Station jam

[bencze]

Hey!

I am trying to build ... ehh something and I am wondering what the next step would be.
I have a factory station, 12 terminals, 140 trains dropping stuff there.

Do I need to expand the station in order to clear the jam? I will try to attach the saved game and you'll find the jam at the sign. Basically the last track to join has difficulties getting a clear signal because of too many trains.

Basically I'd like to know if there's something I could have done better, adding more terminals is a valid last resort solution of course but there may be others for now... maybe some proper balancing would help evening things out, although I am not sure at this point.

[Alberth]

Hi,

Your station is not the problem, see below (from your savegame):

empty.png (284.5 KiB) Viewed 3331 times

7 platforms are empty, 5 are used.

The problem is just in front of a queue, in this case the tracks leading to the station. I did a quick and dirty change, and added more connections:

full.png (146.54 KiB) Viewed 3331 times

By adding more lines (I used path signals), the station quickly filled. The picture is somewhat wrong, as now, the tracks behind the station are fully filled, so trains at the station are waiting for the line to be cleared (only 2 of them are unloading, and 2 are arriving. 8 are trying to leave.

[planetmaker]

Hi,

Your station is not the problem, see below (from your savegame):

empty.png

7 platforms are empty, 5 are used.

The problem is just in front of a queue, in this case the tracks leading to the station. I did a quick and dirty change, and added more connections:

full.png

By adding more lines (I used path signals), the station quickly filled. The picture is somewhat wrong, as now, the tracks behind the station are fully filled, so trains at the station are waiting for the line to be cleared (only 2 of them are unloading, and 2 are arriving. 8 are trying to leave.

In order to get a decent flow, and assuming dense traffic on the tracks, then every incoming track to a station needs approximately 6 ... 8 tracks in the station itself (depends a bit on the actual train length and the load speed of the wagons). Of course the exit of a roro station (as shown in the screenshot) must be at least as good (quick) as the entry - but from what I see in the screenshots , that's ok - but not the whole exit is shown.

[Alberth]

I was bored enough to also take out the back-end, and simplify it.

back_end.png (353.64 KiB) Viewed 633 times

Bottleneck is now in the access to the main line, although it can keep up with traffic (as you can see, I simply merged 3 platforms, and attached the 4 lines to main line. Exist flow from the buffer behind the station can be further improved it seems.

closeup.png (413.85 KiB) Viewed 3309 times

You can see I doubled a few tracks to get better flow. It's not optimal, but in this way, at least some of the time two trains can proceed at the same time, which is better than always one train.
It seems almost sufficient.

(I played with trunk, if you have a nightly, I can give you the save game. On the other hand, I use path signals everywhere, which you probably don't want to have, so you'd need to rebuild it anyway.)

[bencze]

Yeah now that I think about it, there's trains coming from 4 tracks (2 from each direction) and I cram them into 2 and then split them again, so no wonder they jam. Maybe I should keep all 4 separated and just make one balancing in front of station to split them to the station platforms.
The exit, I knew I overdid it, tried to make something smart and it's just killing it. Simply more lanes, less and better balancing then.

I don't need the save, I think I got it now, thanks!

[Ben1338]

Also, the trains are far too short, having larger trains means fewer of them, which leads to less congestion, though the concept is nice.

[bencze]

I am used to the default 4 length because I can get away with much simpler junctions and curves. Once I did a game where I tried 10 length trains but somehow I never finished that one...
Towards the end when industry output starts to grow really strong it's a problem putting more and more trains in, at that point I usually lose interest because I don't feel like adding additional mainline tracks, rebuilding stations, sidelines etc... maybe one day I'll have a 'perfect' network, but for now it's a success for me to use 2x2 MLs and 200 trains.
edit: right now 146 trains use the factory drop station, but I kind of started to hit the 2x2 ML limit on that one (breakdowns disabled ofc).

[ccomley]

Hi,

Your station is not the problem, see below (from your savegame):

empty.png

7 platforms are empty, 5 are used.

The problem is just in front of a queue, in this case the tracks leading to the station. I did a quick and dirty change, and added more connections:

full.png

By adding more lines (I used path signals), the station quickly filled. The picture is somewhat wrong, as now, the tracks behind the station are fully filled, so trains at the station are waiting for the line to be cleared (only 2 of them are unloading, and 2 are arriving. 8 are trying to leave.

Classic! You never really fix the jam, you just move it up the track to the next block!

