And frequent business travelers will eventually be able to use a 'train mile' program across the entire network.

CNN: The high-speed rail revolution

The 220-mile train trip from New York to Boston, for instance, emits the same amount of CO2 as is stored in 2.5 cubic feet of mangrove forests.

BBC: How big is your carbon footprint?

Much of the work is expected to be carried out at night, with a so-called factory train laying a mile of new track and cables every night once construction is underway.

BBC: Electrification of Swansea to London trains 'by 2018'