Are you being purposefully obtuse? The game knows exactly how many lines there are at each and every point in time. It should have no problems telling you whatever it is that we want to know about potential line speeds given consist composition whenever it is queried. It’s only a matter of deciding on what kind of information to present to the user so that it doesn’t become too cluttered and unwieldy.
To put it in the simplest of terms: You buy a loco, you hover over the line selection, out pops a window that shows you what the min/max/average speed of that loco is on this line (obviously not accounting for traffic). There. Done.
Please don’t use “real life” as an excuse for anything in this game. It makes my teeth hurt. This game is about as far from “real life” as Voyager is from Earth.
