Advanced Train Tracks Techniques: Parity, Forced Paths and Pairs
Updated October 3, 2026 · 5 min read
When the basics stall, these three ideas usually unlock a stuck board. They need nothing beyond the rules, just a more careful look.
Forced paths through bottlenecks
If the only open squares that connect two regions form a narrow channel, the track has to run through that channel. Every square in it is track, and its neighbours often become crossed out.
Run-length reasoning
A line's clue tells you how many squares it holds, and the open squares tell you where. Work out whether those squares can be consecutive. If the squares left in a row aren't next to each other, the track enters and leaves that row more than once, which changes what the columns must hold.
No loops, no stray pieces
A closed circuit of track is never part of the solution. If a placement would join pieces into a ring, or leave a piece cut off from the route, it's wrong. This rule resolves a surprising number of late-game forks.
Pair the clues
Look at a row and the column it crosses. When one of them is nearly full and the other nearly empty, the line almost certainly runs along the full one and crosses the empty one once. Pairs like this tell you the shape of the route before you know its details.