Real-Time Arterial-Friendly Ramp Metering System

To balance the benefits between the freeway and arterial users and also to prevent on-ramp queue spillbacks, the authors have developed an arterial-friendly local ramp metering control (AF-ramp) system for time-of-day operations during recurrent congestion. This study presents the real-time version of the AF-ramp (named RAF-ramp) system, with a lane-group-based macroscopic traffic module for predicting traffic state and for executing control strategies, aiming at maximizing the total throughput from the control area, comprising the ramp meter and nearby local intersection signals. Recognizing the discrepancy in the dynamic nature between ramp traffic and arterial flows, the RAF-ramp system with its embedded traffic state prediction and monitoring mechanism can trigger the concurrent optimization of both controls when justified to do so, or only dynamically adjust the ramp metering rate under the pre-optimized local signal environment. The results of extensive simulation experiments have confirmed that the proposed system outperforms the widely-applied real-time ramp control model, ALINEA/Q, under various experimental traffic scenarios, because the produced control strategies can effectively utilize the freeway's weaving capacity and also best coordinate neighboring intersections' signals to maximize the entire network's performance. Such a real-time arterial-friendly ramp metering system, addressing both the time-varying freeway dynamics and the concerns of local traffic users, may well serve as an effective tool for contending with bottlenecks at freeway interchanges.