Priority Merge

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Revision as of 21:28, 6 February 2011


Railway Junctions
Junction Criteria

3-Way junctions

Basic 3-Way
Line Merge
Half Cloverleaf
Half Spaghetti
Compact 3-Way
Compact 3-Way B-M Junction
Ultimate 3-way
Half Transmogrified
Braided Junction

4-Way junctions

Basic 4-Way
Roundabout
Cloverleaf
Spaghetti
Star
Complex Star
Branch-Merge
Tetrathorp
High Speed 4-Way Fly-over/under
Pre-Signaled Roundabout
Advanced Roundabout
Right-of-way Roundabout
Improved Roundabout
Transmogrified
Tightlong
Deepblue2k8 4-way Junction

Enormous junctions

Multi-way/multi-track cloverleaves
Dual Tetrathorp
Dual Transmogrified
Dual Branch-Merge
Quad Branch-Merge
Quad Tetrathorp
6-tuple Branch-Merge
8-Way Star
High Speed 4-way

Other junctions

Right-of-way Depot
Dual tunnels
Sideline U Turn
Right-of-way Lane Change
Right-of-way Merge

Track Layouts

4-Way Triple Axial
4-Way Triple Axial 2
Triple Via Mini
High Hill

Unuseful junctions

Crossover
3/4ths junction
Ultimate 3-way junction for 4 tracks

All merging is bad, especially if either line is very busy. When trains start queueing they merge alternately. This sounds like a great idea, but because the trains are starting from stationary each time it's very slow. Better off giving priority to one line and allowing it to clear at full speed before the other line can merge. This is especially useful for joining a main line.

Using pre-signals in a simplified version of the Right-of-way Lane Change and Right-of-way Depot you can force trains joining the mainline to wait for a gap. With a dual mainline this works even better, as you can let trains on the inside move to the outside to let trains join.

Right of way merging onto dual mainline

All signals are combo signals except at points A and B which are entry signals, and the top right, which are exit signals. Adjust the length of the signal chain according to train length and speed.

Trains joining at point A must wait for the presignal chain along the inside lane to be clear. If a train arrives at point B before train A is out of the way then it will switch to the outer lane (at no speed penalty), but only if the presignal chain for the outside lane is clear. If it is not, the presignals at point B ensure that train B will take the line which clears first.

The vertical section of track at point C is optional. It allows A to continue if the presignal chain for the outside lane is clear, even if the inside lane is not, as the train on the inside will move to the outside to let A out. Without it, A will always wait for the inside lane to clear, regardless of the state of the outside lane.

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