325:
316:
407:
962:
926:
461:(DPU), which is cheaper than splitting it into two track circuits. A DPU avoids the need to change the frequency of a whole series of track circuits in a cascade. The DPU consists of a tuned coil which detects the presence or absence of current in the adjacent rail and picks up or drops a relay accordingly. One use of DPUs is for timing circuits. Each track circuit frequency has its own DPU tuned to that frequency. DPUs can be located almost anywhere; they overcome the limitation that jointless tracks have a minimum length.
939:
979:
1025:
913:
900:
888:
1051:
1038:
997:
129:
675:, saboteurs electrically connected sections of rail which they had displaced to conceal the breaks in the track they had made. The track circuit therefore did not detect the breaks, and the engine driver was not given a "Stop" indication. Another form of sabotage, not intended to cause a train crash but merely to make trains stop and slow down unnecessarily in an effort to sabotage an economy or potential injuries, is to tie a wire between the 2 rails, causing a false obstruction signal.
215:
368:
205:
450:
32:
287:, from 91 Hz up to 10 kHz. The relays are arranged to detect the selected frequency and to ignore DC and AC traction frequency signals. Again, fail-safe principles dictate that the relay interprets the presence of the signal as unoccupied track, whereas a lack of a signal indicates the presence of a train. The AC signal can be coded and locomotives equipped with inductive pickups to create a
355:, the joints being welded during installation. This offers many benefits, except to the signalling system, which no longer has natural breaks in the rail to form block sections. The only method to form discrete blocks in this scenario is to use different audio frequencies (AF) in each block section. To prevent the audio signal from one section passing into an adjacent section, pairs of
137:
659:
Failure modes that result in an incorrect "track clear" signal (known usually in the US as a "false clear") may allow a train to enter an occupied block, creating the risk of a collision. Wheel scale and short trains may also be a problem. They may also cause the warning systems at a grade crossing
515:
The HVIT transmits two pulses alternately, a narrow positive one at about 100VDC and a negative broader one at about 30VDC. The energy of the two pulses is the same. At the receiver end a R-C circuit integrates the two pulses which must be of the correct proportions for the relay to pick up. The R-C
375:
There is often a gap between where frequency A is received and frequency B is injected. This is referred to as a 'tuned zone' and is a section of track where the amplitude of frequency A reduces in the direction of section 2 and the amplitude of frequency B reduces in the direction of section 1. The
294:
There are two common approaches to provide a continuous path for traction current that spans multiple track circuit blocks. The simplest method installs insulated track circuit joints on only one of the two rails with the second being a path for the return current and a ground for the track circuit
863:
An inherent weakness of this arrangement was that it could fail in an unsafe state. For example, a broken wire in the track circuit would falsely indicate that no train was in the block, even if one was. Recognizing this, Robinson devised the closed loop track circuit described above, and in 1872,
848:
during the mid-nineteenth century showed that information could be electrically conveyed over considerable distance, spurring the investigation into methods of electrically controlling railway signals. Although several systems were developed prior to
Robinson's, none could automatically respond to
764:
A short, lightweight and fast train passing over an insulated blockjoint may disappear from the departing track circuit before it appears in the arriving track circuit, allowing false clear signals to be given. This problem can be overcome by introducing a time delay of say 1 – 2 seconds into the
687:
A more persistent problem is rust. Usually the railhead is kept clean of rust by the regular passage of trains' wheels. Lines which are not used regularly can become so rusty as to prevent vehicles being detected. Seldom-used points and crossovers and the extremities of terminal platform lines are
534:
If both rails are needed to carry the heavy traction return current, then insulated blockjoints are provided in both rails, and impedance bonds are provided to carry the traction current around the insulated joints. Impedance bonds are essentially centre-tapped coils, which offer low impedance to
667:
Different means are used to respond to these types of failures. For example, the relays are designed to a very high level of reliability. In areas with electrical problems, different types of track circuits may be used which are less susceptible to interference. Speeds may be restricted when and
469:
In non-electrified areas, DC coded track circuits may be used. These modulate the current going from the powersource end to the relay end and control the signals and cab signals without the need for line wires. The modulated currents can be detected by equipment connected to the track to provide
363:
Consider a railway with two block sections as in the diagram. Section 1 has frequency A injected at the left-hand end and received at the right-hand end. Section 2 continues from the right hand end of section 1 where frequency B is injected and then received at the right-hand end of section 2.
247:
is usually reversed from one section to an adjacent section. Circuits are powered at low voltages (1.5 to 12 V DC). The relays and the power supply are attached to opposite ends of the section to prevent broken rails from electrically isolating part of the track from the circuit. A series
627:
Conditions which partially or completely insulate the wheels from the rail, such as rust, sand, or dry leaves on the rails. This is also known as "poor shunting" ("failure to shunt" in North
America and Australia). Sanding gear which operates on all wheels of an engine traveling light can
860:(aka Kinzua, PA), where it proved to be practical. His design consisted of electrically operated discs located atop small trackside signal huts, and was based on an open track circuit. When no train was within the block no power was applied to the signal, indicating a clear track.
