From: London, Surrey, United Kingdom
Happy for someone to give me an example of how I'm totally wrong
You are correct 100%, but that is also how the design is supposed to work. Historically, the German railheads didn't catch up to the front lines until right before Case Blue, and until then the AG's were constantly fighting over priority. So these Rail Repair Units were designed specifically for D21 to simulate that, and the Repair Rate is also set to simulate these conditions. The player can give priority to an area but still isn't guaranteed what repairs they will get each turn. Otherwise, focus on three lines [one for each AG] and you will get historic results. It all works well for D21.
Won't this result in an unrealistically complete set of rail lines in marginal areas- the branches that connect up the major arteries?
Anyway, if the AGs were fighting over priority yet the player has the complete freedom to choose which troops go where, shouldn't this also apply to the rail repair?
I suppose one of the problems for a scenario like this is that it would simply not be possible to shove half the Wehrmacht down a single rail line, yet TOAW wouldn't bat an eyelid if you tried, and so limiting the advance of the rail lines is one way of mitigating the problem.
"What did you read at university?"
"War? Huh. What is it good for?"