In the interest of giving credit where credit is due, my avatar is a scan of a hand-drawn caricature by cartoonist Jim Naylor which was done at my company's 20th anniversary dinner.
I know this game has been out for quite a while but I cannot find the answer to my question anywhere so I thought I'd throw it out there.
Let's say you build a settlement on the leftmost corner of the trade hex. Then you build a road going up into the middle of the trade hex. Could you then build a road going outward from the center in any of the three remaining directions? I know that you could build a settlement on the rightmost side of said hex and then build a road going in, thus connecting said roads(or would they not be "connected"?)... but my question is if you can build "through" the trade hex coming from a road and not a settlement or city.
I think that you can.
According to the rule book "You may build roads on interior paths, according to the usual rules." The usual rules allow one road to be built on the end of another.
Also, the rule that "You may not build a settlement on the central plaza intersection of a trade hex" implies that one would otherwise treat the central plaza like any other intersection of paths.
Finally, in the illustration of building roads on a trade hex in the rule book it looks to me as if red has done just this and built through the central plaza to the harbour (or from the harbour out).