An experimental study was conducted to define a new model for estimating the speed differential value between tangents and curves, based on the speed profile of each driver along the tangent-curve transitions. The CRISS (Inter-University Research Center for Road Safety) interactive fixed-base driving simulator was used. A predicting model of the speed differential was developed by regression analysis of data recorded in 16 tangent–curve configurations. It shows that the speed differential value depends on the operating speeds, on the approach tangents and on the curve radius. The model was subsequently verified with the data recorded in 5 configurations of a real two-lane rural road reconstructed in the driving simulator. The comparative analysis of the proposed model and the predicting models available in literature shows that the new model avoids some criticalities of the previous models and is fully consistent with the expected driver behavior in the tangent - curve transition.
Keywords: design consistency; driver’s behavior; driving simulator; speed differential