Rail Junction

Rail Junctions are a railway item in Astroneer. They allow for the creation of rail line junctions that splits rail lines in three directions. Each bundle contains 5 Rail Junctions and may be placed in the backpack's Aux Slots for easy placement of posts.

Source
Rail Junctions are placed from a.

Uses
Rail Junction Bundles are used to place on terrain to expand rail lines and change the direction of trains running along the line. The bundles may be placed in the Backpack's aux slots, which allows for quicker placement by pressing the context keys (PC: or ).

Interacting with the Rail Junction will cause the rail connection to switch between the three possible states. When travelling on the rail line using a Rail Engine, Left and Right (PC: and ) can be used to switch the junction direction, when the train is close enough to the junction.

Rail Junctions have three input slots for Automation signals, located between each of the three rail directions. Sending a signal to an automation input will connect the rail on either side of that input signal. Signals can also be sent anywhere on the junction itself, which would just cause the junction to cycle through the connections, similar to interacting with the junction manually.

Placing a Rail Junction within range of another Rail Post or Junction will connect a rail line between them, deforming any terrain that might be in the way.

Rail Junctions may be placed on any terrain, allowing for placement on walls and ceilings of caves.

The maximum placement distance for the junction is shown as a coloured dial on the base of the junction when placing.
 * White indicates valid placement, below the maximum rail length
 * Blue indicates valid placement at optimal rail length
 * Pink indicates invalid placement -- whether from being placed too far, too close, or from creating too sharp of a turn.