Passing Rates to Measure Relaxation and Impact of Lane-Changing in Congestion

Passing rate measurements of backward-moving kinematic waves in congestion are applied to quantify two traffic features; a relaxation phenomenon of vehicle lane-changing and impact of lane-changing in traffic streams after the relaxation process is complete. The relaxation phenomenon occurs when either a lane-changer or its immediate follower accepts a short spacing upon insertion and gradually resumes a larger spacing. A simple existing model describes this process with few observable parameters. In this study the existing model is reformulated to estimate its parameter using passing rate measurements. Calibration results based on vehicle trajectories from two freeway locations indicate that the revised relaxation model matches the observation well. The results also indicate that the relaxation occurs in about 15 seconds and that the shoulder lane exhibits a longer relaxation duration. The passing rate measurements were also employed to quantify the post-relaxation impact of multiple lane changing maneuvers within a platoon of 10 or more vehicles in queued traffic stream. The analysis of the same datasets shows that lane-changing activities do not induce a long-term change in traffic states; traffic streams are perturbed temporarily by lanechanging maneuvers but return to the initial states after relaxations.