With reference to internationally recognized statistical, urban rail transit is categorized into three major types, namely metro, light rail and tram. This analysis reviews the current status of urban rail transit operations worldwide. The findings show that by the end of 2024, 562 cities in 79 countries and regions around the world have opened urban rail transit systems, with a total length of more than 44,730.14 km. Subways, light rails, and streetcars each account for 51.24%, 10.43% and 38.34%, respectively. As of December 31, 2024, 65 cities in China (including Hong Kong, Macao and Taiwan) have operational rail transit systems, with an operating length of 12,844.57 km, of which the operating length in Chinese mainland is 12,168.77 km. In 2023, the metros of 188 cities in 59 countries around the world transported a total of 713.78 million passengers, with an average daily load of 0.85 million trips per kilometer. In China (including Hong Kong, Macao, and Taiwan), metro systems carried 31.81 billion trips annually. China's urban rail transit continues to grow steadily, with the size of its network and passenger volume ranking first globally. Additionally, 233 cities in 54 countries and regions have opened suburban railways, totaling 64,195.23 km, with 21 cities in China (including Hong Kong, Macao, and Taiwan) operating 2,974.40 km of suburban railways. An analysis of the scale and development of rail networks in key countries suggests that the construction of suburban railways in China, as well as the interconnection of different networks, holds significant potential.

By the end of 2024, a total of 28 provinces and 58 cities in Chinese mainland have opened 362 urban rail transit lines, covering a total length of 12,168.77 km, including 9,281.37 km of subway lines, accounting for 76.27%. By the end of the statistical period, 1,486.01 km of Fully Automated Operation (FAO) lines have been opened, representing 12.21% of the total length of operational lines. In 2024, 51 new urban rail transit lines (sections) were added, with a total length of 953.04 km, including 738.26 km of new metro lines and 425.70 km of new FAO lines, all of which were classified as GoA4. It is expected that by the end of the 14th FiveYear Plan period, the total operating scale of urban rail transit in mainland China will exceed 13,200 km. It is estimated that the annual passenger volume at the end of the 14th FiveYear Plan period will double compared to the end of the 13th FiveYear Plan period.

As urban space becomes more complex through rail transit interconnectivity, this study investigates how to improve the spatial efficiency of metropolitan areas. Firstly, this article analyzes the research characteristics and shortcomings of synergy mode between interconnecting rail transit network and urban space through bibliometric methods. Secondly, by incorporating the concepts of networks and mobility into theoretical research and using multilevel network efficiency as the starting point, this study examines the key factors in synergistic development of network structure and function between rail transit and urban space. Based on this analysis, the Interconnection 2.0 model for synergistic development between rail transit and urban space is proposed, with the synergy relationship strengthened through network structure connectivity, network nodes, and element flow. Finally, combined with case analysis, this paper prospects the future development direction of interconnection at a higher stage in China. Theoretically, the study focuses on network hierarchy and nodality as well as the interaction between flows. In practice it provideds improves recommendations for improving the network connectivity and coupling of multilevel rail transit hubs. The research results provide a reference framework for the theory and practice of synergistic development between rail transit and urban space.

With the rapid development of urban rail transit, the subway, as an important public transportation, provides an efficient largescale travel option. Previous studies generally believe that the built environment around subway stations affects the passenger flow, but the size of PCA (Pedestrian Catchment Area) has not yet been unified. The purpose of this study was to verify whether the size of PCA affects the outcome value of the correlation study between metro ridership and the built environment. Taking 25 stations of Nanning Metro Line 1 as an example, five indicators were selected as independent variables, including residential population, jobs and commercial facilities, and the actual passenger volume of the stations was used as the dependent variable. The OLS regression model was used to compare the results of model fitting and influencing factor analysis under different PCA radius variables. There were differences in the research results of the relationship between passenger flow and built environment in the data collection of PCA in subway stations within different catchment areas. For Nanning, the radius of the PCA is 600 m, and the fitting of the correlation model between subway passenger flow and built environment is better than that of 300 m and 900 m. The scope of PCA will lead to inconsistency in the results of the study on the association between subway passenger flow and the built environment. In the future, it is necessary to conduct model analysis for different PCA radii and determine the appropriate PCA scale according to the fitting effect to improve the accuracy of the research.

