TL;DRIt should be possible to determine the fuel level of a locomotive automatically.
What ?We used to be able to pull fuel out of a locomotive with inserters. This was once removed, and with it, our only method of measuring a locomotive's fuel. So now, the only way to check how much fuel a locomotive has is manually, which means we cannot automate any processes around this information.
There are two easy solutions.
a) Allow inserters to remove fuel from locomotives again.
b) Add a 'read fuel' circuit conditional.
Why ?a) Let's be honest. I was working on a project, but this was the limiting factor to my success.
b) Let's automate more things!
c) Returns a previous feature that was removed for (as far as I can tell) no good reason.
d) This would play well with many other ideas (eg. more complex train scheduling - "Go to station 2 only if fuel > X")