Escalator

On the steps most stand on the right hand side, and those in a rush hurry along on the left.
Some people don't know the unwritten rule that extends traffic rules to the escalator, or simply block traffic anyway. This isn't the case on stationary stairs or other parts of the subway where everyone just seems to rush.

Overall I am taken aback by the amount of silent communication that takes place in functioning large cities. It probably wouldn't work without, small tribe creatures that we are...