Direct Traffic Control – An Overview
Direct Traffic Control (DTC) is, put simply, a computerised version of Train Order Working. Station Yard layouts differ to those in Train Order territory and DTC is a much safer and more flexible system.
In Remote Controlled Signalling (RCS) territory, a standard is applied to the way signals are identified. Below is a drawing of a typical RCS crossing loop showing how each signal is identified.
Each signal number is prefixed with a mnemonic to identify the station location. For example, if the above map represented “Flinders”, then the mnemonic would be ‘FS’. Therefore, the Up Home signal at Flinders would be ‘FS14’. In most cases, points are motorised and are operated from the Control Centre.
DTC has been described by many as the “poor man’s RCS”. This is because a station yard layout in DTC territory is almost identical to RCS except “Block Limit” boards (left) are used where colour light signals would normaly be location (see below). These “Block Limit” boards have a signal ID plate on them, just like a colour light signal does in RCS territory. Standard QR “Beacons” (right) are used in place of Approach signals. These do not have an ID plate. In many cases, Trailable Facing Points are used, set for directional running. This way, two trains can cross without crew members having to manually operate the points.
How it works
The basis of DTC is similar to Train Order. The Train Controller issues the driver of each train a computer generated DTC Block Authority to proceed to a particular Block Limit board. This is done by means of computers and a series of numeric codes transmitted by two-way radio.
The Train controller has a workstation that is very similar to a UTC workstation used in RCS territory. Just like UTC, the DTC workstation has a schematic diagram of the track in that Controllers territory.
The driver of each train that enters DTC territory is issued a laptop computer. Locomotive cabs have been fitted with special “soft” cradles and plug in power supplies for the laptops. These laptops are pre-programmed with information that a driver may select from e.g. line section (see below).
Before a train can enter DTC territory, the driver must perform computer start up procedures whilst the Train Controller “Builds” the train into the DTC system. The following procedures are carried out:-
- Mount laptop in cradle and connect power supply lead
- Boot up Computer
- Set time and date
- Select section of line to be traversed (eg. Charters Towers to Stuart)
- Enter train details
- Train Number (eg. 6239)
- Lead locomotive number (eg. 2810)
- Location (eg. Charters Towers)
- Block limit board train is facing (eg. CT21)
- Start up details will be displayed on screen
- If details are correct, hit “Enter”
– system will generate two “Start-up” codes
- Transmit codes to Train Controller
- Select “Start up code” button from menu
– Start up code screen appears on workstation
- Enter codes into system
– a screen will appear requesting train length
- Confirm train length with driver
- Enter length into system
– system will generate a “Display” code
- Transmit display code to driver
- Enter display code into laptop
– This will generate a DTC authority showing the current location of the train
- Read authority back to Controller
- “Driver of 6239 – 2810, starting in Charters Towers yard. Must not pass Block Limit Board CT21”
(This dialogue is actually shown on the drivers laptop screen).
- Check details and click “Accept” or “Reject”, as the case may be
- If accepted, confirm with driver
– Train 6239 will appear on the Train Controllers DTC workstation at Block Limit Board CT21
- If rejected, repeat process.
Although this seems like a lengthy and complicated procedure, it only takes a few minutes and only needs to be done at the beginning of the trip.
Issuing DTC Block Authorities
Once the ‘Start Up’ procedure has been completed and the train is ready to depart, the Train Controller can issue the driver with the first authority to proceed. The basic operation of the Controller’s workstation is very similar to the UTC system. To set a path for a train in both systems, the Train Controller clicks his mouse on the train icon then clicks on the track block at the termination of the route.
This action drives all motorised points to the desired position then clears all signals between the train and the route termination. The route and all applicable signal icons will turn green when complete. This is the end of the process.
When the route is selected, it turns flashing green and a ‘command’ code is generated. The following procedure is carried out.:-
- Contact Train Driver and tell him to be ready to receive an authority.
- Select ‘New Block Authority’ from menu on laptop.
