The Bennie Railplane was a form of rail transport invented by George Bennie (1891–1957), which moved along an overhead rail by way of propellers. Despite superficial appearances, it was not a monorail, as it used both an overhead running rail and a guide rail below. It was intended to run above conventional railways, separating faster passenger traffic from slower freight traffic. A prototype ran over a 130-yard (120 m) line at Milngavie near Glasgow in the 1930s, but Bennie was never able to secure funding for further development and went bankrupt in 1937. The line was demolished for scrap in the 1950s.
(Wikipedia)
This is a great idea...shame it did take off :)