In order to ensure personal safety, overvoltage protection devices (OVPD) are usually installed in stations and depots of operating lines. However, the overvoltage generated during the reset of the rail potential limiting device may cause the OVPD section II to act or even lock, resulting in the rail potential limiting device short circuiting the ground and rail, becoming a path for stray current leakage. With the continuous increase of urban rail operation mileage, stray currents have caused serious problems such as DC bias in the surrounding power system and corrosion damage to the urban pipeline network, which have seriously threatened the safe operation of the power system and oil and gas system. This paper proposes a suppression method for the overvoltage caused by the misoperation of the rail potential limiting device caused by abnormal rail potential, which exacerbates the leakage of stray currents in urban rail transit. The method involves constructing a simulation model of the overvoltage generated by the OVPD opening of the rail potential limiting device, constructing an arc experimental platform using N1250 contactors, and conducting grid mounted testing on actual lines. The results show that after using the overvoltage suppression method proposed in this article, the peak operating overvoltage generated by the opening of the rail potential limiting device is significantly reduced, reducing the possibility of OVPD misoperation and stray current leakage.

Considering the problems of the difficult data collection, nonstandard models, and inaccurate data in the digitalization of existing buildings, the BIMbased digitalization method for existing rail transit projects was studied and proposed, according to the characteristics of rail transit projects. First, based on data requirements of the operation and maintenance management, an overall framework for BIM digitalization and scenario applications in existing rail transit projects was developed. Second, the technical guideline for BIM modeling and delivery was studied and established, and a BIM component standard library was developed to standardize the creation of BIM models of existing rail transit projects. Third, according to the onsite data collection situation, different methods were adopted to create BIM models of existing rail transit projects. When the drawings were complete, models could be created based on the drawings. When some drawings were missing, the BIM model creation method based on the on-site images and point cloud data was studied through component feature recognition and matching component units in the BIM component standard library. Finally, to ensure the quality of BIM models, a compliance checking tool with embedded BIM standard specifications was developed for automatic model verification. Additionally, on-site inspection was conducted for various professional BIM models. The BIM construction of existing operating lines in Shenzhen Metro is being carried out, accumulating BIM-based digital assets, which provides reference for the BIM construction of existing operating lines in other cities.

The Autonomous Train Operation System (TACS) is the development direction of future urban rail transit signal systems and is partly being applied in some urban rail transit. Different from traditional CommunicationsBased Train Control (CBTC), no unified TACS standard has been established yet. This paper aims to analyze the engineering applicability of existing TACS system degradation schemes. Based on the working principle of TACS, this paper discusses the necessity of configuring a degraded system. Drawing from the current development status of the TACS system, this paper summarizes three feasible TACS degradation schemes, introduces the architectures and working principles of different degradation schemes, and qualitatively analyzes the three TACS degradation schemes from the aspects of system composition, application scenarios, and tracking ability under degradation situation. The study establishes the train tracking time model under degradation situation, and simulates the degradation train tracking scenarios of three TACS degradation schemes under the same engineering conditions. Based on the simulation results, it identifies the factors that affect the efficiency of degradation tracking. Building on the above research, the key conditions for the TACS degradation system are summarized, and the engineering applicability and application effects of the three degradation schemes are analyzed, leading to several improvement suggestions. The results of this study have significant implications for the promotion and application of Train Autonomous Operation System.

This study addresses the current lack of experience in network operations of urban express lines based on fully automated operation technology in China, as well as the lack of corresponding operational reference standards and comprehensive technical solutions. Through the study of relevant literature and empirical analysis of the operation schemes of Chongqing Suburban Railway Bitong Line and Urban Rail Express Line 27, this study investigates the network scheduling, train planning, and train organization of urban express lines based on fully automatic operation technology. This study proposes the integration scheme of personnel (except train dispatchers) in the network dispatching hall and the arrangement scheme of multiple lines in the form of grouping under the network operation conditions of urban express lines interconnection. The study also proposes the establishment process and principles of the train operation plan, the operation organization principles under normal and abnormal operation scenarios, and the crossline operation scenarios between fully automatic and nonfully automatic trains. Through research, we aim to achieve an interconnected and network operation technology solution that integrates resources and improves efficiency across the entire line network, which is conducive to achieving automatic crossline operation between urban express lines, improving service levels, and promoting the construction of smart urban rail transit.

