Induced Demand

Here’s a story from Bloomberg CityLab about the futility of trying to reduce traffic congestion by widening freeways.

“We know from experience, in Texas city after city, that a simple addition of lanes will not fix our traffic woes,” wrote Austin city council member Gregorio Casar, in a letter to TxDOT.

There’s a name for the principle behind that apparent paradox: induced demand. Economist Anthony Downs is often credited with first articulating this “iron law of congestion” in 1962, as construction crews were hacking interstates through American cities. Downs published a seminal paper with a stark warning: “On urban commuter expressways, peak-hour traffic congestion rises to meet maximum capacity.” In other words, adding lanes won’t cure snarled traffic; the additional car space inevitably invites more trips, until gridlock is as bad as ever.

. . .

In 1955, urban observer Lewis Mumford wrote a series of essays in the New Yorker titled “The Roaring Traffic’s Boom,” in which he memorably compared a highway planner widening a congested highway to “the tailor’s remedy for obesity — letting out the seams of trousers and loosening the belt. [T]his does nothing to curb the greedy appetites that have caused the fat to accumulate.”

TxDOT’s job is to build highways. They’ve got a big budget to build highways. Not to improve transportation. To build highways.

And widening I-10 in downtown El Paso isn’t even about reducing congestion. If they were really concerned about congestion in El Paso, they’d do something about the traffic east of Viscount during rush hour. They’d move a little faster on the Borderland Expressway, to route pass-through truck traffic around the city, instead of through its heart.

Government doesn’t give real reasons for the things it does. It give rationales.

But people are wising up. The politicians should take notice.

Read the whole piece at Bloomberg.com.