ObjectiveAccording to relevant domestic regulations on metro vehicle gearbox maintenance intervals，the lubricating oil inside the gearbox is required to be replaced periodically every year. Existing test monitoring results indicate that the lubricating oil of metro vehicle gearboxes that has reached the replacement interval still exhibits good appearance and performance conditions. Under the traditional oil replacement mode，the performance potential of the lubricating oil cannot be fully utilized. Therefore，it is necessary to investigate the degradation behavior of gearbox lubricating oil during its service life. MethodTo achieve effective monitoring of gearbox lubricating oil，strict control is applied to sampling time，sampling tools，sampling depth，and preservation methods. Periodic tracking and sampling are conducted on gearbox lubricating oil operating under normal service conditions with accumulated operating mileage ranging from 0 to 200 000 vehicle·km. Key monitoring indicators are identified，focusing on wear elements （ferrum and copper），additive elements （phosphorus and boron），and physicochemical indicators （kinematic viscosity and acid value）. The collected data are summarized to form distribution histograms based on inspection results. The three-line value method and the maximum entropy method are further employed to determine the threshold values of each indicator. Finally，a lubricating oil performance degradation model is established and investigated. Result & Conclusion As the sample size increased，the values of various indicators of lubricating oil samples under different gearbox operating conditions within the range of 0 to 200 000 vehicle·km tend to approximate a normal distribution. The linear regression model for lubricating oil performance degradation exhibits stable degradation characteristics within the range of 0-200 000 vehicle·km. It can be generally concluded that the lubricating oil performance at 200 000 km remains in good condition，indicating that the gearbox oil replacement interval may be extended. Using the same method，the performance threshold values of gearbox lubricating oil at higher operating mileages can be further determined，thereby establishing a full life-cycle degradation model for gearbox lubricating oil.
ObjectiveThe existing EBTS （enhanced base transceiver station） in Shanghai Metro have been in service for a long period of time，and equipment aging issues have become increasingly prominent. In addition，due to spare parts shortages and the inability of manufacturers to provide maintenance services，fault emergency repairs require changes to the original line layout，involving fiber patching between multiple stations. This also requires a large amount of manpower and nighttime construction time，resulting in low emergency response efficiency. To address and above issues，a dedicated wireless MTS4 （Motorola terrestrial trunked radio system 4th generation） mobile base station is proposed as a solution and that does not change the existing network layout. MethodThe problems of the EBTS base stations are analyzed，and the design objectives of the MTS4 mobile base station as well as the design scheme of the movable cabinet are introduced. Using 3D modeling software and CAD drawing tools，the overall structural design of the movable cabinet is designed and optimized，enabling the MTS4 mobile base station to feature easy mobility，compatibility with the existing network，and rapid deployment. To address the issue of unstable long-term operation of EBTS base stations due to heat dissipation，the movable cabinet adopts an enhanced ventilation design with additional heat dissipation openings and parallel cooling paths，achieving the required heat dissipation capacity calculated by the thermal dissipation formula. Result & Conclusion The 72-hour continuous operation test and field-line simulation results of the designed MTS4 mobile base station show that the system meets the expected objectives in emergency communication handling and offline equipment testing and is capable of ensuring long-term stable operation. The adoption of the MTS4 mobile base station can significantly reduce nighttime working hours and on-site manpower input，while improving fault response speed and system recovery capability.
ObjectiveThe reliability of key metro vehicle components is essential to the safe operation of urban rail transit. The reliability of critical components of metro vehicles is analyzed based on the Weibull distribution method. MethodThe Weibull distribution is a distribution function widely used in reliability analysis; however，its computational accuracy is susceptible to the precision of parameter estimation methods. To address the problems of the traditional maximum likelihood estimation method，which exhibits relatively low accuracy in Weibull parameter calculation and is susceptible to the influence of data sample size，resulting in ineffective evaluation of small-sample failure data，a nonlinear least squares method based on the initial parameters obtained through maximum likelihood estimation is adopted to replace the traditional maximum likelihood estimation method for Weibull parameter calculation. The method is validated using failure data of gateway valves and vertical dampers from a metro vehicle type operated by Shanghai Metro. Result & Conclusion The nonlinear least squares method based on the initial parameters obtained through maximum likelihood estimation can effectively improve the accuracy of Weibull distribution parameter calculation. Compared with the direct application of the maximum likelihood estimation method，it delivers superior fitting performance. In particular，for small-sample data analysis，it exhibits higher significance indicators and correlation coefficients，making it more consistent with the actual operating conditions of vehicles. Reliability analysis shows that，during long-term operation，vertical dampers exhibit more stable reliability; however，their reliability in the early stage of operation is lower than that of gateway valves.
