Models of acceleration and deceleration rates on a complex two-lane rural highway: Results from a nighttime driving experiment

This study aimed to model driver’ deceleration or acceleration rates on a complex two-lane rural highway when approaching or departing horizontal curves under nighttime driving conditions. The data used in the study were from a field experiment conducted in Pennsylvania. Research participant speeds were continuously tracked along the experimental roadway. The deceleration and acceleration rate models when approaching and departing horizontal curves were treated as a uni-directional recursive system to account for the effects of upstream rates on deceleration and acceleration rates. This system was estimated using seemingly unrelated regression with random effects to account for the contemporaneous correlation across the two equations. Research participants were included in the model as random effects while several geometric roadway design features along the experimental roadway were included as fixed effects in the model. The results indicate that the explanatory variables associated with deceleration or acceleration rates when approaching or departing horizontal curves in the present experiment included several geometric design variables, such as curve direction, curve radius, horizontal curve length, and a vertical curve index. The deceleration and acceleration rates approaching and departing horizontal curves along the complex, two-lane rural highway included in this study have a larger range than those in past research studies of two-lane rural highways.