all the regions where electrification if lines ahs taken place......all are in AC current ..mumbai alone is an exception where the current is DC and not AC.....due to heavy traffic handling the conversion was done at a very slow pace........now only around 50-60 kms of route remain to energised by Ac current.....DC lines prevent the running of AC current locos like WAP/WAM/WAG etc.....instead express ttrain in mumbai are run by WCAM series loco which can switch from AC to DC and vice versa........