ObjectiveIn response to problems encountered in the operation and maintenance of urban rail transit systems，where the traditional fixed-mileage segmented statistical method for TQI （track quality index） cannot effectively distinguish the inherent attributes of track structures and is prone to inaccurate evaluation due to cumulative mileage deviations generated from inspection data，a differentiated evaluation method based on dynamic mileage correction and feature classification is proposed. The method aims to overcome the limitations of the traditional fixed-length evaluation paradigm and achieve accurate characterization of the local geometric condition of complex railway lines. MethodA physical feature-driven dynamic section classification mechanism is established，in which railway lines are divided according to key parameters such as track bed type，curve radius，and gradient，thereby achieving differentiated separation of track structural conditions. A dynamic window mileage correction technology based on an adaptive matching mechanism is introduced to eliminate mileage drift and nonlinear errors caused by long straight sections or construction segments. An automated calculation platform is developed to realize an efficient closed-loop process for data handling，and empirically verified with the field measured data of Shanghai Metro Line 13. Result & Conclusion The proposed evaluation method effectively overcomes the defect of traditional algorithms that weaken local sensitivity due to data averaging，thereby improving the identification accuracy of weak sections in the track system. It was confirmed that differences in track bed type and curve radius are the core significant features driving the degradation of track geometric conditions.
ObjectiveAiming at the problems of terminal black screens and loss of communication signals caused by the frequent desoldering of the control cable （RL2） aviation plug in DWJ-4SC （A） vehicle-mounted radio stations on Shanghai Metro Line 11，the soldering reliability is analyzed and improvement measures are proposed. MethodBased on an introduction to the system composition of the DWJ-4SC （A） vehicle-mounted radio station，a statistical analysis of the fault data from Shanghai Metro Line 11 between 2021 to 2022 is conducted，identifying that the desoldering of the control cable aviation plug accounted for 32.8% of the total faults. Combining train vibration testing and inspection of the maintenance process，it is confirmed that cable pulling and high-frequency vibration are the root causes of desoldering. Accordingly，a two-stage improvement scheme is proposed，involving the installation of a zip-tie cable fixing base and the pouring and sealing with K-705 transparent electronic silicone adhesive，followed by tracking and verification. Result & Conclusion After implementing the proposed improvement measures，during the tracking and verification period，the number of control cable-related faults for the target trains was both zero，with only two main control board faults occurring during the period. Once these improvement measures are promoted across the entire line，it is estimated to save over 200,000 RMB in rework costs annually，and effectively eliminate the hidden dangers of short-circuits and fire hazards caused by exposed solder joints.
ObjectiveAddressing the issues of high maintenance costs for signaling system spare parts，imperfect control system，and the lack of a closed-loop cost analysis framework under the network operation of Shanghai Rail Transit，a research on spare parts maintenance cost control based on Porter value chain theory is carried out. MethodTaking the CBTC （communication-based train control） signaling system lines with over 10 years of service on Shanghai Rail Transit Lines 6，7，8，9，11，12，13，and 16 as the research objects，the distribution of maintenance volume for two mainstream signaling system standard spare parts is sorted out. Based on the three current maintenance strategies，namely outsourced maintenance，independent maintenance，and joint collaborative maintenance，existing pain points such as spare parts testing and outsourcing pricing are identified. Based on the classical Porter value chain theory，an exclusive value chain model adapted to the signaling system spare parts maintenance business is reconstructed，breaking down four primary activities and four support activities of spare parts maintenance. The full category of maintenance costs is allocated to each link of the value chain to complete a quantitative analysis of the cost structure. Cost control optimization schemes are formulated from three dimensions: optimizing primary activities，improving the efficiency of support activities，and cross-link collaboration within the value chain，and their implementation effects are projected. Result & Conclusion Cost accounting reveals that outsourced maintenance and procurement supply management costs account for 35% and 25%，respectively，taking up 60% in total and serving as the core nodes for cost reduction. Through mutual trust in test reports and unified material coding，the maintenance cycle can be shortened by 30%. Optimizing the value chain through paths such as expanding the scope of independent maintenance，establishing regional shared spare parts libraries，co-building vendor-managed inventory，implementing tiered differentiated maintenance，and reusing scrapped components can significantly reduce spare parts maintenance expenditures. The constructed value chain framework for signaling system spare parts maintenance differs from traditional manufacturing value chains. It can form a closed-loop management system of 'value chain–cost item–control measures,' which is applicable to the cost control of signaling system operations and maintenance under networked conditions.