496:
Where the length of a section exceeds the practical length of a track circuit, cut tracks can be provided. With a cut track, the relay of the last track cuts the powersource feed of the second last track circuit, and so on. Cut tracks are only suitable for unidirectional tracks.
990:
railway station. Broken sand dispenser caused a layer of sand being created on the rail, making it lose the shunt. The station equipment interpreted this as the track is free and allowed another train in to proceed into the station, which then crashed into the previous train from
683:
The track circuit relies upon an adequate electrical contact between the rail and the wheel; contamination can insulate the one from the other. A common problem is fallen leaves, though there have been cases where crushed insects have also caused detection failures.
743:
Insulated blockjoints can be bridged by wheel scale in some circumstances causing one or two track circuits to fail. This problem may be reduced by having a pair of blockjoints in series about 4m apart. The short 4m section would not itself be track circuited.
1017:
Because Track circuits operate by passing a current through one or both of the tracks, they can sometimes detect if a rail has broken completely. However, if the break is only partial or is at a turnout (set of points) detection may not be possible.
631:
Where multiple parallel paths exist for traction return purposes broken rail detection will be lost for the rail that is used for the traction return. If more than one break occurs in that rail a false clear can occur when the train is between the
530:
In electrified areas, a workaround is needed to allow the traction current, of the order of thousands of amperes, to return to the substation. This may be achieved by having no insulated block joints in one of the rails, called the return rail.
867:
Although a pioneer in the use of signals controlling trains, the UK was slow to adopt
Robinson's design. At the time, many carriages on UK railways had wooden axles and/or wheels with wooden hubs, making them incompatible with track circuits.
797:. This is a length of wire connecting two metal spring clips that clip onto a rail. In the event of accident or obstruction a clip applied to both rails will indicate that that line is occupied, putting the signal for that section to danger.
359:
are connected across the rails at the section boundary. The tuned circuit often incorporates the circuit to either apply the transmitted signal to the track or recover the received signal from the other end of the section.
271:
Where DC traction is used on the running line or on tracks in close proximity then DC track circuits cannot be used; similarly if 50 Hz AC electrification is used then 50 Hz AC track circuits cannot be used.
1728:
180:
operation is crucial. Hence the circuit is designed to indicate the presence of a train when failures occur. On the other hand, false occupancy readings are disruptive to railway operations and must be minimized.
834:, an American electrical and mechanical engineer. His introduction of a trustworthy method of block occupancy detection was key to the development of the automatic signalling systems now in nearly universal use.
780:
The track circuit can be split with extra blockjoints and the detectors in the points complete the track circuit when the points are normal and the signal is entitled to receive a green light. This is partially
841:
or station agents. When to change the signal aspect was often left to the judgement of the operator. Human error or inattentiveness occasionally resulted in improper signalling and train collisions.
418:) UM71 is another kind of jointless track circuit. It uses 1700 Hz and 2300 Hz on one track and 2000 Hz and 2600 Hz on the other. To reduce the chance of stray currents causing a
803:
procedure in the UK requires TCOCs to be placed on all affected running lines if contact cannot be made immediately with the signaller following an accident where adjacent lines are blocked.
232:) the rails together. The current to the track relay coil drops, and it is de-energised. Circuits through the relay contacts therefore report whether or not the track is occupied.
228:
coil wired across them. When no train is present, the relay is energised by the current flowing from the power source through the rails. When a train is present, its axles short (
1926:
394:
Restrictions on placing impedance bonds, hence any connection for electrification purposes, in or near tuned zones as this may upset the filter properties of the tuned zone.
555:
Longer trains with more wheels have better conductivity. Short trains, light railmotors or single engines can be a problem. In New
Zealand there were problems with light
567:
railmotor, which are also lightweight, and with discbrakes, had some problems when they stopped, and had to make a double stop to ensure good contact with the rails.
1192:
422:
the modulation frequency is calculated by dividing the base frequency by 128. Different rates of modulation can be detected by equipment on the trains and used for
983:
1218:
264:
schemes, one or both of the running rails are used to carry the return traction current. This precludes use of the basic DC track circuit because the substantial
560:
864:
installed it in place of the previous circuit. The result was a fully automatic, failsafe signalling system that was the prototype for subsequent development.
383:
Eliminates insulated block joints, a component liable to mechanical failure (both of insulation and by introducing stress to adjoining rails) and maintenance.
590:. They may, for example, have carbon-silver contacts to reduce the likelihood of the wrong contacts welding shut after power surges and lightning strikes.
188:
systems to operate semi-automatically, by displaying signals for trains to slow or stop in the presence of occupied track ahead of them. They help prevent
410:
Tuning unit of a ZPW-2000 (Chinese variant of UW71) track circuit and a sign indicating "do not stop at circuit boundary", where loss-of-shunt may occur.
