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restricted speed track and there is no safety consideration in a train occupying it without central authority to do so. For traffic flow purposes the dispatcher needs to record which sidings are occupied. If a train could not use the main track in Bess (due to maintenance, a stuck switch, a disabled train, or an obstacle blocking the track), it would also be possible for the train to have authority from Anna through Bess Siding through Cloy. This is not done when the main track is available, as there is a speed disadvantage to having the train traverse the slower siding track (including having to stop to throw the switches to enter the siding).
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the same time, thereby preventing collisions. (In certain circumstances, dispatchers will authorize more than one piece of equipment—as in the case of track maintenance vehicles—into the same block. When this occurs, the authority is marked as "joint," and all movements must be made at restricted speed, which allows stopping within half the range of vision.) Another key feature of DTC is that only one authority is in effect for any given train at any given time. When a dispatcher issues a new authority to a train, the previous authority becomes invalid and must not be used.
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Anna. Once the 4321 is fully within the Bess block and has cleared Cloy block, the conductor or other crew member will call the dispatcher and release Cloy. The dispatcher will then issue a new authority to the 5432, giving them authority from Bess Siding block through Cloy block. This generates additional radio traffic but ensures that there is no confusion as to which train is allowed to enter a given block at any given time. Some railroads have instituted a practice which allows a train to enter a block contingent upon the passing of the opposing train, although the
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prescribed form. The crew member will repeat the directive back to the dispatcher, who monitors the repeat for any errors. If the crew member correctly repeats the mandatory directive, the dispatcher finalizes the directive by saying, "That is correct," followed by the dispatcher's initials. A mandatory directive cannot take effect until the dispatcher has said, "That is correct," reducing the potential for human error to cause an accident.
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occupied unless authority is granted in blocks on both sides of the switch. For example, a train authorized only in Anna block must stop at the End Anna Block sign, which is a short distance from the switch points. A train authorized in Anna through Bess or in Anna through Bess Siding may proceed past the End Anna Block sign, over the switch, and then past the Begin Bess (or Bess Siding, as applicable) Block sign.
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which lets the two trains talk to each other directly to discuss which blocks the leading train has cleared. Caution must be exercised by the leading train not to release authority on track that the train still occupies, as this could result in a rear-end collision if the leading train slows down or stops or if the train becomes separated and a portion is left standing on the main track.
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be given as "fourteen, one-four." Engine numbers such as 2001 are usually read first as "two thousand one," while numbers such as 4321 are usually read as "forty-three twenty-one," although this is mostly a personal preference about what is easiest to say. Regardless, the repeat will give the individual numerals, as in, "Engine twenty-eight oh eight, two, eight, zero, eight."
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Normally, only one train or piece of equipment may occupy a given block at a time, and a train must release their authority in a block for the dispatcher to authorize another train into that block. Barring human error, this ensures that no two trains are ever authorized on any given piece of track at
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Numbers are always repeated in an alternate format to ensure clarity and prevent misunderstandings. Numbers from zero to nine are spelled out, while numbers greater than ten are given by their individual numerals. For example, the number six would be given as, "Six, s-i-x," while the number 14 would
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In this example, a train may have authority straight through from Anna through Cloy. Or, it could have authority in Anna through Bess Siding, in which case it must throw the switch between Anna and Bess and enter the siding - this will usually be done to clear the main track for an opposing train to
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In the case of two trains traveling the same direction, the dispatcher will only authorize the following train in blocks that the leading train has released. In the case of closely spaced trains, the dispatcher may opt to reduce his or her workload and implement a "radio blocking behind" authority,
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For example, a 30-mile (48 km) length of main line track may be divided into three blocks, Anna, Bess, and Cloy, each 10 miles (16 km) long. At milepost 10, there will be a sign displaying the end of Anna block and the beginning of Bess block, and a similar sign between Bess and Cloy. A
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After the 5432 has released its authority in Anna, the dispatcher may issue a new authority to the 4321 authorizing them through Anna block. Since only one authority is valid at any given time, if the 4321 is still in Cloy block, the dispatcher will give the new authority containing Cloy through
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In modern implementations, dispatchers rely on computerized systems to monitor trains that have received authority. Typically, the computer will prevent the dispatcher from giving two trains authority over the same track. The computer system generally displays a highly simplified diagram of the
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To receive or change a train's authority, the train dispatcher communicates by radio with the train crew and gives "mandatory directives" authorizing occupancy in a specified number of blocks. A member of the train crew, usually the conductor, copies the dispatcher's mandatory directive onto a
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While most DTC blocks are laid out back-to-back, the blocks actually do not touch at sidings. Instead, there is a "gray area" over the siding's switches, and the main track's and siding's DTC blocks begins at approximately the clearance point of the switch. The area over the switch must not be
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Lengths of DTC blocks vary, but usually take about 10 minutes to traverse. The siding itself is not considered a DTC block per se, but in some situations sidings must not be occupied without authority from the train dispatcher. However, in DTC territory all sidings operate as non-controlled,
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For example, a length of track may consist of three blocks. Anna, Bess, and Cloy. There is a siding at Bess, and this siding is specified as Bess Siding. Both Bess and Bess Siding blocks extend to the switches at either end of the siding. Anna and Cloy blocks begin on the other side of their
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Train crew member: "This is a repeat of mandatory directive issued to the forty-three twenty-one, four, three, two, one, with engineer
Johnson. We are authorized to proceed in a westward direction in three, t-h-r-e-e blocks, Anna though Cloy,
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pass. After clearing its authority in Anna siding and the opposing train passes, it might then get authority from Bess Siding through Cloy, in which case it will throw the switch between Bess and Cloy and reenter the main track.
