I'm putting this in the Inspection Pit because it's a pretty scale-agnostic question, actually a prototype operations question. I have this junction on my layout plan... Ooh, sorry. That is rather large. The black line that curves up from lower left to upper right is the MAIN. The blue line that curves from bottom center up to upper left is the BRANCH The grey line running more-or-less horizontally across the upper portion is an industry lead or spur coming off the main. This is modern time (though discussion of older methods would be ok too). Track Warrant control on the main. The branch is ... not controlled except through the track warrant that allowed the train to get there in the first place). My question is this... how would this junction be controlled? If it was just the main and branch, or just the branch and industry spur, this would be easy. With all three there, I'm puzzled. Would there be signals? If so, what type and where? An interlocking tower (in 2015?)? Permissions granted/denied via the Track Warrants? Rules spelled out in the Employee Timetable? And how would these things work? It's at least theoretically possible to have three trains in this area... (1) one on the main below the crossing, either wanting to run through or switching the industry just off-image below (2) One on the main above the crossing, on the industry spur switching that industry (3) One on the branch line passing through. Help?? I'm so confused I'm not even sure how to correctly ask this question... ETA: The semaphore signals shown in the drawing were just my first guess at what would be where...
I've worked out a possible answer to my own question... It's actually already partially marked in the drawing, using semaphores as a stand in for the light signals... Main Line: The north end of the siding below the diamond, together with the diamond form a single interlocking control point. Use the same signals as I would for the siding, but move the points-end signal north of the diamond. Dispatcher can hold these at stop when he wants to allow branch line traffic through, or let them go automatic... Branch Line: A signal north of the industry spur diamond and a second signal south of the main line diamond. These are tied into the main line signals so that they show a restricting indication when the main line signals are at (dispatcher held) stop, else absolute stop. Branch line trains can only go through when the Dispatcher is holding up main line traffic. Industry Spur: Stop signs or a swing gate blocking the spur and allowing branch traffic through. This is protected by rules as follows: A) Branch and Spur traffic are both at Restricting speed. B) Branch: If approaching the diamond, a Spur train is already in the crossing, stop and wait till it is clear. C) Branch: If you get to the branch diamond first, you have right of way. D) Spur: If near or in the diamond, and a Branch train approaches, clear the diamond as soon as safely possible and hold all work, staying clear of the diamond until the Branch train is through. Thus if a branch approaches while the spur is being worked, it will go as follows: 1) Branch train stops short of spur diamond and waits 2) Spur train clears the diamond and holds 3) Branch holds short of spur diamond until signal shows Main is clear. 4) Main train clears 5) Dispatcher holds main traffic, clears branch train 5) Branch line runs through spur and main diamonds 6) Spur train resumes work after Branch train clears 7) Dispatcher releases hold on main, allowing main traffic to resume. This requires the branch train to call Dispatch and request clearance to pass through the diamond. But I think he would have to do that anyway. Because they are at restricted speed, the Branch and Spur trains can handle the situation without outside intervention. Yes???
LOL! Ain't that the truth... Yeah... that would have to be whatever the next signal down the line is on the main... the far end of the siding to the south, and the next point to the north. The layout simply isn't large enough to support any intermediate signals. It's barely large enough to support realistic signals at all. So the approach signal may be "imagined" Based on some other feedback I've received, I've revised this to the following arrangement... The branch/spur diamond is protected by 4 stop signs. Literally a 4-way stop. Both lines are Restricted speed operation anyway, and the rule book will state Branch gets priority over Spur. So if someone is working the spur when a Branch train comes along, the Spur train will clear the crossing and allow the Branch train by. The Spur train is permitted to not stop while actively switching, as long as it clears the diamond and stops as instructed above. The Branch train may continue without stopping if and only if (a) a Spur train is on the spur, (b) the Branch train engineer has a clear view of the Spur train and can visually confirm it is stopped and clear of the diamond, (c) the Branch train contacts the Spur train by radio and confirms the move-without-stopping, and (d) both trains remain in radio and visual contact throughout the move. The Main/Branch diamond will have a swing gate (hopefully animated!) that in its "closed" position blocks the Branch line. In the early version (pre-signals-installation), the rule book will call for Restricted speed on the main between the two stations either side of the crossing, unless the Dispatcher allows faster on the applicable Track Warrant.* Branch trains will have to stop at the gate, then call Dispatch for permission to open it and pass. Dispatch will make sure all is clear, then permit the move. Once the Branch train is clear, it will close the gate behind it, and traffic will resume on the Main**. Once signals are installed on the main, the points-end signal of the siding end just to the south will be placed north of the diamond, and will be tied to the gate and to the dispatcher, so the dispatcher can stop main line trains by changing the signal indication. As a failsafe, if the gate is open, the signals will fall to Stop and Proceed as well. Distant signals will automagically fall to Approach, etc. as appropriate. What do you think? Sounds like a plan? I see a bunch of interesting operational and scenery opportunities here. The branch and spur train engineers conferring, the traffic to the Dispatcher for clearance, the animated swinging gate, a small, dilapidated telephone booth near the gate for pre-radio contact, the gate itself, the stop signs, little walking paths through the grass around the meet points, maybe the wreckage of an old boxcar that was the victim of some distracted engineer... * The branch line is only accessible from the main, and thus only with Dispatcher permission. By defaulting to Restricted and allowing the Dispatcher to authorize faster, the Dispatcher can speed up the main if he knows the Branch is empty (e.g. "The branch train doesn't run on Tuesday..."). And if he forgets, the default rule keeps things safe. ** The dispatcher may, at his option, instruct a stopped Main train to close the gate behind a blocking Branch train, thus relieving the Branch conductor of having to close the gate and walk the length of his train.
If everything is going to be signaled, then the industry spur would have a dwarf signal on each side that will display either red (Stop) or yellow (Restricting). If the entire branch is unsignaled (Track Warrant), then a signal displaying red (Stop) or red/yellow (Restricting) is sufficient to allow access to the branch. Restricting is generally used (at least around here) as a permissive signal to enter a non-signalled track. The rules will usually have something that says "Restricted Speed applies until the head end enters non-signalled territory and the rear of the train has cleared all turnouts and crossovers." So a train would run Restricted Speed until it clears the switch from the main to the branch, and then could run whatever speed is authorized for the branch. Not a complete answer to all your questions, but I hope it helps.
Rick, Thanks for the response. Always nice to get input from someone who is (or was?) actively on the rails. Especially interesting that the branch train would be free to run whatever speed once clear of the switch. I guess it makes sense, just hadn't thought about it.
