Data plays a crucial role in the successful deployment of urban rail transit large language models (LLMs). RetrievalAugmented Generation (RAG) technology emerges as a promising approach for developing industryspecific LLMs and mitigating hallucination issues. However, the lack of comprehensive industry knowledge bases hinders its effectiveness. This study proposes a novel framework for constructing a knowledge graphbased RAG knowledge base for urban rail transit LLMs. This framework consists of four key dimensions: classification skeleton, semantic benchmark, feature rules, and logical relationships. These dimensions are implemented through entity classification systems, terminology dictionaries, attribute libraries, and entity relationship tables, respectively. By incorporating industryspecific attributes for entities, this approach goes beyond the traditional subjectpredicateobject triple structure of knowledge graphs, resulting in a comprehensive and multifaceted representation of industry knowledge. This knowledge base serves as the core component of the RAG system, providing standardized, reliable, and traceable domain knowledge through a systematic pipeline of data collection, structuring, vectorization, and knowledge representation. This process significantly enhances the reliability and domain expertise of the content generated by urban rail transit LLMs, paving the way for a new era driven by both data and knowledge.

Addressing the current challenges in urban rail transit line reconstruction, such as insufficient network synergy, path dependency in equipment updates, and the lack of upgradability design, this study explores theoretical innovation directions. It proposes key strategies, including incorporating upgradability into the equipment performance evaluation system, decoupling equipment from lines for networkoriented reconstruction, and improving the overall network functionality through clustered line reconstruction. These theoretical innovations aim to systematically promote the reconstruction of existing lines, reduce the cost of equipment upgrades, improve maintenance efficiency, and drive the sustainable development of the urban rail transit industry. Based on the framework of Guidelines for reconstruction of existing urban rail transit lines in China, this study addresses critical challenges in urban rail transit reconstruction, including insufficient network coordination, path dependency in equipment upgrades, and inadequate upgradability design. It proposes a comprehensive theoretical framework with four key innovations: integrating "upgradability” into equipment performance evaluation systems; implementing networkoriented decoupling of equipment systems from physical infrastructure; enhancing overall network functionality through clustered line reconstruction approaches; and developing derivative, regenerative, and symbiotic systems for rail transit reconstruction based on the "productionlivingecology" theory of urban renewal. These theoretical advances provide systematic solutions to optimize network functionality, reduce equipment replacement costs, enhance maintenance efficiency, and promote sustainable development in the urban rail transit sector. The proposed framework offers valuable guidance for policymaking and implementation strategies in urban rail transit modernization.

With accelerating global urbanization, traditional rail transportation faces challenges in capacity bottlenecks and the need for efficiency improvements. The development of the lowaltitude economy, particularly Unmanned Aerial Vehicles (UAVs) and electric Vertical TakeOff and Landing aircraft (eVTOLs), provides new solutions for rail transportation systems. This paper explores the integration of the lowaltitude economy with rail transportation, analyzing its potential in improving urban traffic efficiency and promoting the development of smart cities. The paper discusses the key technologies and practical applications of the integration f perspectives: integration motivation, technological foundations, and application scenarios. By introducing visual perception, communication, control, multisensor fusion, and safety technologies, the lowaltitude economy can enhance inspection efficiency, construction monitoring, and emergency response capabilities within rail transportation systems. This paper aims to provide a practical discussion on the integration of the lowaltitude economy and rail transportation, further advancing the development of smart city transportation systems.

This studyexplores the impact mechanism of population socioeconomic, land use, station characteristics, and other transportation attributes on rail transit passenger flow. Using multisource data including LandScan population grid, points of interest (POI), and automatic fare collection system (AFC), a spatiotemporal geographic weighted regression, gradient boosting regression tree, Shapley addition explanatory (GTWRGBRTSHAP) model, was developed to analyze the spatiotemporal heterogeneity and nonlinear effects of the these factors. A case study was conducted using data from Tianjin rail transit network, and the results showed that the mixed model effectively captures the spatiotemporal heterogeneity and nonlinearity between influencing factors and passenger flow. Factors such as population density, officetype land, shopping and leisure land, and betweenness have significant spatiotemporal differences in their impact of passenger flow. Factors such as residentialtype land, transportation facility land, land use entropy, and betweenness have significant complex nonlinear and threshold relationships with passenger flow. The above results provide strategic references and theoretical support for optimizing public transportationoriented urban development (TOD) planning and improving the efficiency of rail transit passenger flow.

