Dual Tetrathorp-Junction

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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
Complex Star
High Speed 4-Way Fly-over/under
Pre-Signaled Roundabout
Advanced Roundabout
Right-of-way Roundabout
Improved Roundabout
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

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

The Dual Tetrathorp Junction is a Tetrathorp-Junction for double mainlines. It is ideally suited for mainlines at different height levels (in the following referred to as "Diff-Lev-Mains"). It consists of a inner Tetrathorp Junction connecting the inner lanes and a outer Tetrathorp connecting the outer lanes. The 4 lanes which are turning to the same direction merge each other first and have a build-in load balancer before they merge the main line. This allows trains to go from inner lanes to outer lanes and vice versa, so that they can pick the new mainline with less traffic.

Original Dual Tetrathorp

Junction Criteria
CostAbout £330,000
Construction DifficultyHard
Broken down trains only affect the one track.
Sharpest Turn1,5
Split Before MergeYes
Direct PathsYes
Natural TurnsYes
Signal type Any
  • Can handle many trains at a time.
  • Requires the building on slopes patch to be enabled.
  • Clearly structured, therefore probably easier to remember and to build than equally big junctions.
  • Modular design: You can build the inner lanes first, with only little more space than the single Tetrathorp-Junction and add the outer lanes later.


  • Start building the inner single Tetrathorp (check if it works) then expand the junction outward.
  • The outer lanes for turning right can easily be made longer, so that they can hold your longest train.


Dual Tetrathorp for flat terrain

This Dual Tetrathorp junction is optimized to be slightly more compact in flat terrain.

Inner part of the Dual Tetrathorp

This is the inner single Terathorp (which is the same for the original junction and the flat variation). The outer landscaping is for the flat variation.

Improved exits for the Dual Tetrathorp Junction

The load balancers of the above variations can be improved like this. The zigzagging exits at the end imply a pathfinding penalty for trains, which otherwise could decide to cross the whole load balancer even if their neighboring mainline is free. Additionally the outer right-turning-lane (2) and the mainlines (1 and 3) have direct access or a shorter accelerating distance to the merging block than the other turning lanes (4). So trains waiting on these lanes (which are more probable to blocking other trains) get priority. (Priority is not to be confused with right-of-way, which is applied at the end of the load balancer).

Furthermore it is possible to make all curves longer to allow for higher speeds and to build some or all tunnels as dual tunnels to improve the throughput. The load balancers can probably also be improved further.

Technical Data

  • 40 free squares inside the junction
  • 38 tunnels

Cost of the flat variation:

  • Landscaping: £59,592
  • Inner Tetrathorp: £134,138
  • Outer Tetrathorp: £132,462
  • Total: £326,984
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