The name derives from a signal station for the Isle of Man TT races and Manx Grand Prix.

The signal station at Signpost Corner was connected to the race scoreboards located in Glencrutchery Road in Douglas by a telephone land-line.

Race officials would instruct local Scouts on the scoreboards to switch a light on above an individual competitor's scoreboard which would indicate to the pit crew and race officials that a particular rider had passed through Signpost Corner and might shortly be pulling into the race-pits located at the Grandstand on Glencrutchery Road to refuel.

George MacDonald Fraser, author of the Flashman series of books, lived on the Isle of Man and titled his 2002 autobiographical memoir of his experiences as a Hollywood scriptwriter as "The Light's On at Signpost".

[3] The section of the Mountain Course from the Cronk-ny-Mona road junction to Governor's Bridge was first adopted for the 1920 Isle of Man TT motor-cycle races and the Manx Grand Prix in 1923.