A Study on Deriving of Adjustment Factor to Estimate AADT
Sunghan Lim, Ju-Sam Oh · 2004
Two methods currently exist to obtain AADT (Annual Average Daily Traffic). One is to install a traffic data collection system at a specific point on the highway for a permanent count, and the other is to estimate the AADT by counting traffic volume over a short period of time. This study deals with the methods for implementing monthly and daily adjustment factors to estimate AADT reasonably by a temporary (or coverage) count data. It involves three methods of deriving adjustment factors. One is the traditional method based on cluster analysis of adjustrment factors (method 1), the other is the method based on permanent traffic data collection system (method 2), and the third is the method based on shortest distance (method 3). Permanent traffic data in 2001 is utilized and three methods are compared by MAPE (Mean Absolute Percentage Error) index. MAPE of adjustment factors for three methods are that method 1 is 5.4%, method 2 is 4.6%, and method 3 is 4.8%, so method 2 is better than others. Method 2 is easy to apply, so it will be useful in practical affairs.