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Author Topic: Question for signal buffs :)  (Read 21437 times)

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Offline Jando

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Question for signal buffs :)
« on: July 24, 2019, 10:45:16 PM »

Please see screenshot, you see a double track main line and a single track regional line departing from the main line east and south. Also shown on screenshot is an express train on the main line travelling at 143 km/h. To achieve that speed the main line uses 3-aspect signalling (here in track circuit block but the same principle would be used in absolute block by usage of distant signals). Problem of course is that the regional slower train also travels on that main line and sees the 3-aspect signals, occasionally reserving through the crossing and causing the express trains to slow down.

To work around that I'm used to build a small siding for the local train (on the screenshot the 3rd track on the northern side of the double track main line) where the local train line has a waypoint. Reason I do this is that the slower train does not see the 3-aspect signals of the main line but a 2-aspect signal instead, preventing the slower local train to reserve through the crossing and causing the express train to slow down.

Any better way to achieve that? How do real life railways handle this situations? Thanks in advance for any hints.

Offline Vladki

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Re: Question for signal buffs :)
« Reply #1 on: July 24, 2019, 11:25:02 PM »
Real railways use scheduling and common sense of the signalman, to prioritize the express trains.

Also a bridge over the double track would help if the line is busy

Offline freddyhayward

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Re: Question for signal buffs :)
« Reply #2 on: July 25, 2019, 12:55:16 AM »
Your solution seems fine. Another way might be to place the 2nd last signal 1/2 the stopping distance of your express train from the junction, and the 3rd the exact stopping distance from the junction. That way the express can still travel at full speed but you also minimise the distance and time between the local train reserving through the junction and clearing it. while expensive, grade separating the junction would be the most reliable way to avoid the problem.

Offline jamespetts

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Re: Question for signal buffs :)
« Reply #3 on: July 27, 2019, 09:42:52 PM »
The solution that you have implemented is, essentially, a passing loop, a solution used frequently by real life railways for this very purpose, especially for slow freight trains.