ObjectiveIn order to rapidly curb the convergence deformation of damaged tunnel lining segments in Shanghai Metro，eliminate potential structural safety hazards，and ensure the structural stability and operational safety of Shanghai Metro tunnels，and in view of the practical situation of tight availability of rolling stock resources and the large number of lining segments requiring reinforcement on a single line，the large steel ring reinforcement process can no longer fully meet the required remediation speed. Therefore，it is necessary to study a new type of small steel ring reinforcement process. MethodThe convergence deformation status of existing Shanghai Metro tunnel lining segments，historical reinforcement processes for lining segments，remediation rates，and key difficulties are analyzed. The feasibility of small steel ring reinforcement is studied through full-scale laboratory experiments. A construction design scheme for the small steel ring reinforcement is introduced. The characteristics of this process are summarized，including its ability to save rolling stock resources，enable multiple working faces，and provide high process flexibility. Case studies are used to verify the effectiveness of the small steel ring reinforcement method. Result & Conclusion The small steel ring reinforcement process can increase the ultimate vertical earth pressure bearing capacity of the tunnel structure from 570 kN to 690 kN，thereby improving tunnel stiffness. It can reduce the use of rolling stock resources by 90%，significantly improving construction efficiency. It allows simultaneous multi-face construction operations，which helps to rapidly complete the remediation of convergence deformation in lining segments. The process is flexible，allowing different construction schemes to be adopted depending on the severity of the convergence deformation of the lining segments. The small steel ring reinforcement process provides a new solution for the rapid and minimally disruptive implementation of convergence deformation remediation in metro tunnel linings.
ObjectiveTo adapt to the networked operation and smart development needs of Shanghai Metro，and to solve issues such as the insufficient capacity and limited service bearing of the existing TETRA （terrestrial trunked radio） dedicated wireless system，the replacement and transformation of Shanghai Metro's dedicated wireless TETRA system with the LTE （long term evolution） system is focused. The importance，interoperation methods，and related problem-solving strategies for the interoperability between the TETRA and LTE systems during the transformation are investigated. MethodCentered on the dedicated wireless trunking services of urban rail transit，an in-depth analysis of the technical characteristics，application scenarios，and key technologies including transcoding，floor-control signaling conversion，and jitter buffer，of both the TETRA and LTE systems is carried out，and a collaborative working mechanism for the dual-systems is established. Result & Conclusion A smooth transition and transformation scheme for the TETRA and LTE systems applicable to the Shanghai Metro is developed. The scheme enables seamless interoperation and uninterrupted calling for trunking services within the jointly covered areas under dual-system and multi-line scenarios. The continuity，stability，and reliability of command communication are guaranteed，providing a technical basis for the transformation of the dedicated wireless system of Shanghai Metro.