The Virtual track train (VTT) has been put into commercial operation as a new type of urban rail transport in China in recent years. To further understand VTT's operational performance, it is essential to develop a specific driving simulation platform to simulate VTT's unique hybrid autonomous/manual driving mode. The main contributions of this paper are as follows: First, a vehicle system dynamics (VSD) model of VTT was established using SIMPACK. Additionally, the control module for simulating the hybrid autonomous/manual driving mode of VTT was developed based on model predictive control and Logitech driving simulation hardware. Furthermore, a driving scene visualization interface was established using Unreal Engine and Blender to simulate the real driving environment. These components form a comprehensive simulation platform for the VTT. Simulation results demonstrate that the developed platform can effectively and accurately simulate the operational performance of the VTT under various driving modes, highlighting its significant engineering value.

Guided by the need to address the shortcomings of subjective selection and the mismatch between capacity and demand in the selection of existing medium and low capacity urban rail transit standards, the standardized and procedural decisionmaking system for standard selection is developed. Firstly, the 4 criterion and 16 index evaluation system is established, considering constraints such as peak hour passenger flow, minimum transport capacity reserve, and the number of train operations. A multiobjective optimization model is constructed to determine the set of candidate rail transit systems. Besides, the CRITICTOPSIS algorithm is constructed to determine the weight coefficient values of each indicator and the optimal solution distance, thereby determining the optimal track system. Finally, using the Sline as the background for example verification, 5 alternative track systems are evaluated through a quantitative model. The CRITIC and TOPSIS algorithms were implemented using Python software. The decision values of rail transportation system rank in the order of selfguided monorail, crossseat monorail, light rail, guideway rubber wheel and low and mediumspeed magnetic levitation, indicating that the optimal rail system for line S is the selfguided monorail. Analyzing the standardized scoring matrix and index weight values of each type of rail system, the research results show that the model and algorithm proposed in this paper can effectively solve the problem of low and mediumcapacity rail transportation system selection.

To address the mismatch between urban rail transit construction and ridership efficiency in China, it is crucial to understand and master the influence laws of network ridership and improve efficiency. However, due to a lack of longitudinal data, research on the relationships between socioeconomic factors, network structure, and ridership remains insufficient. This study uses annual panel data from 2012 to 2020, calculates topological characteristics of the urban rail transit station network, and establishes a time fixedeffects model. The goal is to explore the topology of the urban rail transit network and its coupling relationship with urban layout effects on ridership changes, facilitating rational use of transit resources and improving core competitiveness. The results indicate that as the urban rail transit network develops, the complexity of the transportation network structure increases, and the number of interchange hubs rises, playing a crucial role in network connectivity. Changes in the topological variables of the urban rail transit network significantly enhance passenger flow; the densification of network distribution and regionalization of hubs help improve interchange connections and attract more passengers. The degree of coupling coordination significantly affects passenger flow changes; thus, the coupling relationship between population distribution and line layout should be considered according to local conditions in rail line network planning. Finally, this paper proposes relevant policy suggestions for rail transit network construction planning to provide a theoretical basis for urban rail transportation construction policy formulation.

