Safety-Critical Stabilization of Mixed Traffic by Pairs of CAVs
DOI: 10.23919/acc60939.2024.10644858
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Summary
This paper addresses the challenge of stabilizing mixed-autonomy traffic, where connected and automated vehicles (CAVs) coexist with human-driven vehicles (HVs), while ensuring formal safety guarantees. While previous research has demonstrated that CAVs can mitigate congestion and smooth traffic flow, existing controllers often focus on single CAVs or lack rigorous safety assurances regarding front-end collisions. The authors propose a control framework for a pair of CAVs—a head CAV (H-CAV) and a tail CAV (T-CAV)—traveling among HVs. The primary objective is to design nonlinear controllers that stabilize the traffic flow through inter-CAV coordination while using Control Barrier Functions (CBFs) to formally guarantee collision-free behavior. The methodology involves formulating the dynamics of a vehicle chain consisting of the H-CAV, $N$ intermediate HVs, and the T-CAV. The authors design stabilizing controllers for both CAVs that incorporate adaptive cruise control, state feedback from surrounding HVs, and coupling terms that allow the CAVs to respond to each other via vehicle-to-vehicle communication. Stability is analyzed in the Laplace domain by linearizing the system around an equilibrium state. The authors derive head-to-tail transfer functions to evaluate plant stability and string stability, the latter ensuring that speed perturbations attenuate along the vehicle chain. To enforce safety, the authors integrate CBFs with the nominal stabilizing controllers. This integration creates a safety filter, implemented via a quadratic program, that modifies the control input minimally to ensure the system state remains within a safe set, thereby preventing front-end collisions. The results demonstrate that the coordination between the two CAVs is critical for achieving string stability. Stability charts reveal that when the CAVs do not respond to each other, the system remains string unstable under certain conditions. However, introducing coupling terms in the controllers expands the region of stable control gains, allowing the system to attenuate perturbations effectively. The analysis shows that proper selection of control gains enables the simultaneous achievement of string stability and plant stability. Furthermore, numerical simulations confirm that the integration of the stabilizing controller with the CBF-based safety filter successfully maintains formal safety guarantees while improving traffic flow stability. The study highlights that the response of the head CAV to the tail CAV can significantly enlarge the range of parameters that achieve string stability. The significance of this work lies in its contribution to the safe deployment of CAVs in mixed traffic environments. By providing a control design that simultaneously addresses traffic stabilization and formal safety, the paper offers a robust solution for the transition period before full automation. The findings suggest that inter-CAV cooperation is not merely beneficial for efficiency but is essential for stabilizing mixed traffic flows. This approach enhances public acceptance by ensuring safety-critical behaviors, offering a scalable framework for managing multiple CAVs within communication range to mitigate congestion and prevent collisions.
Key finding
Coordinating the control responses of a pair of connected and automated vehicles enhances the string stability of mixed-autonomy traffic while control barrier functions provide formal guarantees against front-end collisions.
Methodology
simulation_modeling
Provenance
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| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | author_sweep | — | — | 2 | 2026-05-28 |
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| extract | success | cached | — | — | 3 | 2026-06-10 |
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| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-04 |
| enrich | success | — | — | — | 1 | 2026-05-28 |
| promote | success | — | — | — | 1 | 2026-06-04 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 2 | 2026-06-10 |
| tag | success | vector_similarity | — | — | 15 | 2026-06-11 |
| verify | success | — | — | — | 2 | 2026-06-10 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.
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