Operating speed predicting models on two-lane rural roads from driving simulation

This paper shows the results of an experimental survey carried out using the interactive driving simulator of the Interuniversitary Research Center on Road Safety with the objective of: evaluating how crosssection width affects driving speed; validating the data obtained from simulation in order to define predicting models for operating speed (V85); proposing new predicting models for V85, differentiated for cross-section width. An alignment of a two -lane rural road was designed and implemented in a driving simulator with three cross-section widths. 32 drivers were selected in order to have a homogeneous set of people. Each driver performed the simulation drivings on the three two-lane rural roads with different cross-sections. The speeds were sampled every 5 meters along the alignment. The analysis of data highlighted how the driver’s choice of speed is affected by cross-section width. The way the driver adjusts his speed on the different design elements along the alignment is not affected by the cross-section width but only by geometry of axis of the alignment. In order to predict operating speed, the validation of the data recorded in driving simulations was performed through a comparison of the simulation results against Lamm-Institute for Highway and Railroad Engineering model. The study proposes some relationships between Curvature Change Rate of the Single circular curve with transition curves (CCRs) and V85 to predict operating speed on two-lane rural roads with different cross-section widths.