Modern Atlanta may bear little resemblance to the cities of past millennia, but its current residents share something fundamental with urbanites of the distant past: The average one-way commute time in American metropolitan areas today is about 26 minutes. That figure varies from city to city, and from person to person: Some places have significant numbers of workers who enjoy or endure particularly short or long commutes; some people are willing to travel for much longer than 30 minutes. But the endurance of the Marchetti Constant has profound implications for urban life. It means that the average speed of our transportation technologies does more than anything to shape the physical structure of our cities.
—Jonathan English, in “The Commuting Principle That Shaped Urban History”