SPEED ESTIMATION MODEL OF VEHICLE AT HORIZONTAL CURVES ON TWO-LANE HIGHWAY

In this study, 85th and 98th percentile speed estimation models of vehicle on two-lane rural highways were developed using a statistical technique of multiple regression. Models were developed using spot speed data obtained from five sites out of total eight and data of three remaining sites were taken into account for validation. Speed of vehicle at 50m initial to point of curvature, point of curvature, middle of the curve along with Geometric aspects of Horizontal curve and section adjacent to tangent were considered as independent variables. Car and SUVs speed for the 85th and 98th percentile was found to be parallel, so united for further analysis. Vehicle speed at middle of the curvature was found to be dependent on its speed at previous segment and geometric features predicted previously. Speed estimation of car and two-wheeler at middle of the curve was found to be strongly corelated with curve length and deflection angle. Gradient at particular locations was resulted to be a most affecting parameter for 85th percentile speed of HCV and LCV. The 98th percentile speed at middle of the curve were found in strong correlation with speed at 85th percentile speed. Root mean square errors were calculated to be within range of 2 to 8 km/h. study concluded that length of curve could be a very significant factor in the practice of highway geometric design.