Thai railway signalling

Modern railway signalling in Thailand on the Mainline employ Color Light Signal and Computer-based interlocking. SRT currently implementing CTC to link whole country signalling system together using Fiber Optic network. This includes Recent Double Tracking Projects for all mainline extend from Bangkok.

Early double tracking project use conventional interlocking system (Bombardier INTERFLO 200)[1] but later project are design for upgrade to ETCS Level 1 starting from Red Line commuter project [2] and recent double tracking project [3] [4] [5], however mostly in rural areas, which is single track Semaphores Signal still in use.

Color Light System
DistantHome OuterHome with Left IndicatorHome with Left/Right Junction IndicatorStarterStarter with Right Junction IndicatorMain with Shunt Ahead

2 Aspects Distant Signal

Distant signal use to indicate next main signal is red or not. This signal consists of 2 color light signals (yellow and green).

AspectMeaningComment
GreenClearProceed on straight route, next signal at Yellow or Green
YellowReduce SpeedProceed on straight route, prepared to stop at next signal at Red

3 Aspects Main / Starter Signal

This consists of 3 colors light signals (green, yellow and red).

AspectLocationMeaningComment
GreenHome / StarterClearProceed on straight route, next signal at Yellow or Green
YellowHome / Starter
with Junction Indicator		Proceed with cautionProceed through junction or junctions, regulating the train speed through the junction to limit given by the speed board, prepare to stop at next signal at Red.
Home / StarterReduce speedProceed on straight route, prepared to stop at next signal at Red
RedHome / StarterStopStop at the signal

2 Aspects Main / Starter Signal

This consists of 2 color light signals (green and red).

AspectLocationMeaningComment
GreenMain / Starter on Main TrackClearProceed on straight route, next signal at Yellow or Green
Starter with Junction IndicatorClearProceed through junction or junctions, regulating the train speed through the junction to 25km/h until leave station area
Starter on Siding TrackClearProceed through junction or junctions, regulating the train speed through the junction to limit to 25km/h until leave station area
RedMain / StarterStopStop at the signal

Repeater Signal

This signal use when Main Home signal is blocked from driver view (in curve or hills). The signal consists of 3 white signals that display either diagonal, flash diagonal or horizontal that represents green, yellow and red of next signal.

Call-on Signal

Call-on signal, 3 white lamps arranged in triangle pointing up, may installed below or besides Main Signal. Call-on signal use for emergency to allow train or locomotives to pass while signal is red.

SignalMeaningComment
Flashing WhiteCall-on

Shunt Ahead Signal

Shunt Ahead signal, 3 white lamps arranged in triangle pointing down, may installed below or besides Starter Signal. Shunt Ahead signal use for allow locomotive shunting.


SignalMeaningComment
Flashing WhiteShunt Ahead

Ground Shunt Signal

Ground Shunt signal, 2 horizontal red lamps and 2 diagonal white lamps, may installed in shunting area of main tracks (between switches and Home Signal) or in shunting tracks. Ground Shunt signal use for allow locomotive shunting.

SignalMeaningComment
Diagonal WhiteShunt ahead
Horizontal RedStop

Junction Indicator

Junction Indicator (5 in-line diagonal white lamps point left or right) may installed above Main or Starter Signal before switches.

If junction indicator is active, the train must proceed at reduce speed. Speed limit indication sign may present at signal to indicate speed limit when passing switches.

IndicatorMeaningComment
OffNo diverging
To leftExpect diverging left
To rightExpect diverging right

Level Crossing Rail Warning Signal

This signal may placed ahead of Level Crossing to indicate road at level crossing ahead been closed engaged and clear to proceed.

Level Crossing Advance Warning Marker Post is placed 1km ahead of this signal to warn train driver of level crossing ahead. If Signal is not clear driver must slow down the train and proceed with limited speed.

SignalMeaningComment
Flashing WhiteClearRoad barrier of level crossings ahead are closed and clear to pass

Station Yard Signal Layout
Typical signalling layout of medium size station yard

Typical stations which have station yard or siding tracks will have following signal layout.

Distant Signal (Warner Signal)

Distant signal is place before Home Signal of the station yard or signal block.

If signal is yellow, train must prepare to stop at next signal or proceed with limited speed.

