A diesel locomotive is a locomotive powered by a diesel engine. The diesel engine drives the locomotive's wheels through a transmission system. Diesel locomotives are very popular worldwide, due to their ease of use and reliability. They can be more powerful than steam locomotives and do not need an expensive power grid like electric locomotives.
In the 1930s they were often used for runs of very short distances. After the middle 20th century they became the most common kind for long runs, too.