Why were the terms 外回り and 内回り chosen for the directions on Yamanote line (railway) rather than the more straigntforward 時計回り and 反時計回り? Is it expected that people should know which matches which?
In addition to what Chris said about not knowing which side ran clockwise or counter-clockwise (there might not be a train in the station, or it might have an engine on either end and be standing still), another advantage of the concept is explained on Wikipedia:
In nations where automobiles drive on the right side of a road, traffic traveling in a clockwise direction around a loop will always be in the "inner" lane(s) (assuming that there is no lane crossing).
Likewise, in nations where automobiles drive on the left side of the road, traffic traveling in a clockwise direction will always be in the "outer" lane(s).