Immediately after the German reunification, the operators of the East and West Berlin S-Bahns started to work together to create a new type of rolling stock. Although both sides had built modern vehicles in the eighties, these were not up to date anymore and most of the stock still originated from before World War II. A prototype was finished in 1993 and between 1996 and 2004, a total of 500 two-car “quarter trains” were built. Each quarter train consisted of two cars with one cab in total. So only trains of at least two quarter trains were created.

The trains had three-phase traction motors, but cost pressure had resulted in lots of problems and even accidents, what required that all sets had to get upgraded in the area of wheels, brakes and doors. Ultimately all problems could be solved and in 2019, a refurbishment program was launched to increase their service life beyond 2030.