5 ft 6 in/1,676 mm is the size of a broad track gauge commonly used in India, Pakistan, west of Bangladesh, Sri Lanka, Argentina, Chile, and on the BART (Bay Area Rapid Transit) in the San Francisco Bay Area. In the Indian Subcontinent it is simply known as "Broad gauge", while in North America, it is called Provincial, Portland, or Texas gauge. Elsewhere it is known as "Indian gauge". It is the widest gauge in regular passenger use anywhere in the world.
In British India, some standard gauge freight railways were built in initial period, though they were dismantled later. Later, in 1850s, the gauge of 1,676 mm (5 ft 6 in) was adopted as standard for the nation-wide network.
Rail transport in India today is predominantly on 1,676 mm (5 ft 6 in) broad gauge. Small stretches of the network use metre and narrow gauges. Urban rail is 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.
In Nepal all services currently operate on 1,676 mm (5 ft 6 in) broad gauge only.
In Pakistan, all services currently operate on 1,676 mm (5 ft 6 in) broad gauge only.
In Sri Lanka, all services currently operate on 1,676 mm (5 ft 6 in) broad gauge only.
The 1,676 mm (5 ft 6 in) broad gauge was actually first used in Scotland for two short, isolated lines, the Dundee and Arbroath Railway (1836-1847) and the Arbroath and Forfar Railway (1838- ). Both the lines were subsequently converted to standard gauge.
Canada became the first British colony, in the 1850s, to use 1,676 mm (5 ft 6 in) broad gauge. It was known as the "Provincial gauge" in Canada.
The Grand Trunk Railway which operated in several Canadian provinces (Quebec and Ontario) and American states (Connecticut, Maine, Massachusetts, New Hampshire, and Vermont) used it, but was changed to standard gauge in 1873. The Grand Trunk Railway which operated from headquarters in Montreal, Quebec, although corporate headquarters were in London, England. The St. Lawrence and Atlantic Railroad which operated in Quebec, Vermont, New Hampshire and Maine also used it but was converted in 1873.
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.
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 109 miles (175 km) of double tracked routes. The original engineers for the system had background in aerospace (rather than railroads) 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 uses flat-edge rail, rather than typical rail that angles slightly inward. This has complicated maintenance of the system, as it requires custom wheelsets, brake systems, and track maintenance vehicles.
The New Orleans, Opelousas and Great Western Railroad (NOO&GW) used 1,676 mm (5 ft 6 in) broad gauge until 1872, and the Texas and New Orleans Railroad used 1,676 mm (5 ft 6 in) broad gauge, ("Texas gauge") until 1876. The Grand Trunk Railway predecessor St. Lawrence and Atlantic Railroad which operated in Quebec, Vermont, New Hampshire and Maine also used 1,676 mm (5 ft 6 in) broad gauge ("Canadian gauge" or "Portland gauge") but was converted in 1873. Several Maine railroads connected to the Grand Trunk Railway shared its "Portland Gauge". The Androscoggin and Kennebec Railroad and the Buckfield Branch Railroad were later consolidated as the Maine Central Railroad which converted to standard gauge in 1871. The only electric streetcar system in the U.S. to use this gauge was that of Fairfield, Maine.
The national railway network is predominantly on 1,676 mm (5 ft 6 in) broad gauge.
Most installations of 1,676 mm (5 ft 6 in) broad gauge railways are in the south of the country.
The Iberian gauge (1,668 mm or 5 ft 5 21⁄32 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. 1668mm trains can run on 1676mm gauge without adaptation, but for better stability in high-speed running a little wheelset adjustment may be required (for example - Russian-Finnish train Allegro has gauge 1522 mm, intermediate between Russian 1520 mm and Finnish 1524 mm). Backward compatibility - 1676 mm trains on 1668 mm gauge is possible, but no examples and data exist. Due to the narrower gauge, a strong wear of wheelsets may occur without adjustment.
|Argentina||San Martín Railway||operating|
|Argentina||Mitre Railway||except Tren de la Costa in standard gauge; operating|
|Argentina||Roca Railway||except La Trochita, Central Chubut Railway and Ramal Ferro Industrial de Río Turbio in 750 mm (2 ft 5 1⁄2 in) gauge; operating|
|Bangladesh||Bangladesh Railway||682 km (424 mi)||operating|
|Canada||Grand Trunk Railway||converted to standard gauge in 1873|
|Canada||St. Lawrence and Atlantic Railroad||converted to standard gauge in 1873|
|Canada||Champlain and St. Lawrence Railroad||converted to standard gauge in 1873; specific names, Provincial gauge|
|Canada||Grand Trunk Railway of Canada||converted to standard gauge|
|Canada||Intercolonial Railway of Canada||converted to standard gauge in 1875|
|Chile||*Empresa de los Ferrocarriles del Estado||operating|
|India||Indian Railways||114,912 km (71,403 mi)||operating|
|India||Delhi Metro||65 km (40 mi)||Phase-1 lines only; operating|
|India||Kolkata Metro||27.22 km (16.91 mi)||Line 1 only; operating|
|Nepal||Nepal Railways||59 km (37 mi)||operating|
|Pakistan||Pakistan Railways||7,791 km (4,841 mi)||operating|
|Paraguay||Paraguayan railway||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.|
|Sri Lanka||Sri Lanka Railways||1,508 km (937 mi)||operating|
|United Kingdom||Arbroath and Forfar Railway||see Scotch gauge, converted to standard gauge|
|United Kingdom||Dundee and Arbroath Railway||16 3⁄4 mi (27.0 km)||see Scotch gauge, converted to standard gauge|
|United States||Bay Area Rapid Transit (BART) San Francisco Bay Area||109 mi (175 km)||operating|
|United States||Maine Central Railroad||converted to standard gauge in 1871|