Automatic Train Operation controls trains so that, between stations, they will move at the speed specified by the automatic train protection and automatic train supervision sub-systems. All Metro trains are manned by train operators who work the doors, make station announcements, and supervise the train. The train operator also can control whether the train operates in automatic mode or manual mode. From November 17, 1995 until January 6, 1996, Metro management required its employees to use the automatic mode at all times. During the Blizzard of 1996, however, there was a collision on January 6 that occurred when the ATS system failed to pick up proper instructions from the wayside communication system during a snowstorm, and defaulted to the highest speed. This speed would have been safe during dry weather, but because of ice or snow, trains required additional stopping distance, which was not provided for by the ATC system. From the June 2009 collision until 2015, Metrorail operators operated the trains exclusively in manual mode; the ATC system was restored to the Red Line in 2015. The automatic train protection system still limits the maximum speed of every train that is in revenue service.