Factorio Train Signals: Keep Crossings Clear

Prerequisites

• Identify the longest train in your rail system and the direction each automated train will take through the crossing.

Step-by-Step Instructions

1. Hold a signal to inspect the rail block colors and identify the crossing blocks.
2. Place signals on the right side in each direction of travel. Use opposing pairs at signaled points where automatic trains must travel both ways.
3. Place chain signals before the crossing and at any signal positions within it.
4. Place regular rail signals at the crossing exits.
5. Leave enough track between each exit signal and the next signal to fit the longest train in your rail system.

How Signals Control a Crossing

Signals divide rails into blocks. A train waits at a signal leading into an occupied block. Hold a signal to see the block colors on the rails; those colors show the block layout, not the signal light state.

Place signals on the right side of the track in the train's direction of travel. If automatic trains must use a track in both directions, place signals directly opposite each other at signaled points they must pass.

Place Signals at the Crossing

Place chain signals before the crossing and at any signal positions within it, then place regular rail signals at the exits. A chain signal normally checks whether the train can continue through the exit on its route, holding it before the crossing if it cannot. There is an exception: if the train can reach its destination without passing another signal, the chain signal does not consider exit signals. That applies to train stops and temporary stops.

A simple crossing can remain one block. Dividing it into more blocks can let trains use separate routes through it at the same time, but extra blocks are not needed for the basic setup.

Leave Room Beyond Each Exit

Between each crossing exit signal and the next signal, leave enough track to fit the longest train in your rail system. Otherwise, a train stopped at the next signal could leave its tail in the crossing.

If two junctions are too close for that train, replace regular signals between them with chain signals, move the junctions farther apart, or shorten the trains. Correct signals cannot prevent every deadlock: a circular route with more trains than it can hold can still lock up.

Check a Stalled Train

A blinking chain signal may be off the rail or unable to divide it into separate blocks. Check its placement while viewing the block colors. A blue chain signal means some exits are free and others are blocked; check the stalled train's route to see which exit it needs.

If an automatic train reports no path, trace its route through the signals. A left-side signal without a matching right-side signal can make an apparently connected track unusable in that direction.

Troubleshooting

• Blinking chain signal: check that it is on the rail and divides it into separate blocks.
• Blue chain signal: check the train's route; some exits are free and others are blocked.
• No path: check for a left-side signal without an opposing right-side signal along the automatic train's route.
• Train tail blocks a crossing: increase the space beyond the exit, use chain signals between nearby junctions, or shorten the trains.

Alternatives

• A simple crossing can stay one block. Additional blocks can allow simultaneous use of separate routes.
• If nearby junctions cannot fit the longest train between them, replace the regular signals between them with chain signals, move the junctions apart, or shorten the trains.