EVALUATION OF THE EFFECTS OF COMBINING DIFFERENT SIGNAL PRIORITY RULES AND BUS OPERATION AT THE SIGNALIZED INTERSECTION

Abstract

Recently, many metropolitan governments in the world have invested significant amount of budget in the extension of infrastructures and development of new public transportation system to overcome urban transportation problems specially traffic congestion resulting from ever-growing numbers of automobiles6). Among public transportation modes, the public buses have been contributing an important role to provide access to most urban centers serving as a main mode as well as feeder mode for passengers. Thus, the improvement of existing public bus system to provide efficient public bus service is a low capital cost measure for reducing automobile dependence of the metropolitan areas. But, buses share same road with other traffic and need to stop frequently for passenger boarding and alighting. The interaction of buses with other traffic reduces their speed. Furthermore, most of urban activities and developments are concentrated around intersection. The increased activities make it an ideal location for bus stop, thereby producing heavy pedestrian flow, illegal parking etc. Also, intersection is signalized for improving safety and effective movement of conflicting vehicular and pedestrian traffic flows through the intersection at the cost of delay to traffic. As a result, buses suffer significant amount of delay at signalized intersection. Consequences are reduced speed and highly varied travel time etc. Transportation experts are exploring different alternatives ranging from space priority; bus vehicle improvement etc. to the application of advanced Intelligent Transport System (ITS) technologies such as bus signal priority, advanced communication systems, automated scheduling and dispatch systems etc.9). Since Intersection delay is one of the main criteria for evaluating bus performance, Bus Signal Priority (hereafter BSP) have been considered broadly for improving bus service performance by reducing stopped delay of buses at signalized intersection. The form of BSP system in Japan, known as Public Transportation Priority System (hereafter PTPS), has been able to reduce bus delay by providing priority at traffic signals11). With invention of new technologies in the field of intelligent transport system, opportunities for new applications are still increasing for better performance. Moreover, improvements to bus services have been considered through number of bus operation controls such as fare payment system, infrastructure improvement such as bus lanes, queue jump lanes etc. Most BSP researches are independent with these bus operation controls. Rare studies have been made considering integrated approach of bus operation control, BSP and road igfrastructures management. Combination of those elements of transportation supposed to maximize BSP effectiveness. BSP system is usually evaluated in terms of travel time benefit to bus at the cost of travel time disbenefit to cross traffic. Different combination of the above mentioned elements will have different level of impacts on speed and travel time of bus, traffic on priority direction and traffic on non priority direction. The combination of these elements for different traffic condition, bus demand and different bus priority case is to be analyzed for finding significant benefits to bus with permissible impacts on other traffic. This paper aimed to consider four different conditional bus signal priority methods for bus stop operation and bus lane priority for different traffic volume. The different combination will have different travel time impacts which were compared for two objective functions e.g. travel time impact for traffic in priority direction and traffic in non priority direction. The CORSIM2' 1°) simulation package was used for the evaluation of those measures and their results were compared among those priority methods. The current