Østhorn was part of Holmenkolbanen's operating network until 1975, when the municipality of Oslo bought all the company's stock. In 1993, the stations on the Sognsvann Line were upgraded to metro standard, which involved a heightening and lengthening of the platforms, and installation of third rail power supply and a new signaling system. During the upgrade, Tåsen station was moved  further north, and Nordberg station was closed. Many local residents opposed the new station upgrades, arguing that Nordberg had served the area well with its close connection to the elderly center Nordberghjemmet. Many wanted to rather close Østhorn or Holstein than Nordberg, since the latter was the most used station in the area. Oslo Sporveier stated that the access roads to Nordberg were very steep and dangerous, and referred to an incident in the 1950s where some local youth had been tobogganing over the rail intersection at Nordberg, and hit a truck near the station. They also argued that the  distance between Nordberg and Holstein was too short for having two separate stations, and promised to build a walkway from Nordberg to Holstein.