It's fun to read <a href="http://cpz.com/today/2004/february.htm" title="Today's Shanghai News: February 2004">old news</a> about Shanghai:

<quote>Commuters who need to take both of the city's subway lines will require more time to transfer between the two starting tomorrow, due to new government measures taken to control commuter flow during rush hour.

Shanghai Metro Operation Co Ltd, which manages the underground railways as well as one of the two existing elevated metro lines, said it will design new routes for passengers who transfer between the subways, which meet at People's Square.Commuters who get off the trains of Rail Transportation No.1 - the subway stretching in the south-north direction - should walk south to get to the RT No.2 station, the other underground railway spanning across the Huangpu River in a west-east direction.Those transferring from the RT No.2 to RT No.1 should walk along the northern passage.Commuters only need to do so during rush hour on weekdays, from 7:30am to 9:30am and in the evening from 4:30pm to 6:30pm.
The move is to help ensure safe underground traffic at People's Square as crowds of passengers usually jam the area.--2/18/2004</quote>

The People's Square interchange is shaped like a right triangle: the short sides being platforms, and the hypotenuse and right angle bit being passageways between them.  From the news item quoted above, I deduce that before February of 2004, commuters changing trains at the People's Square station were allowed to take either passageway to the other station platform, and would naturally--as I have gone over in my head many, many times--head towards the much shorter "right angle" passageway.  This just goes to show the lack of planning in the design of the station's layout.  Thank goodness plans are being made <a href="http://www.ugcs.caltech.edu/~takoyaki/archive/200506.html#p25" title="China, Shanghai, Books: People's Square metro station will turn into a triangle interchange">to fix it</a>.