 The modernisation had been announced in 1974 by the subway's then operators, the Greater Glasgow Passenger Transport Executive (GGPTE).Although converted to electric traction in 1935 the systems infrastructure and rolling stock was virtually unchanged from its opening in 1896, and improvement to the subway was seen by the GGPTE as an essential part of plans to eliminate transport bottlenecks in the city.As part of the process, which began in 1977, all 15 stations were to be rebuilt.