the JR group studied cab warning device (introduced on the ATS-P promotion ways to correct defects in ATS-S. Tokaido Line in 1957) provided the In September 1988, JR East planned to One method was to install a 123-kHz foundation for ATC with cab signalling. introduce ATS-P to the Chuo Line, Joban trackside coil at the absolute signal to In developing the shinkansen, engineers Line, etc., but it was introduced to the actuate the emergency brakes when the realized that a continuous ATC would be entire line on 1 December 1988, when signal aspect is stop, preventing signal indispensable to high-speed trains running the Keiyo Line opened. A rear-end violation. This is JR East’s ATS-SN. at 210 km/h and that such signalling collision occurred at Higashi Nakano Another method was to implement both systems could be implemented most Station on the Chuo Line just a few days a speed check function in which the on- efficiently by a cab signal with automatic later on 5 December, killing two board equipment measures the time that brake control based on the kilocycle track passengers and injuring more than 100, the train takes to pass two 108.5-kHz circuit (later AF track circuit) and Type-A when a local train collided at about trackside coils and actuates the brakes cab warning device that had just been 40 km/h with the ahead local train when the train speed is higher than the developed and put to practical use. The stopped near Higashi Nakano Station. prescribed limit, as well as a function ATC was characterized by use of many The accident can be ascribed to ATS basic informing the on-board equipment of a newly developed transistors and a triple- functions. Although ATS does issue an stopped ahead train. This is JR Central’s redundant circuit to build a very reliable audible warning, the warning is reset ATS-ST. JR West has introduced ATS-SW system as well as use of a signal device when the driver presses the confirm with very similar functions to ATS-ST but concentration method to facilitate signal button and the driver can then continue using microcomputer-based on-board installation and maintenance. operating the train without ATS equipment. All these systems use The 1955 research on AF track circuits intervention. Since the train was running frequency multiplexing and transmission and AF cab-warning device was on a tight schedule, the driver could have frequency overlapping developed for the followed by testing on the Senzan Line violated the red signal to try to make multi-frequency shift-type ATS-P system. and high-speed testing on the Kodama up time but some experts think that the commuter limited express in 1958. In driver could have failed to detect the Road to Cab Signal July 1962, the first practical ATC was ahead train early enough to stop safely —ATC Development installed in the Kamonomiya signal box because the site is on a sharp left curve for general testing before the opening on a down grade. Tokaido Shinkansen of the Tokaido Shinkansen. After this accident, JR East brought The Tokaido Shinkansen started revenue After the opening, the ATC system forward the planned introduction of the operations Tokyo and Osaka in October continued to operate stably while other new ATS-P system. At the same time, the 1964 just before the 1964 Tokyo signal systems suffered teething troubles. company increased the sections where Olympics. It used an ATC system with Improvements to signal aspects, etc., the new system would be introduced. In cab signalling to display a speed signal were made when extra speed limit levers May 1989, the ATS-P system was first on the driver’s console for automatic were installed for 160 and 110 km/h. introduced to Ueno Station on the speed control. ATC played an important About 10 years after the opening, the Tohoku Line. By late 1991, it was role in assuring the safety and stability of electrolytic capacitors had become so introduced on the main sections (totalling high-speed railways. ATC development deteriorated that they were all replaced.

