how to play Carcassonne - The Signposts

About Carcassonne: The Signposts, from BoardGameGeek:

Carcassonne: The Signposts is a 12-tile expansion that can be mixed with the Carcassonne base game. Each tile features, among other things, one or more road segments and two of three possible signposts, with the signposts indicating a left turn, a right turn, or a straight path. When a road that contains a signpost is scored, for each signpost you look at the next tile adjacent to the signpost, and if the road segment on that tile matches the signpost, then the signpost scores. For example, if the signpost shows a right turn, and the adjacent tile features a right turn (regardless of any other road segments), then the signpost scores. If you score only one type of signpost, then each such signpost is worth 1 point; if you score two types, then they're each worth 2 points; and if you score three types, they're each worth 1 billion, I mean, 3 points. At game's end, each signpost pointing in the correct direction on an unfinished road is worth 1 point.