ObjectivePower cable faults severely threaten the power supply safety of urban rail transit，and these faults are often accompanied by detectable temperature anomalies prior to fault occurrence. By optimizing the implementation scheme of infrared thermal imaging technology，it is aimed to enhance the engineering practicality of cable fault prediction and diagnosis. It addresses issues in cable operation and maintenance，such as low inspection efficiency，delayed fault detection，and the limited applicability of traditional monitoring methods. MethodThe deficiencies in existing applications of infrared thermal imaging technology are reviewed，and a comprehensive intelligent monitoring system utilizing infrared thermal imaging is constructed. The system architecture，networking mode，equipment parameters，and engineering configurations are explicitly defined. Furthermore，application designs are developed for typical scenarios，including indoor terminals，outdoor power feeding cables，interval ring network cables，and confined spaces. The economic viability and feasibility of the optimized infrared thermal imaging application scheme are also analyzed. Result & Conclusion Adopting this optimized scheme enables dual-mode operation of unattended automatic monitoring and handheld inspection. Through a comprehensive network deployment of fixed temperature measurement probes，complemented by inspection robots for blind-spot testing，the system can identify power cable temperature anomalies and precisely locate faults across all scenarios and weather conditions. Integrated with intelligent backend algorithms，it can automatically determine the type and severity of faults. Economic analysis indicates that this optimized scheme exhibits strong feasibility for both newly constructed lines and the retrofitting of existing lines. Infrared thermal imaging technology can effectively compensate for the shortcomings of traditional temperature measurement methods，driving the transition of power cable operation and maintenance from 'scheduled maintenance' to 'preventive maintenance，condition-based maintenance,' thereby significantly improving fault handling efficiency and power supply safety.
ObjectiveTo address the key bottlenecks in urban rail transit vehicle maintenance，including the data silos between quality control and warehousing logistics，the absence of cross-departmental collaboration mechanisms，and the low efficiency of supply chain cost coordination，a digitalized collaborative management framework covering the full chain from suppliers and manufacturers to maintenance depots，aiming at achieving deep integration of quality data and warehousing operations，as well as intelligent decision-making support. MethodLeveraging the phase II digital transformation project of Shentong Alstom （Shanghai） Rail Transit Vehicle Co.，Ltd.，dedicated quality management and warehousing and management modules are developed and integrated into the company's proprietary DTMS （digital train maintenance system for urban rail vehicles）. Real-time bidirectional synchronization of 23 categories of business documents is established through API （application programming interface） integration with the Maximo ERP （enterprise resource planning） system. A dual-track identification mechanism combining barcoding and RFID （radio frequency identification） is implemented，supported by PDA （handheld mobile terminals） and tablet devices. A full-process digital twin model is developed encompassing incoming material inspection，in-process quality inspection，outsourced repair，and warehousing operations. A multi-dimensional visualization dashboard is also constructed，incorporating P8 （in-process quality non-conformance—Alstom internal standard），NCR （non-conformance report），and cost correlation analysis. Result & Conclusion Application of the system in the bogie overhaul project for the Type 12A02 trains on Shanghai Metro Line 12 demonstrates significant improvements: the incoming inspection cycle is reduced from 4.6 hours to 2.8 hours; the handling efficiency for defective products improved by 55.8%; the inventory record-to-physical accuracy rate increased from 85.3% to 99.6%; the quality decision response time is compressed from 48 hours to within 4 hours; and the inventory turnover rate improved by 31.3%. This framework effectively resolves the longstanding challenge of insufficient linkage between quality management and cost control in traditional maintenance models. Through full-chain digital coverage and innovations in collaborative mechanisms，it provides a replicable digital transformation paradigm for the urban rail transit equipment maintenance industry，offering significant value in enhancing supply chain resilience and operational efficiency.
ObjectiveAs Shanghai Metro has entered the stage of ultra-large-scale networked operations，traditional vehicle maintenance modes exhibit deficiencies in resource efficiency and reliability assurance. The O&M （operation and maintenance） costs of the VV120 series air supply units for metro vehicles remain high，creating an urgent need to optimize maintenance procedures. MethodsAddressing the multiple practical demands of tight rolling stock resources，limited technical data，and operational quality assurance，the air supply units of trains on Shanghai Metro Line 17 is taken as the research object to construct an extended maintenance evaluation strategy based on the concept of RCM （reliability-centered maintenance）. This strategy encompasses four core components: RCM-based pre-screening，operational control based on RCM sampling inspection，multi-dimensional performance and structural condition assessment，and on-site O&M assurance. The feasibility of the proposed scheme is verified using full-lifecycle measured data on the deterioration of air compressor motor bearings and low-pressure cylinder sealing rings. Result & Conclusion The developed strategy can drive a three-fold transformation: shifting the extended maintenance decision-making for metro vehicle air supply units from being 'experience-driven' to 'data-driven,' transitioning extended maintenance standards from being 'single and rigid' to 'risk-classified,' and upgrading independent testing capabilities from 'non-existent' to 'established,' providing a quantifiable and traceable scientific basis for the revision of maintenance cycles and the optimization of maintenance strategies for air supply units.
