There is an irony at the heart of traffic engineering. Like all engineering, it is a very precise endeavor. But precision is not necessarily science. The scientific method is a rigorous technique that tests hypotheses against observed results to come to conclusions about the world around us. Traffic engineering from its beginnings in the mid-1950s has never employed the scientific method. It is based instead on social theory.
The social theory derives from the notions of Le Corbusier in the 1920s and ’30s. The Swiss-French architect and ardent modernist despised the messiness and illogic of the old cities of Europe. During the period when Communists, Nazis, and fascists were creating their respective versions of utopia, Le Corbusier proposed a new kind of city to house the new man these new societies would create. His ideals were efficiency and mobility. He envisioned broad urban highways in which automobiles would move speedily among tall towers. Although he tried repeatedly, he never actually got to raze a city. But as even his admirers note, if he could have razed Paris, he would have.
That had to wait until the postwar period, and then it was the New World, not the old, in which Le Corbusier’s theories were put into practice. Robert Moses leveled a good part of New York to create multistoried housing projects and to construct huge bridges and highways. He became a hero of urban renewal for displacing thousands in order to impose a rational new order on the city. His protégés were soon in demand across the United States, and they filled new posts in engineering schools at all the best universities.
In 1964, the new movement swept into Dallas when newly university-trained traffic engineers laid 12 lanes of I-30 through the heart of Old East Dallas. In 1971, they razed 52 blocks in Deep Ellum to construct I-345. That same year, they destroyed the Spence neighborhood in South Dallas by elevating I-45. Their objective was to achieve the Le Corbusier ideal of mobility. Their aim was efficiency, not the flourishing of a city.
But something strange began to be noticed about this new social theory. After Moses had his way, New York faltered, lost population, and listed dangerously close to bankruptcy. The neighborhoods of southeastern Dallas emptied out. Moreover, these new urban highways were producing more traffic and causing more congestion than they were relieving.
Confronted with the paradox, TxDOT traffic engineers—stuck in the old paradigm—continue to argue for more lanes to resolve it. But back in 1969, mathematician Dietrich Braess found that building highways or adding lanes to highways increased rather than diminished congestion. It is a result of how thousands of humans make independent decisions in a closed network by responding to options within that network.
Traffic engineers measure cars, not drivers. They had never accounted for independent human decisions. It is telling that in all of Le Corbusier’s hundreds of futuristic sketches there is not a single human figure.