Escape Depot Train Trap

[Mattintosh]

I've been trying to get escape depots to work right for a while, but I could never manage to get quite the result I wanted. Well, I've finally found it.

TrainTrap.png (33.86 KiB) Viewed 11781 times

What you see above is the "in" side of a RoRo. The first signal on the "in" line is a one-way starting presignal. The depot entrance has a two-way combo presignal. The two halves of the station are balanced using two one-way combo presignals. And each platform has a one-way ending presignal.

Trains come in from the right. If they can take an empty platform, they will. If all platforms are full, they go into the depot. Now, here's the beauty of this setup: They don't leave the depot until there's an empty platform. Eleventy billion trains can disappear into that depot and they'll come out one-by-one as platforms open up. No station-clogging traffic from whack-a-mole-trains popping out of the depot to see if they can go or not, no massive backups onto the mainline, no trains blocking all of a station's entrances while waiting for one particular platform to open up. And you don't have to babysit at all.

If you didn't already know about this, try it out. If you did, well, I'm sorry if I wasted your time, but I couldn't find it in the wiki or these forums, so I figured I'd post it.

[DaleStan]

I know I've seen that before, but I'm not quite sure where.

[AlexW]

Can't say I'm a huge fan of that set up as, correct me if I'm wrong, but trains cannot get to the right 4 platforms without having first gone into the depot. As they will then have to cross the junction to get to the right 4 platforms, this will slow any incoming traffic and reduce efficiency.

Good concept though; for me, it needs some work.

[DaleStan]

Indeed. I just assumed both T intersections were full tees[0], and not just wyes[1].

[0] According to ikypedia, this is called a "wye" in some places. Which is, IMO, an exceedingly stupid overloading.[2]
[1] I'm using the plumbing version of the term here, not the above-mentioned railroading version.[2]
[2] Not to be confused with the village in Kent.

[AlexW]

Indeed. I just assumed both T intersections were full tees[0], and not just wyes[1].

[0] According to ikypedia, this is called a "wye" in some places. Which is, IMO, an exceedingly stupid overloading.[2]
[1] I'm using the plumbing version of the term here, not the above-mentioned railroading version.[2]
[2] Not to be confused with the village in Kent.

A footnote to a footnote - very impressive!

[AntBUK]

From my experience with them, cache/buffer depot's are about as inefficient as you can get as part of the station construction, and how yours is build only 4 platforms can be used until the trains have to use the depot.

[richk67]

I know I've seen that before, but I'm not quite sure where.

I think it was a discussion we had, as I have done and used a similar idea (Infinite Sidings I think I called it). You went on to demonstrate that the trains that go into the depot, do not exit FIFO, but in a different (but non-random) order. (By vehicle ID I think).

FIFO depots would make this more useful, but needs implementing.

[Mattintosh]

Indeed. I just assumed both T intersections were full tees[0], and not just wyes

Actually, you're right. Both intersections are supposed to be full-tees, but I was rushing to build it on a different system that I don't normally play OTTD on (my main OTTD system lacks an internet connection right now), get the screenshot, crop the screenshot, and post here before I forgot how to make this station setup. So basically, a mistake on my part.

Trains are supposed to be able to go to all 8 platforms without having to enter the depot. The 9th train will stow itself at the depot until it can get an open platform. Platforms will load from center to edge, near to far (from entrance), just as you would expect (it's 4-and-4, load balanced). First open platform takes either the next train in from the mainline or the next train out of the depot, whichever breaches the signal block first.

I've found that this setup is quite efficient for a long-run transfer station. I have 30+ trains loading at an 8-platform + dock transfer station (50+ ships drop off at this station, but the secondary industries are across the map, accessible only by train). There are typically anywhere from 2 to 5 trains in the depot waiting for a platform at any time. Ratings at this station are in the 90% range. (Barring a situation where all platforms are taken and one type of train can't get a loading slot, of course.) All trains and ships turn a massive profit (due to the long run), and typically only take one or two round-trips a year.

It's also pretty good from a footprint-size standpoint, taking only a few extra spaces and never posing a lockup problem like a loop-around would.

[HariSeldon]

The depot entrance has a two-way combo presignal.

Actually, it's an entry presignal.
(see here).

[nezzybaby]

^no he is using a 2 way combo as he said. The link you posted explains why you wouldn't use a combo signal if you didnt want to achieve exactly what he is trying.


