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Can someone explain for me what is principal difference between two setups? Why everyone use 1-st?

Because viewtopic.php?f=194&t=46855 probably.

Well the first obvious thing is the tracks are closer together with the left junction: that's the most commonly used spacing probably because it's the minimum spacing that allows a compact "crossover track". In addition the left junction is more efficient (has a higher throughput per minute), one reason is that it uses "split before merge", that is the tracks going in the 3 possible different directions all split off from each other, before crossing other tracks or merging, generally speaking split before merge junctions enjoy fewer "collisions" between trains (a good example of a junction which is "merge before split" is the common roundabout - trains merge onto a shared track before splitting off, resulting in contention for that shared track).

BlakeMW wrote:Well the first obvious thing is the tracks are closer together with the left junction: that's the most commonly used spacing probably because it's the minimum spacing that allows a compact "crossover track". In addition the left junction is more efficient (has a higher throughput per minute), one reason is that it uses "split before merge", that is the tracks going in the 3 possible different directions all split off from each other, before crossing other tracks or merging, generally speaking split before merge junctions enjoy fewer "collisions" between trains (a good example of a junction which is "merge before split" is the common roundabout - trains merge onto a shared track before splitting off, resulting in contention for that shared track).

Big thank you man!

Consider what happens when two trains enter from opposing sides and both want to turn left:

Lilly wrote:Consider what happens when two trains enter from opposing sides and both want to turn left:

junctions.png

Thank you!

BlakeMW wrote:Well the first obvious thing is the tracks are closer together with the left junction: that's the most commonly used spacing probably because it's the minimum spacing that allows a compact "crossover track". In addition the left junction is more efficient (has a higher throughput per minute), one reason is that it uses "split before merge", that is the tracks going in the 3 possible different directions all split off from each other, before crossing other tracks or merging, generally speaking split before merge junctions enjoy fewer "collisions" between trains (a good example of a junction which is "merge before split" is the common roundabout - trains merge onto a shared track before splitting off, resulting in contention for that shared track).

Our of curiosity, is a crossover track one that lets a train onto the opposite direction track? If so when and where do people tend to use them? I have almost never seen them in Factorio train builds. If they don't, I think it might make a lot of sense to pack the rails closer together (1 track width empty between for drive on left, and 0 track between for drive on right) normally and use a longer runup to space them however nescessary for junctions.

Well you can space tracks out in the runup before a junction, but what do you gain by doing that rather than always having them space 2 apart? And if you use a consistent spacing you can readily add junctions into existing track and will have room to place signals when tracks cross. Also if you use a spacing other than 2 all kinds of junctions will be larger (because no spacing expands to 3 for junctions, and 1 spacing expands to 4: a spacing of 2 remains at 2 for junctions, especially T junctions).

Anyway by crossover I mean mainly when a train needs to cross from one track to another. The tracks could be going in the same direction such as when splitting off to multiple stations. Personally in some cases I merge a two-way line down to a single line and players who use 4 (or more) lane trunkways presumably merge them down to smallers ones.