This study employs prevalent international statistical standards to categorize urban rail transit into three types: metro, light rail, and tram. It presents a comprehensive statistical analysis of the current state of urban rail transit systems across the globe. As of the close of 2023, urban rail transit systems have been established in 563 cities spanning 79 countries and regions, with a cumulative track length exceeding 43,400.40 km. Subways, light rails, and streetcars account for 50.07%, 10.69%, and 39.24% of the total length, respectively. Notably, as of December 31, 2023, 66 cities in China (including Hong Kong, Macao, and Taiwan) have commenced rail transit operations, boasting a combined operational track length of 11,900.29 km, with Chinese mainland alone contributing 11,232.65 km to this total. In 2022, the metro systems in 183 cities across 59 countries globally handled a total of 58,652 million trips of passengers, representing an average ridership intensity of 0.81 trips per day per kilometer. Specifically, China's metro systems (including those of Hong Kong, Macao, and Taiwan) registered an annual passenger traffic volume of 21.251 billion trips. The study underscores the steadfast advancement of China's urban rail transit systems, which consistently lead the world in both network scale and passenger traffic. Through an indepth analysis of data subsequent to the release of Document 52 by the State Council, this study anticipates a resurgence of lowcapacity urban rail transit systems, particularly streetcars, in Chinese mainland, especially in the central and western regions, in a bid to drive environmentally sustainable urban development. Further, by drawing on data from major countries and cities worldwide, both preand postpandemic, the study predicts a return of passenger traffic in Chinese mainland to prepandemic levels by 2024-2025.

This paper provides a comprehensive overview of Chinese mainland's urban rail transit development in 2023. By the end of the year, 28 provinces and 59 cities had 338 urban rail transit lines in operation, spanning 11,232.65 km. Subway lines made up 76.10% of this length, with 8,547.67 km, followed by fully automatic operation (FAO) lines with 9.37% and 1,052.43 km. The network expanded by 884.55 km in 2023, with 53 new lines (or sections) opening, including 539.50 km of subway lines and 252.79 km of FAO lines. The new lines involved 7 different system types and 30 cities, 3 of which inaugurated their first urban rail transit systems. In 2023, Chinese mainland's urban rail transit network also set a new record of annual passenger volume, surpassing 80 million passenger trips per day on average.

With rapid urbanization, the refurbishment of urban railway lines is crucial for advancing highquality urban rail development and sustainable urban growth. This refurbishment process presents a host of intricate professional challenges that must be addressed. Meeting current requirements for line reconstruction while addressing safety issues and expanding beyond traditional specialized fields is demanding. Therefore, it is essential to chart a development path for the transformation of existing urban rail transit lines in line with the needs of highquality urban rail development. Drawing on the history of Beijing's line refurbishments, this study examines the challenges and future objectives of urban rail transit line refurbishment and proposes comprehensive concepts for the rejuvenation process. Furthermore, we introduce an innovative approach to investment and financing for line refurbishments, focusing on sustainable urban rail development. We offer recommendations for the transformation of urban rail transit lines in China across six key areas: system development, vitality of components, investment and financing frameworks, technological empowerment, research and development, and relevant standards.

With the early opening of urban rail transit, Shanghai has been a forerunner in urban rail transit operatingline renovation in China. The experiences and lessons learned from Shanghai in operatingline renovations have reference value for other cities in China. First, the operatingline renovation process of the Shanghai urban rail transit was reviewed. Three main development trends indicate that the focus is on a gradual transition from individual conditions to overall conditions, that the renovation contents are gradually being diversified and systematized, and that the renovation demands that align with the development goals of the city and urban rail transit network are continuously deepening and expanding. Second, developing a renovation plan with systematic thinking, minimizing the impact on passengers while ensuring construction safety and quality during renovation, and active postevaluation after renovation are summarized as the key points in the operatingline renovation of Shanghai urban rail transit. The difficulties in operatingline renovation of Shanghai urban rail transit were analyzed in terms of limited financial support, highefficiency requirements for internal and external communication, challenges in project management, and insufficient technology. Important future works for operatingline renovations of Shanghai urban rail transit are discussed, including additional financing channels, research on improvement and innovation of construction plans and management mechanisms, deeper evaluation of the operational urban rail transit network, and the technology of nonclosure renovation of underground stations without prereserved conditions.

