Railways Untold places a starting train on the generated track when a world is first loaded. Train designs are defined via data packs, allowing you to add custom Create train schematics. Multiple train definitions can coexist, with weighted random selection and biome filtering determining which train spawns.

The mod loads train definitions from data packs at startup and on /reload. When the starting train needs to be placed, the mod selects a train using weighted random selection filtered by the biome at the placement position. If multiple train definitions are valid for the biome, one is chosen randomly based on their weights. The random selection is seeded from the world seed, so the same world seed always produces the same train choice.

This setting remains in config/railways-untold/config.toml:

Place your train definition JSON file at:

data/<namespace>/railwaysuntold/trains/<name>.json

Place the corresponding .nbt schematic file at:

data/<namespace>/structure/<path>.nbt

For example, in a data pack called my_train:

my_train/
  pack.mcmeta
  data/
    my_train/
      railwaysuntold/
        trains/
          custom_train.json
      structure/
        trains/
          custom_train.nbt

{
  "schematic": "my_train:trains/custom_train",
  "front_facing": "auto",
  "weight": 10,
  "biome_whitelist": [],
  "biome_blacklist": [],
  "loot": {
    "by_tag": {
      "cargo": "my_train:trains/cargo_loot"
    }
  }
}

Train schematics must be saved as assembled Create trains (not loose blocks):

1. Build and assemble your train in-game using Create's train assembly system
2. The train must have at least one carriage contraption with bogeys
3. Use a schematic tool (like Create's Schematic and Quill) to save the assembled train

The schematic is validated on load. The mod checks for:

• Valid carriage_contraption entities in the NBT data
• Proper bogey layout and spacing
• Assembly direction detection

If validation fails, the mod falls back to the built-in default train and logs a warning.

Multi-carriage trains are supported. The mod detects carriage boundaries by analyzing bogey positions and entity fingerprints, then calculates inter-carriage spacing for proper assembly on the track.

When front_facing is set to "auto", the mod detects the front of the train by searching for these blocks in order:

1. Smokestack blocks — blocks with "smokestack" in the name
2. Steam whistle blocks — blocks with "steam_whistle" in the name
3. Control seats — the FrontControls flag on carriage contraptions

If auto-detection produces the wrong result, use an explicit direction value.

The mod ships with a built-in default train definition:

data/railwaysuntold/railwaysuntold/trains/default_train.json

{
  "schematic": "railwaysuntold:train",
  "front_facing": "auto"
}

This uses the bundled train.nbt schematic with the default weight of 10 and no biome restrictions. To add additional trains, simply create a data pack with more train definitions — they will all participate in weighted random selection.

When the starting train is placed, the mod:

1. Collects all valid train definitions from all data packs
2. Filters out trains whose biome whitelist/blacklist excludes the placement biome
3. Selects one train from the remaining candidates using weighted random selection
4. If no candidates match, falls back to the built-in default train.nbt

The selection uses the world seed as the random seed, so the same world seed always produces the same train.

Add several trains that spawn with equal probability:

data/my_trains/railwaysuntold/trains/steam_locomotive.json

{
  "schematic": "my_trains:trains/steam_locomotive",
  "front_facing": "auto",
  "weight": 10
}

data/my_trains/railwaysuntold/trains/diesel_engine.json

{
  "schematic": "my_trains:trains/diesel_engine",
  "front_facing": "north",
  "weight": 10
}

A snow train that only spawns in snowy biomes:

data/my_trains/railwaysuntold/trains/snow_train.json

{
  "schematic": "my_trains:trains/snow_train",
  "front_facing": "auto",
  "weight": 10,
  "biome_whitelist": ["#minecraft:is_overworld", "#c:is_snowy"]
}

A desert cargo train excluded from cold biomes:

data/my_trains/railwaysuntold/trains/desert_cargo.json

{
  "schematic": "my_trains:trains/desert_cargo",
  "front_facing": "auto",
  "weight": 5,
  "biome_blacklist": ["#c:is_snowy", "#c:is_cold/overworld"]
}

A special train that spawns rarely (1 in 11 chance alongside the default):

data/my_trains/railwaysuntold/trains/golden_express.json

{
  "schematic": "my_trains:trains/golden_express",
  "front_facing": "auto",
  "weight": 1
}

You can assign loot tables to containers (chests, barrels, etc.) on train carriages. The loot system works identically to event loot tables — see the Events documentation for full details on the loot configuration format, container tagging, and resolution order.

Loot tables on trains are applied during assembly. The loot is deferred — items are generated when a player first opens the container on the train, using vanilla Minecraft's loot table mechanism.

{
  "schematic": "my_trains:trains/cargo_train",
  "front_facing": "auto",
  "weight": 10,
  "loot": {
    "by_type": {
      "minecraft:chest": "my_trains:loot/cargo_chest"
    },
    "by_tag": {
      "coal_supply": "my_trains:loot/coal",
      "iron_supply": "my_trains:loot/iron_ingots"
    }
  }
}

Train definitions are loaded as part of Minecraft's data pack system. Changes take effect:

• When starting/loading a world
• After running the /reload command

Note that the starting train is only placed once when the world is first generated. Reloading the definition does not replace an already-placed train.

Some train features (non-standard bogey types, custom track materials) may require the Steam 'n' Rails mod. If the schematic references blocks from mods that aren't installed, the mod logs warnings but still attempts to load the train.