EMU

An Electric Multiple Unit, almost universally abbreviated EMU, is a self-propelled passenger train where traction power is distributed across multiple cars rather than concentrated in a separate locomotive. Each car (or every second or third car, in some designs) carries its own electric motors, drawing current from the catenary or third rail via roof pantographs or side shoes, and the whole consist is driven from cab cars at each end. The same configuration with diesel-electric or diesel-hydraulic power is called a DMU; together EMUs and DMUs are referred to as "multiple units" or simply "units."

The structural advantages over locomotive-hauled trains are significant. With power distributed along the consist, axle loads are lower (kinder to track), regenerative braking is more effective (more wheels means more electrical braking), and the train accelerates faster because every wheelset contributes to traction. EMUs reach line speed on commuter networks in well under a minute and are the dominant configuration on every modern metro, suburban, and high-speed system worldwide — the ICE, TGV, Shinkansen, and most Eurostar variants are EMUs even when superficially they look like a locomotive pulling carriages.

The operational drawback is reduced flexibility: EMUs are typically formed and operated as fixed sets, and a defect in one car often pulls the entire unit out of service for repair. The trade-off is accepted because the maintenance cost of a single homogeneous fleet is lower than that of mixed locomotives and carriages, and modern depot diagnostics handle whole-unit issues rapidly.

For railfans, EMUs photograph cleanly: the absence of a locomotive cab break means the consist is a single long form, and the side profile is the same from both ends. Some of the most visually striking modern trains — the Stadler FLIRTs, the British Class 800s, the Japanese Series N700S — are EMUs designed as a single integrated object rather than a sequence of separately-styled vehicles.