5 ft and 1520 mm gauge railways
Railways with a railway track gauge of first appeared in the United Kingdom and the United States. This gauge became commonly known as Russian gauge because the government of the Russian Empire later chose it in 1843 — former areas of the Empire have inherited this standard. In the 1960s Soviet Railways re-defined the gauge as 1,520 mm (). The primary countries using the gauge include Russia, Mongolia, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, Uzbekistan, Armenia, Azerbaijan, Georgia, Belarus, Moldova, Ukraine, Estonia, Latvia, Lithuania, and Finland. With about of track, Russian gauge is the second-most  common gauge in the world, after . History. Great Britain, 1748. In 1748, the Wylam waggonway was built to a gauge for the shipment of coal from Wylam to Lemington down the River Tyne. In 1839, the Eastern Counties Railway was constructed; and in 1840, the Northern and Eastern Railway was built. In 1844, both lines were converted to . In 1903, the East Hill Cliff Railway, a funicular, was opened. United States, 1827. In 1827, Horatio Allen, the chief engineer of the South Carolina Canal and Rail Road Company, prescribed the usage of gauge and many other railroads in Southern United  States adopted this gauge. The presence of several distinct gauges was a major disadvantage to the Confederate States of America during the American Civil War. In 1886, when around of gauge track existed in the United States, almost all of the railroads using that gauge were converted to , the gauge then used by the Pennsylvania Railroad. Russian Empire, 1842. The first railway built in Russia was built in 1837 to gauge for a 17 km long "experimental" line connecting Saint Petersburg with Tsarskoye Selo and Pavlovsk; the choice of gauge was influenced by Brunel's Great Western Railway which used  . While of almost no practical importance the railway did demonstrate that this gauge was viable. The second railway in the Russian Empire was the Warsaw–Vienna railway (Congress Poland was then a part of the Empire) which was built to Standard gauge and commenced construction in 1840. For the building of Russia's first major railway, the Saint Petersburg–Moscow railway, engineer Pavel Melnikov hired as consultant George Washington Whistler, a prominent American railway engineer. Whistler recommended on the basis that it was cheaper to construct than while still offering the same advantages over and that there was no need  to worry about a break-of-gauge since it would never be connected to the Western European railways. Colonel P.P. Melnikov, of the Construction Commission overseeing the railway, recommended following the example of the first railway and his study of US Railways. Following a report sent by Whistler the head of the Main Administration of Transport and Buildings recommended and it was approved for the railway by Tsar Nicholas I on 14 February 1843. The next lines built were also approved with this gauge but it was not until March 1860 that a Government decree stated all major railways in  Russia would be gauge. Not selected for military purposes. It is widely and incorrectly believed that Imperial Russia chose a gauge broader than standard gauge for military reasons, namely to prevent potential invaders from using the rail system. In 1841 a Russian army engineer wrote a paper stating that such a danger did not exist since railways could be made dysfunctional by retreating or diverting forces. Also the construction of the Warsaw–Vienna railway in was precisely so it could be connected to the Western European network, in that case to reduce Poland's dependence on Prussia for transport. Finally  for the Saint Petersburg–Moscow railway, which became the benchmark, the choice of track gauge was between and the wider , not standard gauge . However, it was just not selected with that in mind. When a railway has wooden sleepers, it is fairly easy to make the gauge narrower by removing the nails and placing them back at a narrower position, something Germany did during WWII. Destroying river bridges had a larger effect. Expansion. The 5-foot gauge became the standard in the whole Russian Empire, and later Soviet Union. Russian engineers used it also on the Chinese Eastern Railway, built  in the closing years of the 19th century across the Northeastern China entry to provide a shortcut for the Trans-Siberian Railway to Vladivostok. The railway's southern branch, from Harbin via Changchun to Lüshun, used Russian gauge, but as a result of the Russo-Japanese War of 1904-1905 its southernmost section (from Changchun to Lüshun) was lost to the Japanese, who promptly regauged it to standard gauge (after using the narrow for a short time during the war). This formed a break of gauge between Changchun and Kuancheng (the station just to the north of Changchun, still in  Russian hands), until the rest of the former Chinese Eastern Railway was converted to standard gauge, too (probably in the 1930s). Unlike in South Manchuria, the Soviet Union's reconquest of southern Sakhalin from Japan did not result in regauging of the railway system. Southern Sakhalin has continued with the original Japanese gauge simultaneously with the Russian gauge railway, constructed in the northern part of the island in 1930-1932 (Moskalvo-Okha). The railway has no fixed connection with the mainland, and before 2019 rail cars coming from the mainland port of Vanino on the Vanino-Kholmsk train ferry (operating  since 1973) had to have their bogies changed in the Sakhalin port of Kholmsk. In 2004 and 2008 plans were put forward to convert it to the Russian gauge. The conversion was completed in 2019. There were proposals in 2013 for north-south and east-west lines in Afghanistan, with construction to commence in 