176:
to short an electrical circuit. This circuit is monitored by electrical equipment to detect the absence of the trains. Since this is a safety appliance,
773:
It is sometimes convenient to wire the detectors of a set of points through the track circuit over those points. This can be done in one of two ways:
852:
Robinson first demonstrated a fully automatic railway signalling system in model form in 1870. A full-sized version was subsequently installed on the
777:
A contact of the points detector can shunt the track circuit when the points are reverse, putting the signals to red, however this is not failsafe.
640:
612:
On the other hand, failure modes which prevent the circuit from detecting trains (known as a wrong-side failure) are possible. Examples include:
598:
The circuit is designed so the vast majority of failures will cause a "track occupied" indication (known as a right-side failure). For example:
1001:
1153:
1683:
1593:
1378:
1673:
1618:
1181:
Letter from
Deborah A.P. Hersman, Chairman, NTSB, to John B. Catoe, Jr., General Manager, Washington Metropolitan Area Transit Authority.
324:
784:
A second relay can be installed on the turnout, with its contacts wired in series with the main relay. This is fail-safe but expensive.
386:
In electrified areas, jointless track circuits require fewer impedance bonds than any other double rail traction return track circuits.
622:
Another relay saw a metal washer slip off and jam the relay contacts up; the half-washers had to be replaced by full-circle washers.
299:
bonds to permit traction current to pass between isolated track circuit blocks while blocking current at track circuit frequencies.
652:
Equipment which is not heavy enough to make good electrical contact (shunt failure) or whose wheels must be electrically insulated.
602:
A broken rail or wire will break the circuit between the power supply and the relay, de-energizing the relay. See exception below.
574:
do not. As a result, some disc-braked vehicles have "scrubber pads" cleaning the wheels to aid in proper track circuit operation.
570:
Cast iron brake shoes tend to clean the wheels of non-conductive debris (such as leaves and sand-based traction compounds), while
1946:
1583:
969:, which occurred when sand on the rails insulated the wheels from the rails, causing a failure to shunt that allowed a trailing
196:
from causing accidents, both by informing them of track occupancy and by preventing signals from displaying unsafe indications.
616:
Mechanical failure of the relay, causing the relay to be stuck in the "track clear" position even when the track is occupied.
1941:
1900:
96:
1743:
1476:
1291:. Vol. Module M: Dealing with a train accident or train evacuation, Emergency Protection. p. Section 2. GERT8000.
302:
AC circuits are sometimes used in areas where conditions introduce stray currents, which interfere with DC track circuits.
1196:
668:
where fallen leaves are an issue. Traffic may be embargoed to let equipment pass which does not reliably shunt the rails.
295:
rail. This has the disadvantage of only being able to detect breaks in one rail so the more popular two rail system uses
68:
1738:
1688:
1658:
892:
1216:
Anarchist News, Southern
Ontario: Solidarity CN Rail Signal Sabotage Tue, 01/15/2013 - 12:53 -- Anonymous (not verified)
1931:
1418:
1222:
1663:
516:
circuits check that the positive and negative pulses are in correct phase. The two pulses operate at about 1 Hz.
500:
Track circuits with ballast contamination will be shorter than those with good ballast, thus needing more cut tracks.
243:, usually in both rails. To prevent one circuit from falsely powering another in the event of insulation failure, the
2037:
2032:
1921:
1311:
115:
75:
1633:
628:
temporarily insulate it from the rails until the sanding ceases and the locomotive has moved further down the track.
2088:
1890:
1371:
1127:
827:
1708:
1956:
1936:
1529:
1284:
315:
1758:
1723:
1519:
1102:
1072:
930:
853:
765:
departing track circuit. Electronic track circuits such as the CSEE can easily incorporate such a time delay.
168:
The basic principle behind the track circuit lies in the connection of the two rails by the wheels and axle of
82:
53:
49:
1987:
1972:
1428:
1055:
987:
535:
traction current at say 50 Hz, while offering high impedance to signalling current at say 1.7 kHz.
943:
1648:
1438:
1062:
but badly twisted continuous welded rail on a bridge that still indicated a clear condition to the signal.
64:
2042:
1413:
1364:
831:
639:
which create stray electrical signals, such as muddy ballast (which can generate a "battery effect") or
2052:
2017:
2007:
1997:
1992:
1982:
1613:
1443:
1268:
672:
655:
A rail break between the insulated rail joint and the track circuit feed wiring would not be detected.
