Assumption of operating speed-profile models on deceleration and acceleration rates: verification in the driving simulator

Drivers’ speeds were recorded on 26 configurations of the tangent-curve-tangent transition of three two-lane rural roads implemented in the CRISS (Inter-University Research Center for Road Safety) driving simulator. 856 speed profiles of each individual driver were analyzed. The deceleration and acceleration rates experienced by each driver were calculated. The values of 85th percentile were subsequently obtained. The operating speeds on each configuration were also calculated. The mean value of the differences of speed of each driver between the beginning and the midpoint of the curve was not significantly different from zero, while that between the midpoint and the end was significantly different from zero. However, considering the low values of the differences of speed between the midpoint and the end of the curve (mean 1.3 km/h), the simplified assumption of the current speed-profiles of speed on the circular curve constant is considered admissible. Different average distances of deceleration and acceleration were found. That underscores the correctness of assuming different values of deceleration and acceleration rate, in accordance with the more recently developed operating speed-profile model. The 85th percentile of the deceleration and acceleration rates experienced by each driver were significantly higher than those obtained by the values of the operating speeds. Consequently, this latter methodology, used for developing the most advanced operating speed-profile model available in literature, leads to underestimating the rates effectively adopted by the drivers. Two models that predict the expected 85th percentile of the deceleration and acceleration rates experienced by drivers were also developed.