The five tower railcars of the 704 series delivered between 1977 and 1978 were developed as successors of the 701 / 702 series on the basis of the 627.0 / 628.0 series of railcars. The twin-engine vehicles were fast at 140 km/h and were able to reach 100 km/h at 5with trailer load. Thus they were quickly applicable at the place of installation and by their excellent technical equipment everywhere applicable. They were often also used to drive cable wagons or additional equipment wagons. During their 30 years of operationfor example, depending on the working situation and the length of major construction sites in the rail networkthey changed the Bw's where they were stationed so that they could be deployed quickly from there practically everywhere in Germany.Since the employees were often affected by engine exhaust gases at the beginning, the 704 got 1986 new, less polluting engines. In addition, exhaust gas pipes were routed to the left and right of the roof, through which the