92 Japan Railway & Transport Review 43/44 • March 2006 Just about the same time, ATC-related accidents occurred in Osaka and Shinagawa. In February 1973, a train ran on an unopened route to the main track in the Torikai carriage depot in Osaka, making the turnout trailable. In September 1974, at the Shinagawa carriage depot, a false proceed signal was caused by harmonic electromagnetic induction from a car-wash machine. These two accidents challenging the fundamental safety of ATC caused great shock to JNR, which soon established an investigation committee. As a result, the conventional single-frequency system was modified to a dual-frequency system Tokaido Shinkansen opening ceremony (Transportation Museum) to prevent false signals caused by spurious harmonics. This was the most subways, because it could be a The Teito Rapid Transit Authority’s (TRTA) important improvement to ATC. The hindrance on level crossings, etc. Hibiya Line opened in March 1961 using modified system was first introduced on Eventually, as it became necessary to ATC based on plans for through services the Tohoku Joetsu Shinkansen. review safety systems for train operations with suburban lines. The ATC system and Subsequently, the Tokaido Shinkansen at higher speeds and shorter headways, not ATS was adopted because the TRTA and Sanyo Shinkansen also introduced introduction of a cab warning system was realized that any system should allow for dual-frequency ATC system when discussed. By that time, JNR had already future automatic train operation. renewing the obsolescent ATCs. prototyped a cab warning device. Therefore, ATC was chosen because it Looking at private railway companies, permits automated braking and improves Introduction of ATC on private Tokyu Corporation began using a cab operation efficiency. Eventually, ATC was and municipal railways warning device similar to JNR’s Type-B on introduced on the Tozai Line and municipal The first subway in Asia was opened the Toyoko Line in November 1957. Next, subways in Osaka as well. Since these ATC on 30 December 1927 between the company introduced the device on all systems were a backup to prevent driver Asakusa and Ueno in Tokyo. As urban its lines. In July 1964, Hankyu mistakes, they were all trackside signalling transportation, the subway Corporation adopted a cab warning types. The easier-to-handle ATC cab incorporated various new technologies. device for its Kobe Line. signalling was introduced first when Adoption of the trip-arm-type ATS is However, an electric ATS was adopted Nagoya Subway No. 2 opened in October worthy of special mention in the history for the first time by the Tokyo 1965 and has been introduced on many of Japanese signalling systems. This Metropolitan Government (TMG) public and private railways. type of ATS was developed to improve Subway No. 1 Asakusa Line (between safety on subways with high density Asakusa and Oshiage) on 4 December Introduction of ATC operation at a minimum headway of 90 s. 1960. Train protection systems were an on JNR narrow-gauge lines It was later adopted by many other important problem because the subway In the 1960s, JNR had plans to add more subways. The trip-arm-type ATS has through operations with Keisei tracks to the Joban Line. At the same time, transmits a stop signal to the train by Electric Railway and Keihin Electric it was planning through operations on mechanical contact between a trip arm Express Railway. Therefore, the three Subway No. 9 (today’s Chiyoda Line) on the ground and a trip switch on the parties carried out joint R&D on signal planned by the TRTA. According to the leading carriage. When the train is systems, and decided to use an electric plan, the Joban quasi-express line and the allowed to proceed, the trip arm is ATS based on JNR’s Type-B cab signal Joban local line would be considered forced down by compressed air, so it system with a speed check ability. This independent revenue lines, so through does not touch the trip switch. This was a great stride forward and the electric service between them should not be type of ATS was used mainly by ATS was called ATS No. 1. implemented even in emergencies.

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Figure 5 ATC Operating Principle Figure 6 ATC with Continuous Braking Control Operating Principle

quality; and a system consisting of many trackside devices and track circuit cables is large and costly. These are all Train Train speed speed hindrances to further improving transportation efficiency and efforts have been made to solve the problems.

