User:Sfalpha/Draft - Railway signalling in Thailand

Mainline Signals (State Railway of Thailand)
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 (Bombadier INTERFLO 200) but later project are design for upgrade to ETCS Level 1 starting from Red Line commuter project and recent double tracking project  , however mostly in rural areas, which is single track Semaphores Signal still in use.

Distant Signal
Distant signal (use to indicate next Home signal is Stop or Clear. This signal consists of 2 color light signals (yellow and green).

3 Colors Main / Exit Signal
This consists of 3 colors light signals (green, yellow and red) with call-on signal.

This type of signal is use in main tracks. If there are switches ahead, the branch direction indicators (5 in-line white lamps) may also be install on top of signal.

Call-on signal (3 white lamps arranged in triangle) use for permit locomotives to do shunting or coupling when track behind signal is occupied.

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

This type of signals mainly use on maintenance yard, depot or sidings (not main tracks). In station without switch, main tracks also use 2 colors Exit Signal instead of 3 colors.

If there are switches ahead, the branch direction indicators (5 in-line white lamps) may also be install on top of signal.

Proxy 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 vertical, diagonal or horizontal that represents green, yellow and red of next signal.

Station Yard Signal Layout
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 (either Inner or Outer) 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.

Home Outer Signal
Home Outer Signal use to protect the waiting area or shunting area outside inner area of the station yard, also act as a Warner Signal for Home Inner Signal and switches before entering station platform or sidings.

If signal is yellow, train must prepare to stop at next signal or proceed with limited speed. Minimum distance from Home Inner Signal to Home Outer Signal is 700m (500m train length plus 200m safety distance), sometimes Home Outer Signal is omitted in case there is limited distance between stations.

Home Inner Signal
Home Inner Signal use to protect the switching area, passing track, platform track and siding area of the station.

If signal is yellow, train must prepare to stop at next signal or proceed with limited speed (usually for stop at station or branching of current track at the switches after Home Inner Signal).

Speed limit sign usually placed along with Home Inner Signal to indicate safe passing speed at switches in case of branching. In large junction station multiple stage of Inner Signal may exists.

Exit Signal
Exit signal use to allow train to leave station or yard. In large junction station multiple stage of exit Signal may exists.

Block Signal
In case distance between stations is too far (distance from Exit Signal to Home Outer Signal of following station), another Home Signal and corresponding Distant Signal may be placed between station to act as a Block Signal