The Renewal of Lost Space under Overpasses in Chengdu City Based on Residents’ Requirements for Cultural Services: The Case of the Longtan Overpass

Abstract

In modern urban development, utilizing the space under overpasses (SUO) contributes to connecting the cityscape and facilitating the transformation of SUO into a public urban space. However, existing studies sometimes fail to properly take into account user requirements, resulting in the neglect of the SUO by the population. The solutions proposed are based on the assumption that the SUO can be renewed, but there is no thorough evaluation methodology to determine if the current state of the SUO can be renewed and in which areas it needs renewal. In this research, all the overpasses within the Third Ring Road in Chengdu are taken as samples. Based on cultural ecosystem services (CES) and external spatial quality (ESQ), an evaluation system for the renewal potential of SUO was established and the overpass with the most potential for regeneration was selected: the Longtan Overpass. Further, the KANO model was used to explore the categories of residents’ requirements for indicators of CES in the space under Longtan Overpass, so as to propose targeted renewal strategies. This study found a positive correlation between the satisfaction of residents living near Longtan Overpass and the natural aesthetics and facade landscape of the SUO. It also suggests that enhancing cultural service indicators such as sports, human aesthetics, customs and humanities, and geographical history can improve the attractiveness of the SUO. This study also found that quantitatively assessing the value of SUO through ecosystem cultural services is feasible, which provides new ideas and methods for updating SUO. These findings help urban designers understand how people feel.

1. Introduction

With the development of urban planning and design theories [1], researchers have shifted their focus towards exploring different sorts of “negative” spaces in the city, which are usually ignored and underutilized in contrast to “positive” spaces [2]. In 1996, the Department of Urban Planning at the University of California, Los Angeles (UCLA) in the U.S. introduced the notion of “lost space” to address the quality of urban architecture. Yoshinobu Ashihara, a renowned modern architect in Japan, introduced the concepts of “positive space” and “negative space” in architecture. Negative space is described as an unstructured and spontaneous environment [3]. Professor Robben Transick from Cornell University introduced the idea of “lost space” in the book “Finding Lost Space” [4]. He described “lost space” as an unappealing, non-traditional urban area that required redesigning. This space was deemed unbeneficial to both the environment and its users, lacking clear boundaries. Chinese scholars are now concentrating more on studying lost urban spaces due to the changing direction of urban development. Researchers identified residual urban space as urban areas that have not been effectively planned or utilized in urban planning. These spaces now lack an adaptive purpose and fail to fulfill their intended role [5]. Other researchers thought that unused areas were frequently disregarded, deserted, or leftover by space occupants, resulting in a failure to completely and effectively exploit their potential [6]. This paper defines lost space as the area within the city’s built-up zone that is frequently overlooked and underutilized and lacks proper planning and design guidance, drawing from theoretical studies at both domestic and international levels and incorporating academic research from various scholars on lost space and related practices.

As the concept of lost space becomes more defined, the renewal of lost space is garnering increased focus. In 1961, Jane Jacobs argued in “The Death and Life of Great American Cities” that extensive demolition and construction behaviors destroyed unique urban spaces and cultures [7], and she advocated periodic small-scale renovations to preserve the energy of spaces and cities. she emphasized the potential of digging urban lost space laterally and acknowledged the beneficial impact that renovations to urban lost space confer upon cities. In 2003, Hendra and Limburg incorporated lost space as temporary use into urban planning and design. This actual case illustrated that the renewal of lost space significantly stimulated the local urban culture and economy. These studies have, to a certain degree, demonstrated the importance of renewing lost space in facilitating urban development [8]. Consequently, it is essential that we conduct contemporary study on the lost space within urban environments.

