Evaluate and Analyze the Characteristics of Subway Transfer Station Facilities Based on Universal Design from the Cases of South Korea

Abstract

This study examines the design characteristics of subway transfer station facilities in South Korea using an expanded Universal Design (UD) framework that integrates principles of sustainability. Five representative transfer stations were selected for evaluation using a customized assessment tool grounded in seven adapted UD principles: equitability, simplicity, perceptibility, safety, low physical effort, accessibility, and sustainability. Facility elements were analyzed across five categories: access routes, internal facilities, sanitary amenities, guidance systems, and other supportive features. Field observations and scoring using a structured evaluation scale revealed both strengths and critical deficiencies. Key issues identified include inadequate vertical mobility infrastructure, insufficient tactile signage for visually impaired users, and inconsistencies in environmentally responsive design. These shortcomings highlight the need for more inclusive and sustainable design interventions. The study emphasizes the importance of integrating accessibility and ecological responsibility in the planning and renovation of transit facilities. By offering empirical data and actionable recommendations, this research contributes to improving the design quality of transfer stations, fostering more inclusive, efficient, and environmentally resilient urban transportation systems–both in South Korea and in global urban contexts.

1. Introduction

1.1. Research Background

Subway networks are a cornerstone of sustainable transportation in South Korea [1,2], serving as the primary mode of transit for residents in major cities such as Busan, Daegu, Seoul, and Incheon [3]. Within this system, transfer stations play a crucial role in maintaining seamless connectivity, linking different subway lines and integrating the network with other modes of transportation [4]. Their efficiency is essential for ensuring smooth operations and enhancing overall urban mobility. Therefore, expanding transfer stations and enhancing their service quality will significantly boost traffic efficiency and optimize urban transportation [5].

Compared to basic stations, transfer stations handle significantly higher daily passenger volumes and require greater investment in infrastructure and amenities. Moreover, they must meet rigorous standards for usability, accessibility, sustainability, and social inclusion, ensuring an efficient and inclusive transit experience [6].

This research focuses on evaluating and analyzing the characteristics of transfer station facilities through the lens of Universal Design. Based on these findings, it aims to provide essential data to inform future enhancements in metro systems.

1.2. Literature Review

1.2.1. Universal Design Principles Theory

Universal Design (UD) was defined by Ronald Mace, founder of the Center for Universal Design at North Carolina State University, as “The design of products and environments to be usable by all people, to the greatest extent possible, without the need for adaptation or specialized design.” [7]. To translate this concept into practice, Ronald Mace initially proposed four core characteristics to describe Universal Design, known as the 4 UD, which include Accessible, Usable, Esthetically Pleasing, and Marketable [8]. Later, in 1997, these foundations were further developed into the Seven Principles of Universal Design (7UD), providing a more detailed framework to guide designers in creating inclusive and accessible environments. Beyond a design philosophy, Universal Design serves as a framework that enhances quality of life by improving human performance, health, and wellness, and social participation for a diverse population. In the United States, the 7UD principles (see Appendix A) have influenced architectural design laws, notably the Americans with Disabilities Act (ADA) of 1990 and the ADA Standards for Accessible Design. These regulations mandate that public facilities be accessible to individuals with disabilities, reflecting the core tenets of Universal Design [9,10,11,12,13].

The concept of Universal Design in public transport planning emphasizes establishing requirements for facilities and vehicles that maximize accessibility and serve the widest possible range of passengers [14]. However, fully realizing Universal Design in subway transfer stations requires a holistic and systematic approach that integrates its principles throughout the entire facility development process. Such an approach ensures that spaces are not only versatile but also thoughtfully designed and optimized, ultimately providing meaningful benefits for all users.

1.2.2. Previous Studies Review

Previous studies on subway and railway systems have largely concentrated on operators, entities responsible for infrastructure ownership and management, emphasizing productivity and profitability [15]. In contrast, relatively few investigations have explored the spatial design and transfer efficiency of subway stations themselves. However, a growing subset of research has adopted the Universal Design (UD) framework to promote equitable access across user groups. For example, Young Hang-Cho evaluated accessibility in the Busan Metro system, revealing superior performance in newer lines, while older stations on Lines 1 and 2 remained deficient in features such as handrails and vertical transportation [16]. Similarly, Chun et al. developed a checklist assessing interior elements—lighting, flooring, signage, and handrails—to improve spatial orientation and safety for visually impaired users [17].

