At the start of the 1970s it was decided to electrify the line, in order to make the Black Forest Railway yet more flexible and economically attractive, and on 25 September 1977, the entire line was switched to full electrical operation. The work to electrify the line had been more complex than anticipated, particularly in the many tunnels, as the rail beds had to be lowered in those instances. Several unprofitable railway stations and other halts were also taken out of service at the time. It is also worth noting that, due to the many sections with steep inclines, locomotives of the type DB Class 139, with rheostatic brakes, were prominently seen in service.