This is approximately one month of traffic sensor data collected from the Minnesota Department of Transportation (Mn/DOT) from 29 Aug 2007 through 29 Sep 2007.
Sensor data was captured every 30 seconds into individual XML files.
This is 11GB when uncompressed!
Mn/DOT Information for Developers: http://www.dot.state.mn.us/tmc/trafficinfo/developers.html
Mn/DOT Tools for Analyzing Data: http://data.dot.state.mn.us/datatools/