Recent studies have extended Universal Design (UD) evaluation in subway stations by incorporating criteria such as amenity and eco-friendliness. Sun Tae-Kim et al. identified critical deficiencies in accessibility and guidance facilities at Byeongjeom and Suwon stations, emphasizing the need for more inclusive infrastructure [18]. Ji, Du, and Li applied machine learning to analyze user satisfaction in cold-climate regions, highlighting the importance of entrance design adaptations like anti-slip surfaces and wind barriers [19]. Other scholars, such as Kim et al., focused on passenger flow optimization using smart card data [20], while Kang et al. stressed integrating national UD standards with local strategies [21]. Lee’s design concept for Fukuoka Subway Line 3 further illustrated how cultural identity can align with comfort and sustainability in transit environments [22].

To enhance objectivity in evaluating transfer station performance, Data Envelopment Analysis (DEA) has emerged as a robust benchmarking method. Chang Hee-Kim applied a bootstrap-based DEA model to assess Seoul’s subway network, revealing a strong correlation between station efficiency and infrastructure quality [2]. Building on this, Sun et al. used DEA to evaluate ten Beijing transport terminals, identifying key input-output indicators—such as terminal size, staffing, and safety—to recommend operational improvements [23].

Recent studies have also emphasized specific design elements influencing user behavior and satisfaction in transfer stations. Zhao et al. demonstrated how the placement of induction facilities at station exits significantly affects passenger flow and wayfinding efficiency [24]. Yao et al. examined service facility adaptability in high-density urban transfer hubs, highlighting spatial mismatches between user demand and capacity, particularly in developing contexts [25]. Addressing environmental and perceptual factors, Wu et al. introduced a multi-criteria framework—based on safety, convenience, practicality, comfort, and esthetics—using fuzzy analysis in Shanghai Metro; safety and convenience emerged as dominant factors shaping user experience [26]. In a more integrative approach, Xu et al. proposed the “Urban Core” and “Pedestrian Network” concepts, merging vertical and horizontal systems to improve accessibility, natural ventilation, and ecological performance—offering a comprehensive model for sustainable, inclusive transfer station design [27].

1.2.3. Research Gap and Significant

Most studies have primarily focused on the effectiveness and usability of train station designs through the lens of Universal Design (UD). While the importance of sustainable design has been acknowledged, it has seldom been explored in depth. Furthermore, the assessment of transfer station efficiency based on Universal Design principles remains largely overlooked, representing a significant yet underexplored area of research.

Although sustainability is increasingly recognized as a critical aspect of transportation infrastructure design, current applications of Universal Design principles tend to emphasize accessibility and usability while neglecting the systematic integration of sustainability strategies. Specifically, considerations such as resource efficiency, environmental impact mitigation, life-cycle durability, and adaptability over time are rarely incorporated into the Universal Design frameworks applied to public transportation hubs. This gap suggests that existing interpretations of Universal Design are overly centered on short-term, human-focused accessibility, without adequately addressing broader environmental, economic, and social sustainability goals.

Integrating sustainability explicitly into Universal Design frameworks is therefore essential to ensure that transfer stations not only accommodate diverse users effectively but also contribute to long-term resilience, ecological responsibility, and future adaptability of urban transportation systems. To address these limitations, a new generation of Universal Design frameworks should be developed, explicitly merging sustainability principles with accessibility and usability considerations.

1.3. Research Objectives

This study aims to investigate the design challenges encountered by persons with disabilities and individuals with limited mobility within metro transfer stations. The research framework is structured around five key categories of facilities: access route facilities, internal movement facilities, sanitary facilities, guidance facilities, and other supporting amenities.

An evaluation tool was developed based on a set of seven newly adapted principles derived from the Universal Design concept, emphasizing improvements in accessibility, inclusivity, and the overall user experience in metro systems. This tool was subsequently applied to analyze five representative transfer stations across three subway lines in South Korea.

Building upon the evaluation outcomes, the study seeks to provide essential empirical data to guide future improvements and expansions of transfer station infrastructure, with the overarching objective of promoting a more equitable, inclusive, and sustainable urban public transportation environment.

