Train shunting puzzle


Train shunting puzzles, also often called railway shunting puzzles or railroad switching puzzles, are a type of puzzle.
Shunting puzzles usually consist of a specific track layout, a set of initial conditions, a defined goal, and rules which must be obeyed while performing the shunting operations.
There are often constraints such as making the minimum number of couplings and uncouplings, or making the minimum number of junction direction changes, or completing the puzzle within a specified time limit.
Other important factors may include the lengths of tracks limiting the number of rolling stock vehicles which can be placed along them. Some shunting puzzles allow certain types of rolling stock to navigate a particular section of track but not other types of rolling stock, for example a locomotive might not be allowed to pass below a low bridge whereas wagons are allowed, or a particularly heavy wagon might not be allowed across a weak bridge, or a particularly tall wagon might not be allowed to pass through a tunnel.
Some train shunting puzzles have been developed as add-ons for railway simulator computer programs such as Auran's Trainz and Microsoft Train Simulator.

Categories

Shunting puzzles tend to fall into the following categories, but this list is not intended to be exhaustive:
Two of the best known model railway train shunting puzzles are: