The Relation between Saturation Flow Rate and Approach Width at Signalized Intersections in Erbil City

Intersection performance, capacity, and delay estimation can be determined from the relationship between lane width and traffic signal operations. The most important parameter that has influence on saturation flow at intersections is the geometric elements. Geometric elements are lane width, approach width, turning radius and grade. Moreover, there are other elements such as proportion of buses and heavy good vehicles, area type, vehicle type, turning movements, parked vehicles, pedestrian activity, time of day, vehicle position in the queue, and road surface condition. Several studies have been carried out to estimate the relationship between turning radius, lane width, approach width, and saturation flow. In this study, relationships concerning cycle time, green time, approach width, radius of left turn, and saturation flow are investigated at signalized intersection approaches by using field data in five selected intersections in Erbil City with the most possible ideal conditions. Research results indicated that the saturation flow rate varies with approach width, which has strong correlation. Average saturation flow rate was in the range from 1526 to 7081 pcu/h/lane group for straight through direction approaches with width of 2.85 to 10.875 m, and from 1253 to 3477 pcu/h/lane group for turning movement approaches with width of 2.7 to 7.0 m. While for total approach width, the average saturation flow rate was in the range from 3103 to 8779 pcu/h/app for approach width 7.5 to 17.5 m. Regression analysis was applied to find the relationship between saturation flow and approach width. Also, regression analysis for the through, and left-turn movements are performed. The relationship between left turn flow, the radius and approach width were found by using the multiple linear regression. All relations have reliable relationship with each other.