Method to Estimate Annual Average Daily Traffic for Minor Facilities for MAP-21 Reporting and Statewide Safety Analysis

Accurately determining Annual Average Daily Traffic (AADT) is critical to many transportation planning, operational, and design decisions. AADT is a key input to geometric design of highways, design of pavements, safety analysis, emissions and air quality studies, and validation of traffic forecasting models. . The most accurate way to determine AADT is from long term traffic counts obtained from Automatic Traffic Recorders (ATR) which count traffic volumes throughout the year. The state of Oregon has 177 ATR sites. The AADT at other roadway segments is estimated from short term traffic counts which are then scaled up using daily, weekly, or monthly adjustment factors. Traffic counts are expensive and labor intensive; extending short-term counts to cover all highway links will not be economical or practical.