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

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

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

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

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

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.

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.

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.

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.

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.