Yearly Variation of Directional Distribution of Highway Traffic

Abstract

Investigated in this technical note is the yearly variation of directional distribution of traffic on rural highways. A total of 60 sites located in the province of Alberta, Canada, are investigated. Two measures of directional split are computed for each of the study sites, and their variation is studied over a period of six years, (1984–1989 inclusive). The results of analysis indicate that, in many cases, the directional split observed on rural roads during a selected design hour (such as the 30th highest volume hour) may be subject to a large variation from year to year. The data presented also indicate clearly that design directional split which is the other method described in this paper, experiences much less variation from year to year. Because of its greater stability over time, the design directional split can be considered as a superior measure of directional split.