To promote the quality and efficiency of inventory areas in metropolitans, urban renewal of transit station areas in cityn centers presents an urgent challenge. By incorporating the Quality dimension into the traditional NodePlace model to indicate the perception of spatial environment, this study constructs the NodePlaceQuality Rubik's Cube state model to assess the renewal potentialof transit station areas in the downtown. Using Tianjin's central area as a case study, the modeling results show that the proportion of dependent and imbalanced types of transit station area is as high as 35.49% and 38.71%, respectively, while balanced and coordinated types account for 22.58% and 3.22%, respectively. The transit station areas with high renewal potential are concentrated in the edge of the Inner Ring of Tianjin, and the renewal potential of transit station under construction is also relatively high, while the transit station areas with low renewal potential are agglomerated in the central business district (CBD). These findings provide theoretical support and policy insights for the urban renewal in the transit station area in the metropolitan's downtown.

In response to the diversified and uneven demand for passenger travel, with the goal of improving service levels, this study proposes an operational mode for urban rail transit, which involves online flexible train composition and fulllength and shortturn routings, and integrates NSGAII algorithm to optimize the operational scheme. Firstly, the study analyzes the turnaround scenarios of trains under flexible composition conditions and determines the relationship between turnaround time and departure intervals. Secondly, using passenger travel costs and train operating kilometers as objective functions, a mathematical model for the operational mode of urban rail transit with online flexible train composition and fulllength and shortturn routings is designed based on the NSGAII algorithm. Finally, a case study is conducted to verify the feasibility and effectiveness of the algorithm for a specific rail transit line. The results show that compared to single routing, fulllength and shortturn routings, and mixed operation modes with multiple compositions, the proposed operational mode reduces vehicle operating kilometers by 42.68%, 22.81%, and 15.98% respectively, reduces vehicle utilization by 35%, 23.53%, and 16.13% respectively, and reduces the maximum load factor from 161.71%, 123.54%, and 135.49% to 119.68%. This operational mode effectively reduces vehicle operating kilometers and utilization while ensuring service levels and improving the balance of line load factor, thereby bringing greater benefits and improvements to urban rail transit systems.

The traditional triple network integration evaluation system only considers the 'presence or absence' of rail connection facilities while ignoring the 'quality' of their operation. This limitation prevents proper evaluation of connection inconveniences caused by supplydemand mismatches and poor travel experiences. This study develops a comprehensive evaluation system for "railbusslow travel” integration by: retaining select indicators of “facility availability", introducing new indicators for "supplydemand matching” and “user experience”, as well as proposing key resource allocation methods across facility, network, and operational integration. The research results show that the optimized evaluation system effectively ensures convenience, comfort, and safety in rail connections. The findings provide valuable theoretical and practical references for systematically improving triple network integration in medium and large cities.

In response to the problems of unclear and insufficient connection paths and depth between urban rail transit industry planning environmental impact assessment (EIA), project EIA, environmental acceptance, law enforcement supervision, and regional ecological environment zoning control (zoning control), this study summarizes the characteristics and key contents of rail transit planning EIA and project EIA. Referring to the linkage requirements of rail transit planning EIA and project EIA, the connotation of listbased management is analyzed, and the feasibility of implementing listbased environmental management in the rail transit industry was analyzed. Lists for zoning control, planning EIA, project EIA, environmental acceptance, and law enforcement supervision are developed. The connection paths and methods for listbased environmental management in the rail transit industry are proposed. Research has shown that inventory management is an important measure for improving environmental management in the rail transit industry and has the conditions for implementation. The zoning control, planning EIA, project EIA, environmental protection acceptance, and law enforcement inspection checklists transmit different management requirements from front to back, while providing feedback on different management effectiveness information from back to front. Through different management lists, the approval department, planning department, construction unit, evaluation unit, and law enforcement department can identify key points that their respective departments and units should focus on, implement environmental access and environmental protection measure requirements, and provide technical paths and methods for promoting comprehensive environmental management of the rail transit industry.

