Ramp metering revealed: a comprehensive literature review

Purpose The purpose of this study is to analyze and synthesize existing research on various ramp metering systems to evaluate their effectiveness in optimizing traffic flow, enhancing safety, reducing congestion, and identifying future research directions for integrating advanced technologies. Design/methodology/approach This literature review synthesizes research spanning several decades to evaluate the effectiveness of various ramp metering systems, including fixed-time, actuated, traffic-responsive and adaptive methods. Findings The success of ramp metering is contingent upon several factors. Public compliance is crucial, as resistance to ramp metering signals can diminish its effectiveness. Effective public education is necessary to convey the long-term benefits of smoother traffic and safer roads. Technological challenges, particularly regarding sensor accuracy and data processing, also present obstacles to system performance. Originality/value This study provides a comprehensive literature review on ramp metering as a traffic management strategy, showcasing its evolution and effectiveness over decades in optimizing highway entry rates, improving traffic flow, enhancing safety and reducing environmental impacts, while also addressing ongoing challenges and future opportunities for innovation.