China’s rapid urbanization in recent decades has resulted in an increase in various lost places [9]. Urbanization has led to an increased demand for public space [5], while the supply is insufficient, raising concerns about utilizing various forms of lost space. The space under overpasses (SUO) has attracted considerable public interest because of its large size and abundance [1]. Overpasses [10] are land bridges with upper and lower levels that allow multi-directional driving without hindrance. They are usually constructed at vital intersections in urban areas. The scope of this paper’s research on the space under overpasses (SUO) is the principal projection section of the SUO in the urban built-up area as well as the surrounding road traffic space affected by it. Presently, the majority of research on the SUO focuses on classification, value, landscape design, and other spatial features [11]. These studies mostly concentrate on the uniform and undifferentiated change of the SUO without offering unique solutions based on its ability to renovate, thereby reducing its attraction to the population [12]. Simultaneously, there is a scarcity of quantitative studies on the practical value of the SUO. The current state and needs of the SUO have not been thoroughly and intentionally assessed. The proposed techniques focus on regularly renewing the SUO without implementing a thorough evaluation system to assess the ability and method of renewing the SUO. Disregarding the requirements leads to a lack of humanization, resulting in disconnection between the SUO and society. Hence, in order to incorporate the SUO into society and utilize it efficiently [13], it is crucial to address the challenges related to evaluating the current value of the SUO and identifying its requirements for humanization [14].

In the realm of sustainable urban development, a growing amount of research integrates cultural ecosystem services (CES) to renovate diverse urban public spaces, including parks and waterfront green space [15], thereby fostering the relationship between citizens and urban environments and yielding positive outcomes [16]. The lost space under the overpass is not merely a singular sort of lost space but also an integral element of urban public space. Consequently, the introduction of CES to renovate the lost space under the overpass is feasible.

Cultural ecosystem services (CES), as one of the components of ecosystem services [17], facilitate the interaction between ecosystems and society [18] as well as the link between human beings and nature [19]. The assessment of it can provide a good grasp of the value of non-material benefits from ecosystems to better guide urban planning and design [20]. Recently, CES has garnered increased attention because of its strong connection to urban renewal and social development. CES are the intangible advantages that individuals receive from ecosystems [21], with their core being the extra value of ecosystem services to the spiritual aspect of humans [22]. They are manifested in activities like spirituality and religion, recreation, aesthetics, education, and culture [23]. The CES assessment provides individuals with a greater comprehension of the site’s present status, thereby facilitating precise adjustments to the site [24].

This research introduced CES and established a system of evaluation for the renovation potential of the SUO. It offers innovative research concepts and methodologies for addressing the current challenges in urban SUO renewal design. This study attempts to investigate three primary research inquiries: (1) What is the current condition of overpasses in Chengdu? How should it be assessed? (2) Are all existing overpasses in Chengdu City suitable for renewal based on their current status? If not, what is the appropriate method for selecting them? (3) After identifying the overpasses that qualify for renewal, how should the consideration of humanized needs be incorporated in directing the renewal process?

During China’s rapid urbanization, numerous cities have arisen with varied degrees of lost spaces. Chengdu, as a provincial capital in China, has experienced significant transportation growth, resulting in numerous lost spaces under overpasses, particularly evident in the range from the Third Ring Road to the city center. Accordingly, this study samples all the overpasses located on the Third Ring Road in Chengdu city and within the Third Ring Road. Two evaluation systems are constructed to quantify the functional value of the SUO based on the non-material benefits of CES and the material spatial conditions of overpasses. This methodology helps in recognizing and analyzing the current situation of overpasses [25], and the results obtained are used to address the first question. Meanwhile, to address the second question, this study assessed the relative value of each overpass in the city based on question 1, using a two-dimensional quadrant diagram to screen and identify which ones have more favorable conditions for renewal. To address the third question, on the basis of the screened SUO, the KANO model is used to analyze the requirements of the surrounding residents for cultural service indicators of the screened SUO, which allows the designer to conduct a detailed study of specific issues based on the needs of residents, so as to improve the acceptance and utilization of the SUO by the users, and to promote the connection between human beings and nature, thus completing answers to all three questions in turn. This study aims to address the issue of an inadequate evaluation system for underpasses and other lost spaces while also offering a practical approach to rebuilding and utilizing these spaces in urban renewal projects [26]. Theoretically, this study presents a new viewpoint on utilizing lost spaces under overpasses, enriching the understanding of its worth in urban areas. Figure 1 illustrates the process of formulating and solving the research challenge (Figure 1).

