Accurate estimation of hourly traffic volumes on transportation networks is vital for transportation planning, operations, and analysis. For transportation planning, hourly traffic volumes, among other factors, dictate priorities in highway improvement plans and allocations of funds. For traffic operations, hourly traffic volumes on links affect signal timing plans, air quality estimation, and traveller information systems. For safety analysis, an accurate estimation for hourly traffic volumes will help in assessing safety of different locations in the transportation networks as well as risk exposure levels. There are many factors that affect the hourly proportion distributions. In general, these factors can be divided into two groups. Factors in the first group include geometric and operational features, socioeconomic characteristics, and land use patterns associated with the highway network. Any changes in these factors, over time and/or location, can affect the hourly proportion distributions. Factors in the second group include hour, day of week and month. They differ from the factors in the first group in that they are temporal in nature and their effects on the hourly proportions are distinctly cyclical. Hence the objective of this work is to investigate whether or not hour, day of week and month have interaction effects on the hourly volume proportions at freeway count stations, and further establish procedures to group these factors into manageable categories. In addition, this research also estimates hourly proportion models using land use data upstream and downstream traffic sheds of counting stations.
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