I've just researched Road Building for the first time, and...it was underwhelming, to put it mildly. A mud track gives double movement, and takes me 4 turns to build with my current civics. A road requires a higher technology, takes 6 turns to make, and costs 2 gold, but also makes travel only cost half a movement point. Was the mud track added at some later point, and the road not adjusted to compensate? Also, it's hard to tell, but I think that if I move a unit with a promotion which should give it double movements on the terrain along a trail path it doesn't get it. Is this correct?