That map of yours is at the wrong resolution, sites in the travel map are huge. So big in fact that the size you made your impassible objects would be considered an (relatively large) obstacle and they would take the pink path.
Yes, yes, I know, It was just an abstraction because it's easier to draw. Think of it as a fictional tiny site, or better yet forget sites altogether: it's just a specific point on the map.
The small grey obstacles are meant to be only 1 "fortress mode tile" wide. as thin as a wall can be.
To reiterate the question more clearly:
Is a "travel map tile" that contains a directional obstacle (i.e. an obstacle that can be traversed
north-south, but
not west-east) marked as passable or impassable?
Maybe this example explains it better:
http://www.mediafire.com/view/74h7h6pdcg6z6ua/asd.pngWhich path(s) is/are valid? 'A' and '1' obviously. But Is 'C' passable? If so, '2' must be passable as well - which means B must too be a vaild route. After all, a "travel map tile" is either passable or not. If there were more information than a binary flag, the check would have to have a higher resolution, no?
If not; if B, C, 2, and 3 are all invalid paths, how does the game decide whether a tile is impassable or not?