Diesel locomotive break down. Hydraulic transmission for locomotives was developed in Germany. There is still debate over the relative merits of hydraulic vs. electrical transmission systems: advantages claimed for hydraulic systems include lower weight, high reliability, and lower capital cost. By the 21st century, for diesel locomotive traction worldwide the majority of countries used diesel–electric designs, with diesel hydraulic designs not found in use outside Germany and Japan, and some neighbouring states, where it is used in designs for freight work. In Germany and Finland, diesel–hydraulic systems have achieved high reliability in operation. In the UK the diesel–hydraulic principle gained a poor
Steam diesel hybrid locomotive a steam engine offered a high starting torque—a tractive force of was available—while a diesel engine offered a high fuel efficiency and it was considered desirable to combine the two. In outline the machine resembled a conventional 2-6-2T steam locomotive, but it had four pairs of horizontally opposed cylinders (13½ inch bore × 15½ inch stroke—343 × 394 mm) mounted longitudinally above the frame and driving a crankshaft placed between them, with the further drivetrain by gears. The cylinders were made double-ended, with the rod end of each cylinder for steam and the closed end fitted with a diesel injector.