FHWA Publishes SEMCOG AADT-Calculation Case Study

As part of their Roadway Safety Data Program the FHWA recently published an interesting case study featuring one of MS2’s oldest and most technical clients, the Southeast Michigan Council of Governments (SEMCOG).  Titled “Innovative Traffic Data QA/QC Procedures and Automating AADT Estimation,” the case study focuses on AADT calculations – an important traffic engineering function to MS2 clients throughout North America.

According to the case study abstract, “This case study highlights two noteworthy practices at the Southeast Michigan Council of Governments (SEMCOG) regarding short-duration traffic count validation procedures and an automated annual average daily traffic (AADT) estimation process. SEMCOG maintains a centralized traffic count database and receives traffic counts from the local agencies in southeast Michigan. SEMCOG conducts 46 validity checks on all traffic count data to identify invalid data available in the database but not adequate for analysis.

After implementing the system, SEMCOG reduced labor costs associated with converting and entering data and was able to spend more time analyzing data. SEMCOG developed an algorithm that works inside its geographic information system (GIS) to improve AADT estimates by searching for uncounted segments with nearby counted segments. When a counted segment is identified, the algorithm calculates the weighted average of two nearby segments and assigns that AADT to the uncounted segment. This process was automated using Python scripts, which results in an increase in the number of AADT estimates without requiring additional field data collection.”