TRAFFIC STUDY: 2012 Indiana mobility report shows 6-18% drop in traffic

Expanded analysis also ranks busiest Indiana highway portions

August 19, 2013

The 2012 Indiana Mobility Report, released at the end of July by the Indiana Department of Transportation (INDOT) and Purdue University, revealed that traffic levels have decreased 6 to 18% since 2011.


For both the 2011 and 2012 reports, researchers focused on traffic patterns and travel times on Indiana’s major interstate highways, utilizing data from third-party providers such as INRIX. In 2011, congestion was studied via three performance measures:

  • Congestion hours (number of hours when speeds on an interstate fragment or series of fragments was less than 45 mph)

  • Distance-weighted congestion hours (congestion hours multiplied by segment length  in miles)

  • Congestion index (total number of congestion hours on an interstate divided by total length of the interstate)


For the 2012 report, INDOT and Purdue researchers added four new performance measures:

  • Speed profile (number of congestion hours grouped by speed ranges)

  • Speed deficit (difference between 45 mph congestion threshold and actual observed speed)

  • Travel time deficit (number of hours of delay [when speeds are below 45 mph])

  • Congestion cost (estimated cost of congestion on a roadway, calculated by multiplying average delay for interstate section by expected traffic volume and value of time)

The report also features two rankings of the most congested interstate segments across Indiana—one based on total congestion hours and one based on travel time deficit. Eastbound I-74 between mile markers 72 and 72.5 accumulated the highest total of congestion hours at 4,028.3. On the other hand, eastbound I-70 between mile markers 22.5 and 36.4 experienced the greatest travel time deficit at 174.1 hours.