dead man’s switch
A safety switch was disconnected in a runaway locomotive which crushed three people to death in Milton on March 14, an inquest was told yesterday. The switch, called a dead man’s switch, first gives a warning whistle and then stops a moving train engine if the operator does not have his foot on the switch pedal.
» —“Safety switch not on when train killed 3, Milton inquest told” by Zuhair Kashmeri Globe and Mail (Toronto, Canada) June 29, 1978. (source: Double-Tongued Dictionary)