2. Research Method and Scopes

First, a literature review was conducted by extracting and compiling information from academic manuscripts, subway station design books, laws, and regulations. Principles derived from Universal Design were then examined to develop an evaluation sheet. Next, the constructed evaluation sheets were applied to case studies of South Korean metro transfer stations. Finally, on-site observations were conducted to analyze the transfer stations, providing fundamental data to support station improvements and expansions in alignment with sustainable development goals. The study process is explained in Figure 1.

Field surveys were conducted at five representative transfer stations on Busan Line 3, Incheon Line 1, and Daegu Line 1, most of which have been retrofitted following universal design principles. These stations exhibit spatial configurations that reflect local identity, aiding user orientation and navigability. However, several shortcomings remain, particularly in the inconsistent or incomplete implementation of accessibility equipment, which limits the stations’ effectiveness in achieving inclusive design goals. Data collection involved on-site observations, photographs, physical measurements, and review of station layouts and facilities. As summarized in

Table 1. Basic information on the five transfer stations.

Name	Floors	Tracks	Type	Lines
Suyeong	3	2	Underground	Busan Metro Line 2 and Line 3
Deokcheon	3	4	Underground	Busan Metro Line 2 and Line 3
Bupyeong	4	6	Aboveground	Seoul Line 1 and Incheon Line 1
Gyeyang	2	4	Underground	Incheon Line 1 and AREX (Airport Railroad Express)
Banwoldang	3	4	Underground	Daegu Metro Line 1 and Line 2

, all stations share comparable functional layouts. The evaluation focused on the transfer area, defined as the segment extending from the entrance/exit to the platform at each site.

The seven newly adapted principles, as summarized in

Table 2. Seven newly adapted principles of Universal Design (7UD*).

7UD Original	Nakagawa Satoshi	Kose Satoshi	7UD*
Flexibility in use	Equitable Use		Equitability
Equitable Use
Simple and Intuitive Use	Simple and Intuitive Use		Simplicity
Perceptible	Perceptible		Perceptibility
Tolerance of error	Tolerance of error	Safety	Safety
Low physical effort	Low physical effort	Usability	Low physical
Size and space for approach and use	Size and space for approach and use	Accessible	Accessibility
	Quality and Beauty	Esthetic	Sustainability
	Eco-design	Sustainability
	Economical	Feasibility

, proposed in this study integrate elements from the original Seven Principles of Universal Design (Ronald Mace) [10,28,29] as well as from the frameworks developed by Nakagawa Satoshi and Kose Satoshi [30,31].

The primary goal of this integration is to conduct a comprehensive evaluation of station facilities, allowing for the creation of adaptable and user-centered spaces that cater to diverse commuter needs. Additionally, this approach supports the development of energy-efficient transfer stations, contributing to a more sustainable and accessible urban transit system.

The seven principles in this study were adapted to fit the specific context of subway transfer station facilities. To ensure a more objective evaluation, detailed assessment metrics were developed by extracting relevant content from other studies and aligning each criterion with its corresponding analysis standard.

3. Constructing Evaluation Tool

The process of developing the evaluation tool for this study is illustrated in Figure 2. Based on the seven principles proposed, the tool was structured as an evaluation sheet to assess the facilities of transfer stations in South Korea, allowing for comparisons between case study analysis and on-site survey results.

The evaluation scores were derived using a 5-point interval scale, adapted from the Likert scale [32,33], where 1 represents “the worst” and 5 represents “the best.” The option (NA) denotes “not applicable”. This scale was specifically modified to reflect the design and condition of transfer station facilities, as well as insights gained from the literature review [34,35].

Evaluating the application of the principles of this study for five transfer stations can be classified into five facilities as Access route facilities, Internal facilities, Sanitary facilities, Guidance facilities, and Other facilities (see Appendix B).

4. Modeling Results

According to the evaluation guideline, the scores were recorded using a 5-point interval scale, representing the current physical condition of each facility (see Appendix C). The final score for each item was calculated as the average of the scores given by five evaluators with a background in design engineering (see

Table 3. Detailed results of Subway transfer stations facilities evaluation.