Renovating existing lines is a key longterm task for achieving highquality and sustainable development of urban rail transit in China. Technical standards are essential for initiating, designing, and implementing renovation projects. This paper reviews the current technical standard system for urban rail transit and examines the suitability of existing standards for each stage of the renovation process. To address the issues of incomplete coverage, low applicability, and poor relevance of existing standards, we propose two approaches and schemes for developing a new technical standard system for renovating urban rail transit lines, along with the principles for constructing and formulating the standards. We focus on the technical standards for renovation, including the requirements for renovation determination, design, construction, acceptance, safety assessment, and postevaluation.

Urban rail transit in China has entered a new stage of transforming from "incremental expansion" to "stock optimization". This requires renovating existing lines, which poses a huge demand for funds and a high standard for longterm sustainability. Therefore, it is important to develop an investment and financing mechanism that matches the renovation needs and ensures the highquality development of urban rail transit. However, there is a lack of comprehensive and unified guidance for different types of renovation projects and various stakeholders. There is also an urgent need for theoretical research to support the innovation of investment and financing modes. This paper analyzes the experiences of typical cases in London, Japan, Beijing, Shanghai, Shenzhen, and Tianjin. Based on the economic, cyclical, and multibody characteristics of the projects, this paper proposes a grading and classification system for investment and financing, and constructs a mechanism that integrates financial subsidies and incentives with the stock of assets and new investment. This study can provide a reference and basis for improving the top-level design of renovation projects and forming a multi-principal synergistic investment and financing mechanism system for the medium and long term.

As subway construction in China continues, the network operation mode of subway emerges, and more transfer nodes are created. Due to planning and other factors, the earlierbuilt subway lines did not reserve future transfer access conditions. Thus, when new lines are built, the existing stations often undergo transfer transformation and upgrading along with the new stations. Among the key tasks involved, the communication transmission system transformation and upgrading is crucial. The communication system is the traffic nerve of urban rail, which consists of public security communication system, civil communication system, and special communication system. It supports the information exchange between the control center and the stations and vehicles, and provides stable communication service for passengers. This paper examines the communication room transformation and communication capacity expansion requirements resulting from the transfer station transformation under the existing line operation conditions, and proposes the enhanced MSTP construction scheme for public security transmission system and the backbone transmission system OTN construction scheme. Xitucheng Station of Beijing Metro Line 10 intersects with the newly built metro Changnan Line, and the transfer station changes in building structure and function have raised new requirements for the communication system equipment deployment and upgrade. This paper applies the design scheme to the transfer project, verifies the rationality of the proposed scheme, and the research results offer an application reference scheme for the communication system upgrade of the existing station transfer transformation.

This paper preliminarily explores the selection range of longitudinal slope for adding stations in existing line renovation project, analyzing the requirements for longitudinal slope from several perspectives, including train stopping smoothness, train starting and braking, station longitudinal drainage, station building and accessibility design, station platform door installation, and station wiring. Some conclusions are presented: (1) Verifying the technical performance of parking braking, starting, and braking of subway trains is the key to determining whether the longitudinal slope of adding stations to existing line sections can be moderately increased; (2) Considering the parking and braking performance of subway trains, as well as the technical performance of train starting and braking, the longitudinal slope of the station should be allowed to be moderately increased. However, considering the design of the station building and the convenience of passenger use, the increase should not be too large; (3) From the perspective of maintenance and repair of switches, it is recommended to ensure that the longitudinal slope of switches does not exceed the existing regulation of 10%.