This study systematically researches and discusses service quality evaluation for the construction of highdensity urban rail transit stations in the context of China's rapid economic and urbanization development. Based on the previous results, 21 evaluation factors in five dimensions, namely, environmental safety, business and service, spatial design, ecology, and humanistic care, are proposed in conjunction with field research and national standard documents. Field surveys are carried out with Shenzhen and Hong Kong metro stations, with a total of 553 valid questionnaires collected onsite, to study the importance of the service elements as well as the satisfaction of metro users as perceived by them. Through the IPAKANO model, this paper constructs the correlation matrix of implicit and explicit importance of service elements and determines the improvement priority of service elements in metro stations. The results show that the comprehensive scores of commercial diversity and station commercial condition elements are low, and the comprehensive scores of guidance system, station rest facilities, and entrance/exit design elements are high. Based on the results, this paper proposes a strategy for optimizing the design of metro station facilities and space based on service quality improvement in terms of different priorities and levels of importance. This paper innovatively applies the IPAKANO model to the optimization of service quality of rail transit stations, and constructs a more targeted evaluation system of service elements by combining the analysis methods of explicit and implicit importance.

Traction current return system is an important part of traction power supply system. System failures can damage primary and secondary equipment and potentially disrupt train operations. At present, there is limited research on realtime measurement of traction return current distribution for 25 kV AC power supply system subway. This study presents a synchronous testing methodology for measuring current in individual return cables to study return current distribution patterns and verify limitations in SCADA system monitoring. Based on return paths, the current is divided into three groups: station return, parking lot return, and ground return. The study analyzes the proportion and variation pattern of return current in different paths and compared findings with SCADA return current data. Results indicated that despite significant temporal fluctuations in return current magnitude, the distribution ratio remains stable most of the time, with only occasional variations. The average distribution ratios across different time periods vary by less than 1%. However, the SCADA system fails to accurately reflect return current changes. This research establishes return current distribution ratios through empirical testing, providing reference values for similar substations and directions for improving SCADA system monitoring capabilities.

This paper investigates potential applications of quantum communication technology in urban rail transit information systems, addressing current and emerging security challenges. Based on existing information system architectures in urban rail transit, we leverage the advantages of quantum key distribution networks for cryptographic applications and data security protection. The paper proposes integration strategies across multiple dimensions including secure computing environments, data storage, and data transmission. We specifically examine how quantum communication technology can enhance data security in computing environments, transmission processes, and storage systems. This research provides a framework for future applications of quantum communication technology in urban rail transit information systems.

This paper presents a comprehensive assessment of embedded rail technology implementation in existing metro line renovation through the case study of Xiaogang Station. The research examines the technical challenges, innovative solutions, and construction methodology employed in this pioneering project. The construction background, distinctive features, construction procedures, and solutions to the construction challenges encountered are introduced in detail. By comparing the preand postrenovation vibration, noise and Track Quality Index (TQI) on track, along with the monitoring of the postrenovation track condition, this study demonstrates the effectiveness of embedded rail track renovation in enhancing the performance of existing lines. The results indicate that this technology can significantly improve the vibration and noise reduction performance of the line while ensuring the continuity and safety of existing line operations.

Traditional fiber optic sensing methods mainly focus on onedimensional or twodimensional displacement monitoring of tunnel segments, making it difficult to effectively monitor threedimensional deformation between segment rings. This paper proposes a diamondshaped layout scheme based on distributed fiber optics, establishing a threedimensional deformation monitoring method suitable for shield tunnel segments. By analyzing the threedimensional deformation patterns of tunnel segments, three methods for calculating segment displacement are introduced. To validate the effectiveness of these methods, a simple and operable experimental device simulating threedimensional deformation of tunnel segments was designed, and indoor tests were conducted. The test results were compared with theoretical calculations, confirming the effectiveness of the proposed diamondshaped fiber optic layout for segment deformation monitoring, as well as the rationality of the three displacement calculation methods. The results demonstrate that the diamondshaped distributed fiber optic sensors, combined with the Kvalue decomposition method, provide optimal monitoring performance for segment displacement. The implementation of Brillouin Optical Time Domain Analysis (BOTDA) technology enables extensive realtime monitoring of tunnel segment displacement variations.