2. Data and Methods

2.1. Study Area

The study area is Chengdu City, also known as “Rong”, which is a prefecture-level city in Sichuan Province. Chengdu, the capital of Sichuan Province, is a contemporary and bustling city noted for its “Chengdu Slow Life” concept. Chengdu has been acknowledged as the “first park city” in recent years, emphasizing ecological conservation and sustainable growth [27]. Chengdu is situated in southwestern China and has a humid subtropical monsoon climate. It covers a total area of 14,335 km². The city comprises 12 municipal districts, 3 counties, and 5 county-level cities under its control. By 2023, Chengdu is projected to have a GDP of 2207.47 billion yuan and a population of 21,403 million people.

Chengdu, a representative domestic city, has been at the forefront of exploring the use of lost spaces and landscape development [28]. The city has actively encouraged the conversion of lost spaces under overpasses into urban public space [5]. Recently, Chengdu has seen a rise in the construction of huge overpasses due to improvements in the city’s transportation system. Undoubtedly, the SUO are becoming increasingly versatile in this trend, with the design of SUO broadening steadily, including under-bridge gardens, sports parks, and more.

The SUO in Chengdu can be classified into two categories: belt areas controlled by road linear viaducts underneath and the planar areas controlled by intersecting overpasses underneath. Overpasses are a common type of bridge known for their significant size and intricate design. This paper focuses on the faceted space under this particular type of bridge, the overpass, because of its rich auxiliary spatial resources. The sample of this study includes the planar spaces under all the overpasses in the Third Ring Road and within the Third Ring Road in Chengdu, Sichuan Province, with a total of 35 overpasses. And a field study was conducted on them [29]. Figure 2 displays the distribution of the overpasses analyzed in this study conducted in Chengdu (Figure 2).

This study undertook field research on all overpasses in Chengdu City’s Third Ring Road and within the Third Ring Road from July to September 2023. The summer season was selected to highlight the variations in greenery among the overpasses.

Measuring tools, including rangefinders and tape measures, were used to assess the site for the efficient documentation of site data. The layout and landscape details within the venue were recorded through mobile phones. Simultaneously, an application called SIXFOOT, version 4.20213, on the mobile phone was used to locate the on-site photos (Figure 3) and record the research route. The SIXFOOT application, version 4.20213, was used for this fieldwork to document the current status of the site. It is an outdoor travel software with powerful GPS tracking that records user routes in real time and supports the addition of multimedia elements such as text, images, and video. These features met the fieldwork needs of this study.

2.2. Applying AHP for CES Evaluation

Firstly, this study provides a summary of relevant evaluation systems and literature by referencing the international general cultural ecosystem classification system [30] and establishes the initial indicator system based on the research objectives. Then, the initial indicator system was refined and adapted based on the spatial features of overpasses to create a cultural service indicator system for the lost space ecosystem under overpasses in Chengdu. The system comprises 4 guideline layers and 12 indication layers. After that, the Analytic Hierarchy Process (AHP) [31] was utilized to determine the weights and ranking of variables for creating an evaluation system for the value of CES under the overpasses in Chengdu. Ultimately, fuzzy comprehensive evaluation (FCE) [32] was utilized for quantitative analysis.

2.2.1. Establishment of a CES Indicator System

The Common International Classification of Ecosystem Services (CICES), which is widely recognized by scholars, provides a clearer explanation of the mechanism and process of cultural service value generation. The framework of cultural services is categorized into four principal aspects, along with 11 subcategories. It suggests evaluation metrics derived from explicit and specific activities, appropriate for small-scale spaces. Consequently, this study used the four main aspects of the CICES to inform the indicator system. Beginning with the attributes of cultural services in the SUO, all of these aspects were redefined while preserving their original meanings, this enhancing their relevance to the SUO as the criterion layer of this indicator system. Simultaneously, an in-depth analysis of important indicators was performed through a summary of domestic and international literature, with a focus on the cultural aspects that emphasize the unique characteristics of overpasses. The 11 categories of this category were further refined, resulting in the establishment of a preliminary indication system. Consequently, in alignment with the research content, objectives, and spatial characteristics of urban overpasses, and adhering to Chengdu’s development policies, the indicator system has been improved to establish a CES indicator system for the SUO (

Table 1. The CES indicator system.

Target Layer	Criterion Layer	Indicator Layer
CES Indicator System for Lost Spaces under Chengdu Overpasses	Athletics and Leisure B1	Physical Education and Sport C1
		Leisure and Recreation C2
	Aesthetically B2	Natural Aesthetics C3
		Engineering Aesthetics C4
		Humanistic Aesthetics C5
		Facade Landscape C6
	Science and Culture B3	Geographical History C7
		Customs and Humanities C8
		Popular Science Products C9
	Spiritual Outputs B4	Inspiration C10
		Sense of Identity C11

).

