Complex Interlockings How to handle them.

HSSRAIL

New member
October 5, 2020

Multi-Play surveyor and Transdem are going to make it possible to model the railroad network in exact scale at various points in time. There is going to come a time when some of these very complicated Interlockings basically Junctions on the railroad are going to come up. By complex I mean that the routes thru these interlockings are complex enough that some of the people playing the game will have difficulty navigating them. Many of these involve double slip switches.

Some solutions:

Simplify
If trains generally keep to the right you can basically model the junctions with diamonds and not provide alternate routings the switches will just be to navigate the most common routes.
Much of the complexity on the railroad is created so that there are work arounds for failures in the plant and Maintenance events that do not need to be simulated.

Only provide routings on the route being modeled

What if you don't want to use simplification?

Among the most complicated Interlockings in the United States is the routing of trains from the Park Avenue Tunnel on the former New York Central into Grand Central Station. Qualifying on these Interlockings there were I believe three of them took months. They involve the junctions from the Upper Level used by Intercity trains and the Lower Level used by Suburban Commuter trains. Other moves were movements from the station to the storage yards under Park Avenue.

Movements:
Intercity Trains: Mott Haven Coach Yard Empty Equipment for Loading as an Outbound Train basically this is a turn.
Intercity Trains Arrival Terminate then to Coach Yard.
Intercity Flip comes Inbound then turns into an Outbound Train this would come thru the loop to turn around.

Suburban
Terminate at Grand Central then Storage Yard Morning Rush Hour
Flip Comes in unloads goes out as an Outbound Train
Storage Yard to Platform then Outbound Train Evening Rush Hour

To realistically handle this in my opinion will require an Asset that has all the tracks built in and thru Scripting can route trains from Park Avenue thru these interlockings to the platforms based on a digit in the train ID.

For Example:

Name a consist Train Number 136 NYC Train from Poughkeepsie. The Asset would use the 1 and automatically line the route from Park Avenue to the Upper Level of the station and then whey the direction is changed to Mott Haven.

Having one Asset for this is needed and would have the advantage that it could be used on multiple routes just by downloading it.
 
Try "Enhanced TRC3 Invisible Interlocking Tower" by author Pguy, <Kuid2:61392:8101:52>, and the associated path set commands and rules, also by Pguy. A bit of a learning curve to get used to how to use them, but once you get the hang of it, a very powerful routeing solution for complex junctions.
 
The method I have found useful with using Enhanced Interlocking Towers with complex (e.g. 4 tracks diverging to 2x4 tracks) is this.

Sketch the junction on paper (you probably did this before laying track, right?). Identify every point where train movements conflict (ignoring switches) and create a unique name; my standard is a 2 letter code for the signal box that the EIT is representing followed by a short code for the tracks involved, in descending order of priority - e.g. "BX UFB-USA" for Bradly Crossing and the diamond where the Up Fast line to B crosses the Up Slow line to A.
At a 4 track scissor crossover (with the tracks designated DS,US,DF,DS), you have 4 points of conflict - e.g DS-DF, DF-DS and US-US; US-UF,UF-US and DF-DF; DS-DF and US-UF;DF-DS and UF-US.
Now, using your sketch, you can trace each path in turn, noting each conflict point that you encounter. In the case of the 4 track to 2x4 track I mentioned above, where we have USM diverging to USA and USB, and UFM diverging to UFA and UFB, and DSA and DSB converging to DSM and DFA and DFB to DFM you will end up with the following notes:
USM-USB: no conflicts
USM-USA: BX UFB-USA,BX DFB-USA,BX USA-DSB
UFM-UFB: BX UFB-USA
UFM-UFA: BX UFA-DFB, BX UFA-DSB
DSA-DSM: no conflicts
DSB-DSM: BX USA-DSB, BX UFA-DSB, BX DFA-DSB
DFA-DFM: BX DFA-DSB
DFB-DFM: BX DFB-USA, BX UFA-DFB
What you hopefully notice is that each conflict point is only shared between 2 paths
Create each path in the EIT, starting at the entrance signal to the exit signal as normal, but then go into the Exception Sets field in the path heading and add all of the conflict points you encountered in your previous step. You can also set the correct diverging aspect for the entry signal, without feathers or theatre controls cluttering up the track.
If you have done this correctly, the EIT will now prevent conflicting moves but happily allow non-conflicting moves.

Note that you don't need anything else - no track circuits, no triggers, no trackmarks, no mission codes - nothing.

When issuing instructions to AI trains, you just use one of the ITSetPath commands (depending on the behaviour you wnat while waiting) and "Autodrive Through" using a trackmark on the other side of the junction.

I have experimented with the timing and am coming down to placing a trackmark just inside each distant signal, representing the train entering the section. I then issue the ITSetPath when the train passes the EnteringSection trackmark of the section before the section that actually controls the junction. This means that the path is requested at the point that the box before would normally send 2 bells to the junction-controlling box. This means that the path is queued well in advance of the train actually arriving, meaning that you do not get signals waving up and down in front of a train while the system works out whether the path is available. Each train gets either greens all the way or a red if a conflicting movement is already signalled, followed by the signal clearing after the other movement is complete.

I have also used exception sets to control traffic on a route with double track at each end but 3 single line sections and passing points at 2 intermediate stations. Each single track section has 2 paths running from the entry signal to an invisible signal just beyond the switch at the exit point and also has a unique code which is added to each path's Exception Set. This ensures that only 1 train can be in the single track section at a time. A trick there is to have a trackmark at the entry to each station's limits. Non-stopping trains issue a path request after they clear that trackmark, while stopping trains do it after they stop. Why do I have an invisible signal for the end of the path? To allow for the path to be released as soon as it is no longer required, freeing the section for a train coming the other way - unless a following train got the path first, of course.

Hope this all helps.
 
Also be careful when using Enhanced Interlocking Tower when naming things, I ran into a problem some years ago because I was using characters that somehow messed with the operation. I can't remember which characters, PGUY would have to chime in on that matter.
 
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