could somebody say about the track construction of mumbai suburban,,,,for eg:in Chennai two tacks (main line) for express,and two track for suburban,,and fast locals run on express track for chennai to arakkonam and for beach to tambaram,,,from tambaram to cgl all emu run on express track,,,,,....likewise somebody could plsss say about mumbai suburban tacks(central,western,harbour,trans),and for kolkatta and delhi,,,