Iberian gauge is a track gauge measuring 1,668 mm (5 ft 5 21/32 inches).
Predominantly used by the railways of Spain and Portugal, it is the second-widest gauge in regular use globally, just 8 mm narrower than the Indian gauge.
Established in 1955, the Iberian gauge was a compromise between the slightly different gauges adopted in Spain and Portugal during the mid-19th century.
Spain’s railways were initially built to a gauge of 1,672 mm (5 ft 5 13/16 inches). Portugal’s railways were constructed to a gauge of 1,664 mm (5 ft 5 1/2 inches).
This close similarity allowed for interoperability between the two countries’ railway systems.