Addressing the compatibility issues of platform screen door (PSD) systems across different lines and vehicle types within the context of "fournetwork integration," this study innovatively proposes a design scheme for an adaptive PSD system, encompassing comprehensive solutions such as improving mechanical structures, optimizing control system algorithms, enhancing intelligence levels, and bolstering gap detection system capabilities. These solutions aim to elevate the flexibility and safety of PSD systems, thereby better accommodating the needs of diverse vehicle types and operational modes. By facilitating the adaptability to multiple vehicle types, they contribute to reducing station sizes and lowering construction costs for urban rail transit. This research provides valuable reference and insights for the upgrading of PSD systems under the backdrop of "fournetwork integration" in urban rail transit. By optimizing the design and functionality of PSD systems, it can effectively mitigate the impact of multiple vehicle types on PSD systems, further facilitating the smooth implementation of "fournetwork integration."

The government has proposed establishing a dedicated public safety chapter within the preliminary design documentation for urban rail transit systems. This study examines the compilation and review processes for this public safety chapter. The research first analyzes public safety risks and security standards in urban rail transit, proposing a modular approach to the chapter's organization. This comprises three key modules: counterterrorism and riot control, emergency management, and law enforcement support. Secondly, the study establishes that the review framework should be comprehensive, hierarchical, and forwardlooking. It systematically categorizes the primary review criteria across three dimensions: legal regulations, technical standards, and policy requirements. Finally, for the review process itself, the research proposes a fivestage framework: project initiation, preliminary assessment, onsite evaluation, formal review, and completion. For each stage, the study defines the participating departments, work scope, and required documentation. The findings have established standardized workflows for all phases and stakeholders involved in both compiling and reviewing the public safety chapter. This framework serves as a valuable reference for provinces and municipalities implementing similar initiatives.

Monorail transportation systems currently face challenges such as relatively independent specialties, numerous workstation terminals, high usage, and elevated management and maintenance costs. Additionally, data interconnectivity between subsystems is lacking, making coordination and command difficult in the event of faults or accidents. This paper presents a comprehensive analysis and research on these issues, focusing on data control, subsystem business implementation, and operation and maintenance requirements. The paper elaborates on an architecture scheme for a deeply integrated monorail comprehensive operation and dispatch system based on a unified software/hardware platform and humanmachine interface across various professional subsystems. It explores the application of this scheme in different scenarios, including upgrading existing lines, constructing new lines, and achieving networklevel integration. The proposed system addresses the needs of data control and comprehensive intelligent operation and maintenance by integrating the architecture of center, station, and depot/parking lot system equipment, as well as integrating or interfacing various subsystems. This allows for monitoring and control of various professional system equipment on a unified platform. The analysis demonstrates that adopting a single track system with comprehensive operation scheduling significantly enhances system integration, simplifies job positions, and effectively reduces construction and operation costs. The comprehensive operation and dispatch system enables the interconnection and sharing of various professional resources, providing users with complete and rich information support within a unified platform during emergencies or equipment failures. Through intelligent linkage and other automatic control technologies, operational efficiency can be considerably improved. The integrated operation and dispatch system solution aligns with the development direction of integrated, simplified, and streamlined monorail transportation systems. It is expected to be the future trend for China’s monorail transportation operation and control systems.

