To bypass traffic, to get rid of elevated trains, and to speed up trafic.
To get there faster
Tokyo's Subway System is a full scale rapid transit. The Sydney CityRail is an extensive commuter rail.
It depends on what subway system you're talking about. Lots of major cities have subway systems.
All German cities offer a subway system, called U-Bahn. Regular light rail train systems known as S-Bahn also operate within cities as well as between cities.
The subway system in Moscow is called the "Metro". A railway station is called a "vokzal" or maybe a "stantsiya", a Subway Station is called a "Stantsii Metro". There are about 200 subway stations in Moscow and the network is growing.
It has everything but a subway. The city does not have a metro, but does have a commuter rail service which passes through the city centre in a tunnel. There is also a dense tram network (one of best in the world).
No, Honolulu does not have a traditional subway system. However, it is developing the Honolulu Rail Transit project, which will include an elevated rail system designed to improve public transportation and reduce traffic congestion. The rail line is expected to connect various parts of the city, ultimately extending to the western suburbs.
The MTA.
The LIRR is a railroad system that has trains that go on train tracks above ground and sometimes underground as it hits Manhatten and brooklyn. The NYC subway is totally different. The NYC subway has buses that run on streets underground and sometimes elevated. The NYC is essentially an urban bus system that has buses that go more underground.
The first attempts to have public transportation were by horse-drawn stagecoaches, as far back as 1793. Eventually, cities moved away from horse-drawn vehicles, and when electrification came along in 1889, Boston had street-cars and trolley cars, which traveled above-ground. In the 1890s, there were also elevated railways. But you may be referring to the subway (called the "underground" in countries like England). Boston had the first subway system, trains that ran beneath the city, in underground tunnels. The subway opened for business in July 1897, and while most of the stations have been updated and the tracks modernized, the subway system is still in use today.
What Caribbean countries have a subway system?
No but they have a bus system.