Town Growth Quirk

Strategy

The “satellite towns” strategy popularized by OpenTTD content creator Master Hellish exploits a clever quirk in the game’s town growth code. By connecting a town center to a remote area using a road tunnel, you trick the game into treating a distant piece of land as if it is right next to the town center. 1, 2

This allows you to spawn a brand-new, isolated pocket of houses (a satellite town) that officially belongs to the original municipality. 2]

Game Mechanic

To understand why this works, you have to understand how OpenTTD decides where to build houses:

1. The Search Area: Every few days, a town attempts to grow. It starts searching outward from its central tile (where the town name is floating) and follows existing roads. [1, 2, 3]
2. The “Zero-Length” Tunnel Bug: The OpenTTD pathfinding algorithm calculates the length of a road tunnel as zero tiles. [1]
3. The Trick: If you place a road tunnel entrance right at the edge of the town center and run it under a mountain, a body of water, or just underground, the game views the exit of that tunnel as being directly adjacent to the town center. [1]

When the town growth engine passes through that tunnel, it immediately starts building roads and houses at the tunnel’s exit, even if it is 30 tiles away from the actual city. [1]

Satellite Town

To build a satellite town using Master Hellish’s method, follow these steps:

1. Prep the Main Town

Find a booming city or town that you want to expand. Clear a straight line of land starting as close to the physical town center as the local authority will allow. [1, 2, 3, 4]

2. Create the Slope and Tunnel

Use the landscaping tools to lower a tile at the edge of the town center to create a slope. Place a road tunnel entrance there. Dig the tunnel in the direction of the empty land where you want your satellite town to appear. [1, 2]

3. Build the Satellite Grid

At the tunnel exit, build a small, pre-laid grid of roads (like a 2×2 or 3×3 block). Make sure these roads connect directly to the tunnel mouth so the town’s expansion AI can seamlessly flow out onto them. Avoid dead ends, as they stop town growth dead in its tracks. [1, 2, 3, 4]

4. Fuel the Growth

To make houses start popping up rapidly around your new satellite exit, you must keep the city active. Place up to five transit stations (like bus stops) around the main city and your new satellite grid. Keep a steady stream of buses running between them. Delivering at least one passenger or cargo piece to these stations every 50 days triggers the game’s maximum town growth rate. [1, 2, 3, 4, 5, 6]

To maximize the layout and speed of your expansion, you can see the exact mechanics of passenger-driven growth in action: (see How To Grow Towns and Cities by Master Hellish)

Highly Effective

• Overcoming Space Limits: Massive train stations, airports, and nearby oceans often box in a city. Tunnels let the town “teleport” past these obstacles to utilize empty land across the map. [1, 2, 3]
• Station Coverage Clustering: You can place a massive airport or railway station right between the main town and the satellite town. As the satellite town expands toward the main city, both locations feed passengers and mail directly into a single, highly profitable central hub. [1, 2]
• No Local Authority Drama: Building an entirely new town from scratch is impossible in standard gameplay, and expanding into neighboring towns requires dealing with picky local authorities who hate construction. Because the satellite town technically belongs to the original city, your existing high rating carries over, allowing you to seamlessly expand your footprint. [1, 2, 3, 4]