Motor-Car Rolling Stock

motor and trailer cars from which multiple-unit (electric), diesel, turbine, and other types of trains are formed. A group of motor or motor-and-trailer cars that are permanently coupled and interconnected by electrical and pneumatic lines and cannot be operated separately is generally called a motor-car section. Compared to trains served by locomotives, motor-car trains have a higher ratio between the adhesion weight (the weight on the drive-wheel pairs) and the total weight, thus providing high acceleration. In addition, motor-car rolling stock makes possible cutting of trains and their movement in the opposite direction without remarshaling. These advantages are particularly important for suburban passenger traffic and in subways. Multiple-unit trains for high-speed passenger traffic are usually made up entirely of motor cars and have a high power ratio (the power of the traction motors relative to the weight of the train), which makes possible the attainment of higher accelerations and speeds than with locomotive traction.