Maglev (derived from magnetic levitation) is a transport method that uses magnetic levitation to move vehicles without touching the ground. With maglev, a vehicle travels along a guideway using magnets to create both lift and propulsion, thereby reducing friction by a great extent and allowing very high speeds.The Shanghai Maglev Train, also known as the Transrapid, is the fastest commercial train currently in operation and has a top speed of 430 km/h (270 mph). The line was designed to connect Shanghai Pudong International Airport and the outskirts of central Pudong, Shanghai. It covers a distance of 30.5 kilometres in 8 minutes.Maglev trains move more smoothly and more quietly than wheeled mass transit systems. They are relatively unaffected by weather. The power needed for levitation is typically not a large percentage of its overall energy consumption; most goes to overcome drag, as with other high-speed transport. Maglev trains hold the speed record for rail transport. Vacuum tube train systems might allow maglev trains to attain still higher speeds, though no such vacuum tubes have been built commercially yet.Compared to conventional (normal) trains, differences in construction affect the economics of maglev trains, making them much more efficient. For high-speed trains with wheels, wear and tear from friction along with the ""hammer effect"" from wheels on rails accelerates equipment wear and prevents high speeds. Conversely, maglev systems have been much more expensive to construct, offsetting lower maintenance costs.Despite decades of research and development, only two commercial maglev transport systems are in operation, with two others under construction. In April 2004, Shanghai's Transrapid system began commercial operations. In March 2005, Japan began operation of its relatively low-speed HSST ""Linimo"" line in time for the 2005 World Expo. In its first three months, the Linimo line carried over 10 million passengers. South Korea and the People's Republic of China are both building low-speed maglev routes of their own designs, one in Beijing and the other at Seoul's Incheon Airport. Many maglev projects are controversial, and the technological potential, adoption prospects and economics of maglev systems are often debated. The Shanghai system was labeled a white elephant by rivals.