2013. Panama, 1850. The Panama Canal Railway, first constructed in ca. 1850, was built in gauge. During canal construction (1904–1914), this same gauge was chosen for both construction traffic, canal operating services along the quays, and the newly routed commercial cross-isthmus railway. In 2000 the  gauge for the commercial parallel railway was changed to to use standard gauge equipment. The original gauge was chosen under the influence of the pre-conversion southern United States railway companies. Nowadays, the electric manoeuvering locomotives along the locks ("mules") still use the gauge that was laid during canal construction. Finland, 1862. The first rail line in Finland was opened on 31 January 1862. As Finland was then the Grand Duchy of Finland, that is, a part of Imperial Russia, railways were built to the then Russian track gauge of , although the railway systems were not connected until the bridge  over River Neva was built in 1913. Russian trains could not have run on Finnish tracks, because the Finnish loading gauge was narrower until the connection was made and the Finnish structure gauge widened. Currently, there are two passenger services between Finland and Russia: "Allegro", a Pendolino service on the Helsinki–St. Petersburg route, which crosses the border at Vainikkala, and "Tolstoi", an overnight daily service between Helsinki and Moscow. For cargo traffic, there are four border crossings in active use. Technical. Redefinitions. In the late 1960s the gauge was redefined to in the Soviet Union. At the same time  the tolerances were tightened. As the running gear (wheelsets) of the rolling stock remained unaltered, the result was an increased speed and stability. The conversion took place between 1970 and the beginning of the 1990s. In Finland, the Finnish State Railways kept the original definition of , even though they also have tightened the tolerances in a similar way. (Tolerance tighter than in the Soviet Union) After its independence from the Soviet Union in 1991, Estonia redefined its track gauge to , to match Finland's gauge. The redefinition did not mean that all the railways in Estonia were changed immediately. It  was more a rule change, so that all renovated old tracks and new railways would be construed in 1,524 mm gauge from then on. (See Track gauge in Estonia.) Tolerances. Finland allows its gauge to be 1,520–1,529 mm on first class lines (classes 1AA and 1A, speed 220–160 km/h). If the gauge of the rolling stock is kept within certain limits, through running between railways and Finnish railways is allowed. Since both 1,520 and 1,524 mm are within tolerances, the difference is tolerable. However, certain Finnish rolling stock do have a tendency to get stuck in Russian railyards due  to the gauge difference. The gauge of the international high-speed train Allegro (Sm6) between Helsinki and St. Petersburg is specified as 1,522 mm. High-speed trains have less tolerance against gauge error, but this way, through running works well. Loading gauge. The loading gauge, which defines the maximum height and width for railway vehicles and their loads, is larger for Russian gauge. This means that if a standard gauge railway, in Europe, shall be adapted for dual gauge, bridges must be rebuilt, double tracks must be placed further apart and the overhead wire must be raised. Or there must  be restrictions on permitted rolling stock, which would restrict the benefit of such a railway. Dual gauge needs more width than single gauge. For double stacking on Russian gauge tracks, maximum height shall be above rails. For standard gauge railways, double stacking maximum height shall be . For Indian gauge railways, double stacking maximum height shall be , and minimum overhead wiring height shall be above rails. Minimum overhead wiring height for double stacking, standard gauge railways shall be , and Indian gauge railways shall be above rails, respectively. This would apply to Russia and Europe (or North America), rather than to Russia  and China (or Iran). Current status. Network. Short sections of Russian gauge extend into Poland, eastern Slovakia, Sweden (at the Finnish border at Haparanda), and northern Afghanistan. There is an approximately 150 km long section in Hungary in the Záhony logistics area close to the Ukrainian border. During 2014 renovation a 32 km section of dual Standard/Russian gauge was installed between Tumangang and Rajin stations in the North Korea. The most western gauge railway is the Polish LHS ("Linia Hutnicza Szerokotorowa") from the Ukrainian border to the eastern end of the Silesian conurbation. Use in rapid transit and light  rail systems. Although broad gauge is quite rare on lighter railways and street tramways worldwide, almost all tramways in ex-USSR are broad gauge (according to terminology in use in these countries, gauges narrower than are considered to be narrow). Many tramway networks initially built to narrow gauges ( or ) were converted to broad gauge. As of 2015, only a few out of more than sixty tram systems in Russia are not broad gauge: in Kaliningrad and Pyatigorsk, in Rostov-on-Don; there are also two tram systems in and around Yevpatoria that use gauge. Finland's Helsinki trams and Latvia 's Liepāja trams also use , and Estonia's Tallinn trams use similar . Warsaw's tramway system, constructed with 1525 mm gauge, was regauged to 1435 mm during post-WWII reconstruction. Underground urban rapid transit systems in former USSR and Finland, like the Moscow Metro, Saint Petersburg Metro, Kyiv Metro and the Helsinki Metro use Russian gauge () or gauge. Similar gauges. These gauges cannot make 3-rail dual gauge with Russian gauge. These gauges are within tolerance. Dual gauge between Russian gauge and another similar gauge can make these bonus gauges.