train service was introduced from Oslo to Ljan Station from 1883, allowing the areas of Nordstrand to open up to large-scale housing. The railway allowed for faster postal services and the trains carried markers with the weather forecast, which was announced at the stations. A direct international train service was not introduced until 1 July 1886, when a direct service to Gothenburg and Hamburg was introduced. Travel time to Copenhagen was at that time twenty and a half hours. The following year sleeper cares were introduced. The commuter traffic increased and in 1893 a new commuter station was opened at Kolbotn. Two branch lines were built from Sarpsborg. A branch to Borregaard opened in 1891 and the Hafslund Line opened eight years later. To avail the problem in Oslo with human manure, depots were built at Drømtorp, Ås and Vestby to give farmers access to the resource. Manure trains ran until 1929. Construction of interlocking systems started on some of the busiest stations in 1897, although fail-safe functionality was not available until the 1920s. A faster inter-Scandinavian service was introduced in 1900, cutting travel time to Copenhagen to 16 hours and 20 minutes. The higher demands caused the railway to order nine new NSB Class 27 locomotives, delivered between 1910 and 1916, which allowed the maximum speed on the line to increase from . NSB introduced Ea 1, an accumulator electric locomotive, on local services between Fredrikstand and Skjeberg in 1916, where it remained in use until 1920. Line upgrades As the main international railway out of Norway, the Østfold Line had some of the highest demands for speed and axle loads. In an effort to increase train weights and speeds, the Norwegian State Railways approved an upgrade plan in 1910 which was initially to be completed by 1919. All bridges and track was to be upgraded to tolerate a higher train weight. The break-out of the First World War led to material and funding shortages, and the upgrades were not completed until a new Sarp Bridge was finished in 1930. The line was originally named the Smaalenene Line (), with the spelling changing to Smålenene () in 1921. During this period it was also commonly known as the South Line (), although this was never official. As the line was named for the county, it changed its name after the county changed its name from Smålenene to Østfold. Parliament