Iberian-gauge railway
Iberian gauge is a track gauge of, 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,, being wider.
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 gauge of six Castilian feet. Those of Portugal were instead built to a and later railways to a gauge of five Portuguese feet – close enough to allow interoperability with Spanish railways.
Standard gauge
Since the beginning of the 1990s new high-speed passenger lines in Spain have been built to the international standard gauge of, to allow these lines to link to the European high-speed network. Although the 22 km from Tardienta to Huesca 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.Plans exist to convert more of the Iberian-gauge network in Spain and Portugal to standard gauge, an indication of which is the use, on several stretches of recently relaid broad-gauge track, of concrete sleepers pre-drilled with additional bolt holes allowing for repositioning of one rail to adjust the track to standard gauge or the narrowing of the gauge by moving both rails closer together maintaining the perfect alignment of the loading gauge.