It is noted that well maintained tramcars of this type are very reliable, a late 2000s survey conducted in Prague tram system has shown 98.9% reliability, best of the Prague tram system fleet. They spread to many other Eastern European cities, especially in Czechoslovakia, the USSR and the GDR. Poland, Hungary and Yugoslavia also got some. The T3SU was delivered from 1963, first to Moscow and later to 33 further Soviet cities.