Classification	Items	Suyeong Transfer Station	Deokcheon Transfer Station	Bupyeong Transfer Station	Gyeyang Transfer Station	Banwoldang Transfer Station	Mean
Access route facilities	Access route to entrance	2.49	3.58	4.20	4.45	4.36	3.81
	Main entrance (door)	2.50	3.50	4.00	3.94	4.33	3.65
Internal facilities	Removing the height difference	3.33	4.50	4.66	4.83	4.00	4.26
	Connection Route	4.49	4.77	NA	NA	NA	4.63
	Ramps	4.37	4.16	4.94	NA	NA	4.49
	Stairs	3.33	3.97	4.85	4.83	4.97	4.39
	Elevators	4.68	4.52	4.70	4.95	4.93	4.75
	Escalators	4.56	3.95	4.71	4.95	4.85	4.6
	Wheelchair lifts	3.88	4.21	4.50	NA	NA	4.19
Sanitary facilities	Restroom	3.16	4.37	4.24	4.12	3.87	3.95
	Toilet for the disabled	3.78	4.09	4.80	4.56	3.87	4.22
	Wash basin	4.40	3.25	5.00	4.53	4.93	4.42
	Urinal	4.53	4.66	5.00	5.00	5.00	4.83
Guidance facilities	Guidance and Signs facilities	3.17	4.17	3.78	3.91	3.71	3.74
	Tactile tile/blocks	4.83	4.50	4.25	4.50	3.75	4.36
	Braille information map	3.33	4.50	5.00	5.00	2.00	3.96
	Alarming and Emergency	4.33	4.00	3.33	3.16	3.16	3.59
	Voice guidance	4.00	5.00	4.00	4.00	4.00	4.2
Other facilities spaces	Platform	3.99	4.23	4.42	4.14	3.85	4.12
	Ticket office and vending machines	3.69	4.18	5.00	4.92	4.88	4.53
	Information/service counter	4.44	4.88	5.00	4.55	4.11	4.59
	Ticket barrier in/out	5.00	5.00	5.00	5.00	3.50	4.70
	Etc Facilities	3.40	3.90	4.09	3.47	3.28	3.62
Rating scale: Very good (5), Good (4), Average (3), Bad (2), Very bad (1), NA (not applicable)

). The detailed assessment items presented in bold font denote features directly pertinent to the usability of station facilities by individuals with disabilities. These highlighted elements serve as critical indicators for evaluating accessibility performance and identifying priority areas for inclusive design enhancement. Evaluation items receiving scores at or below the established average threshold for each station are identified as critical areas requiring targeted improvement. These low-scoring elements serve as indicators of performance gaps in current facility design or implementation and thus warrant prioritized consideration in future planning, retrofitting, or policy intervention aimed at enhancing accessibility, functionality, and user experience within transfer stations.

4.1. Facilities Evaluation

4.1.1. Access Route Facilities

The statistical result indicates that the access route to the entrance at Suyeong Transfer Station received the lowest score of 2.49, while Gyeyang Transfer Station achieved the highest score of 4.45 in this category.

For the main entrance (door) section, the highest score was recorded at Banwoldang Transfer Station (4.33), followed by Bupyeong Transfer Station (4.00). Once again, Suyeong Transfer Station received the lowest score in this category, with a rating of 2.50 (see Table 3).

Regarding intermediate facilities, the statistical analysis highlighted two outstanding stations as positive examples: Gyeyang Transfer Station with a score of 4.19, and Banwoldang Transfer Station with 4.34 (see

Table 4. Evaluation average scores for five Subway transfer stations.

	Transfer Station	Suyeong	Deokcheon	Bupyeong	Gyeyang	Banwoldang
Facilities
Access route facilities		2.49	3.54	4.10	4.19	4.34
Internal facilities		4.09	4.29	4.72	4.89	4.68
Sanitary facilities		3.96	4.09	4.52	4.55	4.41
Guidance facilities		3.93	4.43	4.01	4.11	3.32
Other facilities space		4.10	4.43	4.75	4.41	3.92
Average		3.71	4.15	4.42	4.43	4.13

).

