Double-track railway

A double-track railway usually involves running one track in each direction, compared to a single-track railway, where trains in both directions share the same track.

Overview

In the earliest days of railways in the United Kingdom, most lines were built as double-track because of the difficulty of co-ordinating operations before the invention of the telegraph. The lines also tended to be busy enough to be beyond the capacity of a single track. In the early days, the Board of Trade did not consider any single-track railway line to be complete.

In the United States, most lines were built as single-track for reasons of cost; very inefficient timetable working systems were used to prevent head-on collisions on single lines. This improved with the development of the telegraph and the train order system.

Operation

Handedness

In any given country, railway traffic generally runs to one side of a double-track line, not always the same side as road traffic. Thus in Belgium, China, France, Sweden, Switzerland, Italy and Portugal for example, the railways use left-hand running, while the roads use right-hand running.

However, there are many exceptions:

Metro systems often are RHT, even when the heavy rail network runs on the left.

In Finland, railway traffic uses mainly right, with the exception of the Ring Rail Line and the separate commuter rail tracks to Kerava and Leppävaara in Helsinki area which use the left.