Smart highways have been a focal point in China's road transportation sector in recent years, garnering significant attention from government departments, highway operators, industries, and academia. A series of demonstration projects have been implemented, yielding substantial results. Currently, the field of smart highways still faces numerous challenges. There is an urgent need to integrate interdisciplinary theories, fully apply cutting-edge technologies represented by new-generation digitalization and artificial intelligence, and align with China's social structure, governance models, and practical needs. This will facilitate the transition from "information guidance" to "collaborative optimization" and further to "autonomous operation," thereby supporting the national goal of building a country with a strong transportation network and contributing to China's transportation modernization.

To this end, the editorial office of the Journal of Highway and Transportation Research and Development has organized dozens of domestic professors, scholars, and experts to systematically summarize the research, development, and applications in the field of smart highways and related areas over recent decades. Their work covers the evolution of smart highways, traffic information monitoring, key technologies in traffic control, traffic safety, vehicle-road coordination, and autonomous driving, while also offering insights into future prospects. This is a highly significant undertaking for the digital and intelligent development of China's highway transportation, providing a wealth of resources for academic research and technological development in related fields.

Smart highway refers to a highway system that comprehensively applies new-generation information technologies and intelligent technologies to achieve digital, networked, and intelligent upgrades of highway infrastructure, thereby significantly enhancing transportation efficiency, safety, and sustainability. Although the strategic importance is increasingly prominent, current studies predominantly focus on specific technologies or regional development analyses, lacking a systematic review and comparison of the global evolutionary trajectory of smart highways. By synthesizing the trajectories of representative countries and regions, e.g., the United States, Japan, Europe, and China, the evolution of smart highways can be understood as proceeding through several historical stages, ranging from the early period of emergence and exploration, to the rise of ITS, and further to stages characterized by cooperative vehicle-infrastructure systems and digital-intelligent development. The conceptual characteristics and technological connotations of various stages are investigated. The evolutionary process of system architectures across countries is analyzed, through which a development trend is revealed toward a physical hierarchy structured around the cloud-edge-end paradigm and a logical hierarchy centered on sensing-communication-computing-application. On this basis, key enabling technologies are summarized in the domains of sensing, control, safety, and vehicle-infrastructure cooperation. The findings are expected to contribute to a more comprehensive understanding of the concepts, architectures, and technological evolution of smart highways, while providing the theoretical foundations and decision-making references for technical roadmapping, standards development, and large-scale deployment.

The conventional traffic monitoring methods are struggling to meet the dynamic perception and management requirements in complex road network environments with the continuous expansion of China's road network scale and the rapid growth of traffic demand. Smart highways are the crucial component of national strategy for China's strong transportation network. To achieve this strategy, a comprehensive traffic information monitoring system, covering entire chain of perception, analysis and service, is progressively establishing. The system is driven by new-generation information technologies, e.g., Internet of Things (IoT), artificial intelligence (AI), and big data. Accordingly, this review conducted a systematic study on the core technologies and application scenarios of traffic information monitoring for smart highways. First, it analyzed the evolution status of multi-modal perception technologies from three aspects of roadside perception, vehicle-mounted perception, and collaborative perception, focusing on the key issues, i.e., multi-sensor fusion algorithm optimization, equipment deployment strategy innovation, and complex environment adaptability enhancement. Second, it analyzed the deep analysis framework based on cloud-edge-end collaboration, as well as studied the hierarchical processing mechanism for multi-source heterogeneous data. The intelligent traffic state recognition and prediction were achieved by integrating AI algorithms. Meanwhile, a hybrid solution combining encryption techniques and federated learning was investigated to address the challenges of privacy protection and data security. Third, considering the characteristics of urban and highway scenarios, it elaborated on the technical pathways and practical outcomes of service systems, e.g., traffic flow monitoring, incident response, and parking management. It revealed the application values of individual perception and new energy monitoring technologies in novel transportation paradigms. Finally, an integrated development strategy was proposed through the comparative analysis on differences between urban and highway systems in terms of information acquisition, data processing and service models. The strategy emphasized on standards and specifications coordination, data platforms integration, and service functions optimization. The study findings provide theoretical support and technical references for smart highway construction, facilitating the transition of transportation systems towards greater intelligence and efficiency.

