Third rail

A third rail is a metal railway track that is placed on either side of a train track to provide electrical power to trains traveling along the tracks.^[1] They are often used on subways and local train services.^[2] Before third rails, electricity was carried in overhead wires.^[2]

1. ↑ American Institute of Electrical Engineers (1921). Transactions of the American Institute of Electrical Engineers. American Institute of Electrical Engineers. p. 1625.
2. ↑ ^{2.0 2.1} Marshall Cavendish Corporation (2008). Inventors and Inventions. Marshall Cavendish. p. 1474. ISBN 978-0761477617.