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Rural interstate speed information



  • I-80 speed calculations for July 2011 through September 2011 include westbound only data for sites 110, 120, and 123.




  • I-80 speed calculations for July 2011 through September 2011 include westbound only data for sites 110, 120, and 123.

The calculations for this graph utilize data collected at 10-speed capable continuous automatic traffic recorders (ATR) located in the 70 mph speed zones that went into effect July 1, 2005, for Iowa's rural Interstate Highway System. The quarterly percentages of traffic exceeding the posted speed limit and average speeds are calculated using all vehicles from all days of the quarter in which each ATR point location in the composite was properly collecting speed data.

View the map of the specific ATR point locations with corresponding annual speed averages.

This page is updated generally within 30 days of the end of each calendar quarter. For questions or any further information, contact Brian Carlson at 515-239-1526 or email brian.carlson@dot.iowa.gov.