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
New Zealand DL class locomotive eight would be ordered to replace the EF class electric locomotives on the NIMT. This will result in an intended class total of 71 DL units. The DLs were the first new-build diesel-electric mainline locomotives on New Zealand's rail network since the DF class was introduced in 1979. The order marked one of the first steps of considerable investment in KiwiRail, and the first order for a Chinese-built locomotive from a western country. The acquisition of new locomotives was first proposed by Toll NZ after they purchased Tranz Rail in 2003. When Toll assumed responsibility for the rail operation, the