To explore the optimal scheme for the construction and upgrading of the big data platform in the urban rail transit industry, this study takes the urban rail big data platform as the research object. Our study starts from the development process of the urban rail big data platform, sorts out the three stages of the development of the urban rail big data platform and analyzes the technology and advantages and disadvantages of the big data platform at each stage. Then it focuses on summarizing the advantages of "Data lake and Warehouse integration, stream processing and batch processing integration, OLTP+OLAP, multiple loads" and other advantages of the "Data Lakehouse" big data technology in the current stage, and studies the key points of the architecture upgrade and transformation design of the big data platform based on this technology. The technology was verified in the upgradation and transformation of the big data platform of the Beijing Metro Data Center. The application shows that the "Data lakehouse" big data platform technology combines the advantages of low cost of data lake and high performance of data warehouse, solves the shortcomings of the original big data platform in performance, capacity and multipurpose support, and provides new solutions for the construction and upgradation of big data platforms in the urban rail industry.

Public participation in lowcarbon travel is an effective way to reduce carbon emissions. How to further guide and incentivize public participation in lowcarbon rail transit through carbon inclusive mechanisms is an important research field for rail transit enterprises to carry out green and lowcarbon practices, this paper according to the national carbon peak, carbon neutral and carbon GSP policies, as well as the construction of carbon GSP policy system in Shenzhen; This paper focuses on the "Our LowCarbon Road" project, combines the mechanism of carbon GSP in Shenzhen and the characteristics of the urban rail transit industry, relying on the Internet technology and data aggregation platform to systematic analysis was conducted on the business model, methodology, business process, and data flow, the system architecture and technology program of Shenzhen's carbon GSP application platform, as well as the implementation and application significance of the platform, and puts forward the development ideas of expanding carbon application scenarios, innovating carbon financial products, and crossregional cooperation. This provides Shenzhen's experience for the application of carbon inclusive urban rail transit, which has practical value in tapping into the public's emission reduction potential, stimulating green travel for citizens, and feeding back the rail transit industry.

Fire is one of the most serious accidents occurring at urban rail transit stations. A scientific and reasonable safety evacuation plan is essential to ensure the safety of passengers in the event of a fire. However, it is difficult to dynamically adjust the evacuation routes in the current subway station fire evacuation plan according to the fire situation. This study used computer vision technology to identify personnel distribution information and fire locations based on the monitoring system in the subway station. A spatial topology model was developed, and an improved ant colony algorithm was used to plan an evacuation route that takes the shortest time and has fewer turns to provide a more scientific and reasonable evacuation route for evacuating passengers. The effectiveness of the evacuation plan was verified by applying it to three scenarios.

Addressing the critical issue of subway structure leakage in Beijing due to rising groundwater levels, this study focuses on the development of an effective management framework. The work presents a comprehensive prevention and control technology system tailored for the Beijing subway, encompassing risk identification, assessment, and mitigation strategies. The investigation begins with pinpointing the diverse factors that contribute to leakage and proceeds to evaluate the risks through both qualitative and quantitative approaches, which apply to different segments and stations within the subway system. Risk levels ranging from A through D have been devised to facilitate targeted emergency and routine leakage management protocols. The resultant strategies accommodate both urgent responses and standard leakage rectification processes. The findings of this research aim to serve as a theoretical and technical groundwork for the management of similar urban subway structures.