– The ‘Command code’ screen will appear.
- Inform Train Controller that he is ready to receive the authority.
- Transmit the ‘command’ code to the driver.
- Click ‘accept’ on the workstation.
– The ‘drivers code’ screen will appear on the workstation.
- Repeat ‘command’ code to Train Controller whilst entering it into the laptop.
– This will generate a ‘Drivers’ code
- Transmit the ‘Drivers’ code to the Train Controller.
- Press ‘Enter’ on the laptop keyboard.
– The ‘Control code’ screen will appear.
- Repeat ‘Drivers’ code to Train Driver whilst entering into workstation.
– This will generate a ‘Control’ code.
- Transmit the ‘Control’ code to the driver.
- Click ‘accept’ on the workstation.
– A dialogue detailing the limits of the authority will appear on the workstation.
- Repeat ‘Control’ code to Train Controller whilst entering it into the laptop.
– A dialogue identical to the one on the Train Controller’™s workstation should appear.
- Read the dialogue to the Train Controller.
- Press ‘Enter’ on the laptop keyboard to confirm.
- If dialogue is correct, click ‘Accept’ and inform Train Driver he may depart.
– The route display on the workstation will show the train icon occupying ALL blocks for which the authority is current. This includes ‘Head of train’ and ‘Tail of train’ icons.
- If dialogue is NOT correct, repeat procedure.
To put this procedure into words makes it sounds very complicated and longwinded. In practice, a Block Authority can be completed in 30 to 45 seconds. A Train Order, on the other hand, can take up to 8 minutes even if a CATOS terminal is used. Here is an example of a two-way radio dialogue between a Train Controller and a Train Driver when receiving a Block Authority. Keep in mind, a ‘Start up’ procedure has already taken place:-
TC ‘West Control, Townsville to the Driver of 6239, over’
DR ‘Driver 6239 receiving, over’
TC ‘6239 are you ready to receive your authority to proceed?, over’
DR ‘Control, 6239 is ready, over’
TC ‘Driver 6239, your command code is 301-683-796, over’
DR ‘Command code 301-683-796’¦.. Drivers code is 475-294-094, over’
TC ‘Drivers code 475-294-094’¦.. control code is 898-147-357, over’
DR ‘Control code 898-147-357’¦.. Authority reads ‘˜Driver on Train 6239 locomotive 2810, proceed into Stuart, obey signal ST49 at Stuart’™, over’
TC ‘Driver 6239, Block Authority is correct, you may proceed, out’
DR ‘Acknowledged, Control, Driver 6239 out’.
Releasing Blocks back to Train Controller
After a train has traversed one or more block sections, he may release blocks behind him at his own discretion or as instructed by the Train Controller. The following procedure takes place
* Ensure blocks to be released are clear and no part of his train is occupying any of them.
* Press ‘R’ on the laptop and use the arrow keys to select the blocks to be released.
* Press ‘Enter’
– This will generate a ‘Release’ code and a dialogue.
* Transmit the code to the Train Controller.
* Click on ‘Tail of train’ icon on the workstation.
– The ‘Block Release’ screen will appear.
* Enter the ‘Release’ code given by the Train Driver.
– A dialogue detailing the block(s) to be released will appear on the workstation.
* Read the dialogue to the Train Driver.
* Confirm message is correct.
* Press ‘R’ to release blocks.
* Receive confirmation from Train Driver.
* Click ‘Accept’ on workstation.
– Route diagram will update ‘Tail of train’ icon to current location.
The DTC system is capable of issuing a Block Authority from one end of a line section to the other. Each ‘line’ (e.g. Stuart â€“ Mount Isa) is broken up into ‘line sections’ (e.g. Stuart, Charters Towers, Charters Twrs, Hughenden etc).
Stations at the border of line sections are manned for all train movements and have locally operated signalling systems (note, if the signals are colour light, they do not come under RCS rules). Once a train has arrived intact inside the ‘Home’ signal, the Block Authority can be relinquished and the train is under the control of the Station Master.
