I assume the checkered lines which disallow building across certain hex edges represent the Loire, Gironde, and Seine rivers. Paris Connection has such a ruthlessly parsimonious design and I wonder if this seemingly insignificant rule was retained for gameplay reasons or if it is indeed pure chrome.
Has the checkered line ever become tactically relevant to one of your games?
"For the listener, who listens in the snow, and, nothing himself, beholds nothing that is not there and the nothing that is." -- Wallace Stevens
I don't remember the specifics, but I certainly remember being blocked by the checkered lines in at least one or two games. It's sort of a idiosyncrasy of the game, but adds a bit of flair around the edges (literally and strategically).