In North America, it is called Indian, Provincial, Portland, or Texas gauge. In Argentina and Chile, it is known as "trocha ancha" (Spanish for "broad gauge"). In the Indian subcontinent it is simply known as "broad gauge". It is the widest gauge in regular passenger use anywhere in the world.
In India, the initial freight railway lines were built using standard gauge. In the 1850s, the Great Indian Peninsula Railway adopted the gauge of 1,676 mm (5 ft 6 in) for the first passenger railway in India between Bori Bunder and Thane.[1][2] This was then adopted as the standard for the nationwide network.
Indian Railways today predominantly operates on 1,676 mm (5 ft 6 in) broad gauge. Most of the metre gauge and narrow gauge railways have been converted to broad gauge. Small stretches of the network that remain on metre and narrow gauges are also being converted to broad gauge. Rapid transit lines are mostly on standard gauge, although some initial lines use 1,676 mm (5 ft 6 in) broad gauge.
Bangladesh Railways uses a mix of 1,676 mm (5 ft 6 in) broad gauge and metre gauge. The broad gauge network is primarily located to the west of the Jamuna River, while the metre gauge network is primarily located to its east. The Jamuna Bridge is a mixed-use bridge that contains a dual gauge connection across the river linking both networks.
The Iberian-gauge railways, that service much of Spain and Portugal, have a track gauge of 1,668 mm (5 ft 5+21⁄32 in), just 8 mm (5⁄16 in) different from 1,676 mm (5 ft 6 in). Used rolling stock from Iberia has been employed on broad-gauge lines in Argentina and Chile.
There is a longstanding rumour that the Provincial gauge was selected specifically to create a break-of-gauge with US railways, the War of 1812 still being a fresh memory. However, there is little supporting evidence for this, and this story appears to be traced to a single claim from the late 1800s.[3]
The Bay Area Rapid Transit system is the only operating railroad in the United States to use 1,676 mm (5 ft 6 in) broad gauge, with 120 miles (190 km) of double tracked routes. The original engineers chose the wide gauge for its "great stability and smoother riding qualities"[4] and intended to make a state-of-the-art system for other municipalities to emulate. The use of 1,676 mm (5 ft 6 in) broad gauge rails was one of many unconventional design elements included in its design which, in addition to its unusual gauge, also used flat-edge rail, rather than typical rail that angles slightly inward[5] (although the shape of BART wheels and rail has been modified since then[6]). This has complicated maintenance of the system, as it requires custom wheelsets, brake systems, and track maintenance vehicles.[5]
Frost heaves (swelling of wet soil upon freezing) produce an uneven running surface causing an irregular rocking motion as trains moved past. A wider wheelbase offered a steadier ride with less wear on the machinery and roadbed.
Wider cars offered more room for passengers and cargo. Train length would be reduced for cars carrying the same amount of cargo. Shorter trains would lessen the effects of side winds, and permit more efficient application of power.
Wide gauge locomotives offered more room to place reciprocating machinery inside, rather than outside the driving wheels. Reciprocating machinery was a source of vibration before mechanical engineering encompassed a good understanding of dynamics; and keeping such vibration close to the center of mass reduced the angular momentum causing rocking.
Wider fireboxes and boilers allowed more powerful locomotives. The alternative of longer boilers held the disadvantage of poor firebox draft through the increased frictional resistance of longer boiler tubes.
More powerful locomotives carrying fewer, larger cars would have reduced manpower requirement for engine crews and shop personnel.
For locomotives of equal power, fuel consumption increased as gauge decreased, especially in colder outside temperatures.
More powerful wide gauge locomotives would be more capable for plowing snow; and thereby provide more reliable winter service.
Several gauges were in widespread use, and none had yet come into clear dominance.
Freight transfer was preferable to exchange of cars between railways because unowned cars were abused on foreign railways.
The Grand Trunk Railway system feeding the seaport of Portland, Maine offered little need for gauge transfer prior to loading on export shipping.
Potential advantages of freight transfer to the standard gauge railroad from Portland to Boston seemed insignificant as long as competitive rates were available for transport on steamships between the two ports.
The majority of Canadian freight anticipated to be carried over rail lines to Portland was heavy and bulky in comparison to its value, and must be transported cheaply in large quantities to maintain profitability for producers and transporters.
Most links of 1,676 mm (5 ft 6 in) broad gauge railways are in the center-south of the country. Only a few lines of the Ferrocarril del Sur (Southern Railroad Network) were 1,000 mm (3 ft 3+3⁄8 in) metre gauge or 1,435 mm (4 ft 8+1⁄2 in) standard gauge, the notable exceptions being one of the few active links: the Ramal Talca-Constitución branch and the Metro de Santiago. On the contrary, just a few branches of the FCN (Ferrocarril del Norte) were broad gauge, most notably the Mapocho-Puerto mainline between Santiago and Valparaiso, the Santiago–Valparaíso railway line. This link was directly connected to the southern railroad network using the Matucana tunnel that connected Mapocho and the Central Station in Santiago. The Transandine Railway that connected both Argentinean and Chilean broad gauge networks through the Uspallata pass in the Andes mountains was actually a 1,000 mm (3 ft 3+3⁄8 in) narrow gauge link.
The Iberian gauge (1,668 mm or 5 ft 5+21⁄32 in) is closely similar to the Indian gauge, 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 wheelset replacement may be required (for example, Russian-Finnish train Allegro has 1,522 mm or 4 ft 11+29⁄32 in gauge, intermediate between Russian 1,520 mm or 4 ft 11+27⁄32 in and Finnish 1,524 mm or 5 ft). Backward compatibility—1,676 mm trains on 1,668 mm gauge—is possible, but no examples and data exist. Due to the narrower gauge, a strong wear of wheelsets may occur without replacement.
From Asunción to Encarnación was originally laid in this gauge in the hope that the connecting line from Posadas to Buenos Aires would be built to the same gauge; that line was laid to standard gauge, and when the FCPCAL reached Encarnación in 1912 the whole line had to be re-gauged to standard gauge to allow through-working.