ATC with continuous braking pattern 90 65 65 45 0 G R In 1983, Tokyu Corporation launched a movement to solve the inability of ATC to greatly reduce headways. The company’s Therefore, JNR decided to use the same in Figure 5, an allowable train speed in Den’entoshi and Shin Tamagawa lines link signal systems as Subway No. 9 to each block sections is pre-calculated from Tokyo to the western suburbs and rising implement through service and install ATC data on the presence of a train in a section. passenger numbers year by year forced and cab signalling systems. When The ATC central logic unit transmits a the company to find a way to increase through service started in 1971 between signal indicating the allowable train speed capacity. At that time, Tokyu was using the Joban Line and the Chiyoda Line, JNR to the track circuit. Since the wheels short an ATS system and could not shorten introduced the first ATC for a narrow- the track circuit, the presence or absence headways any more without making the gauge railway. Specifications for the of a train can be determined by monitoring job more difficult for its drivers. Therefore, system were discussed with reference to the level of the receive signal. Therefore, it was decided to introduce an ATC system shinkansen in Japan and several other the ATC signal is also used for train with continuous braking to minimize systems at home and abroad. For a detection. The relationship between the braking distances by reducing headway commuter train, the primary issue is track circuit boundary and allowable train losses due to idle running. In continuous reducing headways as far as possible. speed is set to maintain the headway braking control, after the brakes are Ultimately, the ‘overlap & half-overlap’ required for train control. The ATC central applied, they are not released until the system was adopted in view of logic unit is almost exclusively responsible train stops. However, although the speed transportation demand, vehicle for controlling the interval between indication steps transmitted from the performance, and technical problems. trains—the role of the on-board ground equipment to the on-board Several accidents occurred before and equipment is simply to apply the train equipment are subdivided, the basic ATC after introduction of the ATC system, brakes according to instructions from the operation principle remains unchanged. including a rear-end collision due to a ground equipment. Consequently, there was the problem that mistake by the driver of a following train The ATC controls the train speed in the train speed did not decline to the at Ochanomizu Station on the Chuo Line each block by applying a frequency- specified speed. The company consulted (July 1968: 210 injured) as well as at modulated signal (10 frequencies from with the then Ministry of Transport and Funabashi Station on the Sobu Line 16 to 77 Hz) allocated to each specific obtained a special permit for the new brake (March 1972: 758 injured), and at Nippori speed stepwise (90–65–65–45–0) to control system (Fig. 6). The system started Station on the Yamanote Line (June 1972: limit the speed carrier signal (one of service on both the Den’entoshi Line and 158 injured). After these accidents, four frequencies from 2850 to 3750 Hz) Shin Tamagawa Line in March 1991. introduction of ATC on high-density passed to the track signal and decelerate The TRTA, which had been using the trip- operation sections in the Tokyo the train to that speed. arm-type ATS system since 1927, began Metropolitan area was discussed in Although the present ATC has improved updating its system by improving the earnest, resulting in a decision to train safety and enhanced the efficiency and safety of train operation introduce ATC to the Yamanote and Keihin transportation efficiency there are as it introduced new vehicles around Tohoku lines. Although quick deployment problems. The stepwise braking requires 1983. Eventually, the TRTA developed was planned, the global oil crisis extra braking/releasing, making it difficult CS-ATC with continuous braking based postponed the work which was not to improve traffic density; the sudden, on the system on the Chiyoda Line. The finished until 1981. automatic actuation of brakes at entry new system entered service on the Ginza How exactly does ATC work? As shown into a low-speed section reduces ride Line in July 1993 and was then

94 Japan Railway & Transport Review 43/44 • March 2006 introduced on the Marunouchi Line in between the train position and stop • Own position recognition March 1998 and the Chiyoda Line in position and applies the brakes at the right While the train is running, the on- November 1999. Today, it is the basic moment, taking into account relevant board equipment constantly system of the Tokyo Metro. The ATC factors such as curves and grades. determines the train position (specific system of the Joban Line providing The characteristics of the digital ATC position in specific track circuit) by through service on the Chiyoda Line was system are as follows: counting tachometer pulses from an replaced by CS-ATC in 1999. • Continuous braking control and axle generator. The train receiving the recognition of train position by the on- ATC signal retrieves the relationship Reducing Headways board equipment, reducing headway between the stop point information —Digital ATC and allowing high-density operation given by the signal and the train • Comparatively compact and position from the on-board database, The Yamanote Line and Keihin Tohoku economical ground equipment by calculates the distance to the stop Line—JR East’s important arteries in using general-purpose IT devices and point from that relationship and metropolitan Tokyo—must maintain distributed system configuration generates a braking pattern. stable, high-density transport. The • On-board equipment with sufficient • Brake control existing ATC systems came into use in flexibility to support improved train The on-board equipment checks the 1981 and had become obsolescent after acceleration/deceleration and permit train speed against the braking pattern 20 years, making renewal important. In reduced headways without and applies the brakes if the train renewing the old systems, rather than modifications to ground equipment speed exceeds the pattern. simply replace the old ATC with new ATC • System informing crew of route Immediately after the brakes are systems of the same type, JR East decided conditions and with precision brake applied and immediately before the to undertake a comprehensive review control, thereby improving train train stops, the on-board equipment and develop a system based on an manoeuvrability also applies weak braking to entirely new concept compatible with the minimize the shock of the braking basic purpose of ATC (controlling the The new ATC system is less costly than action. Also, before the on-board headway between trains safely). the existing ATC system and has reduced equipment applies the brakes, it Interval control is one approach to train headways of 150 s to 120 s with stop times indicates that the train is approaching control. As long as the distance between of 50 s and a deceleration of 3 km/h/s. In the brake pattern by flashing a lamp. preceding and succeeding trains is known, addition, the new system has much lower Furthermore, a monitor displays the it is possible to secure safety by controlling construction costs. condition of the route ahead to the train speeds. Implementing interval improve the train manoeuvrability. control required accurate train position How it works detection and high-speed communication The digital ATC functions are outlined Improving safety between train and ground. Clearly such below (Fig. 7). Due consideration is given for the safety an on-board intelligence system is very • Train detection of digital message transmission, train different from conventional ATC. A train detection (TD) signal is position recognition by the on-board transmitted constantly to the track equipment, and other functions that the What is digital ATC? circuit. As soon as a train enters the conventional ATC system does not have. The only data required to stop a given train track circuit, the ATC logic unit detects The ground equipment transmits an MSK- at the rear of a block with a stop signal the train. modulated, 80-bit ATC signal (64 bits for aspect is the position where train must • Stop point information transmission text and 16 bits for CRC) using an HDLC- stop and the distance to that position. Based on the train position information compatible transmission protocol to the Based on this concept, JR East decided to supplied by each track circuit and the on-board equipment, which performs a develop a new on-board digital ATC in route setting information supplied by CRC check on the received ATC text. It which the ground equipment transmits the interlocking device, the ATC logic also validates the serial number, content, only the stop position as digital unit calculates the section permitting etc., of the ATC text and invalid ATC texts information to the on-board equipment, train entry, and transmits it as a digital are not used in control of train operation. which recognizes the train position and ATC signal to the on-board equipment In the digital ATC system, the on-board continuously calculates the distance via the track circuit. equipment must find the train position