Relying on a subway station entrance and exit channel pipe jacking project, combined with the onsite monitoring data for jacking parameter inversion, the refined pipe curtaincorridorstrata pipeline corridor jacking finite element model considering the locking joints was established. The deformation of strata with and without pipe curtain is analyzed comparatively, and the necessity of pipe curtain is verified. Then, the effects of pipe diameter, pipe spacing and pipe thickness on surface settlement, pipe curtain cost and joint gap were systematically investigated through comprehensive tests, and a comprehensive evaluation system of TOPSIS was established to evaluate the adaptability of the pipe curtain with game combination assignment. Subsequently, BPNN was used to fit the mapping relationship between the pipe curtain parameters and the adaptability, and finally the genetic algorithm was used to search for the optimal parameter combinations. The study shows that the parameter that has the greatest influence on the adaptability of the pipe curtain is the diameter of the steel pipe, followed by the clear distance of the steel pipe, and finally the thickness of the steel pipe. Considering the safety, water resistance and economy, the recommended design parameters of the locking pipe curtain are the steel pipe diameter of 990 mm, the steel pipe thickness of 20 mm, and the steel pipe clearance of 160 mm.

In response to the maintenance needs of bridge bearing defects, existing bearing replacement methods all require jacking up the bridge to complete the bearing replacement, significantly impacting bridge structural safety and traffic operations. This study designs and manufactures a “lowmeltingpoint alloy bidirectional heightadjustable forcemeasuring bridge bearing, leveraging its bidirectional heightadjustable characteristics to develop a technology for replacing bridge bearings without jacking up the bridge. Against the backdrop of practical engineering applications, a comparison is made between the "bridge bearing replacement technology without jacking up the beams” and the existing “bridge bearing replacement technology with jacking up the beams." Utilizing this technology, bridge bearing replacement can be achieved without jacking up the superstructure, effectively avoiding stress changes in the bridge structure caused by jacking and enhancing maintenance efficiency and safety. Additionally, this technology is easy to operate, has minimal impact on traffic operations, and possesses broad applicability and promotional value.

An investigation into the current status of the smart operation and maintenance system for urban rail power substations has been conducted. The paper summarizes the challenges faced by the current comprehensive automation system scheduling and operation and maintenance methods of urban rail power substations, which are considered from aspects such as system architecture, hardware configuration, information conditions, dispatching mode, and operation and maintenance management. Requirements for the smart operation and maintenance system of urban rail power substations have been proposed. The overall framework of the smart operation and maintenance system for urban rail power substations has been designed; various independently constructed power supply subsystems have been integrated to form a unified dispatching and operation and maintenance platform, and the full life cycle data of equipment on both the power supply and distribution sides of the urban rail power supply system have been integrated. The smart operation and maintenance system for substations in the urban rail power supply field, which has been constructed, is applicable to the technical specifications of the urban rail cloud, addressing issues such as decentralized construction, inconsistent standards, and redundant investment in multiple subsystems and key equipment of the urban rail power supply system. It meets the current and future development needs of intelligent power supply systems.

The existing decentralized rectification scheme for direct current (DC) lighting systems in metro stations faces several challenges, including low power supply reliability and efficiency, high cable costs, significant distribution losses, and difficulties in unified equipment maintenance and power quality management. To address these issues, this paper proposes a centralized rectification scheme for metro station DC lighting systems. The study begins with an analysis of the system architecture, current status, and limitations of the existing decentralized scheme, followed by a detailed presentation of the proposed centralized solution, including its system architecture, DC power supply configuration, key components, and required system modifications. A comprehensive comparison between the two schemes is conducted using actual engineering data, focusing on system losses, costs, harmonic content, and operational reliability. The results demonstrate that compared to the decentralized scheme, the centralized rectification scheme requires less feeder cable usage and achieves lower system costs. It also shows significant improvements in reducing cable losses, increasing system power efficiency, and decreasing harmonic content. Furthermore, the power modules in the centralized scheme operate under more favorable conditions, leading to enhanced system stability. Based on these advantages, the centralized rectification scheme proves to be a more suitable solution for DC lighting systems in metro stations.