Given that passenger flow distribution in urban rail transit station facilities is limited by the capacity and topology of these facilities, making quantification difficult, this study addresses this issue by analyzing the current state of research on passenger flow in station facilities. First, an analysis of the passenger flow state and its transformation within station facilities is conducted. Based on the capacity and transit capacity of the facilities, a passenger flow state transition model is constructed using queuing theory to describe the probability of congestion and dissipation at facility junctions. Taking an urban rail transit interchange station as an example, an analysis of the passenger flow distribution characteristics on the walking facility topology network is performed. The results show that when passenger flow density exceeds the density of free flow, congestion inevitably occurs in facilities with smaller capacities due to the actual passenger flow surpassing a certain threshold. The actual passenger flow distribution characteristics are influenced not only by the capacity of individual walking facilities but also by bottlenecks within the facility network. The research results provide data and technical support for station managers in developing and implementing flow restriction schemes.

The network operation of urban rail transit has introduced diversity in passenger route choices. It is difficult to accurately determine passengers' network route choices based on existing Automatic Fare Collection (AFC) transaction data and probabilistic inference methods. This difficultyaffects tasks such as rail transit network passenger flow allocation and ticket clearing. This study utilizes network station information to construct an urban rail topology network. The proposed method searches for feasible path sets for OriginDestination (OD) pairs and uses multisource data, including AFC transaction data, mobile signaling data, and train schedule data, to build a nonlinear optimization model to infer passengers' travel route choices. Experiments based on the Nanjing Metro network show that the model is effective and robust. This study can provide guidance for urban rail transit operations and ticket clearing.

In order to solve the problem that the traditional monitoring analysts in the field of urban rail transit have a high falsenegative rates and complex parameter adjustment of abnormal behaviors such as falling, fainting and fighting, making them difficult to apply efficiently to actual urban rail station monitoring scenarios, this paper proposes a human posture feature recognition framework based on skeleton pattern recognition, introducing the attitude estimation technology based on human skeleton. The Alpha Pose model is used to accurately estimate the posture of passengers, and combined with the Spatial Temporal Graph Convolutional Networks model, it achieves abnormal behavior recognition in the monitoring scenario of urban rail stations. By achieving 72.3 mAP on the COCO dataset and 82.1 mAP on the MPII dataset, the performance is improved by up to 17% compared to the OpenPose model, verifying the effectiveness and practicality of the model. The results show that the method proposed in this paper not only improves the recognition speed of passenger behavior but also has the ability to adapt to complex scenarios, providing a new technical solution for urban rail safety monitoring.

In response to the increasing operation and maintenance pressure and efficiency requirements of urban rail transit, a comprehensive management and control platform based on digital twins and multisystem integration is constructed and implemented to achieve intensive and refined operation and maintenance management of subway stations and improve management efficiency and service levels. Through 3D scanning of existing lines, this paper focuses on the development and implementation of an integrated management and control platform based on digital twin technology and multisystem integration, enhancing management efficiency and service quality. Firstly, a digital twin model is constructed to represent the operation of urban rail systems. The study explores model lightweight technology and uses 3D rendering engines to render and optimize large models and large scenes. In addition, this paper studies multisource heterogeneous data fusion technology through data standardize processing to realize the processbased collection and storage of heterogeneous data of various professions. Furthermore, a comprehensive urban rail management and control platform is developed, integrating functional modules to meet the needs of various disciplines. This platform improves the execution efficiency of operation and maintenance tasks by 30%, increases the accuracy of equipment and facility status monitoring to 98%, and increases the success rate of preventive maintenance by 20%. The efficiency of cross-disciplinary data sharing and collaborative work is enhanced by over 60%, resulting in a shortened fault response time, significantly improved accuracy of equipment and facility status monitoring, and enhanced effectiveness of preventive maintenance.

