of the line received centralized traffic control in four phases: from Trondheim to Stjørdal on 11 January 1976, to Levanger on 9 January 1977, to Steinkjer on 6 December 1977 and to Snåsa on 23 November 1984. Di 4-locomotives were introduced in 1981. At first they could only be used to Mo i Rana. After upgrades to the line further north, they could be used to Bodø from 1986. NSB introduced Class 92 diesel multiple units in 1985, cutting travel time on local services between Steinkjer and Trondheim by 25 minutes. A morning service from Mo i Rana to Trondheim with a return in the afternoon was introduced from 1986. A similar morning train from Mosjøen to Bodø with return in the afternoon was introduced from 1990. NSB launched the Trøndelag Commuter Rail on 1 September 1993, of which the main service ran from Steinkjer to Trondheim. The initial plans called to the continued use of the Class 92 rolling stock, but saw change in schedules and the upgrading platforms for NOK 15 million. The service from Trondheim to Steinkjer had ten daily round trips. After six months operation, the service had experienced a 40 percent growth in patronage. This was further increased with the opening of Trondheim Airport Station on 15 November 1994 and a station serving Levanger Hospital on 20 December 1995. On 10 November 1994, the line received automatic train control. NSB was split up on 1 December 1996 and the ownership of the tracks and infrastructure was inherited by the Norwegian National Rail Administration, while the operation of trains was taken over by the new NSB. From 1994, Di 6 and Di 8 locomotives were introduced, but the Di 6 proved unreliable and returned to the manufacturer. NSB decided to improve their commuter rail service with the closing of several stations for the commuter train service. Fifty percent of the stations were responsible for only two percent of the traffic, and NSB instead wanted buses to transport people to the closest railway station, which would reduce overall transport time for most passengers. From 7 January 2001, a fixed, hourly headway was introduced on the trains from Steinkjer to Trondheim. From June 2001, NSB introduced additional rush-hour trains between Trondheim and Steinkjer, giving a half-hour headway. NSB introduced their Class 93 locomotives in 2001: starting on 7 January they were used on the Salten Commuter Rail, which