dead man's handle

plural dead man's handles

1. rail transportA lever used as a safety device, typically on trains, which shuts off power if the operator releases their grip.

   Dead-man's handle, automatic train stop, quick-acting compressed-air brake specially suited for high-speed working, and regenerative braking are among the features of the new locomotives.

   1947 March and April, “Swiss High-Speed Electric Locomotives”, in Railway Magazine, page 94

   1 more example

   There were two engine men in case one of them fainted or died, the 'dead man's handle' of the later Tubes (a fail-safe device that stops the train if the driver does not maintain manual pressure on a lever) not having been perfected.

   2012, Andrew Martin, Underground Overground: A passenger's history of the Tube, Profile Books, →ISBN, pages 103–104