Colorful World Metro While London boasts the world's oldest underground train network and Boston built the first subway in the United States in 1897, the New York City Subway soon became the largest American system. Currently America has the most subway lines in the world. The world's longest running line is in New York. The New York's subway is the only rapid transit system in the world that runs 24 hours a day and seven days a week. Moscow Metro system is not only the most successful means of transportation, but a popular place of interest. It is the collection of engineering and artistic concepts and to a large degree the embodiment of (Soviet) Russian state culture. Moscow Metro is the world's third most heavily-used rapid transit system listing after Tokyo subway and Seoul Subway. Singapore Metro is one of the world's cleanest and safest metro. The train and the station are very clean and bright. In order to prevent fire, subway management system keeps passengers away from any facilities which are made of wood, natural fiber or other flammable materials. At the same time, there is a set of automatic monitoring system for avoiding disaster. There are various colorful subways in the world, and the subway culture has a long history. So far, many cities have built subways. People's life is inseparable from it.