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Train crew member: "This is a repeat of mandatory directive issued to the fifty-four thirty-two, five, four, three, two, with engineer Smith. We are authorized to proceed westward in two, t-w-o blocks, Anna through Bess Siding,
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Train crew member: "This is a repeat of mandatory directive issued to the forty-three twenty-one, four, three, two, one, with engineer
Johnson. We are authorized to proceed eastward in two, t-w-o blocks, Cloy through Bess,
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track, displaying the block limits and sidings. Track occupancy is displayed via bold or colored lines overlaying the track display, along with tags to identify the train (usually the number of the lead locomotive).
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Train dispatcher: "This is mandatory directive to engine forty-three twenty-one, four, three, two, one, with engineer
Johnson. You are authorized to proceed westward in three, t-h-r-e-e blocks, Anna through Cloy,
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Train dispatcher: "This is mandatory directive to engine fifty-four thirty-two, five, four, three, two, with engineer Smith. You are authorized to proceed westward in two, t-w-o blocks, Anna through Bess Siding,
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in
Australia uses the DTC system in some of the lower traffic areas in the western area of the state. CSX uses DTC on their former Georgia railroad mainline from Scottdale, just east of Atlanta, to Augusta.
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Train dispatcher: "This is mandatory directive to engine forty-three twenty-one, four, three, two, one, with engineer
Johnson. You are authorized to proceed eastward in two, t-w-o blocks, Cloy through Bess,
97:. It is known as "direct" traffic control because the train dispatcher gives track authority directly to the train crew via radio, as opposed to through wayside personnel via telephone or telegraph, as in
129:, block limits are delineated by conspicuous signs along the tracks. Every portion of controlled track belongs to a block, as blocks are laid out back-to-back along the entire length of the rail line.
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Once train 5432 has fully entered the siding and restored the switch for movement along the main track, they will call the dispatcher and release Anna block, using the following format:
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has recommended against this practice. A DTC authority given under this practice will include a phrase such as "This line is not in effect until after the arrival of train 7940."
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Entering a block in which the train is not authorized or releasing a block which the train still occupies is considered a main-line violation by the
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When trains must meet en route, one train must be authorized into the siding. For example, train 5432 may be authorized from Anna into Bess Siding:
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and carries stiff penalties for all crew members, which may include time off from work and the suspension or revocation of the engineer's license.
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Train crew member: "The fifty-four thirty-two, five, four, three, two, would like to release our authority in one block, Anna, over."
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respective switches. Neither Bess nor Bess Siding blocks may be occupied without authority from the train dispatcher.
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Blocks are typically named after a distinguishing feature within the block, such as a station, town, or river.
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to occupy) are divided into pre-specified blocks. In addition to being listed by milepost in the railroad's
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changed its Track
Warrant Control territory to DTC and is also implementing CTC in high-traffic areas.
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train authorized in Anna through Bess blocks must stop before Bess block ends and Cloy block begins.
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An opposing train will be authorized in two blocks, Cloy through Bess, using a similar format:
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Crew: "That is correct, dispatcher S.D.K. Thanks, dispatcher, forty-three twenty-one, out."
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Crew: "That is correct, dispatcher S.D.K. Thanks, dispatcher, forty-three twenty-one, out."
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Crew: "That is correct, dispatcher S.D.K. Thanks, dispatcher, fifty-four thirty-two, out."
