> why they can't just make lightweight carriages I would be very surprised if the carriages were any heavier than they had to be. Why would they waste energy c

> why they can't just make lightweight carriages I would be very surprised if the carriages were any heavier than they had to be. Why would they waste energy costs (and engine size costs) on dragging around weight they didn't have to? I'm sure that weight improvements could be made, but I'm also sure that it would cost money and rolling stock is expensive enough.