If the Chief Controllers havent attended their refresher course in past few years,I want to remind them that MEMU stands for Mainline Electric Multiple Unit...These are different from EMU's...While running in Mainline,they're bound to get overtaken by various Mail/Exp/SupFast.Whereas EMU has dedicated tracks for them which mainly run as suburban local.So No Mail/Exp can overtake EMU.MEMU starts with 6----,EMU starts with 3----/9----.