I was surprised at how inefficient some of the drivers' behavior was. I thought after dropping off a fare they would all immediately head to an area they knew of that might have a high likelihood of generating fares. Instead many of them seem to just wander around aimlessly looking for the next fare. edit: spelling / grammar
From the page:
Empty Taxis also follow the "best route" between a dropoff and the next pickup. Just as with the trips, this is just an effective way to move the marker around, but doesn't reflect the reality of where the taxi traveled.