Driver Behavior on Exit Freeway Ramp Terminals Based on the Naturalistic Driving Study

Using trip data from the SHRP-2 Naturalistic Driving Study (NDS) database collected at 12 sites in three states across the United States, this paper investigates driver behavior at freeway exit ramp terminals. First, the study qualitatively assesses driver speed behavior as they navigate the speed change lane (SCL) and the ramp. Starting at the beginning of the SCL and continuing after diverging onto the ramp controlling curve, a trend of continuous vehicle deceleration was evident, which continued throughout the SCL and ramp. It was also evident that a portion of drivers have a tendency to diverge onto the SCL on the taper and before the SCL has begun, where this behavior is dominant on the taper-type SCL. In general, statistical analysis revealed that the speed measures of driver behavior follow a normal distribution. The speed and deceleration measures at the study sites were statistically and significantly different, with the differences likely related to the geometric characteristics of each site. The data were then used to develop prediction models for the speed and deceleration measures. To account for the repeated measures induced by the same drivers in the dataset, linear-mixed models were developed for the speed and deceleration behavior measures.