a decision was made to rebuild the line from Arendal to Nelaug with dual gauge. By 1934, the proposal was changed so that the Grimstad Line was to be closed, the section from Arendal to Nelaug has standard gauge, and the northern part have narrow gauge. After local protests, it was decided by parliament to keep the Grimstad Line. Since 1925, all maintenance on the line had been done with a standard gauge conversion in mind. Among other things, 30,000 narrow gauge ties had been replaced. Work on replacing the remaining ties started on 1 July 1932. Two years later, a third rail started being laid. On both sides of the bridge at Froland, the profile was too narrow, resulting in a curve radius of . Nelaug Station was built, and because the upper part of the line would retain narrow gauge, the new station received transshipment facilities. The last narrow-gauge train to Arendal ran on 19 October 1935. The following evening, standard-gauge operations were introduced. The first train from Arendal to Oslo ran on 2 November, and the new line officially opened on 9 November. The Grimstad Line retained narrow gauge until 9 November 1936. While terminus for the Sørland Line, Arendal experienced a larger increase in traffic, as all transport to the South Coast went through the town. On 21 June 1938, the Sørland Line between Nelaug and Grovane opened, and the Arendal Line became a branch. Arendal District was closed, and the Arendal Line became part of Kristiansand District. Passengers from Arendal had to transfer to the express trains at Nelaug, and the second class carriage was terminated. However, the number of services along the line increased slightly, in part to allow fish to be transported with the express train to Oslo. The section from Nelaug to Treungen had a break-of-gauge, causing increased operating costs and inconvenience. From 1935, the line received two daily trains per direction per day. This was increased to three the following year. In 1938, Class 9 locomotives were introduced on so-called "small trains", where the fireman also acted as conductor. After the Grimstad Line was converted to standard gauge, the class was also used on freight trains between Arendal and Grimstad. It would then back from Arendal to Rise, run forward to Grimstad, back from Grimtad to Rise and then run forward to Arendal. In 1939, the mine at Søftestad reopened, with