Reexamination of Directional Distribution of Highway Traffic

Abstract

The investigation presented in this paper considers the temporal and spatial characteristics of directional distribution of traffic on rural highways. A total of 60 highway locations, representing a wide range of traffic‐stream characteristics, were investigated. The results of this study clearly indicate that directional distribution varies from hour to hour during the day, day to day and month to month during the daily peak volume hours, and from one road type to another. In general, directional distribution does not remain stable even during the highest‐volume hours of the year. A sensitivity analysis was carried out to study the effect of changes in the value of design directional split on the number of highway congestion hours in a year. It was also found that, in some cases, the current practice of taking the value of directional split during the design hour as the design directional split can result in very large errors of estimates. A method was developed in this study to determine the design directional split for use in highway traffic analysis.