Evaluation and Improvement of Signalized Intersections in Amman City in Jordan

The main objective of this study is to evaluate and improve the traffic operations at the signalized intersections in Amman city in Jordan. Wadi-Saqra signalized intersection was chosen for this study. This intersection is located in the western central part of Amman the capital of Jordan. It has heavy traffic volume, with higher delay and heavy congestion traffic more than any other similar intersections in Amman. In this study, the intersection is analyzed as an isolated signalized intersection by using HCM (Highway Capacity Manual) and HCS (Highway Capacity System) computer program. Synchro computer program is also used for improvement through optimization process. The geometric, traffic and signalized data were collected during the morning and afternoon peak time periods. The results indicated that the current delay is 473 sec/veh with Level of Service F (LOS-F). Four alternatives are recommended to solve the current and future problems. The recommended alternatives are: Prohibit left turning at all approaches.Optimization of the existing traffic signals.Construct one through overpass for one direction.Construct two overpasses or one overpass and tunnel for two directions. The first three alternatives will not be able to reduce the level of service significantly. On the other hand, the fourth alternative will reduce the level of service from LOS F with (473 sec/veh) delay to level of service LOS C with (27 sec/veh) delay and will change the cycle length from 190 seconds to 90 seconds. The estimated initial cost of constructing two overpasses is about thirty million Jordan Dinars JD with annual saving of more than eight million JD. If alternative four was selected to solve the existing situation the following advantages can be attained: reducing the congestion on the signalized intersection especially during peak hours, reducing the cost of traveling for the public, increasing the efficiency of the road network, increasing safety, reducing the maintenance cost of the roads, improving traffic flow and traffic operations, and reducing air pollution and preserving the environment. Key Words: Environment, Air Pollution, Traffic Safety, Traffic Flow, Capacity, Level of Service, Signalized Intersections, Intersection Delay, Traffic Control, Intersection Design