The southern part 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.