The arrangement of vertical movement facilities for people with disabilities should be prioritized at transfer stations or gates where user flow and operational efficiency can be maximized. To enhance inclusivity and user satisfaction, it is essential to develop accessible infrastructure and services that accommodate individuals of all ages and physical abilities. Elevators and ramps should be strategically positioned as close to station entrances as possible to support seamless mobility. Additionally, key features such as induction markers, ergonomic handrails, and clearly visible directional signage must be significantly improved to ensure safe and intuitive navigation. Special emphasis should also be placed on the proper installation and maintenance of tactile warning blocks, directional tiles, braille display panels positioned at accessible heights, and anti-slip stair surfaces, as these elements are critical for promoting independent, safe movement for passengers with disabilities. Enhancing sustainability at subway transfer station entrances/exits requires integrated solutions across environmental, social, and economic dimensions. Environmentally, features like LED lighting, natural ventilation, and green materials reduce energy use. Socially, universal design-ramps, Braille, real-time info ensure accessibility. Economically, the adoption of durable infrastructure and integration of commercial services enhances operational efficiency and generates supplementary revenue, thereby contributing to the long-term resilience and inclusivity of urban transit systems.

4.1.2. Internal Facilities

According to the evaluation results, the stairs at Suyeong Transfer Station received the lowest score among all surveyed stations, with a rating of 3.33, while the highest score was recorded at Banwoldang Transfer Station (4.97). Regarding internal facilities, the wheelchair lifts at Suyeong Station also showed weak performance, with an average score of 3.88.

Further analysis identified several significant deficiencies impacting accessibility and safety in subway transfer stations. Some stations lacked ramps entirely or provided only limited access, severely restricting mobility for users with disabilities. Staircases often had no tactile warning blocks, or the blocks were too narrow to be effective, making navigation difficult for visually impaired users. The absence of clearly marked connection routes indicated a failure to ensure equitable access across facilities. In multiple stations, handrails ended abruptly or lacked proper end treatments, posing safety hazards. Many handrails were installed at heights exceeding the recommended 0.9 m, making them non-compliant with accessibility standards. Additionally, some stations did not meet established criteria for handrail diameter or failed to incorporate braille signage, limiting usability for visually impaired passengers. Emergency exits were frequently undersized, making safe and efficient evacuation challenging, particularly for users with mobility aids. These findings highlight the urgent need for design improvements aligned with Universal Design principles, emphasizing safety, accessibility, and inclusivity for all users.

In addition to accessibility issues, the sustainability of interior station environments remains a significant concern. Many transfer stations lack natural ventilation, rely on non-eco-friendly materials, and offer poor air quality and lighting conditions. Enhancing passive ventilation through atrium design can improve air circulation, reduce enclosure, and support CO₂ reduction. However, green elements such as indoor plants, low-energy displays, and renewable energy systems are still largely absent. These deficiencies underscore the need for an integrated design approach that addresses environmental sustainability alongside accessibility and user well-being.

4.1.3. Sanitary Facilities

The statistical table indicates that the Toilet for the Disabled section at Bupyeong transfer station (4.80) and Gyeyang transfer station (4.56) rank highest in this category, largely due to the use of safe and accessible materials, while the Suyeong transfer station received the lowest score (3.78). All five transfer stations are equipped with restrooms specifically designed for individuals with disabilities, generally including features intended to meet the needs of passengers with reduced mobility. However, several design deficiencies hinder full accessibility, such as narrow entrances that are not wide enough to accommodate wheelchair users, the absence of tactile warning strips at restroom entrances that compromise safety for visually impaired users, and non-slip resistant flooring that increases the risk of falls and injuries. These shortcomings underscore the need for continued improvements in the design and implementation of accessible restroom facilities to ensure a safer and more inclusive environment for all passengers, particularly those with disabilities. Beyond accessibility, restroom sustainability in transfer stations remains insufficient. Many facilities lack water-saving fixtures, energy-efficient lighting, and proper ventilation. The use of non-recyclable materials and the absence of waste sorting or eco-friendly cleaning practices further reduce environmental performance. To meet sustainable design standards, restrooms should adopt resource-efficient technologies and environmentally responsible materials that enhance both ecological outcomes and user well-being.

