Most busiest are SDAH-BNJ & SDAH-KNJ Local Trains. Kolkata Suburban is the Biggest in terms of Area & Distance covered. Mumbai is Biggest in terms of Station density & Busiest because of that. Kolkata Suburban station density is 1.96 i.e. 1 station in every 1960 mtrs. Mumbai has station density at 1.565 i.e. 1 station in every 1565 meters.