 Because of the lack of a balloon loop at Rikshospitalet, Line 18 must be operated with SL95 units, while SL79 units are used on Line 19 because the Brikeby Line does not have a high enough permitted axle load to for the SL95 units.The Nordstrand area of Aker was first served by steam ships from the 1860s, which connected the lower areas to Oslo.In 1879, the Østfold Line (then the Smaalen Line) opened in 1879, giving these areas a regular service unaffected by the weather.