In short: Each point is the average direction of travel, the first image showing pick-ups and the second showing drop-offs. The color shows the direction of travel.
Description: Extending the idea in the previous image, this image is a simple geographic representation of all pick-up and drop-offs of each taxi-journey in NYC at the beginning of 2015 (~70 million taxi journeys), but the color palette was chosen to show the directions people were travelling. No component of the image shows the number of journeys, just the average direction taken from that point and so looking closely shows many more individual stories, as well as general behaviors.
Point of interest: Looking closely at the bridges, they seem to tell some stories as people are picked up and dropped off there from and to specific directions. Car broken down perhaps (and hopefully nothing darker)? Other areas show other more obvious stories like visits to a cemetery being dissimilar to the trips taken in surrounding areas.
Technical: 6 months of yellow cab trip data for (Jan-Jun 2015) available at https://nycopendata.socrata.com/. Image shows linear 2D image of all GPS Latitude and Longitude co-ordinates of taxi pick-ups and drop-offs for all journeys within limits of image. Rainbow color scale represents the average direction the journey is due to take or has taken.