Rail transport in the Soviet Union the Soviet Union collapsed. Twenty other stations were under construction in 1985. The country's rapid transit system was the most intensively used in the world. The Soviet Union was a pioneer in the development of the diesel locomotive to replace the steam locomotive (dieselization) on non-electrified lines. But the USSR failed to make steady progress and while they lead the United States at first, they soon fell behind and their last steam locomotives were retired about 15 years later than for the US. The first mainline diesel locomotive in the world began running in 1924 in the USSR but it
Russians in the Baltic states on the basis of the legal continuity of their statehood throughout 1940 – 1991, automatically recognising citizenship according to the principle of "jus sanguinis" for the persons who held citizenship before 16 June 1940 and their descendants. Most of those who had settled on the territory of these republics after their incorporation by the USSR of these states by the USSR in 1940 and their descendants received the right to obtain citizenship through naturalisation procedure, but were not granted citizenship automatically. This policy affected not only ethnic Russians, but also the descendants of those ethnic Estonians and Latvians who emigrated