Prototype maglev trains have been tested in Japan, Germany and China. The first commercial line, built by German company Transrapid, opened between Shanghai, China, and the city's Pudong Airport in 2003, and has clocked a record speed of 500 kilometres per hour. In the United States, projects are planned for Pittsburgh and Baltimore.

But the future of such trains may depend in part on their environmental impact. Previous studies have shown that maglev and intercity trains can be equally loud. But noise-pollution depends on the quality of the noise as well as its volume.

At high speeds, says Vos, "the maglev sound is similar to that of some aircraft".