This paper analyzes the power supply system of suspended monorail transit and emphasizes the necessity of DC system ground fault protection to ensure equipment and personnel safety under various operating conditions. While conventional voltagebased ground fault protection devices can provide basic protection functions, they lack selective tripping capability and may expand the fault area. Based on Kirchhoff's current law, this paper proposes an innovative sectional currentbased ground fault protection scheme. Through the implementation of inverse timecurrent characteristics and differential current components, the scheme achieves accurate and rapid fault section identification, enabling priority tripping of corresponding sections to isolate faults, thus significantly improving system selectivity. Through analysis of protection objectives, coverage, types, and operation time limits of both 64D protection and frame current protection, the study concludes that these two protection methods are complementary and can operate simultaneously. Field applications demonstrate that all protection functions perform sensitively and reliably. By calculating key parameters for 64D protection, this paper proposes protection schemes and system setting values for practical engineering applications, optimizing protection system selectivity, effectively reducing fault ranges, and ensuring operational safety.

The lowaltitude economy has become a new industrial direction pursued in global competition due to its prominent features. The research on lowaltitude economy in the field of urban rail transit is rapidly developing and growing. For the low and medium capacity rail transit systems represented by the straddle monorail system, based on the key technology research of low altitude technology, it is necessary to explore a low altitude unmanned aerial vehicle intelligent inspection system that is suitable for the construction and operation characteristics of straddle monorails, meets operational requirements, and effectively solves maintenance problems. This study proposes for the first time a video intelligent inspection system based on an unmanned aerial vehicle platform applied to straddle monorail transit, analyzes its application plan scheme and value in straddle monorail transit, and explores a practical and feasible low altitudeeconomic economy application scenario for the low and medium capacity rail transit systems mainly based on elevated laying structures. This approach is conducive to achieving the automation of straddletype monorail transit track beam and bridge inspection. This approach is effective in Reducing the workload of manual inspections and minimizing manual omissions has significant implications for the industry.

During longterm operation, the cooling system's heatsink intake can become clogged with environmental impurities and dust, reducing cooling airflow and affecting thermal dissipation efficiency. This can lead to overheating faults in the power converter, significantly reducing its operational reliability. To address the issue of dust blockage in the aircooled system, which can cause overheating faults in rail transit power converters, a realtime online monitoring method for the cooling system's thermal dissipation state is proposed. This method uses the thermal resistance of the heatsink, extracted from the power device and heatsink cooling curves, as a characteristic parameter. The GaussNewton iterative method is employed to extract these parameters, which are used to identify the degree of blockage and achieve online monitoring of the cooling system's thermal dissipation state. Simulation and experimental results validate that the proposed method effectively monitors the cooling system's operational state, demonstrating superior detection efficiency and effectiveness compared to traditional blockage detection methods.

This paper addresses the challenges in onsite engineering acceptance testing of urban rail transit signaling systems in China, which currently face issues such as singlemethod approaches, lengthy cycle times, low efficiency, high costs, and heavy workloads. A method for automatic generation of onsite engineering acceptance test sequences is proposed. The methodology involves three main steps: First, analyzing the constraints of interconnection test case sets for urban rail signal systems; second, dividing the line into independent test sections; and third, converting line characteristics into computerrecognizable formal language to enhance editing efficiency and humancomputer interaction. The proposed method employs an “auxiliary generation tool" to automatically generate fieldexecutable engineering acceptance test sequences. The effectiveness of this approach is validated through tests on actual railway lines. Results demonstrate that test sequences designed using formal language meet engineering acceptance requirements, achieve 100% coverage of interconnection test cases, and significantly reduce field testing time while improving efficiency compared to traditional manual test sequence design methods.

