An article in this week's Weekly Standard tries to argue that yes, highways really do reduce congestion. (story at
The article states: "Between 1982 and 2007, Phoenix decided to build the highways it should have had in the first place. They added so much asphalt that, according to the research firm Demographia, the city’s highway-lane-miles per capita grew by 205 percent. During that period, highway-vehicle-miles-traveled per capita increased by only 12 percent. And, like magic, traffic congestion plummeted." (emphasis mine)
I was curious, so I looked at the Texas Transportation Institute's Urban Mobility Survey. TTI gets criticized quite a bit by smart growth supporters,* so it is a middle-of-the-road, if not downright pro-road, source. TTI's data for Phoenix is here:
In 1982, the average Phoenix peak-hour commuter lost 16 gallons and 24 hours yearly to congestion. In 2007, he/she lost 33 gallons and 41 hours. This is not "plummeting" congestion- it is increased congestion. **
Its just simple arithmetic- 41 is more than 24. 33 is more than 16.
**Though one could argue that congestion increased faster in other regions. This claim, if true, would support the article's argument but it definitely would be quite a bit less sexy.