Yes - path signals for the win - but don't give the trains too many choices, or they end up choosing to do stupid things. I had a pair of parallel tracks, to increase the capacity of a line. To allow trains to overtake a broken-down train instead of queueing up behind it, I put in crossover sections between the two tracks. I used path signals to stop them acting as a single block. On train on the left track decided to cross to the right. So the train on the right track had to wait for it to finish... then the right-track train started up again and swapped to the left track, and so on... causing a complete slow-down of both tracks. I could find no way to have the cross-overs but only have trains use them to avoid a blockage. Sometimes, a train on one track would just decide the other track was quicker, just like moron drivers at traffic lights!

[ccomley]

Yeah now that I think about it, there's trains coming from 4 tracks (2 from each direction) and I cram them into 2 and then split them again, so no wonder they jam. Maybe I should keep all 4 separated and just make one balancing in front of station to split them to the station platforms.
The exit, I knew I overdid it, tried to make something smart and it's just killing it. Simply more lanes, less and better balancing then.

I don't need the save, I think I got it now, thanks!

Also, your trains coming in to the station come down a steep hill - if on leaving the station they go back up that hill they'll slow down considerably.

A train going up ONE 50m step will slow down to about half speed - to have the LINE run smoothly, you need to double up the line for the hill and re-join at the top. If you have to go up more than 50m, ideally you do it with individual 50m climbs at LEAST one full train-length apart. Then you can run the doubled line up the whole "staircase" and rejoin at the top. If you have hills closer together than a train length, i.e. if a train is climbing TWO 50m grades AT THE SAME TIME, it'll slow down even more, and you'll have to add even more parallel tracks to maintain the overall speed of the line.

[Transportman]

A train going up ONE 50m step will slow down to about half speed - to have the LINE run smoothly, you need to double up the line for the hill and re-join at the top. If you have to go up more than 50m, ideally you do it with individual 50m climbs at LEAST one full train-length apart. Then you can run the doubled line up the whole "staircase" and rejoin at the top. If you have hills closer together than a train length, i.e. if a train is climbing TWO 50m grades AT THE SAME TIME, it'll slow down even more, and you'll have to add even more parallel tracks to maintain the overall speed of the line.

That depends on the acceleration model used. The original model really punishes inclines, but if a train has enough power with the realistic model it will just go up without problem.

[ccomley]

That depends on the acceleration model used. The original model really punishes inclines, but if a train has enough power with the realistic model it will just go up without problem.

Ahh - that's a parm I've not played with yet. So MANy variables, it makes some discussions impossible unless all those involve first agree a table of settings, versions, GRFs, etc...

[Alberth]

Classic! You never really fix the jam, you just move it up the track to the next block!

Euhm?
Sorry, but this is the only way I know to solve this type of problem, what do you do in such cases?

Maybe we have a difference in ideas what a "jam" is? For me, there are two kinds of jams.
One kind is what I know as "deadlock", nothing is moving any more. In this case you have to add extra tracks and depots to untangle the mess.
The kind we have here is a "bottleneck". Trains are still moving, but there is not enough room for a nice flow, trains are queuing, waiting for their turn.

I know no other solution to solve a bottleneck than to change the track layout such that trains all flow nicely. A little queuing is ok, but the queue shouldn't grow.

Yes - path signals for the win - but don't give the trains too many choices, or they end up choosing to do stupid things. I had a pair of parallel tracks, to increase the capacity of a line. To allow trains to overtake a broken-down train instead of queueing up behind it, I put in crossover sections between the two tracks. I used path signals to stop them acting as a single block. On train on the left track decided to cross to the right. So the train on the right track had to wait for it to finish... then the right-track train started up again and swapped to the left track, and so on... causing a complete slow-down of both tracks. I could find no way to have the cross-overs but only have trains use them to avoid a blockage. Sometimes, a train on one track would just decide the other track was quicker, just like moron drivers at traffic lights!

Indeed
When doubling up tracks, I make two really separate tracks, in the end that gives the best throughput so far. However, I am still wondering whether it is possible to connect them in some way. Recently, I wondered whether priority merging would work. Haven't really tried it though.

Another direction would be to allow trains to switch tracks without delay. In other words, it's fine that trains swap tracks, but the 2nd train should be able to swap just as easily as the first one (and that should be possible, since the first train isn't using the tracks it used previously). How to do that however is still a open problem for me

[ccomley]

Classic! You never really fix the jam, you just move it up the track to the next block!

Euhm?
Sorry, but this is the only way I know to solve this type of problem, what do you do in such cases?

Maybe we have a difference in ideas what a "jam" is? For me, there are two kinds of jams.
One kind is what I know as "deadlock", nothing is moving any more. In this case you have to add extra tracks and depots to untangle the mess.
The kind we have here is a "bottleneck". Trains are still moving, but there is not enough room for a nice flow, trains are queuing, waiting for their turn.

I know no other solution to solve a bottleneck than to change the track layout such that trains all flow nicely. A little queuing is ok, but the queue shouldn't grow.

Sorry - wasn't accusing you of anything wrong, just pointing out that it's always the case, you fix one jam, you then have to see what jam you caused further along!


As you say, an occasional short queue or a train occasionally having to slow at a merge isn't a problem. (Assuming you're playing for a "realistic" sim not a "perfect world".) Splitting into two to double the track for a slow section and re-merging afterwards is more efficient than doubling the entire track - but you do risk that they don't re-merge as neatly as they split. But actually, they should! If both left and right tracks have the SAME delay during the slow-down phase, whatever causes it, the trains shouldn't catch up during the split phase, so when you get to the merge the one that hit the split first should still be in front, by the same separation, as it was at the split. In theory...

[ccomley]

That depends on the acceleration model used. The original model really punishes inclines, but if a train has enough power with the realistic model it will just go up without problem.

Ahh - that's a parm I've not played with yet. So MANy variables, it makes some discussions impossible unless all those involve first agree a table of settings, versions, GRFs, etc...

Curst you Transportman! With "realistic", i'm going to have to spend *hours* tinkering with junction layouts and stuff, now occasional hills are no longer a problem, but tight turns are!

It's a tough life...

The main thing it blows out is one of my favourite structures - two depots face-to-face either side of a track, with no straight-through, and a path signal on entry. This means one train can be entering depot A even as one is leaving depot B, and forces all trains to service. It also provides a "collapsing" point for a jam if you have an issue, so instead of a hundred mile tail-back down the line jamming up even more of the network and making it hard to find the choke point or breakdown, the first train to jam coming out of a depot forces ALL the following trains into the other depot, leaving the track behind clear and NOT causing jams for traffic in other areas. But with "realistic", the trains slow down SO much entering and leaving the depot, I can't keep doing that. Maybe I just need to set the depots a tile or two back from the main track... tinker time!!

[Jacko]

it still works with the two depots trick it just generates a longer queue.

[ccomley]

it still works with the two depots trick it just generates a longer queue.

Yeah, I could see it was working - but S L O W L Y.

I tried moving the depots back one tile from the line - it's better. But the trains still slow down "realistically" entering the depot itself, it's not just the turn-in that slows them down. So to minimise that you'd need a train-length of "entry track" that's separate from the main track for each side depot. Starting to be a major engineering work!

So I think my new masterplan will still be to put them in place where I might need to solve gridlocks, but "turn them off" by retaining the straight-through option. Then if there is a gridlock, I can just remove one straight-through tile to force trains into the depots, and the system works as planned - I'll take slow over gridlocked whilst trying to work out what caused the jam.

[bear1]

Lots of good advice. I tend to use long exits, so that a platform can be in use before a train has fully merged into the network. I also seperate unloading trains from loading trains-otherwise its easy to end up with a station full of goods trains. I generally do this with waypoints, but I know many people use seperate stations.
In the past I picked one factory and flooded it with as many trains as possible-developing the station and network to keep pace. These days I'm much more likely to use a variety of factories and avoid the problem.

[ccomley]

Lots of good advice. I tend to use long exits, so that a platform can be in use before a train has fully merged into the network. I also seperate unloading trains from loading trains-otherwise its easy to end up with a station full of goods trains. I generally do this with waypoints, but I know many people use seperate stations.
In the past I picked one factory and flooded it with as many trains as possible-developing the station and network to keep pace. These days I'm much more likely to use a variety of factories and avoid the problem.

Yes, problem with a station full of not loaded Goods trains and so no trains of source material can enter. I always make two stations for a factory, refinery, etc. Sometimes I keep them pure - resouce unload at Station A, goods out from Station B. But sometimes it's easier to have a delivery to B - that's fine so long as you still have deliveries to A, as eventually enough product will arrive at A to fill a goods train then it'll move out and clear a platform at B for whatever. Where it's not possible to have two railway stations, having something arrive by ship or truck, even if not per-set profitable, will also serve the purpose of eventually filling a goods train and allowing flow to resume.

I do wish you could set a conditional rule like "wait at the station until full OR until another train with the same shared orders is waiting to enter".