From 1919 until 1978, the HHA operated a large tram network, and from 5 December 1921 the HHA also operated the first motor buses in Hamburg. After the acquisition of the "Straßen-Eisenbahn-Gesellschaft" (SEG) in 1919 and the "Hamburg-Altonaer-Centralbahngesellschaft AG" in 1923, the HHA had a rolling stock of 865 power cars and 930 trailers by 1928. The length of tracks was 217.33 km. In 1970 the length of the lines were only 82.7 km, in 1978 they were 89.5 km with 80 stations.