usually Main lines change karenge sirf baaki loop lines 52kg wali hi rahenge aisa already Vasco-Londa-UBL-GDG-BAY-GTL section me kiya hai recently thode jagah toh maine 68kg tracks pe dekhe hein For freight routes they use more heavy lines UBL-hebsur k nazidik aur Londa-castle rock-Kulem k side bhi mainly 68kg track hein shayad as unka Track head bahot bada hai dekhne mein.