4.1.4. Guidance Facilities

According to statistical data, the guidance and signage facilities at Deokcheon Transfer Station received the highest score (4.17), followed by Gyeyang Transfer Station with a score of 3.91. In contrast, Suyeong Transfer Station (3.17) received the lowest score in this category. Statistical graphics illustrate that guidance systems are generally arranged in accordance with safety and wayfinding principles across the evaluated stations. The color schemes used in signage are also well-coordinated with subway line colors, improving visual recognition and orientation. A notable accessibility issue at Banwoldang Station pertains to the limited provision of Braille information maps. Although such a layout exists, the station received a low evaluation score of 2.0 due to the insufficient quantity of Braille boards, which significantly impedes navigation for visually impaired passengers. To enhance the station’s accessibility and align with inclusive design principles, increasing the number and strategic placement of these tactile maps is recommended in future improvements.

Despite efforts to enhance wayfinding, many new passengers, particularly foreign visitors, continue to struggle with navigating to the correct exits or transfer routes due to persistent issues such as orientation errors, unclear or inaccurate directional signage, lack of residual distance information, and inadequate directional validation. These problems are especially pronounced at Suyeong Transfer Station, which received 3.62 points for the safety field. Additionally, guidance systems at several stations remain overly complex and inconsistent, often featuring confusing billboards, non-standardized pictographic designs, and contradictory direction boards. These shortcomings significantly hinder wayfinding, especially for passengers with visual impairments, who also face challenges such as the absence of directional confirmation signage, missing slope gradient indicators, and insufficient information on remaining distances to key facilities. To improve accessibility and navigation efficiency, directional arrows and visual cues should be placed in highly visible locations and accompanied by international accessibility symbols. Furthermore, stations should implement clearer signage for stair usage and inter-line transfers to facilitate smoother and more inclusive passenger movement.

In addition, future transfer station designs should incorporate sustainable, low-maintenance, and cost-effective solutions through the use of climate-appropriate materials, installation of LED lighting systems, adoption of passive solar lighting and heating technologies, and integration of energy-efficient systems. These enhancements would not only improve user experience and accessibility but also promote environmental sustainability and increase the operational efficiency of the metro system.

4.1.5. Other Facilities

Information and other convenience facilities for people with disabilities were considered across all five stations. The result showed that Bupyeon Transfer Station demonstrated a strong focus on sustainability, with the integration of commercial spaces and community activity areas, earning a score of 4.75 in this category. In contrast, Banwoldang Transfer Station recorded a lowest score of 3.92.

To improve both safety and comfort, a comprehensive plan is needed to reduce train noise and enhance passenger protection, with a key recommendation being the installation of platform screen doors at all subway transfer stations, particularly those experiencing high passenger volumes or featuring wide platform gaps. Additionally, each station should be uniquely designed to reflect its local identity and community character by assigning distinctive color themes, incorporating exhibition spaces or art displays, and utilizing locally inspired bench materials or designs. These enhancements not only support station recognition and wayfinding, especially for passengers with cognitive or visual impairments, but also foster more inclusive, engaging, and socially vibrant environments within the metro system.

4.2. Comparative Summary

Based on statistical data (see

Table 5. Results of Universal Design application on five Subway transfer stations.

	UD* Principles	Equitability	Simplicity	Perceptibility	Safety	Low physical	Accessibility	Sustainability
Transfer Stations
Suyeong		3.57	3.57	3.62	3.62	3.56	3.70	3.65
Deokcheon		3.66	3.64	3.78	3.71	3.60	3.79	3.99
Bupyeong		3.88	3.73	3.37	3.69	3.83	3.95	3.99
Gyeyang		4.09	4.05	3.72	3.91	4.01	4.21	4.06
Banwoldang		3.87	3.85	3.67	3.90	3.85	3.92	3.72

), Gyeyang Transfer Station achieved the highest overall average score across all categories, making it the most successful in applying Universal Design principles. It was followed by Bupyeong, Deokcheon, and Banwoldang Transfer Stations, which also demonstrated relatively high performance in selected categories. In contrast, Suyeong Transfer Station consistently received the lowest average scores, indicating significant shortcomings in Universal Design implementation. These findings are supported by the statistical graphics presented in Figure 3, which visualize the relative performance of each station across the seven Universal Design principles.

