sentences:  From 1 June 1990, new 100 series "Spacia" EMUs were introduced on limited express services, and the maximum speed of these was raised to 120 km/h in 1992.A connecting track at was built to the JR-East Tōhoku Main Line (Utsunomiya Line) from 18 March 2006, allowing through-operations of "Nikkō" and "Kinugawa" limited express services to/from , , and .From 17 March 2012, station numbering was introduced on all Tobu lines, with Tobu Nikko Line stations adopting the prefix "TN" in orange.