A Train Controller will generally give a train authority to proceed to either of three points:-
1. To the first station where shunting or other duties are to be carried out, or
2. To the first station where that train will cross an opposing train or allow a following one past, or
3. To the end of the line section, if traffic permits.
If a train is required to shunt at a station, that train must arrive intact at that station, release his DTC authority and be issued a ‘Shunt station’ Authority. This will block all lines at that station and prevent other trains from passing through. The train bearing the ‘shunt station’ authority is permitted to use any track at that station and may proceed into the block section, for shunting purposes only, as far as the ‘Limit of Shunt’ board (See map above). Once the shunting is complete, the ‘Shunt station’ authority is relinquished and a Block Authority issued to continue its journey. If, for some reason, the train is to depart a different line to that where it arrived, the Train Controller must be informed so he can update the DTC system and give departure from the correct Block Limit Board.
Crossing (Refer map on Page 1)
Imagine the above map is Reid River (RR) and two opposing trains are required to cross here. The Up train will be given an authority as far as Block Limit Board RR16, the Down train to RR23. Let’s say the Up train is first to arrive and stops at RR16. The driver performs a brake leakage test to confirm his train is complete. He then releases the block)s) behind him to Control. The Controller may then update the Down trains’ authority to continue past RR23 and into the next section. When the Down train arrives, the driver of the Up train will observe the ‘Rear of Train signal’ is in place on the Down train and radio that driver to inform him of the fact. The Down train releases the block(s) behind him and continues his journey. The controller can then issue the Up train with an authority to resume his trip.
Positive aspects of DTC
For the most part, no electric signalling equipment is required, only signage, manually operated points and a reliable two-way radio system. Laptop computers are used on locomotives so it is not necessary to fit every locomotive with a computer. Only purpose designed ‘soft’ cradles and external power sources.
Logic would dictate that this should be the first point mentioned but corporations the world over these days tend to opt for economy over safety. However, DTC achieves both. Rules are in place to cater for all types of situations including computer and/or radio failure. The Train Controller has access to safety controls never before seen in ‘dark territory’ operation. For the first time, it is possible to ‘block’ a track to allow maintenance staff to work safely on track. This facility prevents the Train Controller from issuing authorities over the closed section of track. Not even the older CATOS system has this capability.
As mentioned, a DTC Block Authority can be issued in 30 to 45 seconds whereas a Train Order takes from 3 to 8 minutes. DTC specific radio operations are conducted on a separate channel to the normal main line radio channel. This is a ‘party’ channel where a driver can listen in and obtain details and whereabouts of other trains in the area. Therefore it is no longer necessary for the Train Controller to issue each train with a ‘Train Working Advice’, a cumbersome task in itself.
For the Train Driver and the Train Controller. Easy to understand screen layouts are employed and ALL dialogue is generated by the computer system. You don’t even have to think about what to say!! Commands are kept simple and everything is in plain English. Even the most jaded drivers can use this system.
Well? Not necessarily a positive point to QR but rail fans love DTC. If you have a radio scanner tuned in to the DTC specific channel (the freq escapes me), you know EXACTLY where trains are at all times. Rail photographers need never endure poor quality pictures because the camera equipment was set up in a hurry. With DTC, you can anticipate the arrival of a train and have your equipment set up in good time ready for that perfect shot!
Negative aspects of DTC
DTC relies heavily on the usage of Two-way radios. Therefore it is imperative that the best possible, most reliable radio system available is used. Despite this, it is still more economical than RCS.
No ‘dark territory’ safeworking system was ever designed for use in high density traffic areas. DTC is no different although it is possible to run more traffic in DTC territory than any other ‘Dark’ territory.
The biggest enemy of any ‘dark territory’ train operations. The Train Controller has no choice but to take the drivers’ word that he is in fact clear of sections he is releasing back to Control. This is no different to Train Order territory so operations depend on the strict discipline and training of the train crews. Fortunately to date, this has never been an issue.