approved double track from Oslo to Ljan in 1916. Construction took its time and opened in two stages, from Bekkelaget to Ljan on 1 June 1924 and from Oslo Ø to Bekkelaget on 15 May 1929. South of Ljan the line crossed the Ljan Viaduct, which could not be upgraded to the new standards. A new double-tracked line had to be built around, which opened on 15 February 1925. By the 1930s the railway was meeting increased competition from buses and trucks. Although slower, they offered more pick-up locations than the train. NSB therefore decided that the Østfold Line, and especially the section closest to Oslo, needed to receive increased capacity, electric traction and more stations. Double tracking continued southwards, opening to Kolbotn on 15 December 1936 and to Ski on 14 May 1939. Meanwhile, NSB introduced gasoline railcars which stopped at the new flag stops. Electrification was carried out in several smaller steps, with the first part from Oslo Ø to Ljan completed on 9 December 1936 and the last section from Sarpsborg to Halden, on 11 November 1940. NSB Class 66 was introduced as an express service on the Østfold Line, running a round trip from Oslo to Halden each day, bringing travel time down to two hours. This lasted until 1956, when they were replaced with the slower NSB Class 65. The international trains were from 1948 served with the Swedish State Railways' SJ X5 units, able to run from Oslo to Copenhagen in less than ten hours. The fast service was named Skandiapilen. A landslide in 1953 washed away part of the track past Bekkelaget, resulting in the Bekkelaget Tunnel opening there five years later. The regional traffic received the new NSB Class 68 multiple units from the mid 1950s. A regular train with pyrite started running in 1966, hauling up to 600,000 tonnes per year from Hjerkinn on the Dovre Line to Borregaard. They remained until the 1990s. Double track almost to Moss By the 1960s it was becoming evident that the infrastructure was outdated. A particular problem were the many level crossings which were a safety hazard, causing reduced speed, especially between Ski and Moss. Capacity was also used up and the section was the busiest section of single track in the country. Already during the 1950s NSB proposed building double track, but this was dismissed by Parliament. To avail the situation NSB introduced