Reliability Analysis of Freeway Speed Change Lanes Using Naturalistic Driving Study Data

This research investigates and models drivers' behaviour on freeway entrance and exit ramp terminals using SHRP-2 Naturalistic Driving Study (NDS) data from 24 sites located in three different US states. The research included first a qualitative assessment of the driver speed behaviour as they navigate the ramp and acceleration/deceleration speed change lane (SCL). A trend of continuous vehicle acceleration was evident from the beginning of the ramp controlling curve that continued after merging onto the freeway right lane (FRL). A similar finding was noted at exit ramps but with deceleration behaviour from the beginning of taper-type SCL that continued after diverging onto the ramp controlling curve. It was also found that at entrance ramps, a portion of the drivers tends to merge onto the FRL on the taper after the SCL had ended on acceleration. At exit ramps, a portion of the observed drivers tends to diverge from the FRL on the taper before the beginning of the deceleration SCL, with this behaviour being dominant on the taper-type SCL. Statistical tests showed that the driver behaviour measures in general follow a normal distribution at each site. Tests of hypothesis examined the differences of different driver behaviour measures on the study sites, and it was shown that the speed and acceleration/deceleration behaviour of the drivers differs on the different sites indicating that it depends on the complete set of geometric characteristics at the site. Linear-mixed models were developed for driver behaviour parameters such as the speed, acceleration, and deceleration, to account for the repeated measures caused by repeated trips by the same drivers in the dataset. Also, the research involved conducting a reliability analysis to evaluate the performance of acceleration SCLs, taking into consideration essential factors such as driver speeds and behavior, SCL and ramp geometric design, and traffic conditions.