586:, referred to by signal maintainers as "vital relays," are specially designed to reduce the chance of
2047:
2002:
1905:
1763:
1608:
1560:
1408:
1403:
1077:
904:
2057:
2027:
2022:
2012:
1977:
1895:
1703:
1628:
1534:
1496:
485:
406:
2062:
1860:
1845:
1603:
1575:
1395:
1029:
917:
752:
Electric locomotives must avoid generating noise in the frequencies that track circuits use. The
423:
261:
42:
1840:
1830:
1779:
1698:
1693:
1423:
1154:"An Application of Microtrax for the National Rail Corporation on the SRA-NSW North Coast Line"
352:
338:
1348:
236:
2067:
1501:
1491:
1453:
1448:
1244:
1005:
793:
A simple piece of safety equipment which is carried by all heavy rail trains in
Britain is a
646:
881:
Numerous accidents would have been prevented by the provision of track circuits, including:
1623:
1042:
857:
845:
823:
734:
whereby a track circuit cannot pickup unless a train is detected in the next track circuit.
296:
89:
8:
1850:
1733:
1333:
1178:
966:
276:
244:
1463:
1387:
1082:
955:
Much rarer are accidents caused when the track circuits themselves fail. For example:
806:
TCOCs are ineffective where train detection is not by means of track circuits, such as
608:
A short across the rails or between adjacent track sections will de-energize the relay.
587:
548:
Railway wheels are made from steel and provide a good short circuit from rail to rail (
419:
229:
185:
1885:
1789:
1565:
1307:
811:
661:
619:
One perspex case warped in the heat, and touched the relay contacts, holding them up.
509:
474:
if available. They can be overlain by predictor systems to operate level crossings.
1103:"CSEE UM71 AF Jointless Track Circuits – Set-up, Test and Certification SES 06"
519:
The circuit will operate on AC and DC electrified lines, with additional equipment.
1951:
1880:
1855:
1835:
1653:
1219:"Southern Ontario: Solidarity CN Rail Signal Sabotage | anarchistnews dot org"
838:
189:
19:
This article is about an electrical device used on railways. For racecourses, see
703:
527:
In non-electrified areas, insulated blockjoints come in pairs, one on each rail.
284:
156:
to signallers and control relevant signals. An alternative to track circuits are
583:
140:
Track circuit transformer on the right, new axle counter on the left (Slovenia).
1678:
1524:
1511:
1024:
978:
970:
912:
899:
887:
471:
334:
288:
280:
265:
128:
2082:
1865:
1753:
1050:
1037:
996:
807:
753:
724:
356:
240:
173:
1177:
National
Transportation Safety Board (NTSB), Washington, D.C. (2009-09-22).
1799:
1643:
1550:
1481:
1433:
720:- a train mounted system that breaks down the resistance of the rust layer;
564:
556:
367:
193:
157:
1825:
1486:
508:
One common brand of high voltage impulse track (HVIT) circuit is made by
415:
214:
153:
973:
to improperly display a clear aspect, resulting in a rear-end collision.
1875:
1748:
1713:
1471:
830:
at
Brixton in 1864. The failsafe track circuit was invented in 1872 by
571:
169:
20:
204:
16:
Electrical device used to detect the presence of trains on rail tracks
1784:
1356:
961:
925:
177:
449:
426:, so long as the transmitter end (Tx) is at the front of the train.
31:
1870:
1794:
636:
249:
1331:
1267:
Rail
Corporation New South Wales, Haymarket NSW Australia (2012).
132:
Illustration of track circuit invented by William Robinson in 1872
1815:
1718:
457:
A jointless track circuit such as the CSEE can be divided with a
1820:
1668:
1638:
938:
342:
224:
A track circuit typically has power applied to each rail and a
1190:
Ezra Levant, The Source, Sun News Network, "Summer Of Terror"
252:
limits the current when the track circuit is short-circuited.
1598:
1349:"Srážka lokomotivnĂho vlaku Lv 72461 s osobnĂm vlakem Os 5011
397:
Electronic circuits are more vulnerable to lightning strikes.
225:
149:
1588:
235:
Each circuit detects a defined section of track, such as a
136:
1306:. Newton Abbot, Oxford: David & Charles. p. 162.
688:
also prone to rusting. Measures to overcome this include:
268:
currents overwhelm the very small track circuit currents.
605:
A failure in the power supply will de-energize the relay.
1032:(1967) - derailment due to top of rail having broken off
470:
signaling and indication information to activate proper
283:(DC) but typically, the AC frequency is in the range of
512:. The high voltage penetrates rust and other problems.
208:
Schematic drawing of track circuit for unoccupied block
148:
is an electrical device used to prove the absence of a
837:
The first railway signals were manually operated by
876:
660:to fail to activate. This is why in UK practice, a
341:audio frequency track circuit; Right: S-Bond of an
56:. Unsourced material may be challenged and removed.
950:
678:
649:in the equipment that controls the track circuits.
441:jointless track circuits are similar to the UM71.
376:tuned zone can be of the order of 20 m long.
708:(often zig zag in shape) welded on the railheads;
333:Electric "joints" of jointless track circuits on
255:
2080:
788:
538:
371:Track circuited railway with two block sections
1304:A biographical dictionary of railway engineers
1002:June 22, 2009 Washington Metro train collision
522:
1372:
1179:"Safety Recommendations R-09-15 and R-09-16."