The Beijing Northeastern Ring suburban railway renovation project aims to transform the line into a public transitstyle operation, with portions of the route cooperating on shared tracks with Subway Line 19. While enhancing passenger service, the line must preserve its critical function as a connector within the main railway network. The system design requires a maximum throughput of 20 train pairs per hour. The existing Changping Station, which serves as both a turnback station for the Northeastern Ring Line and a connection point to the vehicle depot, is characterized by its large scale and operational complexity, making it the bottleneck for system capacity. This station becomes the critical factor in determining whether the system's maximum capacity requirements can be achieved. The Northeastern Ring Line adopts the CTCS2 train control system with ATO and automatic turnaround capabilities. To enhance Changping Station's capacity and meet system requirements, modifications were implemented to the existing station layout and signaling system. The station tracks, throat areas at both ends, and connections to the main line were optimized. Combined with signaling improvements and verified through traction calculations and multiscenario timetabling, Changping Station ultimately achieved a throughput capacity of 23 train pairs per hour, not only satisfying system requirements but also providing a 15% capacity margin. Through comprehensive analysis of Changping Station's capacity, the study identified that the number of arrival and departure tracks, length of station throat areas, signal configuration, and operating speeds are the primary factors limiting station capacity. The paper proposes solutions for improving station throughput capacity, providing valuable reference for future suburban railway design projects.

Redundancy is a crucial component of network resilience. To address the current gap in time redundancy consideration when identifying critical stations in rail transit networks, this study proposes a comprehensive approach. First, we develop a timeweighted rail transit network model incorporating Space L and multiline coupling, which accounts for interstation transfer times. Second, we employ node deletion to simulate station disruptions and introduce three metrics: station redundancy index, network redundancy index, and a redundancy evaluation model based on shortest travel time variations. Using the 2024 Chongqing rail transit network as a case study, we compare the results between redundancybased and betweennessbased evaluations. The analysis reveals an average station redundancy index of 0.7998, with 3.87% of stations showing a Kmeans clustering center of 0.2788, indicating lower redundancy at critical locations. Redundancycritical stations are predominantly located near the network periphery along extended lines, while betweennesscritical stations are typically found at multiline interchange points, demonstrating distinct spatial patterns between these two categories. Network performance is more significantly impacted by disruptions at redundancycritical stations compared to betweennesscritical stations, validating the effectiveness of our identification method. This approach provides valuable insights for enhancing the resilience of urban rail transit networks.

To improve the inspection level of Beijing Subway interval facilities, and achieve cost reduction and efficiency improvement, the inspection basis of interval facilities was clarified based on the national standard, industry method, local standard and enterprise standard. The automatic inspection equipment and way of inspection of Beijing Mass Transit Railway Operation Corp. Ltd. were discussed. The functional parameters, advantages and disadvantages of typical comprehensive inspection equipment were compared and analyzed. The comprehensive inspection mode of Beijing Subway interval facilities was presented. The results indicate that the enterprise standard can cover the inspection contents and inspection cycles in the national standard, industry method and local standard. The comprehensive detection vehicle is suitable for dynamic inspection, while the comprehensive detection car is suitable for static inspection, both of which are far superior to the handheld equipment. The onboard detection equipment is mainly used for routine inspection. The comprehensive detection vehicle and the comprehensive detection cars combined with the existing professional detection equipment are mainly used for scheduled inspection. The fixed monitoring system and the handheld equipment are mainly used for special inspection. The comprehensive inspection should be implemented by leasing service in the short term, and by purchasing equipment in the long term. This study can serve as a reference for promoting intelligent operation and maintenance of urban rail transit infrastructure.

To study the effectiveness and impact of rail transit development in developing countries and to improve urban development experiences based on the TransitOriented Development (TOD) model, this study takes the Addis Ababa Light Rail Transit (LRT) as a case study to analyze its effects on residents' commuting and the spatial distribution of jobs and residences after its completion. Based on official city maps, resident questionnaires, and interview data, a multiple linear regression model was employed to analyze the influence of different commuting methods on commuting time. The findings indicate that the light rail system has a limited effect on improving residents' commuting efficiency. Further GIS spatial analysis reveals that the overall distribution of residential and employment areas in the city is uneven, with suburban residential density being exceeding five times that of urban areas. The analysis results reflect that the failure to coordinate land use with the development of the light rail corridor is a primary reason for the low commuting efficiency. The conclusions advance the understanding of the adaptability and implementation strategies of the TransitOriented Development (TOD) model in countries with lowdensity sprawl and relatively underdeveloped economies.