Speed Synchronization Process of Merging Vehicles from the Entrance Ramp Empirical Analysis

This paper explores the lane-changing preparation process, defined as the synchronization process, from a new, integrated perspective. A comprehensive study was conducted to analyze the behavioral characteristics of the speed synchronization process of merging vehicles from entrance ramps by tracking their trajectories in the merge lanes. On the basis of gap selection, merging vehicles were classified as either original gap type or overtaking type, and the existence of speed synchronization was proved by comparing the speed differences of merging vehicles in relation to the putative leader (PL) and the putative follower (PF) vehicles. Several rules of merging vehicles during speed synchronization were established in the behavioral study. The merging vehicles tended to maintain a speed 5 to 7 m/s higher than the speed of the PL sons to overtake unsatisfied gaps in the adjacent through lane. When those vehicles intended to accept a gap, they first adjusted their speeds to be within a 2-m/s difference from their PL and PF vehicles and then merged into the targeted gap within 2 to 3 s. Factors affecting drivers' tolerance of their speed with PL and PF vehicles were modeled with the multiregression method. Significant effects in speed synchronization include the number of rejected gaps, acceleration or deceleration, the speed difference between the PL and the PF, the time headway, the remaining distance in the auxiliary lane, and whether the PL is a merged vehicle. Results from this study may contribute to the understanding of the complex lane-changing behavior in microscopic traffic flow modeling.