**5.3 Diesel multiple units (DMUs) and electric multiple units (EMUs)**

Self-propelled diesel railcars can be diesel-electric, diesel-hydraulic, or dieselmechanical units. These traction vehicles (including powered wheels) can accelerate much faster and have a shorter braking distance than locomotive trains and are thus also more energy-efficient than these. As long as the powered vehicles are connected by cable or radio link, they can be used in the decentralized power configuration. Another form of self-propelled railcars are electric multiple units (EMUs). EMUs are individually powered by direct current (DC) from a third rail, but there is also the option of being powered by a vehicle pantograph in contact with the AC overhead line system (OCS). EMUs are more costly than DMUs but are more environmentally friendly and more energy-efficient and can achieve higher speeds [34].
