Yet Another Interlocking and Track Circuit thread

I didn't want to bump or hijack another thread that was going down a different path with these things. I've read a lot of questions and answers regarding TCBs and how they work with EITs to direct trains into a station and figured out some things from the wiki pages, but there's only been a few discussions about using TCBs to protect long stretches of single track between EITs.

I figure this question might be helpful to others too, so while I'm trying to figure this out I figured I'd ask and get confirmation that I'm doing this right. In the accompanying badly drawn track diagram, I'm focusing primarily how to protect the 2-way portion of the branch from cornfield meets while also allowing trains to enter and work the non-signaled industry siding without impeding traffic for the entire time they're in there (Trains working this siding would come north from EIT 2, pull in and back up to work the industry, then back out onto the Branch track and continue north to EIT 1 to continue to other industries). In reality this stretch is about 7 miles long, which is why there are two sets of automatic block signals - this is to allow trains to follow one another in and I'm not sure if setting up the Track Circuit in this way would prevent trains from following each other in?

Obviously at EIT 1 I would need a NB and SB path onto and off of the single track, and at EIT 2 there would be paths for the various combinations, but would I need to setup a specific IT path to get into the Industry siding? How would I then go about getting back out, would that somehow need a path too? Or can that be operated "manually" by the AI or player?

Are there any other problems anyone knowledgeable foresees with this setup?

Hi ctclark1.

Your schema to use a tcb to protect the single track needs also a third track circuit insulator on the track going to/from the industry siding so that the single track tcb remains free and available if a train is occupying only the industry siding. You also need to take care that all paths going to the single track needs to have their exit signal inside the TCB area and have the exit signal TCB option active.

for the intermediate industry siding access, you will need also four paths : one for going from the single track to the industry siding and one for going from the industry siding to the single track (with the exit signal for this path included in the tcb area and the exit signal tcb option active). You will also need two other paths for trains staying on the single track in the two directions (these last paths need to not have the exit tcb option active to avoid deadlocks as requesting trains are already inside the tcb area) these paths should be defined either in a third interlocking tower dedicated to the intermediate industry siding (best option) or may be grouped with either eit1 or eit2 at your preference (to reduce the number of towers - not recommended).

hope this helps.
regards.
Pierre.

Hi

As far as I know there is no way that an EIT will allow two trains into a section controlled by a TCB but I'm sure Pierre will correct me if that is incorrect.

The only way that I've been able to do what you are wanting to do is to use two variables to control the single line section. One variable acts as a token which indicates if the section is occupied and the second one indicates which direction any train already in the section is travelling. Any train travelling into the section increments the token variable by 1 and when it leaves the section it decrements the same variable by 1. By using these two commands the token keeps track of how many trains are actually in the section at any time. This method can be used in conjunction with EITs as long as the paths into and out of the section are set to manual and the IT SetPath command is used to set the paths only when they are actually needed.

The Input Tabel is built in and the driver commands needed to work with variables are all on the DLS by author "trev999". The commands are "Insert buff label", "Jump to label", "Set S-variable", "Skip if session-variable", and "Wait Until S-varable V3". All tracks leading into the single line section require two trackmarks to be added, one just in front of the signal controlling entry to the single line section and a second one on the approach to that section but placed far enough back to enable a train to stop at the first one without causing a SPAD. You also need a TM between the industry track and the exit from the section and another to drive through out of the section.

As an example the two variables may be called "token" and "token_dir". If token_dir = 1 it is travelling SB and if it = 2 it is travelling NB. Of course you can give the variables whatever name you prefer.

The commands for a train approaching from the branch heading SB would be:

Drive via the approach TM
Skip to label 1 if session-variable token = 0 - Indicates section is empty so jump over next 3 commands
Skip to label 1 if session-variable token_dir = 1 - Train is travelling in the same direction as one already in the section so jump over next 2 commands and proceed.
Drive to TM stop - Train already in section travelling NB so prevent this train from entering section.
Wait until token = 0 - Wait until section is clear
Label 1 - Label for the skip commands to jump to
Increment token by 1 - Increments the token variable by 1 to indicate train is in section.
Set tok_dir to 1 - Sets train direction to SB
It SetPath into section - Manually sets path into section
Drive via TM out - Drive through TM out
It SetPath out of section - Manually sets path out of section
Drive through SB out - Drives the train out of the section
Decrement token by 1 - Decrements the token variable by 1 to indicate the train has left the section.

Although this looks quite complicated the commands can be put into the Schedule Library and called by any train. Once they have been proved to work you can copy the schedule and edit the commands that need to be changed. In your example above it would seem that you need 6 main line schedules (one path at the NB end and three at the SB end in each direction). It would simplify matters if you were able to just use 1 track for trains entering the branch NB and another for trains leaving the branch SB. You would also need schedules for any train calling at the industry but the same structure of commands should work there as well.

There are full instructions for the variable commands included with them. Just double click on the commands in CM to be able to read them.

If this interests you and you need any further explanation then please post back.

Regards

Brian

I've added some detail to the drawing here. The bottom part is a blown up drawing of the EIT1 area to show the location of the signals and junction relative to the circuit insulator and detector. Let's also pretend there's an automatic signal on Branch NB about 2 miles down the track (we'll call this SigB7N)



You mention creating extra paths for the Industry siding and needing an exit signal for that path, and I assume I'll need entrance signals to get back out to the Branch, so I've added two invisible signals here, correct? (SigIndE and SigIndX).

At EIT1 the paths I should create are:
Path Branch North (Clear after last junction)
SigBNB / Proceed
EIT 1 Jct / Right
SigB7N / Automatic

Path Branch South (Process TCB for Exit Signal)
SibBSB / Proceed
EIT 1 Jct / Left
SigBNB (back)

At EIT2 I'm already seeing 20 possible combinations of interaction between the 3 main tracks and the branch/bypass lines, and although not prototypical for the area I'll probably set it up to limit Northbound trains taking the Branch and the Bypass need to be on Main 3 at EIT 3 (off the right side of the drawing) and southbound trains coming off of these lines can only go to M3 or M2, although that creates other complications I'm not ready to discuss yet. Using that logic, relating to the Branch and M3 only (ignoring the Bypass and other mains for now), I would need a path from SigCPBranch and SigCPM3NAS in both directions, processing TCB for Exit Signal on the Northbound path and Clearing after last Junction on the Southbound path? And then I'll need four more to get trains into and out of the industry?

With regards to the extra four paths to get into/out of the industry and bypass the industry, what would I use for entrance/exit signals on the Branch here, as SigB2N and SigB2S are about three quarters of a mile away from the industry? (I know, it looks a lot closer in the drawing)

Brian I appreciate you figuring that out, but I'll just keep things "creatively planned" so that trains don't stack up here too much I guess - the only trains using this branch are passenger trains (on an Amtrak schedule) and the one freight servicing the industries so it shouldn't be horrible. I was mostly asking for prototypical action since there are block signals that could allow two trains heading the same direction to be following each other and would be more pertinent elsewhere.