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Figure 7 Digital ATC Operating Principle Figure 8 Performances of Train Control Systems

ATC CS-ATC D-ATC

Train Brake pattern speed Brake pattern Train speed

90 65 65 45 0

11.9, 13.1 kHz (64 bit) Ground equipment type Ground equipment type On-board equipment type ATC signal MSK, 300 bps Characteristics Intermittent braking Continuous braking Continuous braking Train detection signal High-density Headway: Headway: ATC-LAN (optical cables) Headway: 2 minutes train operation 2 minutes and 30 seconds 2 minutes and 10 seconds Front brake warning lamp Monitor on driver console Train manoeuvrability Sudden braking Auxiliary brake and ride quality Auxiliary brake ATC logic controller Feedback control

accurately, using a tachometer on confirming and evaluating system to detect the train position and displays generator. Even if the tachometer functions, performance, constants, etc., the appropriate signal according to the generator error is on the large side, the required during revenue operation from detected train position. However, this data is processed on the safe side. In the system startup to changing driver’s control system requires many trackside addition, to prevent accumulated error, cab, shunting, etc. facilities and huge investment in correction-position transponders are JR East planned to introduce digital ATC construction and maintenance. The installed between stations at intervals called DS-ATC, with ‘S’ standing for recent great progress in IT has now made of about 1 km. The transponder also shinkansen as the control system for the it possible to build a train control system performs distance correction while the soon-to-be-opened Morioka–Hachinohe called ATACS (Advanced Train train is running at a low speed or during section. Testing started near Koriyama Administration and Communications slide detection to ensure safe position Station in 1999 with good results. In System) in which each train determines detection. If the train position becomes 2002, JR East decided to introduce D-ATC its position and exchanges data with other unknown, the system immediately on its narrow-gauge railways and DS-ATC trains by radio (Fig. 9). It is an innovative applies the emergency brakes. on its shinkansen. Both projects went new train control system that uses IT and The digital ATC system is configured to smoothly with the DS-ATC system autonomous distribution technology. secure both higher safety and introduced on the Hachinohe section of reliability; the ground equipment is the Tohoku Shinkansen in December Why develop new train control triplex and the on-board equipment is 2002, and the D-ATC system introduced system? parallel duplex, lowering the critical on the Minami Urawa–Tsurumi section Conventional train control systems using failure rate of the entire system by 10% of the Keihin Tohoku Line in December track circuits for train detection require to 12% or less, compared to the 2003. Then, in November 2005, the DS- huge investment in equipment and electronic interlocking system. ATC system was introduced on the maintenance. There are several reasons: Furukawa–Morioka section of the Tohoku various ground facilities must be installed Putting digital ATC to practical Shinkansen. Presently, construction is on and around the track; train positions use under way to introduce the DS-ATC cannot be detected very accurately; many For about 6 months from October 1998 system on the Joetsu Shinkansen by late signal cables are required to connect before putting the system into practical FY 2008 and the D-ATC system on the ground facilities; etc. In addition, because use, comprehensive final testing (32 night Yamanote Line in 2006, and on train control is implemented by block, tests and about 180 days of day tests) was remaining sections of the Keihin Tohoku conventional systems cannot effectively carried out with new ATC ground Line in 2007 (Fig. 8). support changes in transportation mode, equipment installed between Minami such as development of new, high- Urawa and Omiya on the Keihin Tohoku Next-generation Train performance vehicles. Line and the new on-board equipment Control using Radio However, by utilizing IT as the core and mounted on a Series 209 train set. Since redesigning the distribution of functions the component technologies of the new JR East is now developing a train control between the ground and on-board system had already been validated by the system using radio communication. equipment, it is possible to configure an 1995 on-track testing, the emphasis was Existing train control uses the track circuit ideal control system in which individual

