Railroad Rules, Signalling, Operations:

Track Warrant Control

by Carsten S. Lundsten. Last updated 11-07-1998.


The Track Warrant
     The Track Warrant Form
     Track Warrant Limits
     Track Warrant in Effect when
     Other Information
     Multiple Track Warrants for the same Main Track
A TWC Example


Track Warrant Control (TWC) is a verbal authorization system defined by the General Code of Operation Rules (GCOR), used to authorize trains to occupy Main Tracks. TWC can be used as a stand-alone dispatching and safety system in unsignaled territories, or can be supplemented with Automatic Block Signaling (ABS) to increase flexibility and traffic capacity.

The Track Warrant permits a specific train to occupy a specific piece of Main Track between named locations. The Track Warrant also contains information of its own validity; when comes in effect and in some cases when it becomes void.

The Track Warrant

A Track Warrant is issued in the following steps, usually using radio: The Track Warrant is not in effect until the "OK" time is shown on it. If the Track Warrant restricts train movement or previously granted movement authority, the dispatcher can not consider the Track Warrant to be in effect until his "OK" has been acknowledged by the train crew member.

The Track Warrant Form

The Track Warrant form varies somewhat from railroad to railroad. Below is shown the form suggested by the General Code of Operating Rules:

The upper 2 lines identifies the Track Warrant by a number, a date, the train in question and the location of the train when the Track Warrant is issued.

After this follow 16 standard instruction fields plus one field for non-standardized instructions. Only some of the instruction fields are used in a given Track Warrant. The instruction fields is numbered, and each field has a box to the right of the number. A check-mark in this box marks the instruction field as being in use of this Track Warrant. A typical instruction would then be: "Check Box 1, Track Warrant NO. 234 Is Void."

The instruction fields are described in detail in the following sections.

The 3rd line from the bottom holds information on the "OK" time and dispatcher initials. The 2nd last line states if the Track Warrant is relayed to another person and it states the name of the crew member who copied it. The last line it used to note when Limits are reported clear to the dispatcher.

Track Warrant Limits (Boxes 2, 3, 4, 8 and 10)

Boxes 2, 3 and 4 defines the limits of the Track Warrant. Boxes 8 and 10 helps define the exact end of the Limits on a Station with a Siding, see below .

Boxes 2 and 3 are identical. They simply define that the train may proceed from location A to location B, and in case of multiple Main Tracks, on which track. The need for 2 boxes is to allow for the train to move from Mian Track to another Main Track. It's important to keep in mind that the Track Warrant must include all Main Track allocated to the train, also the Main Track occupied by the rear end of the train. On Double Track it is not necessary to state which track to use as long as the trains are running With the Current of Traffic (i.e. in the normal direction).

While boxes 2 and 3 gives permission to move in the direction specified only, box 4 allows the train to move in both directions on that section of track. This may be handy when a train is doing local switching in an area.

The start point in the Track Warrant is normally referred to as the First Named Point, while the end of the Limits are referred to as the Last Named Point. The named points may be any point that can be exactly identified, such as switches, mile posts or Stations.

To illustrate the exact limits for the Track Warrant at First Named Point and Last Named Point, the following fictional line in unsignalled territory is used:

The line has 4 Stations, Anna, Bolo, Coyote Jct and Danby. Anna and Danby are normal single track Stations with a Siding for meets. Bolo is a Station without secondary tracks amd Coyote Jct is the junction of a branch line. As an example of a non-Station point to be used on the Track Warrant, MP 81.3 is shown.

If the First Named Point is a Station with a Siding, the Track Warrant extends from - and including - the last Siding switch. The Track Warrant thus enables trains to leave the Station, whether it is in the Main Track or in the Siding. If the Last Named Point is a Station without a Siding, the Track Warrant extends to the Station Sign:

If the First Named Point is a Station without a Siding, the Track Warrant extends from the Station Sign. At the Last Named Point the train must stay clear of junction switches:

Similarly a junction switch at the First Named Point is included in the Track Warrant. If the Last Named Point is not a Station, the Track Warrant extends to that point:

If the First Named Point is not a Station, the Track Warrant starts at that point.

Boxes 8 and 10 instructs the train where to go if the Last Named Point is a Station with a Siding. Box 8 instructs to "Hold Main Track At Last Named Point", i.e. to stay on the Main Track. Box 8 checked means that the Track Warrant is valid to, but not including, the last siding switch at the station:

Box 10 instructs the train to "Clear Main Track At Last Named Point", i.e. to enter a secondary track and clear the Main Track. On a Station with a Siding this means, in practical terms, to go in the Siding. On such a station the Track Warrant only extends on to, and including, the first siding switch:

If the Track Warrant ends at the beginning of, say, a CTC territory, the Track Warrant extends to the CTC Limit at that location. Boxes 8 and 10 are not used even if a siding starts at this location, since the first CTC signal will govern the train.

Track Warrant in Effect when (Boxes 1, 5, 6 and 7)

An important part of a Track Warrant is to define when it is in effect. Unless boxes 1, 5, 6 or 7 indicates differently, Track Warrant is in effect as soon as the dispatcher has checked its correct reception by the train, and remains in effect until the train has reported the Limits clear.

Track Warrant is void (Box 1)

Box 1 is used to replace one Track Warrant with another. The typical use is when a train gets its Limits extended due to a train ahead proceeding further away, into a siding or on to another line. The new Track Warrant will include the "unused" Limits of the old Track Warrant.

Time Limits (Boxes 5 and 6)

A Track Warrant may be limited in time. A typical use for this would be a window for a work train or a local switch job necessitating to foul the Main Track. Box 5 defines the start time. Until that time the dispatcher may allocate the track to another train. Box 6 defines the expiry time of the Track Warrant. The train must have cleared the Main Track before this expiry time. However, the Track Warrant remains in effect until the Limits are reported clear by the train.

