Train Collisions, Help!

[Dizzy49]

I am using all basic signals, and I am sure I can be using chain signals for better direction.
I keep getting collisions where the trains come in and out of the base. I'll have one coming from the left, one from the top, and 1-2 from the bottom.

Here is an image of almost my entire track setup. You can zoom in and see the signals and stuff.
https://imgur.com/jXBQdkr

Yikes, Imgur does some serious compression on the images. If you save it locally you can zoom in enough to see the signals.

[CPT Chthonbeard the Pirate]

Ok, looking right away at it I noticed something about your signalling:

I don't normally do bidirectional tracks, but I believe the problem is that your signals are too close to the fork. Trains do not stop on a dime, they need some space to stop, so if one train approaches the block quickly from the left, and another is entering slowly from the top base first, the one moving quickly from the left cannot stop in time to avoid collision.

To avoid this, place the signal for the base further back into the base so it has priority getting onto the track. This way it reserves the block earlier, before the other train can just barrel through the intersection without being able to stop. It may be suboptimal for throughput, but it should stop collisions.

Another option is to put in a switch track at that intersection for trains moving west to east that cannot stop.

[Nailfoot]

Its a little hard to see in that picture, but I would HIGHLY recommend that you break your tracks in to smaller segments using more signals. Its not quite as critical in a double headed train system but can still help.

If you have only one long block, then only one train can be on that section of track at a time. If you break the long track runs into smaller segments, you could have two or more trains traveling on the same track at the same time, one behind the other. That would also give an addtional place for a train to stop before it gets into a problem area.

I recommend that you eventually go to single headed trains, with a double track mainline and branches off of that to your various areas. It requires roughly twice as much track, a bit more planning and a bit more room. But, it is infinitely expandable with minimal work. And you can have trains heading out "into the field" and back to the base at the same time.

[CPT Chthonbeard the Pirate]

Originally posted by Nailfoot:

Its a little hard to see in that picture, but I would HIGHLY recommend that you break your tracks in to smaller segments using more signals. Its not quite as critical in a double headed train system but can still help.

If you have only one long block, then only one train can be on that section of track at a time. If you break the long track runs into smaller segments, you could have two or more trains traveling on the same track at the same time, one behind the other. That would also give an addtionaly place for a train to stop before it gets into a problem area.

I recommend that you eventually go to single headed trains, with a double track mainline and branches off of that to your various areas. It requires roughly twice as much track, a bit more planning and a bit more room. But, it is infinitely expandable with minimal work. And you can have trains heading out "into the field" and back to the base at the same time.

While I do agree with this, this actually is not the cause of his collision problem. The cause of his problem is that trains do not stop on a dime, so they need to be given proper stopping distance when approaching a merge block, especially when one leg of the merge will have a train moving much more slowly than another train.

This is why you don't put signals right at the merges.

[Nailfoot]

Originally posted by CPT Chthonbeard the Pirate:

...
While I do agree with this, this actually is not the cause of his collision problem. The cause of his problem is that trains do not stop on a dime, so they need to be given proper stopping distance when approaching a merge block, especially when one leg of the merge will have a train moving much more slowly than another train.

This is why you don't put signals right at the merges.

I have never used double headed trains, but they work the same as single headed trains with regards to signals. I am a train nut in Factorio, with many hundreds of trains in my bases. Not once have I EVER had two trains collide unless I was manually driving one.

I know trains don't stop instantly (in fact, there is infinite research to increase the braking power), but as long as there are some signals I have always seen trains stop before an impact can occur. Whether they just sit at the station, or stop before the problem area. When a signal is red, a train will start braking well ahead of that signal because it knows its own stopping distance. Additionally, if a signal is red, another train will not attempt to enter that block.

Perhaps two trains are entering one block at precisely the same time? That'd be an interesting experiment.

[CPT Chthonbeard the Pirate]

Originally posted by Nailfoot:

Originally posted by CPT Chthonbeard the Pirate:

...
While I do agree with this, this actually is not the cause of his collision problem. The cause of his problem is that trains do not stop on a dime, so they need to be given proper stopping distance when approaching a merge block, especially when one leg of the merge will have a train moving much more slowly than another train.

This is why you don't put signals right at the merges.

I have never used double headed trains, but they work the same as single headed trains with regards to signals. I am a train nut in Factorio, with many hundreds of trains in my bases. Not once have I EVER had two trains collide unless I was manually driving one.

I know trains don't stop instantly (in fact, there is infinite research to increase the braking power), but as long as there are some signals I have always seen trains stop before an impact can occur. Whether they just sit at the station, or stop before the problem area. When a signal is red, a train will start braking well ahead of that signal because it knows its own stopping distance. Additionally, if a signal is red, another train will not attempt to enter that block.

Perhaps two trains are entering one block at precisely the same time? That'd be an interesting experiment.

Here's the situation though, imagine this hypothetical:

Train A is moving at 30 kph speeding up entering intersection from the north right now, it has now reserved the block and not before!
Train B is moving at 200 kph 3 meters from rail signal to the west of intersection right now, and that is 10 meters from the intersection.

