ANALYSIS OF ALSELMANI SIGNALIZED INTERSECTION IN BENGHAZI - LIBYA

Abstract

Intersections play an important role in the road network, where traffic flows in different directions converge. Because of their influence each other, disturbance of pedestrians and bicycle to vehicles, and the lost of green time for beginning and clearance and so on. The spectacular growth of vehicles, as of the most convenient mode of travel has brought in its wake problems of frustration, accidents, delays, queues, congestion and environmental degradation. This has generated a new branch of the circulation of knowledge, known as traffic management. The argument is gaining importance as vehicles whose population is increasing in recent years, and traffic problems become more alarming. In many situations of daily life, it addresses the problem of providing services to the requirements of random. Consider the simple case of drivers who arrive at a junction with traffic lights, if the arrival rate is high and the rate of supply is unable to cope, it is inevitable that increases in the queue. Delay occurred as a result. In fact, queuing and delays to traffic at intersections, especially at the traffic light is a common problem in dealing with urban traffic. In this perspective, it is necessary to apply appropriate management of traffic at critical intersections to minimize the effect of delays and queues for the global system of circulation. Thus, knowledge on methods of traffic management is essential. In the recent years vehicle ownership and traffic volume in links increase dramatically due to the continuous high speed growth , which cause traffic congestion of different level in Bengazi city.. The objective of this study is to evaluate the performance of intersection and make alternative solutions recommendation. The analysis is done by evaluating the performance of intersection, including the initial conditions of intersection by using Indonesian Highway Capacity Manual (IHCM 1997).so the traffic flow, Then saturation flow rates and delays of the intersection Finally, some countermeasures for enhancing the capacities of the intersection are proposed including channelization of the traffic flow in the intersection, drawing the traffic marking and line in the intersection, strengthen traffic safety education, improving traffic control method, regulation of pedestrians and bicycle flows at the signalized intersection and improving the safety facility and capacity at the signalized intersections and so on. The control was changed from two-phase to four-phase control during , leading to excessive queuing in the area. The calculations for four phase control shows the reason why, the Intersection flow ratio increases , and the degree of saturation becomes higher in all approaches during the studied peak hour. The reason to change from two-phase to four-phase control was probably that the there were many traffic accidents in the intersection. An alternative action would have been to increase the inter-green periods between the phases, and to keep two-phase control which obviously results in a much higher intersection capacity and better level of performance level.The advantage of changed to four phase: inevitably leads to an increase of the cycle time and of the ratio of time allocated to switching between phases (Intergreen). Although this may be beneficial from the traffic safety point of view, it normally means that the overall capacity of the intersection is decreased.