There are currently 190 city metro systems located in 54 countries around the world.
The world's first metro, now the world's oldest system, is the London Underground in England, also known as the Tube, which was opened in 1863. Although known locally as the undergound, it runs both under and above ground.
At 402 kilometers in length the London Underground is also the world's second longest metro system.
Visit our page - Lines And Stations Of The London Underground - to read more about this system.
The world's longest metro system is the Shanghai Metro in China at 434 kilometers long.The system also incorporates the world's only ' tourist tunnel', The Bund Sightseeing Tunnel, which travels under the city's Huangpu River between East Nanjing Road and Pudong stations.The 647 metre long tunnel is encased in a glass capsule which houses a system of strobe lighting which throws vivid, psychedelic patterns upon the tunnel walls.
Visit our page - Lines and Stations of the Shanghai Metro - to read more about this system.
The metro system with the most number of stations in the world is the New York City Subway in U.S.A, with 422 stations.
Visit our page - Lines and Stations of the New York City Subway - to read more about this system.
The country with the highest number of metro systems in the world is the USA, with subways - as they are called in the U.S - situated in at least 32 cities.
The smallest city in the world to have a rapid transit metro is Lausanne in Switzerland. Lausanne is just 41.37 sq kms in size and it's 15 kilometre long Metro Lausanne consists of 2 lines and 28 stations.
The world's smallest metro system is the 3.8 km long Metropolitana di Catania,situated on the Italian island of Sicily, which consists of just one line and six stations.
The world's first metro system to be built solely for the use of religious pilgrims, is the 18.1 km long Al Mashaaer Al Muqaddassah Metro, which opened in November 2010 in Saudi Arabia's holy city of Mecca.
The world's busiest metro system, in terms of passenger number, is the Tokyo / Toei Subway, with 8 million passengers a day, or 3.16 billion a year.
The metro system with the highest number of lines or routes, is the New York City Subway in the U.S.A, with 24 lines.
Only four rapid transit, metro systems in the world run a complete, twenty four hour, round the clock service, and they are all located in the same country.
They are the New York City Subway, the Blue and Red Lines of the Chicago L system, Philidelphia's PATCO System and the New York City to New Jersey PATH - Port Authority Trans Hudson - system.
Some cities offer bus services during the hours that their metros are closed, particularly ones that cover airports or major rail stations on their routes.
Certain cities will offer 24 / 7 services during special occasions, but as a general rule, it is unusual to find a 24 hour, metro system due to the fact that the lines need to be cleared for maintenance, and the best time to do this is overnight, when passenger numbers are low.
The world's deepest metro system is the Pyongyang Metro in North Korea, which is 110 meters deep, built as part of an underground, military facility.
The world's deepest metro, underground station is the Arsenalna Station on the Kiev Metro in Ukraine, at 107 meters deep.
The world's largest metro station is Union Square Station on the Dubai Metro in the United Arab Emirates, which covers an area of 67,056 sq meters.
Only one metro system in the world has been designated an UNESCO World Heritage Site, that is the Budapest Metro in Hungary, which was designated in 2002. The system was opened in 1896, making it the second oldest system in the world.
Thirty three of the world's 180 metro systems offer either a complete network or partial system, of automated - driverless - metros, the longest of which is the Dubai Metro in the United Arab Emirates at 74.6 kms.
The first metro system to implement the use of automated trains was the Lille Metro in France, when it introduced driverless trains on it's new system in 1983.
The metro system with the longest, single escalator in the world is situated at the Park Pobedy Station on the Moscow Metro in Russia, which is 126.8 metres long and takes 2 minutes 40 seconds to ride.
However, the longest escalator on any metro system, which is infact made up of two escalators one above the other, is situated at the Wheaton Street Station on the Washington D.C Subway in the U.S.A, The two escalators are both 70 meters long, have a vertical rise of 35 metres and take 3 minutes to ride.
The world's fastest metro system train is the Maglev or Transrapid, which runs by way of magnetic levitation on the Longyang Road to Pudong International Airport line of the Shanghai Metro.
The train has been known to reach speeds of up to 501 km/h (311 mph) on test drives but normally operates at speeds of around 431 km/h (268 mph).
The world's most northerly, located metro system is Finland's Helsinki Metro.
The world's most southerly, located metro system is Argentina's Buenos Aries Metro.
Image 1 - Nizami Station on the Baku Metro, Azerbaijan - Courtesy Baku87, wikimedia commons.
Image 2 - The Bund Sightseeing Tunnel, on the Shanghai Metro, China.
Image 3 - Escalator at Wheaton Station on the Washington D.C Metro, U.S.A - Courtesy of Theadana, wikimedia commons.
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