ObjectiveAs an essential component of the complex urban rail transit system，traction substations provide electrical energy for trains. Formulating appropriate maintenance strategy is highly conducive to the operational stability of traction substation equipment and the control of operational costs for maintenance entities. MethodThe overall research framework is established according to a hierarchical architecture. First，a structural model for traction substation equipment condition assessment is constructed，defining the objective layer，criteria layer，and indicator layer. Based on the AHP （analytic hierarchy process），a judgment matrix is formulated and consistency verification is completed to calculate the weights of the criteria layer indicators. Secondly，standardization processing is conducted on the raw collected data，and the standard deviation method is utilized to determine the weights of the indicator layer. The comprehensive weight is obtained by combining both weights. Subsequently，the Technique for Order Preference by Similarity to Ideal Solution （TOPSIS） is applied to construct a weighted standardized matrix，identifying the positive and negative ideal solutions respectively. The distance values and relative closeness degrees of the evaluated degrees. Finally，the application value and promotion directions of the model are summarized in conjunction with the calculation results. Result & Conclusion This comprehensive weight model effectively eliminates invalid indicators and avoids the judgment biases of traditional assessment methods. The ranking results can provide quantitative support for the formulation of differentiated maintenance strategies. The model features a simple architecture and strong applicability; its evaluation indicators and objects can also be adjusted according to the condition assessment needs of other operational equipment. Case verification results demonstrate that，based on the relative closeness calculations and ranking outcomes of 16 sets of evaluated objects，the superiority and inferiority of the equipment's operational status can be intuitively distinguished.
ObjectiveBased on field monitoring data，it is aimed to investigate the impact and control mechanisms of the zoned excavation of deep-large foundation pits on the structural deformation of adjacent existing metro stations and interval tunnels. MethodTaking a deep-large foundation pit project within the safety protection zone of Shanghai Metro as a case study，the deformation response data of the adjacent existing metro station and interval tunnel structures under the zoned excavation of the foundation pit were obtained through field monitoring. In-depth analyses and research are conducted from the perspectives of vertical displacement，horizontal convergence，horizontal displacement，and the inclination of the station side walls. Result & Conclusion With the continuous increase in the depth of the zoned excavation of the foundation pit，the station and the interval tunnel structures on both of its sides exhibit heave deformation. Due to the vertical constraint effect of the station structure on the closely adjacent tunnel segments，the heave deformation of the interval tunnel structures is correspondingly affected. Simultaneously，the interval tunnel structures generate horizontal displacement towards the inside of the foundation pit; the closer the foundation pit is to the tunnel，the greater the horizontal displacement of the tunnel. Because the station structure has a lateral constraint effect on the closely adjacent tunnel segments，the interval tunnel structures experience lateral tensile and lateral compressive convergence deformations. The inclination of the station walls increases as the excavation depth increases.
ObjectiveThe retrofit of whole-side isolation switches for PSD （platform screen door） is investigated，aiming to reduce the operational impact caused by whole-side PSD failures. MethodTaking Shanghai Metro Lines 6，8，and 12 as examples，the retrofit schemes for whole-side PSD isolation switches applied across lines equipped with different signaling systems are introduced，as well as the preliminary exploration and preparation for the retrofit，the implementation content of the retrofit schemes，and the risk analysis and disposal after the retrofit. Result & Conclusion By adding a 'whole-side PSD isolation switch' on both the signaling side and the operations side，combined with power supply modifications and software logic optimization，rapid isolation of whole-side PSD failures is successfully achieved. Following the retrofit，the issue of train degradation upon station entry and departure caused by whole-side PSD failures is effectively resolved，thus improving the operational efficiency. In addition，post-retrofit fault localization procedures and safe operation protocols are established. It is further proposed that circuit design should be optimized to better satisfy the fail-safety principle and to meet the evolving requirements of PSD in the context of driverless train operation （DTO） technology.