1684:Interoperable Communications Based Signaling
1008:developed in a track circuit control module.
239:. These sections are separated by insulated
1619:Automatic Train Protection (United Kingdom)
1332:American Railway Association (ARA) (1922).
1133:. Australian Rail Track Corporation Limited
1045:(1996) - undetected broken rail in turnout.
390:Disadvantages of jointless track circuits:
305:
275:To accommodate this, AC track circuits use
220:(series resistor next to battery not shown)
218:Schematic drawing of occupied track circuit
210:(series resistor next to battery not shown)
163:
1379:
1365:
1128:"Microtrax Coded Track Circuits ESM-07-03"
559:railmotors not always being detected; see
464:
822:The first use of track circuiting was by
116:Learn how and when to remove this message
1342:
1301:
448:
405:
379:Advantages of jointless track circuits:
366:
213:
203:
135:
127:
1584:Advanced Civil Speed Enforcement System
1173:
1171:
1108:. Australian Rail Track Corporation Ltd
477:Brands of coded track circuit include:
2081:
1386:
1327:
1325:
1323:
1279:
1277:
759:
503:
1744:Train Protection & Warning System
1360:
1151:
643:from nearby power transmission lines.
1477:Integrated Electronic Control Centre
1283:
1271:. Engineering Standard. Version 4.7.
1242:
1168:
664:is also used in crossing circuitry.
543:
199:
54:adding citations to reliable sources
25:
1739:Train automatic stopping controller
1659:Continuous Automatic Warning System
1320:
1274:
1193:"Sun News : Summer of terror?"
893:Norton Fitzwarren rail crash (1890)
826:on a short stretch of track of the
795:track-circuit operating clip (TCOC)
593:
444:
13:
1419:Communications-based train control
1335:The Invention of the Track Circuit
14:
2100:
768:
728:over the affected section; and/or
561:Railway signalling in New Zealand
1269:"ESC 220: Rail and Rail Joints."
1049:
1036:
1023:
995:
977:
960:
937:
924:
911:
898:
886:
877:Caused by lack of track circuits
828:London Chatham and Dover Railway
484:Microtrax/E-Code by Hitachi née
323:
314:
30:
1901:Westinghouse Brake & Signal
1664:ContrĂ´le de vitesse par balises
1530:North American railroad signals
1295:
1012:
951:Caused by track circuit failure
747:
679:Railhead contamination and rust
453:Data Pickup Unit CSEE; end view
41:needs additional citations for
1759:Transmission balise-locomotive
1724:Sistema Controllo Marcia Treno
1634:Automatische treinbeĂŻnvloeding
1520:Application of railway signals
1261:
1236:
1210:
1184:
1145:
1120:
1095:
1073:Application of railway signals
931:Geurie crossing loop collision
854:Philadelphia and Erie Railroad
256:Circuits under electrification
1:
1709:Punktförmige Zugbeeinflussung
1429:European Train Control System
1088:
1056:Big Bayou Canot rail accident
789:Track-circuit operating clips
671:Sabotage is possible. In the
641:parasitic electrical currents
491:
1649:Chinese Train Control System
1439:Radio Electronic Token Block
1243:Jess, Allison (2009-05-11).
871:
718:Track Circuit Assistor (TCA)
539:Failure modes and prevention
401:
7:
1414:Centralized traffic control
1156:. Union Switch & Signal
1066:
523:Single rail and double rail
481:Alstom née GE Electrocode 5
10:
2105:
1614:Automatic train protection
944:Lac-MĂ©gantic rail disaster
817:
673:1995 Palo Verde derailment
18:
1965:
1914:
1906:Westinghouse Rail Systems
1808:
1772:
1764:Transmission Voie-Machine
1609:Automatic train operation
1574:
1561:Track circuit interrupter
1543:
1510:
1462:
1409:Automatic block signaling
1404:Absolute block signalling
1394:
1078:Track circuit interrupter
905:Hawes Junction rail crash
577:
486:Union Switch & Signal
1704:Pulse code cab signaling
1629:Automatic Warning System
1535:Railway semaphore signal
1497:Solid State Interlocking
1004:, which occurred when a
844:The introduction of the
738:
337:. Left: Wee-Z Bond of a
306:Jointless track circuits
279:(AC) signals instead of
164:Principles and operation
2089:Train detection systems
1604:Automatic train control
1302:Marshall, John (1978).
1030:Hither Green rail crash
918:Quintinshill rail crash
563:. Trains with a single
465:DC coded track circuits
424:automatic train control
262:railway electrification
1780:Level crossing signals
1699:Positive Train Control
1694:Linienzugbeeinflussung
1424:Direct traffic control
984:Moravany railway crash
647:Parasitic oscillations
454:
411:
372:
351:Modern track is often
345:Digicode track circuit
221:
211:
141:
133:
1502:Westlock Interlocking
1492:Rail operating centre
1454:Train order operation
1449:Track Warrant Control
1006:parasitic oscillation
452:
409:
370:
217:
207:
184:Track circuits allow
139:
131:
1624:Automatic train stop
1058:(1993) - undetected
1043:Weyauwega derailment
858:Ludlow, Pennsylvania
824:William Robert Sykes
801:Emergency protection
712:High voltage impulse
50:improve this article
1249:ABC Goulburn Valley
967:Cowan rail disaster
760:Transitory problems
756:had such problems.
