| Abstrakt: |
This paper investigated the effect of some traffic factors such as waiting time and traffic volume increasing on gap acceptance characteristics i.e., driver's behavior, limits of gap acceptance, critical gap, and the facility capacity. The current study depends on real field data collected at selected change direction U-turn within Najaf city highways network (center city of the Najaf governorate located approximately 160 km south of Baghdad, the capital of Iraq). The study focused on the passenger cars and minibus drivers maneuvering at change direction U-turn opening as the primary case study. The statistical analysis approach depended on evaluating traffic factors selected as parameters and their degree of influence on U-turn capacity. The results of statistical analysis established that firstly, waiting time range between 21 - 30 sec, lead driver to enforce opposing direction traffic flow to accept gap size less than that when waiting time fall in the range of 11 to 20 sec at a confidence interval of 95% for a passenger car. While, minibus shows results higher than passenger car by approximately 20%. Secondly, there is a slightly different mean gap acceptance between an interval of (1- 10) and (11-20) sec) for both types of vehicles at the same confidence interval. On the other hand, results showed the studied U-turn change direction median critical gap equal to 3.75 sec. and follow-up time was 1.1 seconds. According to Siegloch's formula the maximum capacity of 3273 pcu/hr. Other results show that the highest wait time group interval (when taken as the mean value) is lower than the critical gap. The main recommendation obtained due to the hazard of studied change direction U-turn is the importance of control and management it. [ABSTRACT FROM AUTHOR] |
