Advanced Roundabout

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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

Unlike the basic roundabout, this junction has 1 level above the default Track-Level. Trains can pass straight through and turn right without entering the circle.

Some problems are minimized by using pre-signals

Advanced roundabout junction


Junction Criteria
CostExpensive (Stepped)
Construction DifficultyModerate
TunnelsYes
BridgesNo
Breakdowns
Broken down trains affect one line or all left turns.
Sharpest Turn3
HillsYes
Split Before MergeNo
Direct PathsYes
Natural TurnsNo
DeadlockYes
LoopsYes
Signal type Pre-Signal
  • Can handle lots of trains moving N-E or S-W
  • Tracks split and only trains going to the left need to take the round-a-bout

Tips

  • To allow left-turning trains traveling at full speed through the roundabout, it's possible to enlarge the circle, but this takes a lot of space to build.
  • If you make the inner circle run the opposite way (obviously modifying exit diagonals and signal direction) throughput is increased at the expense of some speed, since trains going up there just cut across instead of having to go round the whole roundabout as tey would with the above.
  • Area: 16 x 16


Flying roundabout junction
  • Area: 14 x 14


Advanced Roundabout without Deadlock

Image caption


Junction Criteria
CostModerate
Construction DifficultyModerate
TunnelsYes
BridgesYes
Breakdowns
Broken down trains only affect one direction. (Worst case: Inner circle, between two segments, will block 3 left turn directions)
Sharpest Turn2
HillsYes
Split Before MergeNo
Direct PathsYes
Natural TurnsNo
DeadlockNo
LoopsYes
Signal type Pre-Signal

Pros:

  • High capacity
  • Slopes only for left turns (1 up, 1 down in total)
  • Will buffer left turns to free up other lines (entry and exit!)

Cons:

  • Pass through highest signal distance: 4/5
  • Left turn highest signal distance: 7


  • Area: 26 x 26


The presignal logic only lets trains enter, when the next and any of the other segments are empty. This ensures that the junction can always be cleared, if the trains fit completely into the segments.


Advanced Roundabout without Deadlock Compact

Image caption


Junction Criteria
CostModerate
Construction DifficultyHard
TunnelsYes
BridgesYes
Breakdowns
Broken down trains only affect the one direction. (Worst case: Inner circle, between two segments, will block all left turn directions)
Sharpest Turn2
HillsYes
Split Before MergeNo
Direct PathsYes
Natural TurnsNo
DeadlockNo
LoopsYes
Signal type Pre-Signal

Pros:

  • High capacity
  • Slopes only for left turns (1 up, 1 down in total)

Cons:

  • Pass through highest signal distance: 4/5
  • Left turn highest signal distance: 7


  • Area: 18 x 18
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