Estimating Base Saturation Flow Rate for Selected Signalized Intersections in Al-Najaf City

Abstract

The correct saturation flow rates for the specific circumstances must be used to calculate delays and the level of Service at intersections. As a result of a lack of local data, practitioners would often use default values from overseas software developers. Base saturation flow rate is an important factor for timing traffic signals. Despite the 1, 900 pc/h/ln number suggested by the Highway Capacity Manual (HCM), the base saturation flow rate differs from city to city, dependent on the local driving habits and traffic conditions. As a result, it's crucial to estimate, given the local climate. As a result, erroneous decisions may be made that have incorrect results. This study attempts to estimate the base saturation flow rate in Al-Najaf City. The following situations were observed: Turning movement (through or right); Gradient (Up and down); Number of through lanes; and Speed limit (60 and 80 km/h). The mean headway from a total of 9931 through moving vehicles from 187 lineups was calculated to be 1.55. The basic saturation flow rate was therefore determined to be 2, 323 pc/h/ln. This result is substantially higher than the 1, 900 pc/h/ln proposed by the HCM, but it is comparable to results from other nations with similar traffic conditions and driving habits. The results show significant differences between the saturation flow rates when the conditions of the movements are different in terms of the above characteristics. Recommendations are made regarding the most appropriate values to use under different conditions.