TL;DR
The arrows on rail segment visualisation should be bigger/clearer than they are right now.

What?
Rails.png
If you zoom all the way in you can see those are arrows. But who builds rails zoomed all the way in? Even just a bit further away they turn into barely discernable dots. They ...

Fuel: Clearly stated in the tooltip, but if you click you can't look at it, unless you're standing right next to it.
Cargo contents: Tooltip has the exact item types and amounts. Click at best gives a green bar, and only if the train is currently at a station with a cargo condition. There are no ...