Abstract: The development of expressway green energy systems holds significant importance and serves as a pioneering model for integrating renewable energy with transportation infrastructure, advancing the evolution of energy-transportation integrated systems. Establishing highly efficient and resilient expressway green energy systems has become an essential pathway for implementing both the "carbon peaking and carbon neutrality" strategy and the "transportation power" initiative, while fostering sustainable socioeconomic development. This study first outlines the typical architecture of expressway green energy systems and establishes a research framework for the field. Subsequently, it examines three critical technical challenges: optimal planning, energy management, and operational control. The paper then investigates potential networking solutions for such systems. Finally, it synthesizes current scientific and technical challenges while providing forward-looking perspectives on future research directions for expressway green energy systems.