His relevant research work also includes: multimodal traffic control (assisted with machine learning and computer vision techniques), integration with decentralized route choice models and dynamic congestion pricing protocols, vehicle-to-infrastructure (V2I) communication with connected vehicles, energy efficiency optimization, and data-driven self-learning and active congestion management based on performance measurement.

The Smart and Scalable Urban Traffic Control system is a real-time, smart IoT-enabled adaptive traffic control system (in the sense of the Internet of Smart Intersections) that optimally schedules dynamic traffic flows in complex urban road networks, by integrating traffic theory with artificial intelligence (AI). Dr. Xie is the lead inventor of the system. He created the core control engine (the brain) of the system, including schedule-driven intersection control (SchIC) and decentralized coordination mechanisms. He has also designed and realized all strengthening strategies of the system to enable its real-world operations. Some extended work also includes: multi-modal urban traffic control (integrated with machine learning and computer vision techniques), integration with decentralized route choice framework, vehicle-to-infrastructure (V2I) communication with connected vehicles, energy efficiency optimization, and data-driven congestion and incident management.