Am I on to something here? (Junction Design/PBS)

Foo · Post by **Foo** » 16 Nov 2005 01:46

I've been playing around with layouts trying to find efficient station/junction systems (as everyone here does!). I've been trying to keep as compact as possible - some of the junction systems I've seen here are incredibly large and that's just not my focus.

I've come up with a design for tributary lines/stations leading off from a dual-track mainline (picture below). As you should be able to see in the image, I've used PBSignals for the junction + station, and a single regular signal on each main line.

Can anyone see a drawback with this design? It can take pretty high traffic to a single or pair of platforms, and is fairly extensible up to higher platform counts.

Just looking for better analysis than I myself can give. Thanks in advance

Conditional Zenith · Post by **Conditional Zenith** » 16 Nov 2005 03:04

You have 90 degree turns which are either not allowed or very slow with realistic acceleration. Another problem is that if a train is waiting for a train that just came out of the station, it blocks trains that may want to go into the station. If the station is full, trains will queue on the main line, blocking any other trains from going past.

Why the 2-way signals on the main line?

Foo · Post by **Foo** » 16 Nov 2005 03:20

The 2-ways were a mistake. I've slimmed it down to 1-ways now.

About the traffic problems you highlighted: I'll take those onboard, but I don't know of any compact junction system that doesn't suffer backing up problems. That seems to be directly related to the amount of floor space you use up. I guess the reality is the more trains you need to support the larger it must grow.

It's still a valid point tho.. I might try and extend this system to create some kind of sidings system using tunnels under the mainline. That would alleviate pressure on the mainline and hopefully do so without extending the trip distance into the station!

On a related note, I can't get PBSignals to work quite how I anticipate they should do. I've attached another image. In this scenatio trains can only approach on the top line, and exit on the bottom line. I have an entry PBSignal just in front of the incoming train there, and Exit PBSignals outside the station platforms, and a 1-way Exit on the exit track... Trouble is it doesn't work. The incoming train attempts to go into one of the stations and only stops when it hits the exit signal outside the platform. I've tried changing the platform signals to be combos (yellow vert bar?) but this doesn't change things.

Conditional Zenith · Post by **Conditional Zenith** » 16 Nov 2005 03:33

I think you are getting Presignals and PBS mixed up.

The signals in that picture are presignals. The fix is to change the bottom signal (the one way exit presignal to exit the station are) into a normal signal.

Presignals show green if the block they are protecting is clear, and there is a green exit presignal. In this case, the bottom exit signal is green, so the train is allowed in. You want it to only show green when one of the platforms is empty, so you only want the platforms to be exit presignals.

Foo · Post by **Foo** » 16 Nov 2005 04:14

You've just made a lot of things much clearer for me. Sincerely, thank you. Apologies if I'm asking newbie questions that have been asked a million times over. I have read the available wiki documentation (where I could find it) and have played around quite a lot. It's like IC logic gates only even more confusing

From what you've said, I understand that if I alter the setup in the way you describe, then trains heading for the stations will work perfectly, but I will encounter problems with:
* Incoming trains destined for the depot when both stations are full
* Incoming trains destined for the exit line (turning around)
If both station platforms are full at that point, the signal will show red, hence even though the depot is available and the exit line is clear, the train will halt.

However, you've answered a lot of questions for me on this one, so I'll go and experiment a whole bunch more and hopefully it'll all go smoothly! Back to the earlier example, I've been working on it some more as per your feedback and have come up against another hurdle:

------

I'm experimenting with PBSignals (now you've corrected me, these are proper Path-Based Signalling Signals). In the attached screenshot, I've created 3 connections between the station and the west-bound mainline. These work well for multiple trains heading out from the station to the west-bound mainline, but they do not work when a train arrives inbound from the west-bound line at the same moment.

In the screenshot, there are trains waiting in 2 of the 3 tunnels to exit onto the west-bound mainline. There is a small diesel engine inbound from the west-bound mainline, and I would expect that train to pass through the third (empty) tunnel. However, the signal lights for the third tunnel still let a train leave the station and head for the empty tunnel! As you can see in the image, the train has left the station and now blocks the path of the small inbound diesel.

Am I pushing PBS beyond its intended use, or still misunderstanding the concept? Once again, thanks in advance for any help you're willing to offer!

