求翻译：墨尔本的市内公共交通也非常发达，有火车、有轨电车和公共汽车。墨尔本主要公共交通工具是火车，多数行驶是在地面以上，只有在市中心时才是在地下行驶。是什么意思？

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melbourne City Public transport is also very well developed, there is a train, tram and bus. melbourne public transport is mainly driven by train, and the majority is more than on the ground, it is only in the heart of the city only when it is traveling in the ground.

Melbourne's local mass transit extremely is also developed, has the train, the tramcar and the bus.The Melbourne main mass transit tool is a train, the most travel are above the ground, only then when town center is in underground goes.

Public transport in the city of Melbourne are also very developed, trains, trams and buses. Major modes of public transport in Melbourne by train, most are above the Earth, and only when travelling on the underground in the city centre.