AADT (Annual Average Daily Traffic Volume): What is the base?

11/05/2015
4 min read
Blurry cars with headlights on moving quickly on a multi-lane road at dusk.

When finding the best locations for business expansion, traffic metrics are used for understanding customers’ behavior and estimation of potential clientele. AADT, which stands for Annual Average Daily Traffic Volume, is being commonly used for business site analysis. For limited locations, AADT values are available from state DOTs. For most sites, though, prospective owners hire transportation engineers to generate a special analysis and report. Such a report is usually based on the use of portable hardware, e.g. tube counters or video detectors. A hardware installed for one, rarely 2 weeks, measuring traffic volume for 15-min or 1-h bins. AADT is being calculated as an average of measurements taken. Ticon estimates AADT on the basis on full-year monitoring. This case study is to understand the difference in results obtained by these two approaches.

Site and initial data for case study

Table detailing site location in Pennsylvania, USA, showing road type as secondary highway with signalized intersections, 2 lanes in each direction, 45 mph speed limit, 25754 tracks sample size, and study period from July 1, 2016 to June 30, 2017.

AADT according to:

• Tube counting 9144 vpd*

• DOT counting Y2014 6265 vpd

• Ticon 7526 vpd

*vpd – vehicles per day

Conclusion 1: Any attempt to establish AADT on the basis of week-long measurement shall cause significant error

Tube counter comparison chart showing monthly and weekly AADT values for two datasets; one averaged 7526, another 9144, with annotations indicating differences and similarities.

Conclusion 2: When using standard AADT, make sure it is current

Bar chart comparing VPD values with DOT AADT in 2014 at about 6200 and Ticon AADT in 2017 at about 7500.