Aiming at the problem of excessive settlement of the station caused by the new tunnel close to the existing station, relying on the project of Xi'an Metro Line 8 close to the Convention and Exhibition Center Station of Line 2, the numerical simulation and onsite monitoring are used to analyze the control effect of various control measures on the deformation of the existing station during the construction of the underpass. The recommended values of construction parameters of the tunnel in the loess area are given. The results show that: (1) The construction method and excavation footage have obvious effect on the deformation control of the station when it is close to the underpass. After the construction method is adjusted from the upper and lower step method to the onsite CRD method, the maximum settlement of the station is reduced by 50%. After the excavation footage is adjusted from 1.5 m to 0.5 m, the maximum settlement of the station is reduced by 30%. (2) The staggered distance between the upper and lower pilot tunnels and the erection of temporary steel support have a weak effect on the deformation control of the station, which can be appropriately adjusted according to the engineering geology and onsite monitoring. (3) Based on the project, the construction scheme of onsite CRD method +0.5 m excavation footage +5 m singleside cavern upper and lower guide hole staggered distance +5 m spacing temporary steel support is adopted. The onsite monitoring data are basically the same as the deformation law obtained by numerical calculation. The maximum settlement of the station side wall, ballast bed and track is 3.76, 2.91, 2.51 mm respectively, and the maximum differential settlement at the deformation joint is 3.54 mm, which meets the requirements of the station deformation control standard.

The control of micro deformation of adjacent buildings during the construction of deep foundation pits in weak strata is one of the challenges in the geotechnical field. Taking the construction project of subway deep foundation pit of adjacent buildings in soft ground in Hangzhou as an example, this paper introduced the micro deformation control technologies such as the reinforcement technology of underground continuous wall trough wall, sleeve valve pipe grouting reinforcement technology, servo steel support system, and the reinforcement and excavation technology of underground middle wall, and analyzed the deformation characteristics and the effect of micro deformation control technology in the construction of deep foundation pit of adjacent buildings in soft ground. The results indicate that the sleeve valve pipe grouting reinforcement technology reduces the impact of construction on the surrounding building group and suppresses its deformation; the deformation of the enclosure structure and surrounding deformation can be suppressed through slot wall reinforcement technology, and the quality of the enclosure structure has been improved; the servo steel support system effectively suppresses the deformation of the enclosure structure and reduces the impact of construction on the surrounding area; cross wall and block excavation technology suppresses building deformation and weakens the impact of spatiotemporal effects. In the end, the surrounding buildings of the deep foundation pit basically achieved the goal of "micro deformation”.

To address the issue of not being able to provide an opencut receiving well at the receiving end of rectangular pipe jacking, this study analyzes the soil prereinforcement scheme used in the construction of rectangular pipejacking reception. It explores the appropriate structural type for the castinplace section of the abandoned shell and proposes a waterproofing scheme between the castinplace section of the abandoned shell, the precast pipe joints, and the hidden beams and columns of the station. t This study is based on the new entrance project of Jingjiang Road Station on Tianjin Metro Line 2. The processes, including the shutdown of the pipe jacking machine and grouting, are also optimized. Practical results show that the proposed scheme ensures the safe construction of the abandoned shell reception, with monitoring data indicating a maximum surface settlement of 12.12 mm. The key technology proposed in this paper are highly feasible and effective, offering a new design approach for similar projects, such as abandoned shell reception, where construction site limitations exist.

The urban rail transit projects in China have adopted overhead contact system power supply and dedicated rail return current scheme to solve the problem of stray current leakage. However, there are currently no applications of dedicated rail return under contact rail power supply systems in China. This article proposes four dedicated rail return current schemes based on the contact rail power supply systems. It analyzes and evaluates these four schemes through quantitative and qualitative methods, considering aspects such as equipment impact, vehicle current return, networked operation of lines, power supply system protection, safety, and costeffectiveness. It discusses the feasibility, advantages, and disadvantages of each scheme, and ultimately recommends a dedicated rail return scheme based on the contact rail power supply system. Finally, it proposes a recommended dedicated rail return scheme based on the contact rail power supply system, and summarizes the impact of dedicated rail return on other disciplines.

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.