It is easy to see why a book about traffic would become a bestseller. Congestion on the roads robs people of time. A book that promises to explain it has the same potential appeal as one that tells people how the Internal Revenue Service robs them of money or cholesterol robs them of longevity. But it is for different reasons that Traffic, by the science journalist Tom Vanderbilt, has become the big succès d’estime of the US summer publishing season. Critics have treated it almost as a work of philosophy. The book is intensely researched and quite readable, albeit in that bantering, overly personal, hey-what-the-heck style of much US pop economics writing. Traffic is not just about slow commutes. It is about the way things flow through networks more generally, and the hazards and opportunities that result. For Mr Vanderbilt, the highway is “a living laboratory of human interaction, a place thriving with subtle displays of implied power”.
Automobile traffic is one of the most studied phenomena in advanced societies. Managing it is a main function of government. Private institutions study traffic, too – Disney World must shuttle visitors efficiently between its attractions and Wal-Mart needs to estimate its parking needs for each new store. The result is a mountain of university research, government policy documents, consultant reports and industry journalism. Mr Vanderbilt has mastered all of it. Arresting facts appear on every page: three-car households outnumber one-car households in the US, iPods are more dangerous to adjust while driving than car radios and cyclists who use proper hand signals cause more accidents than those who do not signal at all.
When you analyse such data, as Mr Vanderbilt does, with the help of sociobiology, Nash equilibriums, Poisson distributions and Pigovian welfare economics, you get something like a treatise on human nature. People who have just been going at 70 miles per hour run through 30mph zones at up to 15mph faster than people who have not, Mr Vanderbilt notes. People honk less at high-status cars than they do at low-status ones and more at women than at men. Since gauging whether a fellow driver is paying attention is so vitally important, drivers can immobilise other drivers by withholding eye-contact. Hence the games of chicken that get played at intersections.
Mr Vanderbilt sees that traffic engineering is social engineering. Simply expanding infrastructure solves few problems. Intersections, for instance, become less efficient as they become larger. Building a second left-turn lane will allow more turns, but not twice as many. Meanwhile, it will slow down everything else in the vicinity. It is now well known that building more roads can sometimes induce people to drive. Mr Vanderbilt shows that building more parking spaces does the same. Copenhagen cut congestion by eliminating parking spaces. Donald Shoup, a Californian economist, found that in one 15-block section of Brentwood, cars drove 3,600 miles a day looking for parking.
What is most valuable about Traffic is its power to generate metaphors. Roads are the physical antecedents of the more ethereal networks that have turned our world upside down in the past two decades. They are centrally planned passageways through which autonomous individuals pursue their whims and ambitions. But the relationship between the person and the structures is unclear. Is the heavily subsidised US road system best thought of as transport for a country of individualists? Or is it a de facto public transport system that is (at almost one driver per passenger) ludicrously overstaffed and ecologically unsound? Similar questions can be asked of other structures: are high credit-card debts best thought of as family choices or privately held pieces of a larger national debt?
In this metaphorical light, one consideration will disturb thinking readers: the more technologically efficient a network becomes, the harder it is to tell people the whole truth about it. We are on the eve of a “revolution in traffic”, Mr Vanderbilt writes, thanks to global positioning systems. Once everyone gets the same reliable, real-time information about traffic, everyone mobs the same routes. When Chicago authorities announced the closure of eight lanes of the Dan Ryan Expressway in 2006, the recommended detours moved slower than the expressway. Predictions about traffic become “self-destroying”. The scattering of traffic that used to result from imperfect information and personal idiosyncrasy is no longer the norm. It must be artificially recreated. How do you recreate it? Either by coercing drivers (assigning them to routes, in which case the car ceases to be private transport) or by lying to them. “You have to structure the information,” the German physicist and traffic expert, Michael Schreckenberg, says to Mr Vanderbilt. “Telling them the whole truth is not the best way.”
We do well to study driving for the same reason that captains of mechanised steamships, until well into the last century, studied sailing. Of this custom, Richard Hughes wrote in his 1938 novel, In Hazard: “Landsmen are inclined to smile, as at a piece of foolish conservatism as if London bus-drivers were required to serve for seven years as stable boys and grooms, before they were allowed to handle motor-buses. With so much technical knowledge to acquire anyhow, why waste the man’s time in learning a useless and outmoded technique as well? The answer is a matter of Virtue, really ... Every common action in the working of a sailing-vessel, all the time, partakes of something of the nature of an emergency.”
So it is with traffic. Funny no one ever noticed that before Mr Vanderbilt.