I have a fundamental problem with this station design. To me it seems flawed from the outset. If a station has 8 platforms with 1 line going in and is still filling, this means you have either too many trains or an incredibly inefficient network. The problems need to be solved further down the line rather than just letting trains pile up in a depot. If i have a station with 8 platforms there will be at least 2 entrances and exits, and if they clog i will build more platforms. I cannot see a use for this.

[HariSeldon]

^no he is using a 2 way combo as he said. The link you posted explains why you wouldn't use a combo signal if you didnt want to achieve exactly what he is trying.

Oh, I undestood:
Depots have bult-in entry pre-signals.

But here a combo pre-signal was put in front of the depot.

I have a fundamental problem with this station design. To me it seems flawed from the outset. If a station has 8 platforms with 1 line going in and is still filling, this means you have either too many trains or an incredibly inefficient network. The problems need to be solved further down the line rather than just letting trains pile up in a depot. If i have a station with 8 platforms there will be at least 2 entrances and exits, and if they clog i will build more platforms. I cannot see a use for this.

Yes, this way does not worth much at a 8 platforms station, it's not very efficient.
(Keep in mind that trains enter and exit depot at low speed).

Escape depot way is more useful at small (2-3 platforms) station.

At large and important stations, incoming trains should managed in different way.
(long entrances , waiting bay , double entrances , etcetera ).
But a nearby depot maybe userful anyhow: for servicing (expecally at a load station, to have the trains serviced before they load) , and as an escape depot (if exceptional events clog the line).

[VoxDissident]

Eleventy billion trains can disappear into that depot and they'll come out one-by-one as platforms open up.

ELEVENTY BILLION TRAINS. Oh. My. God. I don't believe it. I really don't. Th-tha-THAT'S IMPOSSIBLE.


Interesting setup. I usually use the simple entry presignal / exit presignal setup with no depots anywhere near the station. I prefer to have my depots along the side of my mainlines on a dedicated ro-ro maintenance line. This is after deciding that I'm fed up with depots slowing down my train stations once I'm building maglevs with 20-30 or so wagons attached. That is, assuming I'm playing with the standard trains.

I used to have my depots placed at the entrances to stations in the middle of the junction between the entry and exit presignals leading into the station itself. Back then, I never noticed my trains coming out of the depot to get in the way when all the station platforms were full. They only ever came out when at least one platform was empty.

However, I do see the advantage of this depot setup; this way you can have all your waiting trains sit inside that depot without costing you a dime and without losing any % reliability so that when a platform empties up, the trains come out with max reliability and load up or drop off without a hitch. BUT. I'm still not a fan of the speed with which trains leave depots. If it comes to a tradeoff between having trains come into stations off the mainline with questionable reliability or having trains come out of a depot with max reliability, I'm somewhat indifferent. I'm a fan of big, long trains, and that means lots of moving slowly out of depots, which tends to get annoying unless you have your railways set up with dedicated ro-ro repairlines.

In any case, its something I've never seen before, quite a good idea and you can ignore my sarcasm in the first sentence I wrote .

Good stuff.

-Vox

[HariSeldon]

I used to have my depots placed at the entrances to stations in the middle of the junction between the entry and exit presignals leading into the station itself. Back then, I never noticed my trains coming out of the depot to get in the way when all the station platforms were full. They only ever came out when at least one platform was empty.

This is because the signal in the depot is a entry (ewo way )pre-signal , so it's red if all the exit presinglas at the platforms are red.

However, I do see the advantage of this depot setup; this way you can have all your waiting trains sit inside that depot without costing you a dime

Do trains that are waiting to get in stations at a red signals ouside depots cost anuthing?
How much? (the same of a running train?)

BUT. I'm still not a fan of the speed with which trains leave depots. If it comes to a tradeoff between having trains come into stations off the mainline with questionable reliability or having trains come out of a depot with max reliability, I'm somewhat indifferent.

I think that escape dopots are usefull in case of all the platforms being full, but station should be dimensioned and organized so that such "in case" whould not be too often.

(An exception is at load-only station, so where only empty trains get in. You can even provide a mandatory service -using a "go to depot" order, for example- there).

[VoxDissident]

This is because the signal in the depot is a entry (ewo way )pre-signal , so it's red if all the exit presinglas at the platforms are red.

Yep. Aware of that fact.

Do trains that are waiting to get in stations at a red signals ouside depots cost anuthing?
How much? (the same of a running train?)

