Estimation of Average Daily Traffic (ADT) Using Short - Duration Volume Counts

Abstract

The average daily traffic (ADT) is utilized as an important basic data in transportation and road sector to predict the future service level of the road based on the planned traffic volume and to determine the geometry of new roads. As the installation of traffic counters to obtain long duration volumes like ADT is expensive, carrying out a short duration survey and extrapolate the volumes to ADT would be more economical. Use of “Expansion Factor Method” to extrapolate short duration volumes to ADT will be discussed in this research. The analysis was carried out using 148 count stations located at national AA roads, dividing them into three categories based on their flow variations. The expansion factors for 1h, 2h, 3h, 4h, 5h and 6h durations and the best time interval to carry out the survey for each time duration were found. Using 37 locations the results obtained from the analysis were validated and the comparison between the actual ADT and the calculated ADT shows the results from the research are satisfactory.