INDOT, through its Traffic Statistics Section, collects, summarizes, and interprets information on the traffic traveling on the state's highway system. The data is used to assess transportation needs, system performance and to develop highway planning and programming recommendations. Traffic data also plays a very important role in route planning and in the design of highway projects.
To collect this information, the department operates two traffic-monitoring systems:
The first system is the Statewide Traffic Monitoring System, which consists of more than 100 permanent continuous count stations that can collect volume, speed, and vehicle classification data 24 hours per day, 365 days per year. Nearly 50 of these sites also utilize weigh-in motion (WIM) technology to collect continuous truck weight data. These sites are located throughout the state to monitor overall traffic trends. Information from these counters is used to determine Annual Traffic Growth trends and develop axle, weekday, and seasonal adjustment factors used with the state’s coverage count program to determine estimates of annual average daily traffic (AADT).
The second system is the Statewide Coverage Count Program, which utilizes portable traffic counters to collect 48-hour traffic counts on all state highway system traffic sections and in rural and small urban areas and all highway performance-monitoring sections. In 2010, this expanded to include non-state maintained high volume Federal Aid Routes; bringing the total number of short term counts to 48,000. The coverage count program operates on a three-year cycle, counting one-third of all sections annually. Meeting this need requires that 10,000 counts be collected on the state-owned route system and that 6,000 counts be collected on the non-state owned Federal Aid Route System each year. INDOT uses portable classifiers whenever possible; 65 percent of all coverage counts are classified counts. Additional counts are taken within this program to support specific state projects. In addition, INDOT also contracts with Metropolitan Planning Organizations (MPOs) to collect coverage count data.