Speed Estimation Model of Different Category of Vehicle at Horizontal Curves on Two-lane Rural Highway

Abstract

In the study, Operating and Design speed estimation models of different class of vehicle on two-lane rural highways were developed using a statistical technique of multiple regression. Models were developed using spot speed data obtained for six sites out of total eight and data of remaining sites were taken into account for validation. Speed of vehicle at 50m starting to the 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 speeds at middle of the curvature was fond to be reliant on on the situation speed at previous segment and geometric features predicted previously. Speed estimation of car at middle of the curve was found to be strongly corelated through curve length and angle of deflection. The 98th percentile speeds 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 6 to 11 km/h. study concluded that length of curve could be a very significant factor in the practice of highway geometric design.