699:to detect vehicles;
588:wrong-side failures
504:High voltage tracks
437:) and Westinghouse
353:continuously welded
277:alternating current
245:electrical polarity
1464:Signalling control
1388:Railway signalling
1245:"Millipede mayhem"
1083:Wrong-side failure
637:trackbed (roadbed)
635:Conditions in the
455:
420:wrong side failure
412:
373:
222:
212:
186:railway signalling
142:
134:
2076:
2075:
1886:Smith and Yardley
1289:Railway Rule Book
1152:Callender, Earl.
849:train movements.
544:Wheels and brakes
510:Jeumont-Schneider
285:audio frequencies
200:The basic circuit
126:
125:
118:
100:
2096:
1952:Transport Canada
1836:General Electric
1773:Crossing signals
1654:Cityflo 650 CBTC
1576:Train protection
1381:
1374:
1367:
1358:
1357:
1351:
1346:
1340:
1339:
1338:. New York: ARA.
1329:
1318:
1317:
1299:
1293:
1292:
1281:
1272:
1265:
1259:
1258:
1256:
1255:
1240:
1234:
1233:
1231:
1230:
1221:. Archived from
1214:
1208:
1207:
1205:
1204:
1195:. Archived from
1188:
1182:
1175:
1166:
1165:
1163:
1161:
1149:
1143:
1142:
1140:
1138:
1132:
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1054:
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1041:
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1028:
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1000:
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982:
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965:
964:
942:
941:
929:
928:
916:
915:
903:
902:
891:
890:
832:William Robinson
594:Circuit failures
550:shunt resistance
459:data pickup unit
445:Data Pickup Unit
327:
318:
121:
114:
110:
107:
101:
99:
58:
34:
26:
2104:
2103:
2099:
2098:
2097:
2095:
2094:
2093:
2079:
2078:
2077:
2072:
1961:
1910:
1804:
1768:
1570:
1544:Train detection
1539:
1506:
1458:
1390:
1385:
1355:
1354:
1347:
1343:
1330:
1321:
1314:
1300:
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1253:
1251:
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1191:
1189:
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1159:
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1136:
1134:
1130:
1126:
1125:
1121:
1111:
1109:
1105:
1101:
1100:
1096:
1091:
1069:
1048:
1035:
1022:
1015:
994:
976:
959:
953:
936:
923:
910:
897:
885:
879:
874:
820:
791:
771:
762:
750:
741:
714:track circuits;
704:Stainless steel
693:Depression bars
681:
596:
580:
546:
541:
525:
506:
494:
467:
447:
404:
349:
348:
347:
346:
330:
329:
328:
320:
319:
308:
258:
219:
209:
202:
166:
122:
111:
105:
102:
65:"Track circuit"
59:
57:
47:
35:
24:
17:
12:
11:
5:
2102:
2092:
2091:
2074:
2073:
2071:
2070:
2068:United Kingdom
2065:
2060:
2055:
2050:
2045:
2040:
2035:
2030:
2025:
2020:
2015:
2010:
2005:
2000:
1995:
1990:
1985:
1980:
1975:
1969:
1967:
1963:
1962:
1960:
1959:
1954:
1949:
1944:
1939:
1934:
1929:
1924:
1918:
1916:
1912:
1911:
1909:
1908:
1903:
1898:
1893:
1888:
1883:
1878:
1873:
1868:
1863:
1858:
1853:
1848:
1843:
1838:
1833:
1828:
1823:
1818:
1812:
1810:
1806:
1805:
1803:
1802:
1797:
1792:
1787:
1782:
1776:
1774:
1770:
1769:
1767:
1766:
1761:
1756:
1751:
1746:
1741:
1736:
1731:
1726:
1721:
1716:
1711:
1706:
1701:
1696:
1691:
1686:
1681:
1679:Integra-Signum
1676:
1671:
1666:
1661:
1656:
1651:
1646:
1641:
1636:
1631:
1626:
1621:
1616:
1611:
1606:
1601:
1596:
1591:
1586:
1580:
1578:
1572:
1571:
1569:
1568:
1563:
1558:
1553:
1547:
1545:
1541:
1540:
1538:
1537:
1532:
1527:
1525:Cab signalling
1522:
1516:
1514:
1508:
1507:
1505:
1504:
1499:
1494:
1489:
1484:
1479:
1474:
1468:
1466:
1460:
1459:
1457:
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1426:
1421:
1416:
1411:
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1398:
1392:
1391:
1384:
1383:
1376:
1369:
1361:
1353:
1352:
1341:
1319:
1312:
1294:
1287:(2012-12-02).
