Exploring Driving Behavioral Characteristics in Pre-, In- and Post-Conflict Stages Based on Car-Following Trajectory Data

A conflict consists of different stages, and a previous conflict may have an impact on the following one because of the existence of memory effect from the recent driving maneuver and risky conflict experiences. In this study, we aim to explore driving behavioral characteristics of different stages of rear-end conflicts using vehicle trajectory data. The NGSIM trajectory dataset is adopted and three conflict stages (i.e., pre-, in-, and post-conflict) are defined based on time-to-collision (TTC) indicator. Four indexes are selected to capture the within-group and between-group characteristics of the different conflict stages. Results indicate that the number of dominant driving characteristic categories and the predictive importance of selected indexes vary in the different conflict stages. Besides, there is a heterogeneity in the driving behaviors, as seen from the differences among different clusters in the same conflict stage. In addition, most drivers slow down in the in-conflict stage and continue to decelerate thereafter, while the speed reduction magnitude decreases as the conflict stage progresses. About the reaction time, most drivers facing a conflict become insensitive and the drivers mainly react faster in the post-conflict stage. Additionally, an insufficient space gap could cause a rear-end conflict because of the smaller space gap in an in-conflict stage. Findings of this study are expected to provide a valuable perspective to deeply understand the driving behavior of human-driven vehicles by exploring the within-group and between-group driving characteristics of different rear-end conflict stages.