Labor costs were the transit operators’ biggest single cost. Up until the advent of the Birney Safety car in 1915, nearly every mass transit vehicle regardless of traction type had a crew of two men; a motorman and a conductor. The motorman operated the car, the conductor was responsible for passenger safety, collecting fares and all other aspects of customer service. Eliminating one man cut labor costs in half on the cars. The Birney Safety car introduced automatic interlocks that prevent the car’s brakes from releasing until switches confirmed that the car doors were fully closed. The single truck Birney car was less comfortable than larger double truck cars and the more harried motorman, now doing the work of the conductor also, tended to