Conditional Zenith · Post by **Conditional Zenith** » 16 Nov 2005 04:48

Many people have tried setups similar to what you have just posted, and PBS as it is currently coded does not handle situations like that. Any setups where tracks can be entered from both ends can cause problems with PBS, people usually try this with stations.

Back to your other example. You should use PBS instead of presignals. That will fix both the problems you describe. Just make all 4 signals PBS.

spaceman-spiff · Post by **spaceman-spiff** » 16 Nov 2005 05:07

Foo, Please don't use that color, you can't read that brownish on the tt-style forum

^Cartman^ · Post by **^Cartman^** » 16 Nov 2005 15:19

Why not build something like this?

The trains can wait for a free platform without blocking the main track (if there is enought extra tracks to keep them from blocking the main track, ofcourse), and you do not have to mess around with the two ways tracks.

chairface · Post by **chairface** » 16 Nov 2005 15:26

In my experience, having a depot inside a PBS junction can be bad, the signal built into depots isn't a PBS one, so if a train is exiting that depot, other trains can't "see" it and risk crashing into it.

^Cartman^ · Post by **^Cartman^** » 16 Nov 2005 15:28

You must have used an old version of the PBS-patch then, because I believe that bug has been fixed.

chairface · Post by **chairface** » 16 Nov 2005 15:30

I'd like some confirmation from someone who, uh, actually works with the code before I'm gonna try sticking a depot in there.

Also, from what version onward was it fixed? I'm still playing with i3019.

^Cartman^ · Post by **^Cartman^** » 16 Nov 2005 15:38

chairface wrote:I'd like some confirmation from someone who, uh, actually works with the code before I'm gonna try sticking a depot in there. Also, from what version onward was it fixed? I'm still playing with i3019.

The bug was removed in the PBS-patch v063 (Apr 11, 2005)... Not sure which nightly that used this version and above, but you could try the newest (integrated) nightly build...

Hackykid wrote: Yay! In the new version (v063) depots inside pbs blocks should also work! Lemme know how it works out

DaleStan · Post by **DaleStan** » 16 Nov 2005 15:46

^Cartman^ wrote:The bug was removed in the PBS-patch v063 (Apr 11, 2005)... Not sure which nightly that used this version and above, but you could try the newest (integrated) nightly build...

No nightly ever used that version. PBS v080 was added to the trunk. (r2516)

And, yes, you could try the integrated nightly, but there's no mention of PBS in the IN release post.

Foo · Post by **Foo** » 16 Nov 2005 18:05

I think I'm getting the hand of PBSignals now! The attached image is a (massively) reworked version of the same station. I could do a couple of extra things to improve it, like moving the station out to the south side and using the extra space for more rails, but as it stands this station can handle a massive amount of traffic for its size.

Thanks again for all the help!

PS There's also a missing rail, I know. That was to see what happened when traffic built up, as shown. (Edit: and a signal facing the wrong way on the west mainline entry path, oops)

csuke · Post by **csuke** » 16 Nov 2005 18:41

This station has limitless waiting capacity in a very small area:
you could of course update the junctions to the main line using tunnels but that's not what i'm trying to show
you just have to make sure that the length of track shown in the picture is as long as the longest train that visits the station

Maverick · Post by **Maverick** » 29 Nov 2005 04:29

csuke wrote:This station has limitless waiting capacity in a very small area:
you could of course update the junctions to the main line using tunnels but that's not what i'm trying to show
you just have to make sure that the length of track shown in the picture is as long as the longest train that visits the station

However the trains stored in the depot are limited to 60kmh.

Foo · Post by **Foo** » 29 Nov 2005 05:08

So... wait. That works because all trains are forced into the depot, right?

csuke · Post by **csuke** » 29 Nov 2005 11:54

yup, thats right, and the pbs block is to stop trains coming out of the depot while still letting them in, as they are allowed to reserve a path into the depot

Commie Si · Post by **Commie Si** » 29 Nov 2005 14:05

looking at it, you have a lot of trains using that station, so it may be worth having it as a RoRo station...just a thought

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Am I on to something here? (Junction Design/PBS)

Am I on to something here? (Junction Design/PBS)

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