Lighter vehicles tend to have less durable construction. When it comes to low floor trams/railcars, the lack of space is another engineering problem. Plus, with

Lighter vehicles tend to have less durable construction. When it comes to low floor trams/railcars, the lack of space is another engineering problem. Plus, with a high-floor vehicle, you have lots of space during rebuilds to install newer power electronics and auxiliary equipment, in order to extend the service life. Regular heavy-rail, high floor metro EMUs can go for over half a century.