ObjectiveThe operational safety of urban rail transit highly depends on signaling equipment. Axle counter equipment is a core device for controlling train headways，monitoring track conditions，and ensuring operational safety. With the continuous expansion of urban rail transit networks，axle counter log data presents issues such as large data volume，disordered formats，dispersed information，and the inclusion of technical foreign-language content. Traditional manual analysis methods are inefficient and have limited accuracy and cannot meet the requirements of refined and intelligent equipment operation and maintenance. It is necessary to study new analysis tools based on informatization and digitalization. MethodTaking the axle counter system of Shanghai Metro Line 11 as the research object，a fault diagnosis and analysis model for axle counter equipment is constructed by combining Power Query tools，VBA programming，and PivotTable technologies. Through data standardization and cleaning，the establishment of a fault database，the improvement of maintenance processes，and the implementation of a visual monitoring mechanism，rapid fault localization，cause analysis，and equipment condition monitoring are achieved. Result & Conclusion Test results show that the model can reduce the analysis duration of 280,000 log entries from 6 hours using traditional manual methods to 1 minute，with full statistical accuracy. The model enables a transformation in the operation and maintenance of urban rail transit axle counter equipment from experience-based reactive maintenance to data-driven preventive maintenance，effectively improving maintenance quality and efficiency.
ObjectiveThe foundation brake rigging is an essential component for ensuring train operational safety. Abnormal wear of brake discs affects train operational stability，increases maintenance costs，and undermines the operational efficiency and economic benefits of urban rail transit systems. Therefore，investigation is carried out on the abnormal issues of brake disc wear on trailer cars exceeding that on motor cars of a Shanghai Metro Type A train. MethodThrough a comprehensive survey of a Shanghai Metro Type A train，brake disc wear data is collected and analyzed，concluding that the wear on the trailer car brake discs is abnormal. Furthermore，combined with real-time data from the metro train braking process，the causes of trailer car brake disc abnormal wear are explored from the perspective of braking force distribution methods. Result & Conclusion The primary cause of the abnormal brake disc wear on the trailer cars of Shanghai Metro Type A train is a response delay during the train braking process. This delay requires the trailer cars to provide pneumatic braking compensation during the high-speed phase，which triggers the foundation brake units and increases brake disc wear. The braking force management interface software is optimized and output of the braking force setpoint to the brake control unit is delayed by 128 ms. Following the optimization measure，the trailer car pneumatic braking compensation is alleviated，and no longer triggers actions by the foundation brake units.
ObjectiveIn response to the high incidence of loosening defects in key connecting parts in OCS （overhead catenary system） under high-frequency metro operations，the principles，applicability，and effectiveness of various anti-loosening technologies are systematically investigated and evaluated，so as to provide technical solutions and practical references for establishing a long-term safety protection framework. MethodBased on data collected during the concentrated maintenance practice of Shanghai Metro Line 1 in 2024-2025，the distribution characteristics and root causes of loosening defects are statistically analyzed. From the perspectives of mechanical mechanisms and on-site adaptability，a systemic comparative study is conducted on the anti-loosening mechanisms，advantages，and limitations of friction-based locking methods （double nuts，self-locking nuts），mechanical locking methods （cotter pins，locking washers），and structural reinforcement techniques. An effectiveness verification and condition monitoring methodology based on intelligent inspection technologies is also proposed. Through the development and application of a multi-tiered anti-loosening technical framework，the total number of OCS defects identified during the 2025 concentrated maintenance period decreased by 85% compared to 2024，with fastener-related defects achieving zero occurrence，thereby validating the effectiveness of the technical measures adopted. Result & Conclusion The principles for technology selection at different OCS connection points under varying vibration environments are established: high-performance self-locking nuts are applicable in conventional sections，while a redundant design combining self-locking nuts with mechanical locking，or structural reinforcement，is recommended for critical sections and those subject to intense vibration. Practice demonstrates that a comprehensive strategy centered on systematic anti-loosening technologies and supplemented by intelligent monitoring is key to ensuring the operational safety of OCS across super-large-scale metro networks.