In response to the problems of insufficient crosslevel, crossstandard, and crossregional integration in the development of multilevel rail transit in the Guangdong Hong Kong Macao Greater Bay Area, empirical analysis methods were used to study the deepseated influencing factors from the aspects of policy system design, planning and construction, and coordination of operating entities. On the basis of analyzing the current situation and existing problems of multilevel rail transit development in the Guangdong Hong Kong Macao Greater Bay Area, this paper explores the successes, failures, and lessons learned from the development of multilevel rail transit in urban agglomerations at home and abroad. It proposes countermeasures such as establishing an integrated integration system mechanism and policy norms, strengthening integrated planning and construction management, promoting the integration of comprehensive transportation hubs, improving land support policies and investment and financing supporting policies, and establishing a multilevel rail transit operation enterprise alliance in the Greater Bay Area. The research results can provide a reference for the decisionmaking of multilevel rail transit integration in the Guangdong Hong Kong Macao Greater Bay Area.

This paper addresses the problem of mismatch with the surrounding urban renewal when applying the TOD stationcity integrated development model to domestic rail transit stations. Based on the classic nodeplace (NP) model and the introduced nodeplaceridership (NPR) model with passenger flow, this study takes Xi'an Metro Line 3 as an example. Relying on spatiotemporal big data, passenger flow data within 24 hours for six consecutive months are selected to calculate the basic indicators of 26 stations, which are classified into six categories: placeahead and low ridership, deficient and low ridership, matching and midlow ridership, nodeahead and midhigh ridership, nodeahead and midlow ridership, and saturated nodeahead and high ridership. This results indicate that Xi'an Metro Line 3 has the characteristics of a relatively higher node value and a lower place value. Given the identification of the same characteristics across the six station types, we propose precise matching strategies for placeahead, coordinated, and ahead type stations. Specifically, placeahead stations should prioritize connection with other transportation modes and pedestrian accessibility, coordinated stations should optimize supporting facilities and explore the potential of place features on this basis, and ahead stations should integrate resources to form railway microcenters. These three processoriented transformation measures can be applied to other regions and contribute to improved station function and service.

Electropneumatic braking is the most common braking method adopted by most urban rail trains. However, the disadvantages of poor controllability and slow response of air brakes result in inaccurate parking and poor comfort. In addition, there are issues, such as greater losses. The solution to address these issues is to replace existing air braking with electric braking, which is an ideal solution. Based on the development history of full electric braking, this study elaborates on the current situation and the main problems that must be overcome in the application of full electric braking. From the perspectives of high and low speeds, this paper provides a detailed introduction to the difficulties in achieving full electric braking and their corresponding solutions. Each difficulty is analyzed and summarized, and future development directions are discussed.

To monitor rail health in realtime and provide early warning of rail fracture damage, this study proposes a broken rail detection method that combines ultrasonic guided wave detection and variational mode decomposition signal processing technologies. The system workflow and hardware circuits of each module were designed and constructed according to the requirements for rail fracture detection. A threedimensional rail model was created using finite element simulation software to analyze the propagation speed of ultrasonic guided waves within the rail and assess the feasibility of the noise reduction technique. The system's effectiveness was verified through equipment installation tests on Suzhou Metro Line 5, where artificially simulated rail fractures were used. The results demonstrated that, upon rail fracture, the system achieved a remote alarm time of 3 minutes and the defective positioning error is 1.1%, providing a reliable approach for rail fracture monitoring.

To verify the effects of rail damping devices in the rail corrugation treatment for vibration reduction tracks, rail damping devices were added to a laddertype sleeper track and a steelspring floating slab track, respectively, in this study. The vibration and trackside noise characteristics of the two vibrationreduction tracks were reported, and the development of rail corrugation was tracked. The results show that the rail damping devices installed on the laddertype sleeper track can achieve positive effects in vibration and noise reduction in a wide band range, which can reduce rail vibration and trackside noise by 9.7 dB and 11 dB (A), respectively. The rail damping devices installed on the steelspring floating slab track can reduce rail vibration and trackside noise by 8.3 dB and 3 dB (A), respectively, within their operational frequency range. Longterm tracking tests revealed that the installation of rail damping devices can at least halve the rate of rail corrugation development on vibration reduction tracks.

To explore the impact of travelers' subjective spatial perceptions on travel behavior in the context of distinct urban terrain, this study takes Lanzhou, a typical rivervalleytype city, as an example. It establishes an integrated model of SEMLogit and explores the impact of the spatial perception of rivervalleytype city travelers on rail transit travel mode choice based on questionnaire data. The results show the following: ① Compared with the logit model without considering travel space perception, the goodness of fit of the logit model considering travel space perception by SEM increased by 0.234, and the prediction accuracy increased by 7.75%. ② The spatial perception of travelers in rivervalleytype cities has a significant positive impact on the choice of rail transit travel intention and behavior. ③ The spatial perception of travelers in the rivervalleytype city from five aspects, including the unnecessary detour, rivers in the river-valley-type city, wasp waist blockage, convenience of inter-group travel, and degree of being affected by road slope, l significantly influences travelers in the river-valley-type city to choose rail transit. The degree of influence decreases sequentially among these factors.