Factorio Forums

Mr. Tact wrote:So, here is your solution on the left and mine on the right, is there a functional difference? If so, what is it?

I havent seen anyone post either solution ,so you are making a mistake here?

And it is questionable to post a "solution" and then ask for functional differences. Because finding functionality is the basis for any solution, you cant seriously be asking for an explanation of your own solution? Thats just as confusing as the OP who asked for help and then answers himself in his own thread.

Chain signals is a efficency trap, don't use them if they can be avoided and if they can't be avoided you should look very closely at whatever your track layout is messed up.

ONLY time you use chain signals in a well flowing system, is if you actually want the train that crosses the chain signal to have priority over other traffic.

Trains flow soo much better with rail signal only T sections.

Word of warning: Yeah rail signal only T-Sections is a lot harder to signal right, if you want easy to not mess up, you should stick with 3 chain and 3 rail signals pr. intersection (chain on input rail on output), because it's bloody easy to remember and never get wrong. Even if you add more chain signals inside to improve the range of blocking, you can never ever get it wrong.

I just learned, from watching heavy rail streamers, and created this version for my own world and I'm shocked how bad my old chain system worked compared to this. I'm just trying to duplicate the experts work, so I'm not sure this is the "OPTIMAL" placement of signals, I just know it doesn't deadlock. I may have added one to many signals, or placed one in a less optimal location.

Mr. Tact wrote:So, here is your solution on the left and mine on the right, is there a functional difference? If so, what is it?

That's not my solution on the left, you've used the same signals but on the wrong side of the track which introduces some minor problems. Basically instead of chain signals on the exits (as I said this can potentially cause problems if there is a nearby signal) you've got them on the entrances which unnecessarily stops trains approaching the junction when it's occupied.

As for the differences between my actual intersection and yours, there isn't much difference. I've basically used less chain signals so the trains wait further along the rail if the intersection is blocked, which is only a very minor advantage though it does allow more "wait" room on the tracks.

Miravlix wrote:Chain signals is a efficency trap, don't use them if they can be avoided and if they can't be avoided you should look very closely at whatever your track layout is messed up.

[snip]

There is only one way to deadlock an improperly signalled three-way intersection and as long as your rails are laid out accordingly it's not a problem, HOWEVER if you bolt a loop with a train stop directly onto one of those directions, then send three 1-loco 2-wagon trains to it, you'll get deadlocked. The trains will queue up over the intersection and block the first train from leaving. Might not sound like a big problem but more trains will block a bigger loop. Sure this will work for a little train network utilising waiting bays but it should not be advertised as a sturdy junction.

Chain signals are to prevent trains from stopping on a junction that other trains may pass through unhindered, while allowing two trains (whose paths do not intersect) to pass each other, for example a train going east and a train going west. I guess you could look at them like "filtered" signals that only separate the rail block where the train is not going.

Mr. Tact wrote:

Deadly-Bagel wrote:After much monitoring and tweaking, I deem this to be the perfectly signalled 3-way intersection:

Okay, your intersection was slightly different from what I use. And I can't wrap my brain around if the differences matter or not... I use driving on the left despite being in the US because I like having the signals inside the rails...

So, here is your solution on the left and mine on the right, is there a functional difference? If so, what is it?

T interscetion signalling.jpg

If your trains are short enough, the design on the left is actually advantageous as it would allow an Eastbound train entering from the north to begin its turn even if Eastbound traffic is backed up. Provided that it is shorter than the distance between the two non-chain signals on that path it would exit the Southbound entrance block (and stop between said signals) and thus allow Westbound traffic coming from the North to get by.

Miravlix wrote:~snip~

This is not a well-designed junction, consider what happens if an Westbound train, entering from the East stops at the 3rd of 4 rail signals it encounters (because the block it precedes is obstructed by a train). Now in this scenario, suppose another Northbound train enters from the West. It's turn is now blocked by the Westbound train stopped in the junction. This is exactly what Chain signals are designed to prevent. The proper place for the chain signal is in front of the T-junction, as well as at any intermediate points that separate non-overlapping pairs of paths through the junction (this is the part that even experienced train network designers seem to struggle with and how you optimize junction throughput).