Evaluation of Driving Behavior at Roundabout: A Case Study in Bole Sub City

Abstract

The capacity of roundabout depends on several factors which include the high traffic volume of vehicle, geometry of roundabout, high pedestrian volume and driving behavior. This research focused on the study of driving behavior at roundabout and the factors that influence the priority right. Always, the vehicles that inside the roundabout have the priority right, while the vehicle that approaching to the roundabout have to wait and look for gap accepted. However, the driving behavior in Bole Sub City was different and many drivers did not give priority for the vehicle inside the roundabout. Due to this reason, the vehicles in the circulating flow have forced to stop and wait for gap to cross the roundabout. This behavior reduces the performance of the roundabout. The objective of the study were to describe the general characteristics of driving behavior at roundabout, to identify the percent of drivers who are familiar with traffic law at roundabout especially priority rule, to analyze the reasons behind that make drivers not to follow priority rule as well as to evaluate capacity of roundabout. The pivotal necessary for this study was used primary data such as geometrical or road data during site survey and field measurement comparing with HCM standard, interview and questionnaire, and secondary data were collected from traffic office and referring journals and books. Data analysis was made by aaSIDRA and SPSS software. The results were presented in the form of pie charts, bar charts, figures and tables. After analyzing driver survey data and questionnaire, the result showed that 85.8% of the study sample knows the base of priority right, while the practical results obtained from video analysis proved that only 42% of the sample gives priority right at the roundabout. Regarding to speed, the video result showed that, 47% of drivers did not reduce their speed when they enter to the roundabout and they drive beyond the permission speed. Based on questionnaire and field survey, the problem showed in Bole sub city roundabout was due to the several reasons such as inadequate island diameter, inadequate lane number and width, absence of geometric features of roundabout, inadequate circulatory lane width, driving over speed, high pedestrian volume and unfamiliarity with the knowledge of traffic rule at roundabout. Based on the result of aaSIDRA software, the studied roundabouts found in Bole sub city were under critical condition that all studied samples were categorized under LOS F according to Highway Capacity Manual. And it cannot handle the current traffic volume. It was recommended that the geometry of roundabouts must be revised and the education of traffic rule at roundabout have to be given to the drivers and pedestrians. By detail study, it was recommended that changing roundabout to traffic light control was preferable to reduce delay time and increase safety and capacity.