The invention of the fail-safe railway air brake provided an external means for stopping a train via a physical object opening a valve on the brake line to the atmosphere. Eventually known as "train stops" or "trip stops", the first mechanical ATS system was installed in France in 1878 with some railroads in Russia following suit using a similar system in 1880. In 1901 Union Switch and Signal Company developed the first North American automatic train stop system for the Boston Elevated Railway. This system was soon adopted by the New York City Subway and other rapid transit systems in the United States.