effect · `build_railway`

Definition

Supported scope:any
Supported target:any

Description

Builds/adds railway level between two provinces or along a path. Example:
build_railway = {
  level = 1 # Defaults to 1
  build_only_on_allied = yes # No by default. If yes and the effect scope is country, it will only build on allied territories for the country

  # You can specify a weight function that will be used in pathing. The scope will be the controller of the province it is trying to path to.
  # A negative value will make it not to path to that controller.
  # Non-negative values will be used as a path cost for that province.
  controller_priority = {
    base = 1

    modifier = {
      tag = MAN
      add = 2
    }
  }

  # The following options are used for picking a path. You can specify multiple options and it will pick in following order:
  fallback = yes # Default no. If yes, each option will try to fallback to next one.
  # option 1: List of provinces to draw railways. If fallback = yes uses start and end provinces of the path as fallback in option 2.
  path = { 10 20 30 40 }
  # option 2: Specify start & end province IDs. It will pick the shortest path. If provinces are not valid and if fallback = yes it will use states of those provs and use in option 3.
  start_province = 42
  target_province = 84
  # option 3: Specify start & end state IDs. It will pick provinces with the best node (capital > nodes > naval )
  start_state = 50
  target_state = 100
}

实战 · 配合 · 坑

实战内容由 AI 生成,并已对照 vanilla 命令词表校验 —— 请当作起点而非权威依据。上方的定义节才是游戏自带文档原文。

实战用法

build_railway 常用于战役事件或国策完成后，在指定区域自动铺设铁路基础设施，例如模拟"大基建计划"或战时后勤保障场景。也可在占领事件中，根据控制方的阵营关系选择性地在友军领土上修建铁路网络。

# 国策完成后，在两州之间自动寻路修建一级铁路，仅限盟友领土
complete_national_focus = {
    effect = {
        build_railway = {
            level = 1
            build_only_on_allied = yes
            fallback = yes
            start_state = 42
            target_state = 67
            controller_priority = {
                base = 1
                modifier = {
                    is_ally_with = ROOT
                    add = 5
                }
            }
        }
    }
}

配合关系

[can_build_railway](/wiki/trigger/can_build_railway)：在执行 build_railway 前先判断路径是否可修建，避免因路径不可达导致效果静默失败。
[has_railway_level](/wiki/trigger/has_railway_level)：用于检测目标省份/州已有的铁路等级，配合 if 条件决定是否需要升级，防止重复建设。
[has_railway_connection](/wiki/trigger/has_railway_connection)：验证两地之间是否已存在铁路连接，作为 build_railway 的前置或后置校验条件。
[custom_effect_tooltip](/wiki/effect/custom_effect_tooltip)：由于 build_railway 本身的 UI 提示有时不够直观，搭配此命令向玩家显示更清晰的建设说明。

常见坑

path 与 start_province/start_state 混用导致逻辑冲突：三种寻路选项有优先级顺序，若同时写入多种选项但未开启 fallback = yes，游戏只会使用最高优先级的 path 字段，其余字段被完全忽略，新手常误以为会"自动选最优方案"。
在非国家 scope 下使用 build_only_on_allied = yes 无效：该字段仅在 scope 为 country 时生效，若在 state scope 或 province scope 下设置此项，不会报错但也不会产生任何过滤效果，容易造成在敌方领土意外建设铁路的 bug。

Hands-On Notes

Hands-on notes are AI-generated and checked against the vanilla command vocabulary — treat them as a starting point, not authoritative reference. The definition above is the game's own documentation.

Hands-On Usage

build_railway is commonly used in campaign events or upon completion of national focuses to automatically construct railway infrastructure in a specified area, such as simulating "major infrastructure projects" or wartime logistics scenarios. It can also be used in occupation events to selectively build railway networks on allied territory based on the controlling faction's alignment relationships.

# After national focus completion, automatically pathfind and build a level 1 railway between two states, limited to allied territory
complete_national_focus = {
    effect = {
        build_railway = {
            level = 1
            build_only_on_allied = yes
            fallback = yes
            start_state = 42
            target_state = 67
            controller_priority = {
                base = 1
                modifier = {
                    is_ally_with = ROOT
                    add = 5
                }
            }
        }
    }
}

Synergy

[can_build_railway](/wiki/trigger/can_build_railway): Check whether the path is buildable before executing build_railway to avoid silent failures due to unreachable paths.
[has_railway_level](/wiki/trigger/has_railway_level): Used to detect the existing railway level of target provinces/states and combine with if conditions to determine whether an upgrade is needed, preventing duplicate construction.
[has_railway_connection](/wiki/trigger/has_railway_connection): Verify whether a railway connection already exists between two locations, serving as a pre-check or post-check condition for build_railway.
[custom_effect_tooltip](/wiki/effect/custom_effect_tooltip): Since build_railway itself sometimes lacks clear UI feedback, use this command in conjunction to display more explicit construction instructions to the player.

Common Pitfalls

Mixing path with start_province/start_state causes logic conflicts: The three pathfinding options have priority ordering. If multiple options are written simultaneously without enabling fallback = yes, the game will only use the highest-priority path field, with all other fields completely ignored. Beginners often mistakenly assume it will "automatically select the optimal solution."
Using build_only_on_allied = yes outside country scope is ineffective: This field only functions when the scope is country. If set in a state scope or province scope, it will not error but also will not produce any filtering effect, easily causing bugs where railways are unexpectedly constructed on enemy territory.

effect · build_railway