The AP has an interesting look at gridlock in America, with details on individual metropolitan areas.
There are a couple of surprises in the data, including that the percentage of commuters who carpool in Atlanta (10.4 percent) on average is higher than in other metropolitan areas (9.4 percent). The percentage of solo drivers (77.7 percent) is also higher than the national average for other cities (79 percent), but not as high as I would have thought.
The average commuter in metro Atlanta spends 30 minutes traveling to work, which is slower than the national average of 26 minutes.
For more details, check out these nifty infographics: http://www.ajc.com/news/traffic/commuting-america/; or read about how cities around the country are managing gridlock in the accompanying story: http://www.ajc.com/ap/ap/general/avoiding-future-freeway-congestion-could-come-with/nmmgb/.