Roads constitute the largest human-made artifact on earth...Ted Conover, The Routes of Man: How Roads are Changing the World (New York: Alfred A. Knopf, 2010) 9-10.
[W]ithout roads and cars -- or a viable alternative, which has yet to appear -- all human progress, all economic activity, would stop. The kids need to get to school, Mom and Dad to work, food (and everything else) to market. Watching roads can be a way to look at history, to measure human progress and limitation. In the past century, the global road network has become a thing that might finally, truly, impress the Romans. With near unanimity, we proclaim their usefulness. They are the human world's circulatory system.