The development of new rolling stock to replace the W-class began in the early 1970s with a modern design, based on the Gothenburg, Sweden M28 design. The Z-class trams, built by Comeng, were introduced in 1975, starting with the Z1-class. 100 Z1-class trams were built between 1975 and 1979. The design was unpopular due to the limited number of doors and the position of the conductor's seat. In 1978 and 1979, fifteen Z2-class trams, having little difference from the Z1-class, were built. As with the Z1-class, the Z2-class trams have been withdrawn from service. From 1979 to 1984, Z3-class trams were introduced. They have an additional door on each side of the tram, no conductor's console was provided, and smoother acceleration and braking compared to the Z1-class. 115 were built, 112 of which are in service.

Photograph courtesy Mr. Roberto D'Andrea.