Under the major strategic deployment of a dualcarbon strategy, studying the whole lifecycle carbon emissions of rail transit and reasonably quantifying its carbon emission level is essential to achieve peak carbon and carbon neutrality in the transportation sector. Based on a new metro line in Beijing, this study analyzes the whole lifecycle carbon emissions of rail transit, establishes a carbon emission calculation model for the whole line and the whole lifecycle of rail transit, and quantitatively calculates the carbon emission of the whole line and the whole lifecycle of the new metro line. Carbon reduction measures in the construction and operation phases are analyzed simultaneously, and their carbon reduction potential is quantitatively assessed. The carbon emission calculation for the 81km long new metro line yields a carbon emission of 2.57 million tons of CO2eq in the construction phase, 54,000 tons of CO2eq per year in the operation phase, and a total carbon emission of 5.24 million tons of CO2eq in the 50year operation cycle. The use of renewable materials and prefabricated structures in the construction phase can reduce carbon emissions by 7%. The use of comprehensive carbonreducing measures in the operation phase can reduce carbon emissions by 27%, and the carbon reduction potential of the 50year operation cycle is 17%. The establishment of the model has guiding significance for the quantitative calculation of carbon emissions in the whole life cycle of urban rail transport, and the research results of the carbon reduction measures can provide a reference for urban rail transport to achieve a green and lowcarbon transformation and carbon peak and carbon neutrality in the transport sector.

The maximum operating speed of urban rail expresses is 160 km/h. As the main technical parameters of the gauge in the current national standards do not cover this speed, this study uses theoretical analysis and dynamic simulation methods to research the gauge system and calculation methods. The calculation formulas in the Standard of Metro Gauges (CJJ 962003) were adjusted to be suitable for the 160km/h express project. The optimal structure gauges of the station, tunnel, and bridge were formulated in combination with the express project characteristics based on research on the basic gauge parameters. 1) Compared with the stopping condition, when the train passed the station at 100 km/h, the distance between the station platform and the central line of the track was 1,600 mm. 2) The size of the circular tunnel section was determined by the space requirement for equipment layout in the urban rail express project. When the flexible overhead contact system was used, the optimal tunnel diameter was 7.5 m (the gauge diameter was 7.2 m). When the rigid overhead contact system was used, the optimal tunnel diameter was 7.1 m (the gauge diameter was 6.8 m).

Current solutions for enhancing the efficiency of existing urban rail transit lines are limited. As a pioneering initiative, the concept of running express/local trains on these lines presents a versatile solution for Shighquality development scenarios. After systematically reviewing the methods for running express/local trains on existing lines, this paper introduces four distinct strategies tailored to the unique features and operational needs of different lines: employing extended intervals for rapid trains, implementing alternate stationskipping for accelerated service, utilizing malfunctioned train stop lines for express/local runs, and operating partialroute shuttles for express/local trains. Drawing from domestic and international case studies, this research delves into the operating principles, advantages, disadvantages, and operational requirements of the aforementioned methods. Additionally, the necessary modifications for implementing express/local train services on existing lines are discussed.

Passenger flow forecasting for the initial operation stage of a new rail transit line is fundamental for operational safety assessment and organizational preparation. This study analyzes the characteristics of forecasting work in terms of the forecasting period, research objects, basic modeling data, and forecasting models. The technical difficulties in carrying out such forecasting work are also summarized. Considering the characteristics and difficulties of forecasting, this study introduces a new forecasting framework, and the key procedures in the framework are then explained, including data collection, traffic surveys, analysis of the operational characteristics of urban transport, travel demand forecasting from macroscopic and intermediate perspectives, forecasting evaluation, and sensitivity analysis. Finally, the study also discusses main research points of forecasting work with respect to network passenger flow indices, the impact of a new line on the existing network, and the necessary concerns of essential stations. It is suggested that the forecasting work should focus on the current state of urban systems. Thus, it is essential to collect and understand the current information on urban traffic and the city itself and to analyze shortterm development trends. Because the macroscopic demand analysis models may have lower accuracy, it is also necessary to construct a thematic model for rail transit systems based on urban transport macroscopic demand analysis by conducting traffic surveys. The results of this study can provide references for technical methods and research content of passenger flow forecasting in the initial operation stage.

