Driving simulation for design consistency

Drivers’ speeds were recorded on 32 tangent-curve-tangent configurations of four two-lane rural roads implemented in the CRISS (Inter-University Research Center for Road Safety) driving simulator. 147 driving tests were used for the analysis in order to verify if: a) the midpoint of the tangent and the midpoint of the curve are the most appropriate locations for speed data collection to evaluate the speed differential through the subtraction of operating speed on two locations; b) the speed differential obtained by the subtraction of the maximum operating speed on the last 200 m of the tangent and the minimum operating speed on the curve is significantly different from the 85th-percentile of the distribution of maximum speed reduction experienced by each driver. The results were the following. The maximum operating speed on the last 200 m of the tangent (V85max_200) is higher than the operating speed at the midpoint of the tangent. The operating speed in the midpoint of the curve overestimates the minimum operating speed on curve (V85min,c). A relationship between the point along the curve where the minimum operating speed is achieved and the geometric features of the tangent-curve transition was defined. Speed differential obtained using V85max_200 and V85min,c tends to underestimate the amount of speed reduction experienced by the drivers. Predicting models of the maximum operating speed on the last 200 m of the tangent, of the minimum operating speed on curve and of the 85th-percentile of the distribution of maximum speed reduction experienced by each driver were developed.