In the Soviet Union, in urban areas, trams were 3 kopecs, trolleybus 4 kopecs and bus/metro were 5 kopecs. These applied nationwide, whether right across Moscow or in small urban areas. These fares lasted from the 1960 currency reform to 1990 perestroika.If a differential fare structure between bus/tram/metro is advantageous in terms of maximising patronage, why is that principle not widely used in developed countries?