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
Electro-diesel locomotive whose electricity source is overhead line include: In 2010, Bombardier had plans, apparently known as "Operation Thor" or "Project Thor", to convert 500 existing diesel multiple units (DMUs) into electro-diesel multiple units (EDMUs). Whilst exact details are unclear, one source specified that these would involve their Voyager family DEMUs, and entail the construction of additional intermediate cars with a pantograph and a transformer which would feed power into the traction motors of the existing diesel-electric cars when running off overhead lines. Several, primarily diesel locomotive types and a multiple-unit have been built to operate off a third rail into the