One of the main difficulties in China's current road traffic safety contradictions is that drivers on the road cannot obtain road traffic and environmental information about the position ahead in a timely manner, thus they cannot take evasive actions such as slowing down or changing lanes to avoid accidents before they occur. To address this issue, it is urgently necessary to develop and innovate a set of key technologies for active traffic safety warning through seamless high-precision vehicle positioning in cities. With the support of projects such as the National 863 Plan, National Natural Science Foundation, and National Science and Technology Support Program, after 12 years of joint research by academia, industry, and research institutions, this project has broken through the online location service and seamless high-precision vehicle positioning technology for active traffic safety warning in road domains, and has developed Beidou high-precision positioning vehicle terminals and high-precision lane-level road map generation systems with independent intellectual property rights. These have effectively supported the construction of an active traffic safety warning guarantee system based on high-precision location services in cities. Reduced the incidence of road traffic accidents. The main innovative achievements of the project are: (1) Constructed an active traffic safety model based on high-precision positioning, and proposed an index system for online location services in active traffic safety. For the first time, a systematic basic research was carried out on the foundation of active traffic safety warning models based on high-precision positioning, proposing real-time warning models for driving behavior states coupled with accident causes based on high-precision positioning, real-time traffic conflict risk assessment and warning models, and emergency accident warning models. A set of online location service index systems for active traffic safety was established, breaking through the technology of real-time collision warning based on instantaneous vehicle driving state conflicts and the spatiotemporal prediction technology for the persistence and dissipation of traffic accidents. Achieved large-scale application relying on basic research results for intellectual property transformation. (2) Developed a seamless navigation positioning system combining satellite navigation, visual navigation, and inertial navigation. We have independently developed a high-precision Beidou vehicle networking terminal aimed at active traffic safety. In response to the operating environment of road domain vehicles and the characteristics of sensor loading, we invented seamless multi-scale positioning and service vulnerability detection technology that integrates satellite navigation, visual navigation, and inertial navigation for road domain vehicles. We have developed the 'Beidou Instant Judgment' onboard terminal, which achieves low-cost consumer-grade electronic devices in urban complex environments with wide-area sub-meter level seamless positioning and proactive traffic safety warning services. It possesses lane-level positioning capabilities, proactive traffic safety services, and the function of collecting evidence of traffic violations. (3) We have developed a high-precision lane-level road network mobile collection and generation system that supports proactive traffic safety, and established industry standards for high-precision lane-level road network information collection that serve proactive traffic safety. A high-precision lane-level road network mobile collection system based on multiple sensors has been developed and implemented, inventing several technologies for automatic processing and generation of high-precision road maps, and establishing industry standards for surveying and mapping applicable to active traffic safety at the lane level. The project has obtained 20 authorized invention patents, 5 utility model patents, 1 appearance patent, applied for 6 invention patents, granted 29 software copyright licenses, one software product, published 69 papers, including 37 SCI-indexed articles, drafted 3 industry standards, and formed large-scale application products such as 'Beidou Instant Judgment' and 'Yishi Tong'. The achievements have surpassed 260,000 comprehensive demonstration users in Pudong New District, Shanghai, providing all-weather real-time safety supervision for 126,000 operating vehicles in Shanghai. The project has achieved integrated and scaled-up applications in cities such as Shanghai, Wuhan, and Ningbo, completed data sharing and docking with enforcement platforms like the Ningbo Public Security Traffic Police Bureau, and has secured over 300,000 market contracts. It has signed agreements with more than 10 insurance companies, including PICC and Sunshine Insurance. The implementation of this project has generated a direct economic benefit of 213 million yuan, and has also produced indirect benefits of 172 million yuan in key user units such as Tencent and Baidu. The number of traffic accidents involving inter-provincial passenger vehicles in Shanghai has decreased by 53.95% over the past five years, achieving significant economic and social benefits.