Way to go! High-tech roads

In Europe, much of the built environment is historical and difficult to alter, but in the United States, where the historical record is much shorter, the scope for evolution is greater. No part of the built environment illustrates this better than the interstate transport infrastructure. It has evolved from jalopies and graded roadbeds to electric hybrids and electronic toll collection. Wherever we live, we tend to take roads for granted, until they are closed by accidents or restricted by roadworks. It is no secret that the US is defined by its road network: viewed from space at night, the nation resembles a classical topological network of nodes and links, formed by the cities and freeways. On closer inspection, the links are, in fact, chains of smaller nodes joined together by the interstate road network.