Maglev (Earth-5875)

Maglev (magnetically levitated) is a human system of train transportation that uses two sets of magnets, one set to repel and push the train up off the track as in levitation (hence Maglev, Magnetic-levitation), then another set to move the 'floating train' ahead at great speed taking advantage of the lack of friction. Within certain "medium range" locations (usually between 200-400 miles) Maglev can compete favorably with high speed rail and airplanes.

With Maglev technology, there are no moving parts. The train travels along a guideway of magnets which control the train's stability and speed. Maglev trains are therefore quieter and smoother than conventional trains, and have the potential for much higher speeds. They are located in big cities and are the main source of public transportation.

History
A maglev exited in New Mombasa, on Earth, falling under the New Mombasa Transit Authority. It provided major public transportation through the city, and thus became one of the first targets of the Covenant during the Battle of Earth in late 2552.

The Chicago Greater Industrial Zone was home to a maglev system, which used elevated tracks upon the older Chicago train models. Both Inner Colonies Reach and Tribute were home to maglev rail systems: in Tribute's case, one system was connected by sea from its capital, Casbah, through the entire planet, forming the most important part of the planet's economy. Operation TREBUCHET saw UNSC Marines placing bombs around maglev stations so that Insurrectionists would not sabotage the whole system.

Source

 * Maglev on Wikipedia.