Complex sentence: Each unit consists of a Driving Motor car (DM), Trailer car (T), Uncoupling Non-Driving Motor car (UNDM), with a standard train formation of DM-T-UNDM + UNDM-T-DM.
Split into simpler sentences: Each unit consists of a Driven Motor car (DM), Trailer car (T), Unmanned Non-Driven Motor car (UNDM). A standard train formation would be DM-T-UNDM-UNDM-T-DM.