UK Signalling: Junction Signalling on the Birmingham Cross-City Line (TSW | tutorial)

[@SireMoon]

Speed measuring on approach control from red. The speed of the approaching train is measured by a track circuit (or a pair of axle counters). When the track circuit goes occupied (or the train reaches the first axle counter) a timer is started. If the timer expires before the train occupies the next track circuit (or the train reaches the second axle counter) then the interlocking knows the train has slowed down enough and clears the junction signal. If the timer is still running the signal is held at red. The length of the track circuit (or distance between the axle counters) and the value of the timer are chosen to suit the speed limit of the divergence.

[@tygerways6615]

Thank you for this information! I have been pondering about the two solutions that you describe, but I wasn't able to verify what method is actually used. Especially I wasn't sure if it is acceptable to use track circuits for that (that must be rather short then, no?). It is more or less the inverted model of the TPWS OSS loop, with the timer running on the junction equipment instead of on the electronics on the train.

[@SireMoon]

@@tygerways6615 Yes, and the track circuit sections concerned are indeed typically quite short.

[@SireMoon]

Rear clear marker. The numbers are train length. They are typically used after (usually very low) speed limits, neutral sections etc

[@tygerways6615]

Thank you again! Do you know how the numbers are read? Is it number of cars? Standard Length Units (SLU)? Or something else?

[@SireMoon]

@@tygerways6615 It's number of cars

[@關昌基]

Arrrr.. Really tempting offer for the sale. I still hasn't got TSW game. Considering it now.

[@tygerways6615]

Go ahead! :)

[@ferrocarrilesvascos]

Hi, i have a question about the signal on the isle of wight 2022 that apear a 5 number and the "W"letter on it. What's the meaning? Thanks 👍👍

[@tygerways6615]

I haven't played the Isle of Weight 2022 route so far, but I will check it out and report! :)

[@tygerways6615]

Ah, now I know what you mean. It is the combined speed and whistle board at Brading (running towards Shanklin), right? It limits the speed limit to the number indicated (not implemented in the game, though) and at the same time requires you to sound the horn/whistle. It is used to protect open level crossing (see RSSB Handbook, RS521, section 6.1). It actually exists at this point in real life, too: kzbin.info/www/bejne/pme9q56deduMi8U

[@SireMoon]

Flashing yellow. Your description and the game's implementation of it are not quite right. At a predetermined point after the train passes the flashing yellow signal, the junction signal will step up to the aspect determined by the signal ahead of it. It does not stay on yellow as you describe (and the game implements) unless the signal beyond it is at red. One of the reasons for the flashing yellows is to eliminate the delays to trains inherent in approach control from red if the line beyond is clear. If the junction signal was to stay at yellow as implemented in the game then the driver has to assume the next signal is red and brake accordingly until that signal comes into sight and the delay that flashing aspects are designed to eliminate occurs anyway.

[@tygerways6615]

Thank you for clarifying this! Apparently I mixed up too many different situations in my explanation. In my understanding, the junction signal CAN be held at yellow or CAN be released, depending on how much I want the train to slow down (and on the aspect on the signal after the junction). The description in the RSSB rulebook doesn't really specify what happens with the junction signal when the train is approaching it, so I would have thought you can release it or hold it at need, balancing safety and speed in every single implementation. In the defense of the game: At 1:45:00 the junction signal actually clears when the train is approaching.

[@SireMoon]

@@tygerways6615 Ah ok - I didn't get to that point in the video. On everything DTG has done before that I've seen, both TSW and TS, the junction signal stays at yellow after flashing yellows so I assumed this would be the same. Having said that they never had an implementation of approach control from red before that I'd seen so that appears to be new and welcome. It's always been my biggest gripe with the game actually so seeing they've done on it on this DLC is a definite improvement.