Traffic Down 30% in Cities: How?

The decline in congestion -- which analysts have labeled 'startling" -- was almost universal. Traffic congestion actually declined in 99 of the nation's 100 largest metro areas, according to Inrix, which monitors traffic around the nation. The company's data come from tens of billions of reports from GPS-equipped vehicles traveling the nation's roads, the same data that provides real-time traffic information to commercial users and web-services like Mapquest, Garmin and On-Star.

Their key conclusions: 'peak hour congestion on the major roads in urban America decreased nearly 30 percent in 2008 versus 2007,' and nationally, 'congestion was lower every hour of every day in 2008 versus 2007 – between 15 percent and 60 percent lower depending on the hour and day.' See the full report here.

How did such a small decline in travel produce such a big drop in congestion?"