Train B needs 50 meters to stop. Train A will be in the intersection in 2 seconds, but train B is going to be in the intersection in 2.5 seconds, as it cannot stop for the rail signal that just turned red.

The reservation for the intersection does not happen until a train actually enters the rail block. If the slow train enters first, and the fast train cannot stop, it simply cannot stop. To counter this, move the rail signal back for the SLOW train back far enough that the fast train is signaled early enough that it can stop.

[ConductorSavy TTV]

Another area that is affecting your trains with the collision stuff is the base area itself for the lines there.

You have too many signals in that spot in my opinion, I would reocmmend removing a lot of the signals that lead down to the bottom platform, like the image attached so it is one block instead of many. I even have chain signals shown in spots I think would benefit it, and would recommend you having your exit be similar into a 2-line branch for your areas where one line is going one way and the other is going the other way. https://steamcommunity.com/sharedfiles/filedetails/?id=2214031974

[The_Mell]

As far as i recognize the signals those are all normal signals (3 lights).
Problem could probably solved if all except those leading into a dead end station are substituted by chain signals (2 lights).
Even if there were no collisions, there should be a dead lock sooner than later...

After all two-way-rails are an intersection and the golden rule for signals still is:
Chain signals before & in intersections and normal signals after intersections & on straights with space for train length.

[juliejayne]

I would suggest that you have signals directly on either side of that junction where the 2 tracks join to come into the station. Try chain signals too. And the best option would be to provide a 2nd track/ Otherwise you are going to have constant issues with so many trains trying to share a single section of track.

[AlexMBrennan]

Originally posted by CPT Chthonbeard the Pirate:

I don't normally do bidirectional tracks, but I believe the problem is that your signals are too close to the fork. Trains do not stop on a dime, they need some space to stop, so if one train approaches the block quickly from the left, and another is entering slowly from the top base first, the one moving quickly from the left cannot stop in time to avoid collision.

Nonsense - that is not how Factorio trains work at all: Automatic trains reserve all blocks they would need to stop, and no other trains are allowed to enter these blocks. As a result, it is only possible to get collisions if you either 1) do not use any signals at all or 2) manually drive a train.

If OP thinks that they are getting collisions in automatic mode then they are simply wrong. He will get deadlocks due to incorrect signalling but no collisions.

[Modran]

Originally posted by Nailfoot:

Its a little hard to see in that picture, but I would HIGHLY recommend that you break your tracks in to smaller segments using more signals. Its not quite as critical in a double headed train system but can still help.

In contrast, I wouldn't recommend that at all as you don't want two trains enter the same long track from opposite directions. Never subdivide two-way-rails when there is no fork.

[juliejayne]

Originally posted by AlexMBrennan:

Originally posted by CPT Chthonbeard the Pirate:

I don't normally do bidirectional tracks, but I believe the problem is that your signals are too close to the fork. Trains do not stop on a dime, they need some space to stop, so if one train approaches the block quickly from the left, and another is entering slowly from the top base first, the one moving quickly from the left cannot stop in time to avoid collision.

Nonsense - that is not how Factorio trains work at all: Automatic trains reserve all blocks they would need to stop, and no other trains are allowed to enter these blocks. As a result, it is only possible to get collisions if you either 1) do not use any signals at all or 2) manually drive a train.

If OP thinks that they are getting collisions in automatic mode then they are simply wrong. He will get deadlocks due to incorrect signalling but no collisions.

I was thinking that... and would like to see the proof that they are actually colliding, like you I suspect that they are just deadlocked.

[Ploppy]

I'm new to the game too and struggled a bit, these tutorials helped me a lot:

https://imgur.com/a/PVL6I/all

https://www.youtube.com/watch?v=OH8L_hTIIJg&feature=youtu.be

[CPT Chthonbeard the Pirate]

Originally posted by AlexMBrennan:

Originally posted by CPT Chthonbeard the Pirate:

I don't normally do bidirectional tracks, but I believe the problem is that your signals are too close to the fork. Trains do not stop on a dime, they need some space to stop, so if one train approaches the block quickly from the left, and another is entering slowly from the top base first, the one moving quickly from the left cannot stop in time to avoid collision.

Nonsense - that is not how Factorio trains work at all: Automatic trains reserve all blocks they would need to stop, and no other trains are allowed to enter these blocks. As a result, it is only possible to get collisions if you either 1) do not use any signals at all or 2) manually drive a train.

If OP thinks that they are getting collisions in automatic mode then they are simply wrong. He will get deadlocks due to incorrect signalling but no collisions.

If that was the case, then no train ever in Factorio would collide. Yet here we are talking about how the OP has trains colliding, are we not? Clearly you are not correct, sir.

[Doom Sayer]

Yeah i dont know with trains i am questioning whether its worth trying to figure them out.

[Nailfoot]

Originally posted by Degeneratus:

Yeah i dont know with trains i am questioning whether its worth trying to figure them out.

Oh, ABSOLUTELY!! Yes! Yes x1000!