# Track laying

*Mechanic* · `track-laying` · status: **asserted**

The player builds rail or coaster track segment by segment under grade, curvature, terrain, and cost constraints, and vehicles then run on the resulting path.

| field | value |
|---|---|
| aliases | rail building, coaster track building, track construction |
| family | Space & construction |
| substrate | Cellular grid, Rule system |
| math basis | Optimization, Combinatorics |
| feedback | None |
| player interface | Placement |
| legibility | 4 |
| emergence potential | 3 |
| authoring cost | 2 |
| compute cost | 1 |
| tuning difficulty | 2 |
| ai leverage | 2 |
| maturity | Classic |
| core count *(computed)* | 1 |
| earliest game *(computed)* | [Railroad Tycoon](../game/railroad-tycoon.md) |
| earliest year *(computed)* | 1990 |
| prevalence *(computed)* | 5 |
| prevalence rank *(computed)* | 113 |
| prevalence share *(computed)* | 0.028 |
| subgenre spread *(computed)* | 3 |
| technique count *(computed)* | 0 |
| technique exposure *(computed)* | 0.0 |

## Definition

Owns a set of track pieces joined end to end, each with a type (straight, curve, slope, switch, bridge, tunnel, or special element such as a loop), an entry and exit position and heading, and a cost. Construction extends an open endpoint with a piece whose entry matches it; the game checks grade and curvature limits, terrain clearance, and collisions with other structures, then charges a cost that depends on terrain (slopes, water, demolition) and piece type. Railroad Tycoon and Transport Tycoon lay track on a tile grid, with slopes, bridges, and tunnels in Transport Tycoon; RollerCoaster Tycoon builds coasters piece by piece on a tile grid by direction, height, steepness, and elements such as loops and corkscrews; Planet Coaster adds spline editing; Factorio places straight and curved rail pieces. Outputs: a track graph that vehicles traverse, used by scheduling, signaling, and ride rating. Unlike free-placement, the unit of building is a connected chain rather than a footprint; unlike road-network, it owns segment geometry and its constraints rather than building connectivity; unlike modular-assembly, the result is a path.

## Player Experience

Drawing a line through the world under constraints. Players hunt for the gentle grade around a hill, decide whether a bridge is worth its price, and fit a coaster's drops and turns into a cramped park. A clean line that vehicles run smoothly on is a craft object players admire and share.

## Design Levers

- grade and curve radius limits and their effect on vehicle speed
- terrain cost model for slopes, water, tunnels, and demolition
- piece set: fixed tiles, free splines, or both
- auto-routing tools that pick a path between endpoints
- special pieces such as switches, loops, lifts, and brakes

## Failure Modes

- Tile-locked pieces make every layout look the same; free splines without snapping make clean joins hard.
- Construction controls that need many precise clicks per segment make building tedious.
- Costs too low make terrain irrelevant, so lines ignore the landscape.

## Dynamics

- Terrain shapes networks and rides: lines follow valleys, and coasters use hills for drops.
- Junction and switch layouts couple track design to signaling and throughput.
- Track geometry feeds ride ratings and train speeds, so building quality shows up in revenue.

## Open Questions

- Can route-finding assistants that propose track under grade and cost constraints keep the craft while removing click work?
- Could generative models propose coaster layouts that hit target ratings for players to refine?

## Backlinks (computed)

**used by:** [Factorio](../game/factorio.md), [Planet Coaster](../game/planet-coaster.md), [Railroad Tycoon](../game/railroad-tycoon.md), [RollerCoaster Tycoon](../game/rollercoaster-tycoon.md), [Transport Tycoon](../game/transport-tycoon.md)

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Provenance: created in run `2026-10-24-taxonomy-triage-b`.