• Gyeyang Transfer Station: Achieved the highest score in Accessibility (4.21); Scored the lowest in Perceptible Information (3.72). Overall, this station exemplifies a well-integrated application of Universal Design in both space layout and facility efficiency.
• Suyeong Transfer Station: Although it scored the highest in Accessibility among its own categories (3.70), it had the lowest score in Low Physical Effort (3.56). It held the lowest average scores overall among all stations analyzed.
• Deokcheon Transfer Station: Scored lowest in Low Physical Effort (3.60); Achieved its highest rating in Sustainability (3.90).
• Bupyeong Transfer Station: Performed well in Sustainability with a top score of 3.99; Scored the lowest in Perceptible Information (3.37), highlighting a need for better signage and guidance systems.
• Banwoldang Transfer Station: Displayed strong Accessibility (3.92); Scored 3.67 in Perceptible Information, indicating moderate performance in communica-tion-related design.

Overall, all five evaluated subway transfer stations received fairly good evaluation scores, with all scores across the seven aspects being greater than 3; they all demonstrate commendable efforts in ensuring safety, high mobility, and clear information accessibility. Most stations incorporate features that enhance comfort and accessibility for passengers with visual, hearing, or mobility impairments, reflecting the application of Universal Design principles.

However, several issues remain that require attention. These include the need to make stations more easily identifiable, as well as to better utilize natural ventilation and lighting to enhance sustainability and user comfort.

The identification of best-performing elements across stations and the comparative evaluation established in this study can serve as foundational data for improving the design of future subway transfer stations, ensuring they are more inclusive, efficient, and aligned with sustainable development goals.

4.3. Design Integration of Universal and Environmental Sustainability Features for Future Projects

To shape the future of inclusive and sustainable urban infrastructure, policymakers and architectural designers must take an active role in integrating Universal Design features and environmentally sustainable strategies into the architectural planning of subway transfer stations. As awareness grows, the necessity and significance of these elements will likely gain broader public and institutional support, encouraging their implementation in appropriate contexts.

The environmental evaluation of transfer stations in South Korea highlights several components that exemplify effective Universal Design in practice, including clearly defined movement lines for simplified navigation, restrooms accessible to wheelchair users equipped with automatic sensor technology, directional arrows on stairs and transfer paths, multi-language audio announcements and visual information systems on platforms and trains, braille maps at key station points, tactile warning and directional tiles extending from entrances to platforms, and variable lighting levels tailored to different functional zones to enhance visibility and spatial clarity. Additionally, simple and intuitive signage, platform screen doors for safety and noise reduction, wide corridors and waiting areas for easier movement, and distinct station identities using symbolic colors and icons further reinforce inclusivity. In parallel, many stations either demonstrate or are encouraged to adopt environmentally responsible features such as motion-sensor escalators, sensor-activated toilet fixtures to minimize water and energy waste, rainwater harvesting systems, on-site renewable energy options, atrium cores to support natural airflow and reduce reliance on mechanical ventilation, and expanded use of natural lighting, especially in underground facilities, to conserve energy and improve indoor environments. Integrating these elements into future subway transfer station projects will significantly elevate the quality of life, operational efficiency, and environmental performance of transit spaces, supporting users of all abilities while aligning with broader goals for sustainable urban development.

5. Conclusions

Based on the analysis and comparison of subway transfer station types evaluated through a structured Universal Design assessment framework, this study presents several key conclusions:

• The implementation of Universal Design principles in South Korea’s subway transfer station designs is notably advanced, providing valuable benchmarks for future development and redevelopment projects, especially in promoting accessi-bility and inclusivity for diverse user groups in interconnected urban environments.
• The seven newly adapted principles of Universal Design (7UD*) offer a valuable foundation for creating sustainable mass transit systems, promoting inclusivity, efficiency, and environmental resilience in the ongoing expansion of global trans-portation infrastructure.
• The proposed evaluation framework, grounded in the newly adapted Seven Uni-versal Design (7UD*) principles, is designed for application by both professionals and end-users. It facilitates the systematic identification of architectural and oper-ational features that enhance station accessibility for all user groups, particularly individuals with disabilities. Furthermore, the tool serves as a foundational resource for guiding environmentally responsible retrofitting and future design interven-tions within transit infrastructure.
• The assessment identified several best-practice elements, such as the use of elevators instead of wheelchair lifts, ramps replacing stairs for barrier-free access, accessible restrooms, ticket offices, and vending machines, integration of audio and visual information systems, universal signage, distinct station symbols and color schemes, and the inclusion of atrium cores for improved vertical circulation and environ-mental performance.