# Urban Traffic State Sensing and Analysis Based on ETC Data: A Survey
### Research Opportunities  
Although ETC systems have achieved large-scale deployment and application nationwide, their primary application has been in highway scenarios, with their potential value in urban traffic management far from being fully exploited. Current ETC applications mainly focus on toll collection functions, while the massive high-quality traffic data resources generated remain largely \"dormant,\" lacking deep mining and systematic utilization.  
From the perspective of technological development, ETC system construction has provided important infrastructure support for urban traffic digitization transformation. As of 2023, China has built and networked 29,500 ETC gantries and 250,000 license plate recognition devices on highways, successfully constructing and optimizing the world's largest highway ETC system that operates safely and stably, serving nearly 240 million ETC users. Meanwhile, China has approximately 12,000 toll stations with 96,436 toll lanes, including 42,554 ETC lanes. This massive infrastructure network provides a solid hardware foundation for data collection and analysis.  
From a policy perspective, the government has given high importance and strong support to the application of ETC technology in urban transportation. In February 2021, the Ministry of Transport officially issued the \"Notice on Launching Pilot Work for ETC Smart Parking City Construction,\" clearly proposing to strengthen the integrated development of \"ETC + Internet\" industries through the deep integration of emerging technologies such as big data, artificial intelligence, and 5G with ETC technology. The policy document particularly emphasizes creating a comprehensive ETC + industrial chain, including ETC + IoT (Internet of Things) sensing, ETC + intelligent connected communication, ETC + big data platforms, ETC + static traffic management, and ETC + vehicle owner services, forming a new data-driven urban traffic management service model [2].  
From a market demand perspective, urban traffic management departments urgently need more precise, real-time, and comprehensive traffic state sensing methods. Traditional traffic survey methods, such as manual observation and questionnaire surveys, are not only costly and inefficient but also have difficulty meeting the requirements of refined and intelligent modern urban traffic management. ETC data-based traffic sensing technology can achieve large-scale, high-precision traffic state monitoring at a relatively low cost, providing scientific and reliable data support for traffic management decisions.  
From a technological maturity perspective, ETC systems have achieved high maturity in hardware equipment, communication protocols, and data processing through years of development and improvement. Particularly, the standardized application of Dedicated Short-Range Communication (DSRC) technology has provided technical assurance for reliable ETC data collection and transmission. Meanwhile, the rapid development of emerging technologies, such as big data processing, artificial intelligence, and cloud computing, has created favorable conditions for the deep analysis and intelligent applications of ETC data [3; 4].