With the rapid evolution of intelligent transportation systems, traditional highway systems are accelerating their evolution towards digitalization, networking, and intelligence, thereby giving rise to the concept of smart highways. A smart highway comprehensively applies new-generation information and intelligent technologies to upgrade highway infrastructure, significantly improving transportation efficiency, safety, and sustainability. As a key component of smart highway systems, traffic control technologies have become hotspots in current research and engineering practice. This review systematically reviews the research progress in ramp, mainline, special section, and coordinated control technologies for smart highways. It covers ramp metering methods including fixed-time, actuated, and adaptive strategies; mainline control approaches e.g., variable speed limits, part-time shoulder use, and high-occupancy vehicle lanes; control algorithms designed for special scenarios like construction work zones and tunnels; as well as coordinated control methods encompassing ramp-mainline and expressway-urban road interactions. This review identifies existing challenges in the adaptability of control algorithms, coordination of opposing traffic flows, and microscopic behavior modeling. Furthermore, the real-time performance and practical applicability of intelligent control systems require improvements. Finally, this review delivers future developments in smart highway traffic control from the perspectives of connected environment, intelligent algorithms, and multi-scenario coordination, emphasizing the trends of connectivity, intelligence, and collaboration. The study aims to provide theoretical guidance and research references for establishing efficient, safe, and sustainable smart highway traffic control systems.

Smart highways refer to the comprehensive perception and autonomous decision-making intelligent highway system constructed through the integration of new generation information technologies, e.g., big data, cloud computing, Internet of Things, and artificial intelligence. China’s highway mileage ranks the first in the world, but the traffic safety situation is still severe. The smart highway construction has become an inevitable choice to improve traffic safety, efficiency, and management capabilities. This study systematically reviews the research progress of theoretical methods and technological applications in the field of smart highway and traffic safety from multiple dimensions, e.g., human, vehicle, road, environment, and digital intelligence management. The focus is on exploring the research themes, i.e., road infrastructure and traffic safety, vehicle-infrastructure coordination and traffic safety, and digital intelligence management and traffic safety. The domestic and overseas comprehensive research and application practices indicate that smart highways can effectively reduce accident risks; however, there is an urgent need to break through issues, e.g., human-machine interaction complexity, data security, and technical standardization. By systematically summarizing the existing theoretical methods and technological application bottlenecks, it is proposed to deepen the research on mixed traffic flow theory, digital twin safety management system, and autonomous prevention and control technology in the future. It will provide the theoretical support and practical reference for the sustainable development of smart highway traffic safety.

With the continuous advancement of sensing, communication and computing technologies,and coupled with rapid deployment of intelligent transportation infrastructure, the cooperative autonomous driving is becoming a key development direction in intelligent connected vehicle (ICV) systems. This paper aims to systematically review the core technical architecture underpinning the integration of smart highways and cooperative autonomous driving, while summarizing the current progress and emerging trends in this field. First, it introduces the conceptual evolution of smart highways, their classification framework, and their functional role in supporting autonomous driving, along with representative development paths and engineering practices in major countries and regions. Second, it analyzes the development status and limitations of core single-vehicle autonomous driving technologies, highlighting their performance bottlenecks in complex scenarios. Third, the paper focuses on key enabling technologies for cooperative autonomous driving,e.g., vehicle-road-cloud integration, cooperative communication, sensor fusion, and joint decision-making and control;and discusses the challenges of multi-source data fusion and mixed traffic flow management. Finally, it reviews current testing and validation approaches for cooperative driving systems, and addresses the major issues in their engineering implementation, followed by an analysis on future development trends in smart highway-vehicle cooperative systems.

[Objective] In the context of global warming, the existing highways in permafrost regions of Qinghai-Tibet Plateau are facing a series of challenges, i.e., surface settlement, roadside water accumulation, groundwater saturation, melting interlayer thickening, and permafrost ongoing degradation. To address the severe challenges to in-service subgrade defects treatment and modification,it is urgent to propose more refined and adaptable design and disposal concepts beyond current design principles. [Method] The development of foundation design methods for permafrost regions abroad and the evolution of highway subgrade design methods for permafrost regions in China were reviewed. Based on latest field investigation data, the causes and contents, should be improved in current design system of subgrade settlement on existing highways in permafrost regions of Qinghai-Tibet Plateau, were analyzed. [Result] It is recommended to develop and enhance the third design principle, named proactively improving foundation conditions, based on the two existing principles, i.e., protecting permafrost and allowing permafrost thawing. The concept of treating permafrost foundation is introduced, along with a corresponding collaborative design method for pavement-subgrade-foundation system in permafrost regions. The influences of foundation property changes (induced by climate change) on subgrade deformation and stability are finely investigated. [Conclusion] According to the categorization, characteristics and engineering applications of treatment techniques for current subgrades, 0-3 m shallow foundations, and deep foundations over 3 m, the urgent technical challenges are highlighted, i.e., the refined hydrological and geological survey, the improvement on engineering geological evaluation index system, the establishment of long-term efficacy characterization system for permafrost foundation treatment methods, and the development of new treatment materials and equipment.