Iberian-gauge railways

Track gauge
By transport mode
Rapid transit Tram Miniature Scale model
By size (list)
Minimum   Fifteen inch 381 mm (15 in)   Narrow   600 mm 600 mm (1 ft 11+5⁄8 in) Two foot 610 mm (2 ft) Two foot three inch 686 mm (2 ft 3 in)   750 mm 750 mm (2 ft 5+1⁄2 in) Bosnian gauge 760 mm (2 ft 5+15⁄16 in) Two foot six inch 762 mm (2 ft 6 in)   Swedish three foot 891 mm (2 ft 11+3⁄32 in) 900 mm 900 mm (2 ft 11+7⁄16 in) Three foot 914 mm (3 ft) Italian metre 950 mm (3 ft1+13⁄32 in)   Metre 1,000 mm (3 ft 3+3⁄8 in)   Three foot six inch 1,067 mm (3 ft 6 in)   Four foot 1,219 mm (4 ft)   Four foot six inch 1,372 mm (4 ft 6 in)   1432 mm 1,432 mm (4 ft 8+3⁄8 in)   Standard 1,435 mm (4 ft 8+1⁄2 in)   Broad   Italian broad gauge 1,445 mm (4 ft 8+7⁄8 in) Dresden gauge 1,450 mm (4 ft 9+3⁄32 in)   Leipzig gauge 1,458 mm (4 ft 9+13⁄32 in)   Toronto gauge 1,495 mm (4 ft 10+7⁄8 in)   1520 mm 1,520 mm (4 ft 11+27⁄32 in) Five foot 1,524 mm (5 ft)   Pennsylvania gauge 1,581 mm (5 ft 2+1⁄4 in) Pennsylvania gauge 1,588 mm (5 ft 2+1⁄2 in) Five foot three inch 1,600 mm (5 ft 3 in)   Baltimore gauge 1,638 mm (5 ft 4+1⁄2 in)   Iberian gauge 1,668 mm (5 ft 5+21⁄32 in) Five foot six inch 1,676 mm (5 ft 6 in)   Six foot 1,829 mm (6 ft)   Brunel 2,140 mm (7 ft 1⁄4 in)   Breitspurbahn 3,000 mm (9 ft 101⁄8 in)
Change of gauge
Bogie exchange Break of gauge Dual gauge Conversion list Variable gauge
By location
North America South America Europe Australia

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,^[1] 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.^[2]

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.^[3][4]

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 to dual gauge) or the narrowing of the gauge by moving both rails closer together maintaining the perfect alignment of the loading gauge.^[5][6]

The Indian gauge (1,676 mm or 5 ft 6 in) is closely similar, with only 8 mm (5⁄16 in) difference, and allows compatibility with the rolling stock. For example, in recent years Chile and Argentina have bought second hand Spanish/Portuguese Iberian-gauge rolling stock. 1,668 mm trains can run on 1,676 mm gauge without adaptation, but for better stability in high-speed running a replacement wheelset may be required (for example, the Russian-Finnish train Allegro is built for a 1,522 mm track gauge, intermediate between the Russian 1,520 mm and the Finnish 1,524 mm). Backward compatibility—1,676 mm trains on 1,668 mm gauge—is possible, but no examples and data exist. Due to the somewhat narrower gauge, a strong wear of the wheels may occur if the wheelset is not replaced.