1273:
1260:
1235:
1209:
1183:
1167:
1144:
1119:
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1075:
1068:
1065:
1064:
1063:
1046:
1033:
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1011:
1010:
1009:
992:
986:, occurred in
974:
952:
949:
948:
947:
934:
921:
908:
895:
878:
875:
873:
870:
839:signal tenders
819:
816:
790:
787:
786:
785:
782:
778:
770:
769:Siding turnout
767:
761:
758:
749:
746:
740:
737:
736:
735:
729:
721:
715:
709:
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680:
677:
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653:
650:
644:
633:
629:
625:
624:
623:
620:
610:
609:
606:
603:
595:
592:
582:Track circuit
579:
576:
545:
542:
540:
537:
524:
521:
505:
502:
493:
490:
489:
488:
482:
472:cab signalling
466:
463:
446:
443:
403:
400:
399:
398:
395:
388:
387:
384:
357:tuned circuits
335:Shanghai Metro
332:
331:
322:
321:
313:
312:
311:
310:
309:
307:
304:
289:cab signalling
281:direct current
257:
254:
201:
198:
165:
162:
124:
123:
38:
36:
29:
15:
9:
6:
4:
3:
2:
2101:
2090:
2087:
2086:
2084:
2069:
2066:
2064:
2061:
2059:
2056:
2054:
2051:
2049:
2046:
2044:
2041:
2039:
2038:North America
2036:
2034:
2031:
2029:
2026:
2024:
2021:
2019:
2016:
2014:
2011:
2009:
2006:
2004:
2001:
1999:
1996:
1994:
1991:
1989:
1986:
1984:
1981:
1979:
1976:
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1971:
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1968:
1964:
1958:
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1950:
1948:
1945:
1943:
1940:
1938:
1935:
1933:
1930:
1928:
1925:
1923:
1920:
1919:
1917:
1915:Organisations
1913:
1907:
1904:
1902:
1899:
1897:
1894:
1892:
1889:
1887:
1884:
1882:
1879:
1877:
1874:
1872:
1869:
1867:
1866:Progress Rail
1864:
1862:
1859:
1857:
1854:
1852:
1849:
1847:
1844:
1842:
1839:
1837:
1834:
1832:
1829:
1827:
1824:
1822:
1819:
1817:
1814:
1813:
1811:
1809:Manufacturers
1807:
1801:
1798:
1796:
1793:
1791:
1788:
1786:
1783:
1781:
1778:
1777:
1775:
1771:
1765:
1762:
1760:
1757:
1755:
1754:Trainguard MT
1752:
1750:
1747:
1745:
1742:
1740:
1737:
1735:
1732:
1730:
1727:
1725:
1722:
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1627:
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1617:
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1610:
1607:
1605:
1602:
1600:
1597:
1595:
1592:
1590:
1587:
1585:
1582:
1581:
1579:
1577:
1573:
1567:
1564:
1562:
1559:
1557:
1556:Track circuit
1554:
1552:
1549:
1548:
1546:
1542:
1536:
1533:
1531:
1528:
1526:
1523:
1521:
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1461:
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1445:
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1435:
1432:
1430:
1427:
1425:
1422:
1420:
1417:
1415:
1412:
1410:
1407:
1405:
1402:
1401:
1399:
1397:
1396:Block systems
1393:
1389:
1382:
1377:
1375:
1370:
1368:
1363:
1362:
1359:
1350:
1345:
1337:
1336:
1328:
1326:
1324:
1315:
1313:0-7153-7489-3
1309:
1305:
1298:
1290:
1286:
1280:
1278:
1270:
1264:
1250:
1246:
1239:
1225:on 2013-09-12
1224:
1220:
1213:
1199:on 2013-12-04
1198:
1194:
1187:
1180:
1174:
1172:
1155:
1148:
1129:
1123:
1104:
1098:
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1079:
1076:
1074:
1071:
1070:
1061:
1057:
1052:
1047:
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1039:
1034:
1031:
1026:
1021:
1020:
1019:
1007:
1003:
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985:
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975:
972:
968:
963:
958:
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956:
945:
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935:
932:
927:
922:
919:
914:
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896:
894:
889:
884:
883:
882:
869:
865:
861:
859:
855:
850:
847:
842:
840:
835:
833:
829:
825:
815:
813:
809:
808:axle counters
804:
802:
