I've walked on the overpass above Yan'an Road a number of times, and only 
this time did I notice the strange traffic flow.  Notice the lane 
markings: there's a straight-only lane to the left of the two 
left-turn-only lanes!  I guess it's related to the highway off-ramp and 
the ability of cars to get from where they are across two lanes of traffic 
to get in the proper lane for where they want to go.  Nonetheless, it's an 
unusual design that I've never seen before.