Iberian-gauge railways

Iberian gauge (Spanish: ancho ibérico, trocha ibérica, Portuguese: bitola ibérica) is a track gauge of 1,668 mm (5 ft 5+21⁄32 in), most extensively used by the railways of Spain and Portugal. A broad gauge, it is the second-widest gauge in regular use anywhere in the world, with only Indian gauge railways, 5 ft 6 in (1,676 mm), being wider (by 8 mm (5⁄16 in)).

As finally established in 1955, the Iberian gauge is a compromise between the similar, but slightly different, gauges adopted as respective national standards in Spain and Portugal in the mid-19th century. The main railway networks of Spain were initially constructed to a 1,672 mm (5 ft 5+13⁄16 in) gauge of six Castilian feet. Those of Portugal were instead built to a 1,435 mm (4 ft 8+1⁄2 in) and later railways to a 1,664 mm (5 ft 5+1⁄2 in) gauge of five Portuguese feet – close enough to allow interoperability with Spanish railways.