sentences:  While the Birney was one of the first public transport vehicles designed for one-man operation, it was not the first public transport vehicle to be equipped with a dead man's switch.In 1903, the Metropolitan District Railway equipped two of their A Stock trains with a dead man's switch.The dead man's switch was introduced so that one man could operate in the driving cab on his own, which became standard for all train companies operating the London Underground in 1908.