Bidirectional stations and PBS

[Uwe]

Hello,

I just digged through some older postings and found an old one from me which pointed out some problems with bidirectional stations: http://www.tt-forums.net/viewtopic.php?p=278388.

Now I have thought about that problem again, and I think I came up with a solution which is more general.

Basically, I want to set up a station like what's shown in the attached picture. Trains should be able to use both platforms in both directions. Now, there is no signal setup which avoids that trains try to get to the same platform from both directions. To do that, the signals at either end of the platform need to be connected somehow, i.e. signal a and c as well as b and d need to depend on each other in some way.

Some theory: The two-way signals are necessary as the station tracks need to be accessible from both directions. Trains only reserve a path towards a green two-way signal, i.e. when a path towards a station platform is reserved, the platform is free. Still, trains can reserve paths towards the same platform from both directions.

Idea: If a path towards a two-way signal is reserved, the block behind it (in the picture this would be exactly the station platform) needs to be marked as blocked, as if the train approaching is already in it. This would trigger the two-way signal at the other end, so that no train from the other direction tries to get to that track, except it reserves the path at exactly the same moment, which I think is somewhat unlikely.

This should work regardless of what the next block looks like, if it's a station or not, so it might be just general enough to actually work. At least I did not find a track combination which would not work anymore, apart from setups that would not work anyway such as using two-way signals everywhere. But maybe I'm just blind, so feel free to point me to a setup that this suggestion would break.

Quite a long post, thanks for reading Feel free to bash me for suggesting yet another change to the signalling code. I know it's a very complex topic, and I really appreciate all that has been accomplished in this field. Yet I think there is still room for improvement

[White Rabbit]

I've also tried out the station layout in that picture and it gave me a big headache and I never technically solved the problem. What I did was set thet two-way signal wait time to 4 seconds, so that if two trains reserve paths to the same platform, the one that reaches the platform last will wait at the signal, reverse, hit a one-way signal in the wrong direction (this of course requires trains and signal spacing to be at an appropriate length), then go to the alternate platform. If that one is also occupied, the train will just wait at the pre-signal (which will naturally be there).

[Tekky]

My proposed new PBS system would solve this problem. This system would prevent a train from attempting to enter an already occupied station platform, since the train would be unable to reserve a route into this occupied station platform. Therefore, the train would instead wait in front of the last signal on the regular track and would not try to enter the station, until it is able to reserve a route into the platform

Please see
http://www.tt-forums.net/viewtopic.php?t=31172
for the details of my proposed new PBS system, which, in contrast to the old PBS system, also supports bi-directional double track.

[Hyronymus]

Tekky, try not to dig up old topics. And definetly don't post the same content on 2 different sections of the forum. It are both violations if the forum rules but for now I give you this friendly prod.

[Tekky]

Tekky, try not to dig up old topics. And definetly don't post the same content on 2 different sections of the forum. It are both violations if the forum rules but for now I give you this friendly prod.

I just read the forum rules again and am unable to find any rule which my above post violates. Also, I consider my post appropriate, for the following reasons:

1. Digging up old topics
This topic may be old, but not outdated. The problem described in this thread still exists in the latest TTDPatch/OpenTTD. Therefore, I consider it meaningful to mention in this thread that I have found a possible solution to the described problem.

2. Posting same content into 2 different sections of the forum
My content is relevant to both sections of the forum. However, I didn't post the same content more than once. Instead, I created only one single thread. In all the other threads, I only posted links to my main thread.

For the above reasons, I am unable to see any inappropriate behavior on my side. If you still consider my post inappropriate, please explain why.

[SuperTycoon]

I have to agree with Tekky that his content is relevant to both sections of the forum, and if not for this post may have been overlooked by patch developers. I like the idea, it certainly seems to work, and I can see it being useful, however I think implementation into the patch could be difficult, since the internals of the patch's pathfinder are quite different to OTTDs (If I'm not mistaken)

Would a member of the patch team care to have a look over it?

[Pookey]

I have a question. You have a large flaw if a train reaches the pre-signal and all platforms are occupied. What is it supposed to do then?

[Tekky]

I have a question. You have a large flaw if a train reaches the pre-signal and all platforms are occupied. What is it supposed to do then?

Since your question is relevant to both OpenTTD and TTDPatch, I have answered your question in my main thread (http://www.tt-forums.net/viewtopic.php?t=31172).

In this post in my main thread, I explained in detail how the bi-directional station would work and also attached a screenshot of the layout.

[Pookey]

Thanks.