Saturation Flow Rate at the Work Zone–Straddled Intersections with Interweaving Movements: Lane-Based Modeling Study

Abstract

This study explored how the presence of work zones could influence the saturation flow rate (SFR) prevailing at an intersection. Specifically, it researched construction-ridden intersections with interweaving movements (CIWIMs) of vehicle flows that proceed across the stop line and down the connective lanes on the downstream approach to the adjacent intersection. First, image recognition and tracking algorithms were used to extract 2,545 vehicle trajectories from the video captured on-site. Then, the trajectories were manipulated based on lanes to obtain the saturated headway time of the entry-lane stop line during effective green time and the variables related to lane-change behaviors after passing the stop line (e.g., lane-change percentage, lane-change position, lorry percentage, and average passing speed). In addition, certain linear and nonlinear regression methods were employed to estimate lane-focused SFR models in a parsimonious fashion. Subsequently, the Highway Capacity Manual (HCM) model, along with Schroeder’s model, was pairwise compared with the newly proposed Box-Cox model for validation. The results indicate that the mean errors are 28.86% and 17.70% for the HCM and Schroeder’s models, respectively, while the estimation error for the Box-Cox model is merely 7.20%. This sensitivity analysis reveals that the proportion of bidirectional lane changes, spatial use rate of lane changes, and proportion of heavier vehicles significantly compromises the CIWIM-based SFR. One important finding is that the models accounting for microscopic channel-change behaviors, with higher estimation accuracy compared with existing models, can also be used for traffic simulation parameter calibration and road delay estimation to obtain higher validity and precision.