The subway engineering department regularly operates track inspection vehicles to detect the state of the tracks, which is crucial for residents' safe travel. The operational path of track inspection vehicles mainly relies on expert judgment, which is not only a timeconsuming practice but is also ineffective. To address the shortcomings of the current lack of systematic planning for the operational paths of track inspection vehicles, this study, set against the backdrop of the urban rail transit network, constructs a largescale subway inspection vehicle routing optimization model named Urban Track Inspection Vehicle Routing Problem (UTIVRP), under the conditions of a complex network. Considering the characteristics of subway networks, a cultural genetic algorithm with a special encoding method is designed and validated using practical examples from the Beijing subway. The computational results indicate that under the conditions of meeting the established inspection requirements, the optimization solution can not only reduce the idle mileage of vehicles by 48.88%, but also decrease the maximum deviation rate of the network's inspection interval by 93.33%.

This study comprehensively summarizes the testing scheme and results of a laddersleeper ballastless track in urban rapid rail transit for safety, stability, and vibration reduction performance compared with an ordinary ballasted track at a maximum speed of 220 km/h on the National Railway Test Center Circular Line in 2023. The test used eight CRH380AJ comprehensive inspection units, including the safety and stability of the wheelset derailment coefficient, wheel load reduction rate, wheelrail lateral force, vertical and lateral dynamic displacement indicators of the rail and sleeper, vertical and lateral vibration characteristics of the rail, and vibration reduction performance of the roadbed surface at a distance of 3.5 m from the centerline of the line. The test results for these indices were lower than the limits of the corresponding standards and close to those for the existing ballasted track. The test results show that the safety, stability, and wheelrail vibration characteristics of the laddersleeper ballastless track in urban rapid rail transit can satisfy the requirements of the line at a speed of 220 km/h. According to different weighting methods, the average vibration reduction of the laddersleeper ballastless track compared with an ordinary ballasted track in urban rapid rail transit can reach 3.35.1 dB and 4.46.8 dB. The test results provide a reference for urban rapid rail transit and intercity railway track vibration reduction technologies.

To evaluate the vibration reduction effect of urban express, similar sections with essentially the same line conditions were studied. Different vibration reduction measures and corresponding common overall track bed sections were tested onsite to study the vibration reduction effect of urban express vibration reduction measures. Through the time domain, frequency domain, and onethird octave analysis of the measured data, the vibration reduction measures and maximum Zvibration level (VLZmax) of the ordinary section of the tunnel wall were obtained, and the vibration reduction effects of different vibration reduction measures were compared. The vibration acceleration of the tunnel wall at the measuring point and the ground vibration were analyzed in onethird of an octave to obtain the propagation attenuation of the vibration. The results show that the three vibration reduction measures reduced vibration. The vibration reduction of the doublelayer nonlinear vibration reduction fastener was 7.3 dB; the vibration reduction was 16.2 dB for the vibration damping pad floating plate and 19.7 dB for the steel spring floating plate.

This study examines shield direct cutting techniques on largediameter piles within the construction project linking Guanzhou Station to University Town North Station on the Guangzhou Metro Line 12. Focusing on piles with diameters of 1,200 mm and reinforcing bars with diameters of 25 mm and 28 mm, the research evaluates the efficacy of critical measures and the resultant quality of pile cutting within shield construction. Findings indicate that a cutter head configuration, incorporating a hob and a tearing knife, successfully penetrates concrete pile foundations containing rebar of the specified diameters. However, a challenge arises when a toothed hob attempts to sever the reinforcing bar directly. It is observed that the tearing knife's secondary action exerts adequate shear force to dissect the reinforcement at the precut location by the hob. Furthermore, employing a boring strategy characterized by a low advancement rate, high rotation speed, and consistent torque has proven to enhance the cutting process for both the pile body and its embedded steel bars. Additionally, the use of split hydraulic rebar shears delivers an improved response to the complications presented by intertwined steel bars within the shield machine's path.

