 Bus transport started in 1927 with line 18 between Kværner and Alexander Kiellands Plass.In 1931 the bus ring around the city is opened, and by 1937 Oslo Sporveier operated 113 vehicles.A test for the Oslo trolleybus service was performed in 1939; the breakout of World War II induced strict fuel rationing making it profitable for Oslo Sporveier to take into use trolleybuses using abundant electricity.