After the take-over Oslo Sporveier immediately started expanding the network; on 1 August 1925 the Homansbyen Line was extended from Adamstuen to Ullevål Hageby (becoming the Ullevål Hageby Line). Further expansions were the Kjelsås Line that opened on 25 September 1934 from Storo to Kjelsås and the expansion of the Sinsen Line from Sinsen to Carl Berners Plass. At this point the city has its most extensive tram network. The new company also decided that the permitted car width be , allowing wider suburban trams to run in the city streets. During the 1930 Oslo Sporveier decided they needed more rolling stock, and cooperated with Strømmens Værksted to create the Goldfish-series. Forty-six units were delivered in 1937–40, with twenty-four delivered in the street version, series E and twenty-two in the suburban version, series B. Built with an aluminum chassis, they were quick and light, with a distinct shape, making them look like a goldfish.