A diesel multiple unit (DMU) is a multiple unit train powered by on-board diesel engines. A DMU requires no separate locomotive, as the engines are incorporated into one or more of the carriages. When additional carriages are coupled on, their controls are connected through and a single driver can control every engine in the train. This also allows the driver to drive from a cab at either end, simplifying reversing. Diesel-powered single-unit railcars are generally regarded as DMUs for most operations, at least with smaller trains.