Challenge
The 7-km Xuefengshan Tunnel on Hunan's G60 Expressway—the province's longest highway tunnel—required a reliable all-weather monitoring solution after 17 years of service. Conventional CCTV systems struggled with poor lighting, exhaust fumes, and multipath reflections from tunnel walls, making it difficult to continuously track high-risk "two-passenger-one-hazard" vehicles and detect incidents quickly on this busy route.

Solution
A network of ClairWav-U24 tunnel radars was deployed at 350–400 m intervals along the entire tunnel. Key technologies employed:

• MIMO antenna arrays + super-resolution angle estimation – effectively suppress multipath ghosts and accurately assign vehicles to lanes, even on curved sections.
• AI-based clutter filtering – distinguishes moving vehicles from static infrastructure and debris.
• Kalman-filter trajectory tracking – maintains continuous vehicle IDs across overlapping radar zones, ensuring seamless lifecycle tracking from entry to exit.

Each radar tracks up to 128 targets over 400 m, providing real-time position, speed, lane occupancy, and vehicle length classification.

Data Fusion & Monitoring
Data from all radar nodes is stitched into a central platform to generate a unified 7-km traffic status map, updated every 500 milliseconds. The system delivers:

• Macroscopic metrics: section traffic volume, average speed, density, and occupancy per lane.
• Microscopic tracking: continuous, uninterrupted monitoring of every "two-passenger-one-hazard" vehicle throughout its tunnel journey.
• Real-time heatmaps: congestion levels visualized per 100-meter segment.

Incident Response
The onboard AI detects and classifies events within ≤ 3 seconds, including:

• Stopped vehicles (stationary > 5 seconds)
• Wrong-way driving
• Sudden deceleration (< -4 m/s²)
• Lane-change violations in no-overtaking zones
• Slow-moving vehicles (< 40 km/h)

Alerts are instantly pushed to the traffic control center, upstream VMS signs, and emergency response teams with precise lane-level GPS coordinates.

Conclusion
The ClairWav-U24 radar system has transformed the Xuefengshan Tunnel into a smart, self-aware corridor. By overcoming environmental limitations and providing millisecond-latency, all-weather detection—with a special focus on dangerous-goods vehicle tracking and instant event alerts—it has significantly enhanced both safety and operational efficiency on one of Hunan's most critical expressway sections.