I spotted this visualization of an underground line in Tokyo and thought that I can use this as an interesting introductory example in information visualization. The very simple question is: what does this visualization communicate to the user? The bi-lingual labeled picture is quite rich in the way it communicates the information. Take as one example the visualization of "Where am I?" and "Where is the train going to?". This is visualized in multiple and redundant ways: (1) the station where the user is highlighted with a red background color, (2) the visualization of the underground line has a break at the current station, (3) the stations the train has already passed are lighter colored (pink) as the stations to come, and (4) there is an arrow showing the direction.
Overall I think this is a good example of how to efficiently communicate such information. But be careful if you travel … there are also much more confusing signs around here.