Iberian gauge
Iberian gauge (Spanish: ancho ibérico, trocha ibérica, Portuguese: bitola ibérica) is the name given to the track gauge most extensively used by the railways of Spain and Portugal: 1,668 mm (5 ft 5 21⁄32 in). This is the second-widest gauge in regular use anywhere in the world.
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.
Since the beginning of the 1990s new high-speed passenger lines in Spain have been built to the international standard gauge of 1,435 mm (4 ft 8 1⁄2 in), to allow these lines to link to the European high-speed network. Although the 22 km from Tardienta to Huesca (part of a branch from the Madrid to Barcelona high-speed line) has been reconstructed as mixed Iberic and standard gauge, in general the interface between the two gauges in Spain is dealt with by means of gauge-changing installations, which can adjust the gauge of appropriately designed wheelsets on the move.
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