What I occasionally do is take examples from reality.
People familiar with Dutch railway layout will recognize Gaasperdammerweg Aansluiting in the junction below, people who don't, will get the idea on
Sporenplan.nl - asd-o (I pasted the image on my screenshot)
This juction has the following qualities:
-Independent traffic A<-->C and B<-->D at the same time.
-Independent traffic A<-->D and B<-->C at the same time.
-Maximum 1 heightpoint rise or descent on any traffic A/B<-->C/D (and on A->B, 2 on B->A)
Possible Connections:
A-->B,C,D
B-->A,C,D
C-->A,B(,D)
D-->A,B
Select-First (meaning that all branches diverge to all directions before ever converging, which is good)
No Loops
Relatively small footprint.
Two reasons it's not fully connected:
- There's no need for a connection C<-->D yet
- As in reality, the connection A<-->B was built later, so that's why there are 2 heightpoints difference there.
Don't pay attention to the bypasses A and B.
A was to prevent trains from going up then immediately going down (near point C, it's hard to see, but there's a track next to the fruit plantation).
B is a leftover to get from a supplier (oil pump) on the C spur to a demandor (refinery) on the D spur, this has been fixed now by putting the supplier on the D spur as well (D only goes to a refinery, no oil pumps in direction C).
Disadvantages to the current layout:
-No connection C<-->D
-Connection B-->A has 2 height points
-Quite hard to correctly build without example
-Conversion from a "normal" junction impossible without major service disruption.
-Offset connection B<-->B
Differences from the real layout:
-Tracks to C go over instead of under tracks to D
-Station Weesp omitted
-A-->B connector tracks connect on the inside instead of outside
-Some Crossover tracks omitted
Please tell me what you think of this junction and whether it's "wiki-worthy"
I'm working on a fully connected version of this which preserves all beforementioned qualities, and have a footprint not much bigger, I will post that later. Only problem I have is the 2 heightpoint difference on the A-->B connector (even if I raise the B track)
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