With the growing network of lines, additional rolling stock was required. Thus, starting in October 2015, 37 additional vehicles were rebuilt for Lot 1 of the Rhine-Neckar S-Bahn in addition to the 40 original S-Bahn trains (425.2), which had previously been mostly used for regional services in the Rhine-Neckar area. But rolling stock was also acquired from Hanover and North Rhine-Westphalia. In total, 77 vehicles (11x 425.0, 40x 425.2, 6x 425.3 and 20x 425.4) were converted during the first phase. A further 14 vehicles were converted in a second phase to April 2018, being first used on line S 6 to Mainz.
