MEMU (Mainline EMU) was first produced by ICF in 1993, intended to extend EMU-style operation onto main lines beyond the dense suburban networks where conventional EMUs run. Its coach structure and rake-building rules are genuinely different from EMU formations — this is a frequently confused distinction in exams.
Two Coach Types
- Driving Motor Coach (DMC) — has both a driving cab and traction motors. It can be driven by itself and can also pull attached coaches.
- Trailer Coach (TC) — has neither a driving cab nor traction motors, and works purely as a trailer. It can never be driven by itself, so it's always attached to a DMC.
Unit & Rake Formation
A single MEMU unit is formed by attaching 1 DMC (as the leading coach) followed by 3 TCs behind it — so a unit is always 1-DMC + 3-TC. A full rake is built by attaching more than one unit, and the exact attachment pattern depends on how many units are needed.
Rake Formation Patterns
- 2-unit formation (8 coaches): 2 DMCs at the outer ends (cabs facing outside), coupled to 6 TCs (all with multiple-coupler sockets facing the middle/MCT side): DMC-TC-TC-TC-TC-TC-TC-DMC.
- 3-unit formation: same 8-coach base as above, then one additional unit (1 DMC, cab facing the MCT end, + 3 TCs) is attached at the MCT end.
- 4-unit formation: same 8-coach base, then TWO additional units are attached at the MCT end (one DMC facing the MCT end + 3 TCs, and another DMC facing outward + 3 TCs).
Exam Focus — Always Count in 4s
Since each unit is always 1-DMC + 3-TC = 4 coaches, total rake length is always a multiple of 4 (8, 12, 16 coaches for 2/3/4-unit formations) — a quick sanity check for formation questions.