Two more PBS crashes

[jonty-comp]

More PBS crashes... These are from a savegame I recently found that was made before PBS was implemented. I had just started upgrading the signals when these happened:

1. A train crashes after turning straight around at the junction, only to crash into nothing.

Savegame before the crash at the bottom... Watch Train 3. I can't reproduce this though...

2. A train drives in a complete circle, going through itself, to get to Windhead.

Again, savegame at the bottom, however, it was saved while the train was 'curling' around itself, so wait until the next time it comes along, or set the game to very slow first. Watch Train 6 (from Fetbridge to Windhead). It happens everu time it goes over the junction...

Also, ttdpatch.cfg and newgrfw.cfg in zip.

[Menno]

1. I see a dark track part coming out of the depot, might it be possible that the train visible has crashed into one that was just coming out of the depot and isn't visible right now?
2. I think this is a known problem. Please correct me if it isn't.

[jonty-comp]

1. I see a dark track part coming out of the depot, might it be possible that the train visible has crashed into one that was just coming out of the depot and isn't visible right now?

Now that I look more carefully, you might be right.
It still doesn't explain why the train that crashed went into the signal block, though. I hadn't even upgraded that block to PBS yet!

2. I think this is a known problem. Please correct me if it isn't.

It might be, but I couldn't find anything with the search function. It is a bit hit and miss sometimes, though. You don't know whether to put 'curly train', 'train driving over itself' or something even more strange.

[Patchman]

2. is pretty hard to fix, but easy to workaround. If it happens, it means the train couldn't find a good path to its destination. In your particular case, just adding the waypoint to its orders should help.

In general it's best to design junctions in a way that no looping paths are possible, though.

[jonty-comp]

is pretty hard to fix, but easy to workaround. If it happens, it means the train couldn't find a good path to its destination. In your particular case, just adding the waypoint to its orders should help.

I see what you mean, but wouldn't that mean every train that goes that way does that? I have other trains that go from Fetbridge to places near Windhead that don't do that. And before you ask, they don't have the waypoint in their orders.

And I've had a thought about the first problem:- does the Depot act as a PBS signal? That might explain why two trains entered a non-PBS block at the same time...

[Patchman]

I see what you mean, but wouldn't that mean every train that goes that way does that? I have other trains that go from Fetbridge to places near Windhead that don't do that. And before you ask, they don't have the waypoint in their orders.

Don't ask me about logic behind the pathfinder. Sometimes it works, sometimes it doesn't. Except, it always works if the target is reachable within 64 tiles and 7 junction pieces.

And I've had a thought about the first problem:- does the Depot act as a PBS signal? That might explain why two trains entered a non-PBS block at the same time...

Only if the depot is within a PBS block.

[jonty-comp]

Don't ask me about logic behind the pathfinder.

OK, I won't then.

Only if the depot is within a PBS block. [will it act as a PBS signal]

Then why did the train that crashed enter the non-PBS block at the same time as a train came out of the depot? The junction used Pre-Signals, but not PBS.

[Patchman]

Then why did the train that crashed enter the non-PBS block at the same time as a train came out of the depot? The junction used Pre-Signals, but not PBS.

To answer that, I would need to see a savegame from before it happens.

[jonty-comp]

The first attachment (in my first post) is before the crash, but not long before, and it didn't happen when I tried it again, so I don't know if it's reproducible. If you do try it, view Train 3 or click the train that performs a U-turn at the junction in the 'curly train' screenshot (it comes from the North) not long after the save starts.

Knowing TTD, it'll probably never happen again and be yet another mystery to add to the collection...

[Flamelord]

Knowing nothing about the internals of PBS, I am going to guess (more of a hunch really) that the train entered the junction heading for a depot. For some reason, the depot was PBS, while the rest of the junction wasn't. The train entering the depot did not reserve a path therefore, and so the train inside the depot did not realize that it was entering an unsafe area.

Actually, it seems kinda silly to me, but it might be right.

[Menno]

it seems reasonable to me, save for one thing: the crashed train should then never have entered the signal block

[Smaug]

Hi,

If I may give a humble sugestion, in the ttdpatch.cfg there is an option in the pbs section that stops the train if it is going to enter an unsafe rail block and the train window of that train will pop up. Select that option if you haven't done that already. It prevented a few train crashes in my games...

[aahz77]

I just found this topic via Patchman's ToDo-List (I reported the out-of-depot-bug on ttdpatch.net). A savegame in which I reproduced the bug in a simulated figure-eight track can be found at http://wiki.ttdpatch.net/tiki-view_trac ... eated_desc

I don't know if the bug report has been caught up yet by anyone (nobody ever seems to reply there), so I post the link here.

[Raichase]

The ONLY PBS crashes I get now, using the nightlies, is when I activate a signal to be PBS when another train is already in the block. Becuse the train in the block has not reserved a path, it is invisible to the PBS pathfinder, and thus trains will reserve paths through the original train.

Perhaps this is whats happened at the depot, the approaching ICE has had a pre-signal, but the rest of the junction (and indeed the train in the depot) was acting normally, and thus paths were not reserved for the train going out of the depot, and the ICE didn't know it existed.

[3iff]

As Raichase says...

I've often fiddled with signals in a PBS block and been surprised when trains crash...I guess it's always been my fault when that happens. Be very careful of such signal changes when a train is in or near the block. Also, save the game just before you do something like that to protect yourself should things go bang!

[sc79]

In reference to #1....

I vaguely recall a while ago, when loading a really old game in OTTD (and I assume that 'before PBS' in TTDP would be considered really old), that I had a problem with trains on bridges crashing 'into' trains underneath. I dont recall the specific details though.

[Ameecher]

Not sure where else to post a PBS Crash so I put it here instead of starting another thread. I post here my Save game, when you open it, you may want to hit F1 immediately. This crash has happened a number of times and this is the first time I have caught it. I have a feeling that this might be something to do with the number of junction tiles a train can reserve (7) but this train only reserves 4 in this instance. Any help would be much appreciated.