ESTIMATION OF DEPARTURE HEADWAY AT UNCONTROLLED INTERSECTION

Abstract

An intersection is a node of highway network, and usually a bottleneck of traffic flow in highway network. Capacity of intersection restricts the total capacity of highway network. Traffic characteristics of intersection are more complex than those of road section, and the data are more difficult to obtain. Two general types of capacity analysis model have been used in unsignalized intersection; gap acceptance model based on probability theory and empirical model based on regression technique. Gap acceptance model is mainly used for theory analysis, and the evaluation of traffic performance. Based on gap acceptance theory, the number of vehicles in minor stream that can cross an intersection depends mainly on two variables, the distribution of headway in major stream and critical gap, follow-up time of drivers in c?v V4--the minor stream. In the present study, among various types of headway distributions, hyperlang ? distribution is used, as it was found to be best descriptor of headway under mixed traffic condition. For capacity analysismodel given by Li et al. (2003) is used. This model is an extension of earlier models for mixed traffic flow. Analysis shows that capacity reduces as types of vehicles increases in traffic stream. Model capacity is very close to field capacity when three categories of vehicles are considered.