Iberian Gauge

Iberian gauge (Spanish: ancho ibérico, trocha ibérica, Portuguese: bitola ibérica) is the name given to the track gauge (distance between the two rails of a track) most extensively used by the railways of Spain and Portugal: namely 1,668 mm (5 ft 5 2⁄₃ 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 5⁄₆ in) gauge of six Castilian feet, or two Castilian yards. 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.