Diesel locomotive Therefore, diesel traction became economical for shunting before it became economical for hauling trains. The construction of diesel shunters began in 1920 in France, in 1925 in Denmark, in 1926 in the Netherlands, and in 1927 in Germany. After few years of testing, hundreds of units were produced within a decade. Diesel-powered or "oil-engined" railcars, generally diesel–mechanical, were developed by various European manufacturers in the 1930s, e.g. by William Beardmore and Company for the Canadian National Railways (the Beardmore Tornado engine was subsequently used in the R101 airship). Some of those series for regional traffic were begun with gasoline motors
Diesel locomotive provide the power needed on a heavy train. With steam traction a single very powerful and expensive locomotive was required for the heaviest trains or the operator resorted to double heading with multiple locomotives and crews, a method which was also expensive and brought with it its own operating difficulties. Diesel engines can be started and stopped almost instantly, meaning that a diesel locomotive has the potential to incur no fuel costs when not being used. However, it is still the practice of large North American railroads to use straight water as a coolant in diesel engines instead of coolants