This is the international E-road network, a road network located mostly in Europe. The network is undirected; nodes represent cities and an edge between two nodes denotes that they are connected by an E-road.
Data downloaded from http://konect.uni-koblenz.de/ orginaly from http://lovro.lpt.fri.uni-lj.si/support.jsp
Jerome Kunegis. KONECT - The Koblenz Network Collection. In Proc. Int. Web Observatory Workshop, pages 1343-1350, 2013.
Lovro Subelj and Marko Bajec. Robust network community detection using balanced propagation. Eur. Phys. J. B, 81(3):353--362, 2011.