The single-stage ZF metro gearbox E-Rail SH 15 F is optimally designed for little service effort, low life cycle costs, and a long product service life. These are advantages based on a special technical feature: While in conventional helical-toothed metro gearbox axial forces put stress on the bearings and reduce efficiency, two innovative tapered thrust washers in the E-Rail: SH 15 F prevent this effect. They are mounted to the left and right of the drive pinion, slide on an oil film on the output gear, and thus absorb the axial forces. This makes it possible to use cylindrical roller bearings instead of tapered roller bearings for input and output shafts. These need not be adjusted and considerably minimize assembly effort and maintenance requirements. Additionally, the design is largely resistant to varying outside temperatures. The operating temperature of the bearings which are not subjected to axial loads and are installed in a nondistorted way is only 2 °C above the oil pan temperature, which reduces stress on the bearings and contributes to increasing product service life. One special feature of the E-Rail SH 15 F which already makes for a sustainably positive cost-benefit ratio in the metro in Moscow is the hollow shaft drive design. This design reduces logistics effort during initial installation as well as during all subsequent vehicle inspections.