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In DTC, controlled tracks and sidings (those requiring authority from the
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254:Dispatcher: "All right, thanks. Dispatcher out."
43:but its sources remain unclear because it lacks
113:A DTC block sign for the Luthman block on the
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719:Interoperable Communications Based Signaling
654:Automatic Train Protection (United Kingdom)
386:Railroad Signalling: Direct Traffic Control
238:Dispatcher: "Thanks, train dispatcher out."
232:Dispatcher: "That is correct, S.D.K., over.
216:Dispatcher. "Thanks, train dispatcher out."
210:Dispatcher: "That is correct, S.D.K., over.
194:Dispatcher. "Thanks, train dispatcher out."
188:Dispatcher: "That is correct, S.D.K., over.
176:A sample issue format would be as follows:
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306:does not use DTC; it uses mostly CTC with
74:Learn how and when to remove this message
108:
619:Advanced Civil Speed Enforcement System
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421:
779:Train Protection & Warning System
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512:Integrated Electronic Control Centre
381:Southern Pacific's changeover to DTC
310:in its non-signalled territory. The
298:(most of the rest of UP's lines use
265:National Transportation Safety Board
252:Crew: "That is correct, dispatcher."
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774:Train automatic stopping controller
694:Continuous Automatic Warning System
13:
454:Communications-based train control
258:Crew: "Fifty-four thirty-two out."
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1129:Railway signalling block systems
20:
936:Westinghouse Brake & Signal
699:ContrĂ´le de vitesse par balises
565:North American railroad signals
276:Federal Railroad Administration
794:Transmission balise-locomotive
759:Sistema Controllo Marcia Treno
669:Automatische treinbeĂŻnvloeding
555:Application of railway signals
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744:Punktförmige Zugbeeinflussung
464:European Train Control System
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684:Chinese Train Control System
474:Radio Electronic Token Block
344:Radio Electronic Token Block
7:
449:Centralized traffic control
329:Centralized traffic control
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300:Centralized Traffic Control
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649:Automatic train protection
366:GCOR Rulebook (Section 16)
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941:Westinghouse Rail Systems
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799:Transmission Voie-Machine
644:Automatic train operation
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596:Track circuit interrupter
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444:Automatic block signaling
439:Absolute block signalling
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288:Southern Pacific Railroad
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739:Pulse code cab signaling
664:Automatic Warning System
570:Railway semaphore signal
532:Solid State Interlocking
29:This article includes a
639:Automatic train control
58:more precise citations.
815:Level crossing signals
734:Positive Train Control
729:Linienzugbeeinflussung
459:Direct traffic control
376:Railroad Controls GCOR
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87:Direct traffic control
537:Westlock Interlocking
527:Rail operating centre
489:Train order operation
484:Track Warrant Control
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659:Automatic train stop
388:(contains diagrams)
499:Signalling control
423:Railway signalling
339:Railway signalling
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31:list of references
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987:Transport Canada
871:General Electric
808:Crossing signals
689:Cityflo 650 CBTC
611:Train protection
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334:Rail terminology
123:train dispatcher
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1093:Switzerland
1068:New Zealand
1063:Netherlands
769:Slide fence
522:Lever frame
354:Train order
56:introducing
1118:Categories
1001:By country
784:Train stop
749:RS4 Codici
507:Block post
360:References
290:, now the
156:Procedures
1008:Australia
861:AŽD Praha
820:Crossbuck
724:Crocodile
127:timetable
1098:Thailand
906:Safetran
896:Magnetic
881:Griswold
830:E-signal
323:See also
1043:Germany
1033:Finland
1018:Belgium
1013:Bavaria
916:Siemens
891:Hitachi
866:Federal
851:Adtranz
754:SelTrac
601:Treadle
547:Signals
302:). The
95:signals
52:improve
1088:Sweden
1083:Poland
1078:Norway
1048:Greece
1038:France
1023:Canada
926:Thales
856:Alstom
825:Wigwag
704:EBICAB
674:Balise
230:over."
225:over."
208:over."
203:over."
186:over."
181:over."
105:Layout
1058:Japan
1053:Italy
1028:China
962:AREMA
911:Saxby
764:SACEM
709:IIATS
634:ATACS
479:Token
37:, or
982:IRSE
977:HMRI
886:Hall
629:ASFA
624:ALSN
286:The
992:UIC
972:FRA
967:ERA
957:AAR
876:GRS
282:Use
91:DTC
1120::
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