uh, this is manhattan they're talking about. the far left lane is not the 'slow lane,' as he said the far left was a curbside lane, which implies that it was on a one-way street. people will be making abrupt stops from the left lane as well, so if any lane is the 'fast lane', it's the middle lane[s]. also, if he made a left onto the street or was turning left in the near future, this was a much more prudent move than crossing multiple lanes of traffic to ride on the right for a few blocks, then cross all those lanes again to make a left.