ObjectiveAddressing the issues of lengthy design time for track realignment operations and the occasional lack of accuracy in adjustment schemes under complex conditions，it is necessary to research methods for improving efficiency of construction scheme design. The track alignment and profile parameters measured by the track inspection instrument play an important role in the calculation of TQI （track quality index）; therefore，a targeted study is conducted based on the track alignment and profile data measured by the track inspection instrument. MethodStarting from the measurement principles of the track inspection instrument，its geometric measurement mechanism is systematically analyzed，and the physical and mathematical significance of the measured values is summarized. On this basis，a calculation model based on geometric analysis is established，the mathematical characteristics of the model are clarified，and the calculation formulas for two key parameters of track alignment and profile are derived. Data processing methods involving matrices and iterative calculations are introduced，completing the workflow and implementation of the adjustment amount algorithm based on data collected by track inspection instrument. Combined with actual on-site working conditions such as curved sections and realignment amounts，and operational requirements，targeted supplements and revisions are made to the proposed algorithm，including the elimination of design information，constraint handling，and boundary condition setting. The guiding effect of this algorithm on-site operations is discussed，such as track quality assessment，maintenance recommendation generation，and expected effectiveness of the proposed plan，thereby validating the practicality and reliability of the method. Result & Conclusion Building on the experience gained from existing design operation schemes，the proposed algorithm and scheme design are improved. Adopting the improved algorithm and scheme can provide relatively reliable guidance data for operation schemes，which can reduce design time by 5 to 10 minutes. However，due to the lack of optimization in the adjustment amount calculation method and the immense adjustment workload，it can only serve a theoretical guiding role in field applications. Manual adjustment of operation priorities and workloads remains necessary，hindering its direct extension to practical engineering applications.
ObjectiveTo ensure the operational stability of PSD （platform screen door） systems under high-density train operation conditions and to address the problem on Shanghai Metro Line 18 where strong piston wind generated by train crossings during peak hours causes sluggish closure or even failure of some PSDs to close，it is necessary to investigate the couped effects of tunnel ventilation shaft conditions and train operating parameters on the wind pressure distribution acting on PSDs. MethodTaking a typical linear island-platform station on Shanghai Rail Transit Line 18 as the research object，field measurements and data analysis are conducted. Multi-condition tests are performed on wind pressure，wind speed，and door-closing friction force for sliding doors at different locations，thereby clarifying the force characteristics and failure mechanisms of PSDs. Result & Conclusion When the tunnel ventilation shafts are closed，the maximum wind pressure acting on certain PSDs can reache 235.00 Pa，far exceeding the safety pressure threshold of 70.00 Pa，resulting in door-closing friction forces exceeding the upper limit of the driving force. Based on the measured data，optimization schemes for door-closing sequences and enhancement of driving force are proposed. These findings can provide a scientific basis for the design improvement and operational optimization of metro PSD systems.
ObjectiveTo overcome the problems of low efficiency，high safety risks，and slow review rates associated with the manual inspection of three types of apparent defects，namely water leakage，breakage，and cracks，in underground confined spaces such as flue layers，equipment maintenance layers，and tunnel box structures of urban rail transit，an engineering detection method for apparent defects in urban rail transit confined spaces based on YOLOv8s model is proposed. MethodBased on manually captured photographs，a dedicated image dataset containing multiple categories of confined space defects is constructed. YOLOv8s is adopted as the baseline model; parameters are set and the model is trained specifically to address characteristics such as uneven lighting and insufficient photo clarity. By simulating a scenario where an independent inspection vehicle equipped with a panoramic camera captures images on-site，the feasibility of identifying apparent defects in confined spaces using this model is verified. Result & Conclusion The test results indicate that the detection efficiency of manual inspection is 0.8 m/s. When the confidence threshold is set to 0.4，the precision and recall rates of this model for detecting the three types of apparent defects in confined spaces are 60% and 65%，respectively，with an F1-score of 60%. The overall mean average precision （mAP） of the model is 59.5%，and the model inference speed is 30 frame/s，demonstrating the feasibility of directly applying the YOLOv8s model in such complex scenarios. By simulating dynamic scenarios and constructing a dataset oriented toward real-world sites，it is verified that the dynamic detection capability of the model is relatively stable. It exhibits practical potential for dynamic inspection tasks and holds engineering application value.