Meets (Box 7)

When trains meet in single track territory, it is important for the met train to be able to depart as soon as possible. Box 7 facilitates issuing a Track Warrant to a train waiting for a meet by stating that the Track Warrant is "Not In Effect Until After Arrival Of <train> At <location>". Location should be identical to First Named Point.

In the example below, a Track Warrant permitting train 908 East to proveede eastwards would be accompanied by the instruction "Check Box 7: Not In Effect Until The Arrival Of 602 West at Anna.":

The National Transportation Safety Board has suggested that box 7 not be used on unsignaled lines, due to head-on collisions caused by misunderstanding the box 7 instruction.

Restrictions (Boxes 11, 12, 13 and 14)

Restricted Speed (Boxes 11 and 12)

Though a Track Warrant usually assigns a section of Main Track to one train only (see below ), it is sometimes necessary to be a little more flexible. Boxes 11 and 12 instructs the train to move at Restricted Speed between named locations, typically mileposts.

Box 11 is used when another train is on that particular section of track. The perhaps most typical use of box 11 is when several work trains are working in the same are. The trains must move at restricted and thus keep a lookout for each other.

In the example below, a train is working on the line and has authority to work between MP 92.0 and MP 90.8. Both trains would receive a Track Warrant including the instruction "Check Box 11: Between MP 92.0 And MP 90.8 Make All Movements At Restricted Speed. Limits Occupied By Train Or Engine.":

Box 12 is used when work crews are at work on the track.

Speed Reductions (Boxes 13 and 14)

Boxes 13 and 14 instructs the train of speed reductions on the line. The speed reduction is in effect between 2 named locations, typically mileposts. Boxes 13 and 14 are identical and thus allows for 2 separate speed reductions within the Limits

Other Track Warrant Information

Relief of Flag Protection (Box 15)

Box 15 relieves the train of providing Flag Protection for itself. When a train is providing flag protection for itself it is possible for another train to follow on overlapping Track Warrants, even in unsignaled territory.

Box 15 seems to be a remnant of practices dating back to Timetable and Train Order days. It is doubtful that this is used much anymore.

Track Bulletins in Effect (Box 16)

Box 16 informs the train of all relevant Track Bulletins in effect within the Limits.

Other Instructions (Box 17)

Box 17 facilitates passing other safety related information to the train. In unsignaled territory such information could for example be that may be that a previous train has left a Main Track switch open after a meet.

Multiple Track Warrants for the same Main Track

Only one Track Warrant Authority may be issued issued to the same segment of Main Track, except in the following cases:
  • In ABS territory, multiple Track Warrants may overlap in the same direction.
  • In Dark Territory, a train may be permitted to proceed at Restricted Speed (Box 11) to follow a train ahead. This could allow a train to pull out of a siding and line the switch back immediately after being passed.
  • At meets, when the Track Warrant will not take effect before arrival of an opposing train (Box 7).
  • Under Work and Time Authority when trains are instructed to move at Restricted Speed (Box 11).

A TWC Example

The following is an example of how Track Warrant Control may be used to control an unsignaled, single track, line. To the west is the Station Anna with a siding and to the east is the Station Danby which is controlled by CTC. In between are the stations Bolo and Coyote Jct. The timetable text would read something like:

TWC in effect between <Somewhere West> and Danby.

CTC in effect between west switch Danby and <Somewhere East>.

This means that the siding at Danby is under CTC, while the siding at Anna has manual switches.

Two trains are to meet at Anna. The trains will be called 585 East (Eastbound) and 5032 West (Westbound). 585 East will be arriving first to the meet and is to go in the siding. Since the switches are hand-thrown and there's no train crew members on the rear end of the train, the dispatcher lets 585 East leave the west switch at Anna lined for the siding. This way the Conductor won't have to line the switch back and walk up to the locomotive.

The Track Warrant for 585 East would read:

5032 West is somewhere beyond Danby and has not yet been issued a Track Warrant to go further than Danby. Only the signal into the Main Track at Danby has been cleared, but even if the signals were clear through Danby, 5032 West would no be permitted to depart Danby without a Track Warrant:

As 5032 West approaches Danby it is time to issue a Track Warrant:

since there is no previous Track Warrant in effect for 5032 West. When the Track Warrant has been issued, the dispatcher clears the signals out of Danby:

585 East has how arrived at the west switch at Anna and prepares to head into the siding. 5032 West is approaching Danby:

585 East is now in the siding and reports clear of Main Track. This automatically voids their Track Warrant 123.

With 585 East in the clear, 5032 West can be permitted to continue past Anna. The dispatcher first contacts 5032 West for its position. 5032 West reports to be at Coyote Jct, meaning that they have cleared Coyote Jct. The dispatcher now issues a new Track Warrant for 5032 West:

Box 17 informs the crew of 5032 West that they will have to stop and line the west switch at Anna.

The dispatcher also issues a new Track Warrant for 585 East:

Neither Box 8 nor Box 10 are used since Danby is under CTC. Box 7 permits 585 East to continue as soon as 5032 West has cleared the east switch at Anna.

As soon as 5032 West clears the east switch at Anna, 585 East's Track Warrant NO. 131 comes in effect.5032 stops to normalize the west switch before proceeding westwards:

Since the next train due at Anna is a hotshot, our conductor is not saved a bit of walking this time. As 585 East is not explicitly relieved of doing so, the east switch at Anna must be normalized before 585 East can get running again. The dispatcher has set up a new meet for 585 East at Danby, but this time all controlled by CTC:

Comments, corrections and more information about TWC are very welcome. Please use this contact form

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Text, Images and HTML: Carsten S. Lundsten.