Why some railways run on the left while roads stay on the right
In short: From the UK's early industrial lines to modern European metros, the direction of rail traffic is rarely a coincidence. It is a complex legacy of telegraph technology, cost-cutting measures, and even the physical design of station buildings and locomotive cabs.
The fundamental difference between single-track and double-track railways lies in capacity and coordination. In the early days of the United Kingdom's railways, most lines were built as double-track to manage heavy traffic and bypass the coordination difficulties that existed before the telegraph. Conversely, in the United States, many lines were built as single-track to save costs, relying on inefficient timetable systems and the later development of the train order system to prevent head-on collisions.
The 'handedness' of rail traffic—whether trains run on the left or right—often diverges from road traffic. In countries like Belgium, France, and Switzerland, railways use left-hand running while roads use the right. In Portugal, the national heavy rail and Lisbon Metro use left-hand running, though light rail systems use the right to accommodate shared road tracks. Even within a single country, exceptions exist; in Sweden, the metro and railways generally use the left, but Malmö uses the right due to its connection to Denmark.
Infrastructure design is also heavily influenced by these tracks. The distance between track centres, often as little as 4 metres for standard gauge, impacts cost and safety. Narrower centres can lead to fatal accidents, such as the 1917 Bere Ferrers tragedy or the opening day accident of the Liverpool and Manchester Railway. Conversely, wider spacing—6 metres or more—simplifies the mounting of signals and overhead wiring. In extreme cases, such as in desert regions, tracks may even be separated entirely to ensure that sand dunes do not render both lines unusable at once.
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Sources
- Summary by Intellect · source: Double-track railway
- Also: Sensors (Basel, Switzerland) — Ventilation Design of an Extra-Long Single-Bore Double-Track Railway Tunnel with High Traffic Density. · CC BY
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