This map represents the tonnage of goods transported by road between Swedish counties. Color and line width are proportional to tonnage, volume of the spheres represents intra-county transports, their location corresponds to the county capital. Note that the translucent arrows allow one to (waguely) see in what direction the goods flow (e.g. Norrbotten sends much less goods to Vasterbotten than vice versa).
As the author explains: "I first did a version in Matlab, but it was so ugly that I did this one directly in the PoVRay renderer. Since the layout was already given by the coordinates of the capitals it was just a matter of writing a macro in Emacs to convert the data table into different widths of arrows. Very much brute force and (nearly) by hand."