96 Japan Railway & Transport Review 43/44 • March 2006 Figure 9 Outline of ATACS

Train control information transmission trains exchange train position information Digital Radio with each another to control train 400 MHz (328 bit) intervals. This new train control system QPSK, 9,600 bps utilizing IT has the following purposes: • Cutting costs Brake pattern Reducing the number of ground facilities cuts construction and Brake control maintenance costs. In addition, the costs of large-scale improvement and signal installation works during Train position detection Moving authority renewal of train control systems can be cut. • Facilitating system renewal brake performance, grade, curves, appropriate. If one radio station goes Since the system does not depend speed limit and all other relevant down, the neighbouring station on ground facilities, it can easily factors, the system prepares a braking automatically backs it up, keeping the support changes in transportation curve to stop the train before the LMA system functioning. mode, such as higher train speed and performs braking control. and shorter headway. • Level crossing control Toward pratical application • Improving safety and reliability ATACS controls level crossings by An ATACS system configuration and exchanging data between the ground specifications were prototyped with future The system does not depend on the train and on-board equipment. To adjust the practical application in mind. Seven radio crew for control. It improves safety by warning time of an approaching train, stations were installed on the 17-km positively preventing entry of trains into a the system uses the train speed and train Aobadori–Higashi Shiogama section of closed section and by providing a performance to estimate the time when the Sengoku Line and on-board ATACS protective pattern for brake control at level the train will arrive at the crossing, and was installed in each of 18 train sets. The crossings. In addition, the fewer ground transmits it to the ground control test section is divided into several control facilities reduce problems, contributing to equipment to actuate the crossing areas, each of which has control improved transportation reliability. signal. Then, the system transmits the equipment and a radio station. The information to the train and recalculates control equipment has a number of Using radio in train control the brake curve. If the crossing signal functions, including train detection, train ATACS has many function; the main is not actuated, the system stops the interval control, switch control, level functions—train interval control and level train before the crossing. crossing control, and track-work safety crossing control—are described here. • Other functions management. The radio stations • Train interval control The other functions include track- exchange information with the on-board The train speed is not controlled work safety management, switch computer and are installed at appropriate directly—it is controlled by control, bidirectional distance control, intervals according to radio area; some are calculating the allowable speed from and temporary speed regulation. linked to the control equipment. The on- the limit of movement authority (LMA) The distributed ground equipment are board computer controls the train brakes for each train. Control of the interval linked by a network. Each on-board according to data received from the between trains begins with system performs autonomous brake ground control equipment. It also transmitting the train positions to the control according to LMA data. The transmits train position information to the trackside control equipment. Next, ground equipment consists of a traffic control equipment. the control equipment determines the control system and a train control First, the on-board equipment determines LMA for each train from the train system, and each device is configured, the accurate train position. The initial position and route information and so that it works independently and train position is obtained when the train sends it to each train. Then, the on- even the failure of one device does passes the trackside coil installed at the board computer of each train not affect any other device. boundary between train departure section calculates the allowable running Consequently, the system can be built and train entry section. Next, the on- distance. Taking into account the on a step-by-step basis where board equipment continues recognizing

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Figure 10 JR East’s Network of Train Control Systems