Yep. Costs are same as those of running trains.

[HariSeldon]

Sorry for answering this here again, but I have not uderstood something:

1) In the very first message of this thread

And each platform has a one-way ending presignal.

(and the same in the image in that message).

Why "one-way"? Should not them be two-way, so that the train will chose the free platform (green signal) ?


2) I have understood this

^no he is using a 2 way combo as he said. The link you posted explains why you wouldn't use a combo signal if you didnt want to achieve exactly what he is trying.

Oh, I undestood:
Depots have bult-in entry pre-signals.

But here a combo pre-signal was put in front of the depot.

so I have understood which signal you were talking about

though I can not understand why that two-way combo presignal (in front of the depot) is needed (and why the signal in the main in line need ti be an entry presignal).


I've thought about it
and I've considered these two situations (It's a bit more complex in the station depicted in the first message, 8 platform divided in two half using combo signals. It's easier to think about a less complex station with just 4 platform):

* When a train is in depot and going to come out from it:
the signal inside the depot is an entry presignal,

**If another train is coming in the station (from the main "in" line), the signal inside the depot will be red (just as a normal signal does),

**If the railway track is free but there are no free platforms ( = all the exit presignals are red) the signal inside the depot will be red (because it is an entry presignal).

** So the train will go out from the depot only if one, at least, platform is free (and so one, at least, exit presignal is green -and in this more complex station, one at least combo presignal is green).


*When a train is coming from the main "in" line" (when it's at the signal that is an entry presignal in the picture in the first message) :.

** If the railway track in front of the entry presignal is in use (there is another train in front of him that is getting into the station from the main in line or getting into the station from from the depot or getting into the depot from the main in line), the entry presignal will be red (just as a normal signal does), .

** If the railway track is free and one, at least, platform is free (and so one, at least, exit presignal is green), the entry presignal will be green.

** If the railway track is free but there are no free platforms ( = all the exit presignals are red) , the entry presignal will be red. But if the signal were a normal signal (and not a entry presignal) it will be green. The train will go on and then it have to choose among different track, all with two-way signals: those going to the paltforms have red two-way signal, the one going to the depot have green two-way signal (the depot have infinite room), so the train will choose the track to the depot and will get into that.


So, with
- no presignal, but just normal signa in the mainlin
- no (combo)signal at all in front of the depot
- two-way entry signal in front of each platform
should work fine.

[Yexo]

Sorry for answering this here again, but I have not uderstood something:

1) In the very first message of this thread

And each platform has a one-way ending presignal.

(and the same in the image in that message).

Why "one-way"? Should not them be two-way, so that the train will chose the free platform (green signal) ?

That is only true in TTD (and maybe openttd before pre-signals were introduced).

[DaleStan]

Um. No. That's a feature of NPF and YAPF, and it appeared when they did, not before.

[Yexo]

Um. No. That's a feature of NPF and YAPF, and it appeared when they did, not before.

With YAPF at least trains will also choose the free platform when using 1-way signals. Anyway, in case all platforms all full the train will randomly choose one, so he should use pre-signals / pbs anyway.

[audigex]

IMO you have the right idea with this, as long as you want efficiency and not realism.

My suggestion would be a combination of waiting tracks and one or more "escape depots"; if you have several waiting tracks you can "buffer" the station, the waiting tracks fill up from the depot, and the station fills up from the waiting tracks. You don't have to pay running costs for all the trains because some are in the depot, but the slow depot exit speed doesn't harm the filling up of the station because the train entering is already out.

I've not quite found the solution to this yet which allows it to flow perfectly, but I believe it could be done that the entry track leads either directly to the platforms+ platforms if they're empty, or into a waiting area if the platforms are full but a waiting track is empty, otherwise going into the depot. Then in the same way the trains from the depot go either straight into a platform if one and the waiting areas are empty, or into a waiting area if one is free.

If nothing else, you can have the station full at all times but still allow some trains to not be incurring runnning costs.

[HariSeldon]

My suggestion would be a combination of waiting tracks and one or more "escape depots"; if you have several waiting tracks you can "buffer" the station, the waiting tracks fill up from the depot,

But a train that come out from the depot to a waiting track have still to wait. A better solution would be more platforms at station (*) so the train ca go to the station and unload (**) it's cargo.


(*) of course, if it's possible. Lack of space maybe a problem.


(**) = if it's a loading station, the better strategy may be different, depending on "Use improved loading algorithm" patch setting.