798:
796:
783:
779:
776:
775:
774:
766:
757:
755:
754:SNCB Class 13
745:
733:
732:Tunnel sticks
730:
727:
726:
725:Axle counters
722:
719:
716:
713:
710:
707:
705:
701:
698:
694:
691:
690:
689:
685:
676:
674:
669:
665:
663:
654:
651:
648:
645:
642:
638:
634:
630:
626:
621:
618:
617:
615:
614:
613:
607:
604:
601:
600:
599:
591:
589:
585:
575:
573:
568:
566:
562:
558:
553:
551:
536:
532:
528:
520:
517:
513:
511:
501:
498:
487:
483:
480:
479:
478:
475:
473:
462:
460:
451:
442:
440:
436:
432:
427:
425:
421:
417:
408:
396:
393:
392:
391:
385:
382:
381:
380:
377:
369:
365:
361:
358:
354:
344:
340:
336:
326:
317:
303:
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298:
292:
290:
286:
282:
278:
273:
269:
267:
263:
253:
251:
246:
242:
238:
233:
231:
227:
216:
206:
197:
195:
191:
187:
182:
179:
175:
174:rolling stock
171:
161:
159:
158:axle counters
155:
151:
147:
146:track circuit
138:
130:
120:
117:
109:
98:
95:
91:
88:
84:
81:
77:
74:
70:
67: –
66:
62:
61:Find sources:
55:
51:
45:
44:
39:This article
37:
33:
28:
27:
22:
1896:Union Switch
1800:Wayside horn
1644:Catch points
1555:
1551:Axle counter
1482:Interlocking
1434:Moving block
1344:
1334:
1303:
1297:
1288:
1263:
1252:. Retrieved
1248:
1238:
1227:. Retrieved
1223:the original
1212:
1201:. Retrieved
1197:the original
1186:
1158:. Retrieved
1147:
1135:. Retrieved
1122:
1110:. Retrieved
1097:
1059:
1016:
1013:Broken rails
971:block signal
954:
880:
866:
862:
851:
843:
836:
821:
805:
800:
799:
794:
792:
772:
763:
751:
748:Immunization
742:
731:
723:
717:
711:
702:
696:
692:
686:
682:
670:
666:
658:
611:
597:
581:
569:
554:
549:
547:
533:
529:
526:
518:
514:
507:
499:
495:
476:
468:
458:
456:
438:
434:
430:
428:
413:
389:
378:
374:
362:
350:
301:
293:
274:
270:
259:
234:
223:
183:
167:
145:
143:
112:
103:
93:
86:
79:
72:
60:
48:Please help
43:verification
40:
2058:Switzerland
2033:New Zealand
2028:Netherlands
1734:Slide fence
1487:Lever frame
572:disc brakes
416:Ansaldo STS
190:dispatchers
170:locomotives
154:rail tracks
1966:By country
1749:Train stop
1714:RS4 Codici
1472:Block post
1254:2012-10-22
1229:2013-07-12
1203:2013-07-12
1089:References
781:fail-safe.
492:Cut tracks
433:(formerly
414:CSEE (now
76:newspapers
21:race track
1973:Australia
1826:AŽD Praha
1785:Crossbuck
1689:Crocodile
872:Accidents
846:telegraph
402:CSEE UM71
297:impedance
194:operators
178:fail-safe
106:June 2009
2083:Category
2063:Thailand
1871:Safetran
1861:Magnetic
1846:Griswold
1795:E-signal
1160:13 April
1137:13 April
1112:13 April
1067:See also
1060:unbroken
988:Moravany
812:treadles
697:treadles
557:Rm class
431:EBItrack
291:system.
266:traction
260:In some
250:resistor
2008:Germany
1998:Finland
1983:Belgium
1978:Bavaria
1881:Siemens
1856:Hitachi
1831:Federal
1816:Adtranz
1719:SelTrac
1566:Treadle
1512:Signals
991:behind.
818:History
662:treadle
632:breaks.
90:scholar
2053:Sweden
2048:Poland
2043:Norway
2013:Greece
2003:France
1988:Canada
1891:Thales
1821:Alstom
1790:Wigwag
1669:EBICAB
1639:Balise
1310:
946:(2013)
933:(1963)
920:(1915)
907:(1910)
706:strips
584:relays
578:Relays
439:FS2500
343:Alstom
241:joints
92:
85:
78:
71:
63:
2023:Japan
2018:Italy
1993:China
1927:AREMA
1876:Saxby
1729:SACEM
1674:IIATS
1599:ATACS
1444:Token
1131:(PDF)
1106:(PDF)
739:Scale
237:block
230:shunt
226:relay
150:train
97:JSTOR
83:books
1947:IRSE
1942:HMRI
1851:Hall
1594:ASFA
1589:ALSN
1308:ISBN
1285:RSSB
1162:2012
1139:2012
1114:2012
565:Budd
435:TI21
429:The
192:and
172:and
69:news
1957:UIC
1937:FRA
1932:ERA
1922:AAR
1841:GRS
856:at
810:or
695:or
552:).
339:GRS
152:on
52:by
2085::
1322:^
1276:^
1247:.
1170:^
814:.
160:.
144:A
1380:e
1373:t
1366:v
1316:.
1257:.
1232:.
1206:.
1164:.
1141:.
1116:.
119:)
113:(
108:)
104:(
94:·
87:·
80:·
73:·
46:.
23:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
