Effect of Encroaching Vehicles on Saturation flow at Signalized Intersections in Mixed Traffic conditions

Saturation flow is the most significant parameter used in the design of signalized intersections. Reliable estimation of saturation flow is essential in order to evaluate level of service and capacity. The aim of the present study is to find out the effect of encroaching vehicles (vehicles standing beyond the stop line when red is given to that particular approach) on saturation flow and capacity at signalized intersections in mixed traffic conditions. In the present research work, from the regression analysis, two separate saturation flow models are developed from significant variables: approach width, proportion of two-wheelers and cars, one with considering encroaching vehicles (considering vehicles passing through reference line 2) and another without considering encroaching vehicles (considering vehicles passing through reference line 1 (stop line)). The data are collected from five signalized intersections: Suchitra, Malaparamba, University Cross roads, Gandimaisamma and Kazipet railway station Intersections in India. Saturation flow corresponding to 30 signal cycles are considered for each approach at selected five intersections, of which 20 cycles data are used for model calibration and 10 cycles data are used for model validation. The developed models showed variation in saturation flow with and without consideration of encroaching vehicles. The model which is developed considering encroaching vehicles is showing higher saturation flow value than the other one without considering the encroaching vehicles.