Unveiling the Capacity Drop Phenomenon Through Traffic Microsimulation: Modeling, Calibration, and Sensitivity Analysis

The Capacity Drop (CD) is a sustained drop in a freeway bottleneck outflow when its upstream section becomes congested. Understanding how to replicate CD with microscopic models can help us to better understand its properties and mechanism. However, there is no published study replicating an observed occurrence of CD using microscopic models. In this study, we combine a lane-changing model with two widely known car-following models and calibrate the combined model parameters against field data, to replicate the CD in a merge bottleneck. We confirm that both car-following models can reproduce the CD. Moreover, we show that including the cooperative lane-changing behavior in the model is critical for the replication success. Further, we perform a sensitivity analysis with respect to the ramp demand and maximum acceleration parameters, showing: (i) slower acceleration rate leads to a lower bottleneck throughput, and (ii) higher ramp demand leads to decreased bottleneck throughput.