 Complete the following phrase:  After the war, economic growth returned only slowly to the Estonian Soviet Socialist Republic; yet in 1951, the single-track line between the city centre and Kopli was doubled up to create a conventional two-way tram line, and in 1953 it was linked up with the rest of the network. 1954 saw the completion of a three-year project to build a tram depot at Vana-Lõuna, and a year after that, the stretch on Tartu Street Tartu maantee was extended to Ülemiste. Various further local developments followed. In 1970s tram routes were planned in Lasnamäe, in 1980s Laagna tee have been constructed for this purpose, but the new authorities discontinued this project after the 