As you might know, I am working as the Data Analyst for carpooling.com in Munich. carpooling.com is the company maintaining the leading web platform for organizing carpoolings (in the world, actually). Many people don’t know what “carpooling” means, so let me explain it you:
Tanja lives in Stuttgart and wants to visit her family in Hamburg next weekend. This is quite a long distance and hence pretty expensive – and also kind of dull sitting in a car alone for several hours. Having three free seats in her car left, she thinks to herself … “Why not offer those seats to other people and share the expenses with them?!”. So she advertises her planned lift on www.mitfahrgelegenheit.de – the biggest German web-site for carpoolings. Peter who also wants to travel to Hamburg next weekend finds her ad and gives her a call to seal the deal. Okay, so far so good, but few passengers aren’t as reliable as Peter and might just forget about the ride and Tanja would then be left with a free seat and no money. So carpooling.com came up with the idea of a “booking system” to make carpooling agreements more binding. Next weekend Tanja, Peter and further passengers meet and drive to Hamburg together.
Now in the animations below every circle represents a driver (red) or a passenger (blue). The day they took a ride together a link is drawn connecting them and the size of a circle grows with the number of its links.
The booking system was introduced gradually in Germany (which is currently the biggest market). “L1”, “L2”, “600km” and “Cash” indicate four major milestones. Which is why the frequency of new carpools increases after those steps for the larger selection. “600km” marks the biggest milestone which was the day when the usage of the booking system became obligatory on all German routes longer than 600 km.
The graphs are created with R / igraph using the Fruchterman-Reingold algorithm for the positioning of the vertices. The number of vertices involved in the large animation is about 70’000 and the calculation of the layout took 11 hours on my laptop. Afterwards the PNGs plotted with R are joined into a clip using ffmpeg.
Carpoolings all over Europe during two years
The above animated graph is comprised of a (…n actually small) selection of carpools that took place during April 1 2011 until March 20 2013 all over Europe.
Carpoolings on a route between two German towns during two years
The two German towns the above visualized carpoolings are travelling to and from are more than 600 km far from each other. The “600km” label appears when the usage of the booking system for routes longer than 600 km became obligatory. Hence the accelerated increase of appearing carpoolings after that day.