Level junction

A level junction (or in the United Kingdom a flat crossing) is a railway junction that has a track configuration in which merging or crossing railroad lines provide track connections with each other that require trains to cross over in front of opposing traffic at grade (i.e. on the level).

The cross-over structure is sometimes called a diamond junction or diamond crossing in reference to the diamond-shaped center. The two tracks need not necessarily be of the same gauge. A diamond crossing is also used as a component of a double junction, like the one illustrated on the right.

The opposite of a level junction is a flying junction, where individual tracks rise or fall to pass over or under other tracks.

Risks

Conflicting routes must be controlled by interlocked signals to prevent collisions.

Level junctions, particularly those of fine angles or near right angles, create derailment risks and impose speed restrictions. The former can occur as the flanges of the wheels are momentarily unsupported and unguided and can slip through the gaps in the rails, and the latter because the assembly contains elements that can break or vibrate loose.