Train won't turn around

krtaylor · Post by **krtaylor** » 21 Dec 2004 17:05

I'm using a42 with PBS, and I've got a train stuck in the station. It refuses to turn around. I'm guessing it's a PBS problem but I'm not sure. It is generating smoke and all, shoving against the back wall of the station. The thing is, the station is too short, so the back of the train hangs out the end, but that shouldn't be a problem as there are no signals in the way. Here's the savegame, and it's train 30.

SHADOW-XIII · Post by **SHADOW-XIII** » 21 Dec 2004 23:22

it happens sometimes in 2 cases:
- train at station stuck, then you need to rebuild a crossing at station
- train stuck at signal, mostly because it turned around once (and can only once) and you can't turn it again, just demolish square with signal and make a loop so train can go the proper way again

krtaylor · Post by **krtaylor** » 22 Dec 2004 02:57

I don't really understand your explanation.

And is this an acknowledged bug that's being researched?

Rob · Post by **Rob** » 22 Dec 2004 07:03

I reported this bug already to patchman, even before he went on holidays.
He'll probably won't do much about it the next two weeks, and that's a good thing.

But I have no doubt in my mind he'll find a solution for it when he gets back, since this bug cripples your network quite badly.

Patchman · Post by **Patchman** » 22 Dec 2004 14:26

It's a Feature-not-a-bug. The train can't reverse if it's in a PBS block but is unable to reserve a path out of the signal block (to prevent crashes).

krtaylor · Post by **krtaylor** » 22 Dec 2004 14:34

Then I think something about the feature needs to be reconsidered. Or maybe the PBS-block-maker is too agressive, making PBS blocks where they ought not to be? When you get a chance, please look at the savegame I posted and you can see a prime example of that.

DaleStan · Post by **DaleStan** » 22 Dec 2004 21:43

I've gotten a train stuck in a PBS block, one end in a depot, and the other end at a red two-way signal. It could not find a path back to the depot. I don't know if it could have found a path anywhere else.
With a42, I still see trains leave depots into PBS blocks, and reserve paths that conflict with already reserved paths.

Unfortunately, I don't have a savegame for either of these, but I'll see if I can manufacture one later.

Would it be possible to have ctrl-click on the U-turn button force a U-turn, even if the train can't find a path?

krtaylor · Post by **krtaylor** » 22 Dec 2004 21:55

That might work. Another thing that might help, is to be a little less agressive about putting in automatic PBS blocks. I've seen them show up in intersections where they have no business being, because there is no separate choice of paths. I mean, the way the track is laid out, any train in the block MUST cross the same piece of track. Thus there's no possibility for more than one train to be in the block, hence no need for a PBS block at all - it should be left as normal signals.

DaleStan · Post by **DaleStan** » 22 Dec 2004 23:10

Hence the reason I use noautomaticpbsblocks on.
If I want a PBS block, I put in a PBS signal. If I don't, I don't, and they stay as pre/combo/exit signals; just the way I wanted them.

How would you analyze a block to determine if PBS would be useful for it?

krtaylor · Post by **krtaylor** » 22 Dec 2004 23:13

A PBS block is exceedingly useful at an entrance to a station, where the tracks have to interchange to allow incoming and leaving traffic to access all the platforms. It's not useful in several other situations where it likes to automatically appear, such as one-way splits and single-track stations.

DaleStan · Post by **DaleStan** » 22 Dec 2004 23:27

But how do you explain these checks to the computer?

One-way splits can have useful uses of PBS. That's what the entrance to a Ro-Ro station is, for example.
I'm also rather confused as to why a single-track station needs anything more than standard signals.

krtaylor · Post by **krtaylor** » 23 Dec 2004 00:09

DaleStan wrote: I'm also rather confused as to why a single-track station needs anything more than standard signals.

My point exactly. It doesn't need PBS. But it gets it automatically for some odd reason.

krtaylor · Post by **krtaylor** » 23 Dec 2004 19:09

Having a depot in a PBS block also seems to screw things up.

It seems to me that we need one additional requirement for PBS blocks. When the automatica-PBS-er considers a block, it needs to analyze the various possible routes that a train could take in the block. The block should become PBS if, and only if, there are at least two possible routes in the block that don't intersect. Otherwise, there's no point to having it be PBS, and making it so will just screw things up. That's the situation I'm finding - it wants to automatically make PBS blocks where they serve no purpose and cause reversing problems. Since the PBS block already calculates routes, I would think it would be possible to perform this check.

DaleStan · Post by **DaleStan** » 23 Dec 2004 22:04

krtaylor wrote:The block should become PBS if, and only if, there are at least two possible routes in the block that don't intersect.

Not sufficient. Consider the case where a single line splits into (say) 5, like this:

Code: Select all

     _>_
    /_>_
_>_/_>__
   \_>__
    \_>_

All paths through the block intersect, but why should a train that wants to go to the top track have to wait for a train headed to the bottom track to completely clear the block?

krtaylor · Post by **krtaylor** » 23 Dec 2004 22:16

Mmm. I see your point, but I don't like it. Maybe it should be a switch?

Or, it would also work to check if the trains could be leaving out the other side, as is implicit in your example. If so, then a PBS block would be useful. If not, then not.

Patchman · Post by **Patchman** » 23 Dec 2004 23:54

This is far too complicated. In particular, all possible routes include loops and backtracking, with this in mind it's about impossible to detect whether independent paths are useful.

If you don't like the automatic blocks, turn them off. That's all I can give you...

krtaylor · Post by **krtaylor** » 24 Dec 2004 00:41

True. So the other solution would be to make it easier to manually change what sort of signals you have.

I did come up with an idea there. You can use the ? button to find out what sort of signal it is. It would be nice if that would refresh when you change the signal. So you use the ? to open that info window, then use CTRL to change the signal type, and you can watch the description change in the info window until you get the one you want. Is that possible?

Patchman · Post by **Patchman** » 24 Dec 2004 08:45

Not really. When you click with the "?", the tile information is stored in a temporary location, which won't get updated if the original tile changes.

However, with the new PBS signal graphics it's a lot easier to tell what type of signal you have, so the biggest problem then is that you have to click up to seven times to get the signal you want.

krtaylor · Post by **krtaylor** » 24 Dec 2004 14:41

I suppose it would be too complicated to support a pop-up drop-down selector when you right-click on a signal, letting you pick which kind you wanted?

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