Groundsurface deformation characteristics caused by jacked rectangular pipes differ from those caused by jacked circular pipes or shield tunnels. The groundsettlement characteristics during the construction of a shallowburied rectangular jacked pipe and its impact on the existing shield tunnel below the jacked pipe were clarified. Using the onsite monitoring results from jacked rectangular pipe construction, the deformation patterns of the ground surface during jacked rectangular pipe construction and the deformation of the existing shield tunnel below the jacked pipe were analyzed. The traditional Peck formula was applied to circular pipejacking and circular shield tunnels; the improved Peck formula was used to describe the surface deformation caused by rectangular pipejacking. The surface deformation, pipeline deformation, and settlement pattern of the submerged tunnel caused by jacked pipes were analyzed based on field monitoring. The results show that the improved Peck formula can describe surface deformation caused by jacked rectangular pipes more accurately than the traditional Peck formula. The settlement patterns of the surface and pipeline caused by jacked pipes were consistent; however, there were differences in the settlement patterns of the underlying tunnel.

Field experiments and simulation analyses were conducted on a Kaifengsuspended monorail demonstration line to evaluate the service performance of rubbertire suspended vehicles and steel guideway bridges and provide appropriate criteria and operating and design parameters for this type of vehiclebridge system. A rubbertire suspended trainsteel and guideway bridge coupling analysis program was developed. The vehiclebridge coupling model was built according to the measured parameters, including the stiffness and damping of the pneumatic spring and travel wheels. The calculated and measured dynamic responses of the vehicle and bridge were compared. The dynamic performance of the vehiclebridge structure was evaluated based on the calculations and related specifications. The results show that 1) it is feasible to use the vehiclebridge coupling simulation method to investigate the structural vibration performance of a suspended monorail system; the simulation results were consistent with field measurement results; 2) the ratio of the vertical deflection to the span of the steel guideway girder was less than the limit given in the specifications and the vertical stiffness of the structure was reasonable; 3) the maximum vertical and lateral rotation angles between two adjacent beams at the beamends were 4.5‰ and 1.5‰, respectively; 4) the maximum dynamic factors of longitudinal and lateral stress of the steel guideway beam were 1.17 and 1.14, respectively, at a vehicle speed of 80 km/h; 5) the unloading factor of the wheel and lateral acceleration of the guideway bridge were larger than those of conventional railway systems; the limits of these two indices could be set higher than in the current railway specifications as the suspended trains were unlikely to derail.

Quality defects in segment assembly, such as misalignment and ellipse deformation, often occur during shieldtunneling excavation. Construction quality defects threaten tunnel stability and safety. To ensure the safe construction and service of shield tunnels, a quality assessment of the shield segment assembly is necessary during construction. Limited by manual detection methods, traditional sitequality assessment is challenged by low efficiency, limited accuracy, and missing data. Three dimensional laser scanning was introduced to collect pointcloud data during the assembly of the shieldsegment lining. The ellipticity and misalignment values of the shield segments were calculated by the long and shortaxis algorithms and the improved slope segmentation algorithms. Based on the theory of centerpoint extraction of ringseam data, a method for extracting the central axis and center point of a tunnel through ringsegment data fitting was proposed for high precision, efficiency, and automation to detect shieldsegment assembly quality. A shieldtunnel project was conducted to demonstrate and validate the proposed method. The results show that the proposed method can efficiently and automatically assess the assembly quality of shieldconstruction segments.

Addressing shortcomings in the current customer service system, including low awareness of passenger service needs, limited service channels, high costs, and inefficient operation control, this study starts by examining highquality and efficient travel demand in the modern era and analyzing diverse passenger group travel needs. We advocate for new service goals centered on timeliness, convenience, accuracy, and proactivity. The proposed smart passenger service architecture for urban rail transit embraces the multitude of online and offline demands, overcoming existing system limitations in data integration, equipment platform unification, service quality, and efficiency. Emphasizing adherence to passenger service schedules, it also prioritizes efficient lastmeter service delivery. By showcasing representative Beijing subway lines, we present a replicable technological system and application model that can comprehensively enhance the intelligent service and management processes of China's urban rail transit system.