Junction (rail)

The physical connection between the tracks of the two routes (assuming they are of the same gauge) is provided by turnouts (US: switches) and signalling.

[1] In a simple case where two routes with one or two tracks each meet at a junction, a fairly simple layout of tracks suffices to allow trains to transfer from one route to the other.

More complicated junctions are needed to permit trains to travel in either direction after joining the new route – for example by providing a triangular track layout.

[2] With more complicated junctions such construction can rapidly become very expensive, especially if space is restricted by tunnels, bridges or inner-city tracks.

The installation of junctions into a rail system poses many challenges, including increased maintenance costs, and problems in on-time performance.

Chicago Transit Authority signal tower 18 guides elevated Chicago 'L' north and southbound Purple and Brown lines intersecting with east and westbound Pink and Green lines and the looping Orange line above the Wells and Lake street intersection in the loop .