ATTENTION: I know that upgrading rails is mostly broken for elevated rails, and I'm sorry but this is a limitation by Wube, you can see my ticket about it here:

https://forums.factorio.com/viewtopic.php?p=702850

Adds a separate item "Rail (minimal)", which doesn't have visual gravel or plates. They can connect to the electric network.

Inspired by Naked Rails, but I ended up not doing the same thing in the end.