 In December 1940 the first trolleybus route opened, line 17 from served as a shuttle for the tram at Rodeløkka.Line 21 was the next to be converted—opening on 5 December 1943—running from Carl Berners Plass to Skillebekk, on route north of the city center.After sabotage against the a German aircraft engine facility co-located with the bus depot, line 17 was terminated on 21 August 1944 so the vehicles could be used on line 21.