banner

Rural interstate speed information




  • Interstate 29 speed data is unavailable from April 2008 through December 2009 due to road construction at the data collection sites.
  • Lower speeds on I-29 for the October through December 2009 quarter were due to only having valid speed data in December 2009.
  • I-29 speed numbers for April of 2008 through March of 2009 were calculated using only the northbound traffic speed data from the Honey Creek site.
  • I-80 speed calculations for July 2011 through September 2011 include westbound only data for sites 110, 120, and 123.




  • I-29 speed data is unavailable from April 2008 through December 2009 due to road construction at the data collection sites.
  • Lower speeds on I-29 for the October through December 2009 quarter were due to only having valid speed data in December 2009.
  • I-29 speed numbers for April 2008 through March 2009 were calculated using only the northbound traffic speed data from the Honey Creek site.
  • 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.