Typical distance of Distant Signal from Home Signal is 1000m-1500m.

Home Signal

Home Signal use to protect station's inner area (switching area, passing track, platform track, sidings).

Minimum distance from Home Signal to inner area of station is 850m (650m maximum train length at limit shunt post plus 200m minimum safety distance).

Speed limit sign usually placed along with Home Signal with Junction Indicator to indicate safe passing speed at switches in case of diverging.

In some stations, 2 stages of Home Signal used, this separate Home signal into Home Outer Signal and Home Inner Signal, in this case, Home Inner Signal is placed immediately before station inner area and Home Outer Signal is place at least 850m before Home Inner Signal to allow a train wait on main track before entering station.

Starter Signal

Starter signal use to allow train to leave station or yard.

In large junction station 2 stage of starter signal may exists. Inner Starter Signal use to protect switch and shunting area after leave inner area, Outer Starter Signal use to permit train to leave outer area. I this case, 3 Aspects Signal are use for Inner Starter Signal.

In some stations, If next station are too close (less than 2000m from Home signal of next station), 3 Aspect Signal are use as Starter Signal instead of 2 Aspect Signal and thus, this signal will also act as a Distant Signal for Home Signal of next station.

Block Signal

In case distance between stations is too far (distance from Starter Signal to Home Signal of following station), one or more 2 Aspects Main Signal and corresponding Distant Signal may be placed between station to act as a Block Signal.

This Block Signal usually not controlled by CTC or Station but work automatically using track circuit which is referred to as Automatic Signal

Semaphores System

Signalling in Urban Rapid Transit

SRT Red Lines

SRT Red Lines will operate on SRT mainline tracks which use ETCS Level 1 along with color light signals.

BTS Skytrain

BTS Skytrain currently use Bombardier CITYFLO 450 CBTC virtual block for signalling and ATP system. Originally, BTS use Siemens LZB 700M during early operation from 1999 - 2009. In 2009 new extensions to Wongwian Yai are equipped with CITYFLO 450 Signalling, then finally convert the whole system to CITYFLO 450 in 2010.

MRT Blue Line

MRT Blue Line use use Siemens LZB 700M for signalling and ATP system.

MRT Purple Line

MRT Purple Line Bombardier CITYFLO 650 CBTC moving block for signalling and ATP system.

Airport Rail Link use use Siemens LZB 700M for signalling and ATP system.

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References
  • "การออกแบบระบบอานัติสัญญาณรถไฟโดยคอมพิวเตอร์" (PDF). thaiscience.info. Retrieved 21 July 2019.
  • "SIGNALLING AND TELECOMMUNICATIONS DOUBLE TRACK RAILWAY PROJECTNAKHON PATHOM – CHUMPHON TENDER DOCUMENTS" (PDF). procurement.railway.co.th. Retrieved 24 July 2019.

Notes
  1. "Worldwide projects". Bombadier. Retrieved 21 July 2019.
  2. "Bangkok's suburban train will boost its capacity by up to 40% with ThalesBangkok's suburban train will boost its capacity by up to 40% with Thales". Thales. Retrieved 21 July 2019.
  3. "ประกวดราคาจ้างก่อสร้างโครงการจัดหาและติดตั้งระบบอาณัติสัญญาณและโทรคมนาคม ในโครงการก่อสร้างรถไฟทางคู่ ช่วงมาบกะเบา - ชุมทางถนนจิระ โดยการประกวดราคานานาชาติ". State Railway of Thailand - Procurement. Retrieved 21 July 2019.
  4. "ประกวดราคาจ้างก่อสร้างโครงการจัดหาและติดตั้งระบบอาณัติสัญญาณและโทรคมนาคม ในโครงการก่อสร้างรถไฟทางคู่ ช่วงลพบุรี - ปากน้ำโพ โดยการประกวดราคานานาชาติ". State Railway of Thailand - Procurement. Retrieved 21 July 2019.
  5. "ประกวดราคาจ้างก่อสร้างโครงการจัดหาและติดตั้งระบบอาณัติสัญญาณและโทรคมนาคม ในโครงการก่อสร้างรถไฟทางคู่ ช่วงนครปฐม - ชุมพร โดยการประกวดราคานานาชาติ". State Railway of Thailand - Procurement. Retrieved 21 July 2019.


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