Driving Behaviors for Mitigating Capacity Drop at Freeway Sag and Tunnel Bottlenecks

Abstract

This study investigates driving behaviors for mitigating the capacity drop (CD) phenomenon, which means the queuing discharge flow rate is less than the traffic capacity before congestion, at freeway sag and tunnel bottlenecks. Specifically, exploiting a recent advanced continuum traffic flow theory that describes the CD phenomenon endogenously, we first propose two CD-mitigation driving behaviors and discuss their qualitative properties. We next examine the quantitative relationship between the penetration rate of the (autonomous) vehicle implementing each of the proposed driving behavior and the reduction of the queue discharge flow rate through theoretical and simulation analyses. It is then revealed that (i) the prevention of the slow speed recovery due to the sluggish car-following behavior (i.e., the compensation delay for gradient change) at the bottleneck section is essential to mitigate the CD and (ii) the improvement of the acceleration behavior downstream of the bottleneck of only some vehicles has limited impact.