A Methodological Framework to Assess Road Infrastructure Safety and Performance Efficiency in the Transition toward Cooperative Driving

Tumminello, Maria Luisa; Macioszek, Elżbieta; Granà, Anna; Giuffrè, Tullio · 2023 · OpenAlex-citations

DOI: 10.3390/su15129345

archive: archived pipeline: cataloged verified

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Summary

This paper addresses the challenge of assessing road infrastructure safety and performance efficiency during the transition toward cooperative driving, specifically focusing on roundabouts. As connected and automated vehicles (CAVs) are expected to transform transportation systems, there is a critical need to understand how mixed fleets of CAVs and human-driven vehicles (HDVs) interact on curvilinear trajectories. The authors aim to fill gaps in existing literature by proposing a simulation-based methodological framework to evaluate the impacts of increasing CAV market penetration rates on roundabout capacity, safety, and efficiency, particularly when operating at high-capacity utilization levels. The study employs a six-step methodological framework applied to a two-lane, large-diameter roundabout in Palermo, Italy. The researchers built a microscopic traffic simulation model using Aimsun Next software. To establish target capacity values, they developed CAV-based capacity curves using adjustment factors from the Highway Capacity Manual, accounting for different CAV penetration rates (0% to 100% in 20% increments). The model was calibrated by comparing simulated data against these target curves, ensuring accuracy with a GEH index below five in over 95% of cases. Safety and performance were assessed using surrogate safety measures via the Surrogate Safety Assessment Model (SSAM). The experimental design compared mixed traffic scenarios against a base case of HDVs only, and further examined the impact of dedicating a specific lane to CAVs versus having CAVs and HDVs share lanes. The results indicate a general improvement in roundabout performance with the introduction of CAVs compared to the HDV-only baseline. The analysis demonstrated that CAVs, utilizing cooperative adaptive cruise control (CACC), can safely accept smaller gaps than human drivers, thereby increasing entry capacity and throughput. The framework successfully identified parameters governing cooperative driving behavior on roundabouts, showing that higher proportions of CAVs lead to reduced delays and improved traffic flow. Additionally, the study provided insights into the safety benefits of dedicated CAV lanes, highlighting that separating automated vehicles from human-driven traffic can further enhance operational efficiency and safety metrics. The significance of this research lies in providing transportation engineers and decision-makers with a validated tool to assess the level-of-service of road infrastructures during the gradual transition to smarter mobility. By offering a stepwise approach to model mixed traffic interactions, the paper helps bridge the gap between theoretical CAV benefits and practical infrastructure design. The findings support the integration of CAV technologies into urban planning strategies, emphasizing that proper assessment of safety and efficiency is crucial for managing heterogeneous fleets and optimizing roundabout operations in future transportation networks.

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• intersection design