Traffic Safety Data and Analysis

ROADWAY Reports and Summaries

Iowa's roadway system is one of the largest in the nation, totaling approximately 115,000 miles of city, county, and state roads. The Iowa Department of Transportation is responsible for roughly 10,000 miles of the system. Counties have the responsibility for the largest part of the public road system with approximately 90,000 miles, and cities are responsible for about 15,000 miles.

Who maintains the data system?
The Iowa Department of Transportation is responsible to collect data from all roadway systems.

roadway

30-year historical vehicle-miles traveled (VMT) by system

VMT by county/system

Historical VMT by county/system

VMT by city for 2008-2012

VMT by classification

Monthly VMT

Iowa Miles of Secondary Roads

Miles of public roads by surface type

Rural interstate speed information

Average speeds on Interstate

  • 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.
Percent over map

  • 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.

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.

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@iowadot.us.

County and city maps

State traffic maps

County traffic maps

City traffic maps

What data records are collected?

Data collected for all road jurisdictions includes geographic information, geometric data, roadway configuration, pavement and bridge condition, jurisdictional responsibilities, and traffic levels.

How are the data records used and what standards are applied?

This roadway information supports other disciplines, such as operations, asset management, and maintenance of Iowa’s roadway data. This roadway data, as well as rail crossing data, is contained in the Iowa DOT’s Geographical Information Management System and complies with the guidelines set forth by Model Inventory of Roadway Elements for all public roads in the state.