ATS-P Aomori ATC Hachinohe D-ATC or DS-ATC I believe that train control systems will Others Akita continue developing in the years ahead Morioka driven by improvement in transportation Omagari needs and progress in communications Shinjo and information technology. I Utsunomiya Niigata Takasaki Yamagata Fukushima Mito Nagaoka Kofu Further Readings Omiya Koriyama Tetsudo shingo tattatsu-shi (Railway Signalling Nagano Echigo Yuzawa Chiba Developing History), Signalling Safety Tokyo Narita Matsumoto Utsunomiya Association, 1980. Takasaki Atami Saishin no kokutetsu shingo gijutsu (JNR’s Latest Omiya Mito Signalling Technology), Signalling Safety Tokyo Narita Association, March 1987. Atami Chiba S. Yamanouchi, Naze okoru tetsudo jiko (Why Railway Accidents Occur), Asahi Bunko, December 2000. Y. Hiyoshi, Kokutetsu ni okeru shanai keiho sochi no rekishiteki keii (JNR’s Historical Movement of Cab Warning Systems), Signalling Safety the train position using the cumulative Conclusion Association, October 1962. running distance calculated from the train M. Matsumoto, Denki tetsudo (Electric Railway), speed. The distance is corrected each Morikita Shuppan, April 1999. time the train passes each trackside coil The former JNR and now JR East have M. Matsumoto, Ressha seigyo system no gijutsu installed at appropriate intervals. The train continually developed and refined train henkan (Technical Transformation of Train Control position is allocated as a unique number control systems, which have evolved from Systems), Institute of Electrical Engineers of Japan, January 2006. to the associated control equipment, and the cab warning system to ATS-S to ATC M. Matsumoto and Y. Nakano, Tokyo Kyuko data about train positions in virtual (Fig. 10). As a result, the number of train Dentetsu Den’en Toshi Sen, Shin Tamagawa Sen sections (divisions of control area), related accidents, especially rear-end collisions, no Shin ATC system (New ATC System of Tokyo sections, etc., is processed by the ground has dramatically decreased. Kyuko Electric Railway’s Den’en Toshi and Shin and on-board computers. Radio stations Recently, an innovative new train control Tamagawa Lines), JREA, June 1991. M. Matsumoto and A. Hosokawa, Yamanote system using IT technology is being are installed at intervals of about 3 km Keihin Tohoku sen yo no atarashii shajo (varies according to reach of radio wave). developed from dual standpoint of shutaikei ATC no kaihatsu (Development of To avoid mutual interference between preventing railway accidents and New On-board ATC for Yamanote and Keihin adjacent radio stations, four different improving passenger services. Tohoku Lines), JREA, October 1999. frequencies are used so stations in With the successful completion of ATACS M. Matsumoto, Jiritsu bunsan-gata ressha seigyo system (Distributed Autonomous Train Control individual control areas can select a testing, we expect to see it in practical use System), Institute of Electrical Engineers of Japan, suitable frequency. Each station in the near future as a 21st century control February 2001. communicates with trains in its area every system replacing more conventional T. Kobayashi et al, Musen ni yoru ressya seigyo 1 s. Since transmission errors can occur, signalling. Autonomous distributed train system no shiken kekka to sinraisei (Test Results space diversity and Reed-Solomon error control will permit individual trains to of Train Control System using Radio and Its Credibility), Institute of Electronics, Information correction are used to improve exchange information with each another and Communication Engineers, June 1999. transmission quality. to control their own speeds. Day running tests (cumulative distance of more than 1 million km) and night Masayuki Matsumoto control running tests (28 times) were performed from October 2003 to Dr Matsumoto is General Manager of Facilities Department at JR East. He joined JNR in 1972 after obtaining masters degree in physical electronics from Tokyo Institute of Technology. After joining JR February 2005. Since the test results East in 1987, he held posts such as Deputy Senior Manager of Tohoku Construction Office and showed no functional or safety problems General Manager of Transport & Rolling Stock Department. He was Executive Director of Railway with the prototype system, R&D has Head Office at Hoan Kogyo Co., Ltd. before taking present post in 2004. He obtained his doctorate started into practical application. degree in computer science from Tokyo Institute of Technology in 2003. He is the author of Electric Railway published by Morikita Shuppan in April 1999.

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