2.2.2. Calculating and Ranking the Weight Values of CES Indicators

The questionnaire is established based on the cultural service indicator system of the lost space ecosystem under overpasses in Chengdu. To enhance the scientific validity and rationality of the weight results, 32 experts, including landscape planning and design managers and university professors from related fields, were invited to complete paper or online questionnaires in a non-face-to-face and non-communicative manner. The initial section of the questionnaire focuses on personal information and establishes the foundation for the indicators’ source and the scoring technique. The second phase involves providing an explanation for the meaning of each indicator. Once the questionnaires were gathered, the weights were determined based on the questionnaire’s rating using the YAAHP program, version 10.1, in accordance with the AHP [32].

We organized the questionnaire data we received and created a judgment matrix [33]. A judgment matrix for the target layer was developed using the relative criterion layers beneath it, pairwise comparisons were conducted among the criterion layers at the same level, a judgment matrix for the criterion layer was developed based on the relevant indicator layers, and then pairwise comparisons were conducted among the indicator layers at the same level. For instance, using the four B-level indicators corresponding to A-level, the judgment matrix for A was formulated as shown.

In the judgment matrix of A (

Table 2. Example of a judgment matrix.

A	B1	B2	B3	B4
B1	1	B1/B2	B1/B3	B1/B4
B2	B2/B1	1	B2/B3	B2/B4
B3	B3/B1	B3/B2	1	B3/B4
B4	B4/B1	B4/B2	B4/B3	1

), formed using B-level indicators, B1/B2 indicates the relative significance of B1 and B2, with its level determined through a comparison of the questionnaire scores of both of them. The judgment matrix compares indications in pairs, utilizing a comparison standard categorized into nine categories. If the significance of pairwise comparisons is equivalent, it is assigned one point. Minor importance is valued at three points. Moderate importance is valued at five points. Significant importance is valued at seven points. Critical importance is valued at nine points. Two, four, six, and eight serve as intermediate values between two levels, whereas the reciprocal in the assessment signifies the contrary meaning of importance. The judgment matrix is calculated using YAAHP, version 10.1. Once the calculation is finished, the results are verified for consistency [34]. If the test fails, the matrix is adjusted. If each indicator passes the test, the relative weight of each indicator is determined compared to the preceding level.

The total ranking of the indicator layers for the CES of the lost space under overpasses in Chengdu City can be calculated by determining the weights of the indicators in each indicator layer relative to the target layer, based on the relative weights of the indicators in the criterion layer relative to the target layer and the relative weights of the indicators in the indicator layer relative to the criterion layer (

Table 3. Weighting and ranking of CES indicators.

Target Level	Standardized Layer	Relative Weight	Indicator Layer	Relative Weight	Absolute Weight	Ranking
CES Evaluation System for Lost Spaces under Chengdu Overpasses A1	Athletics and Leisure B1	0.4912	Physical Education and Sport C1	0.7500	0.3684	1
			Leisure and Recreation C2	0.2500	0.1228	3
	Aesthetically B2	0.2677	Natural Aesthetics C3	0.5217	0.1397	2
			Engineering Aesthetics C4	0.0499	0.0134	11
			Humanistic Aesthetics C5	0.3455	0.0925	4
			Facade Landscape C6	0.0828	0.0222	9
	Science and Culture B3	0.1742	Geographical History C7	0.4160	0.0797	5
			Customs and Humanities C8	0.4577	0.0724	6
			Popular Science Products C9	0.1263	0.0220	10
	Spiritual outputs B4	0.0669	Inspiration C10	0.6667	0.0446	7
			Sense of Identity C11	0.3333	0.0223	8

).

2.2.3. CES Questionnaire Content and Distribution

A questionnaire was created to assess the CES value of the lost space under each overpass in Chengdu using the indicator system that was established. Please see Appendix A for a more detailed example (Figure A1 in Appendix A). The questionnaire includes photographs depicting the current condition of the space under each overpass, acquired through field investigation. A multitude of photographs was chosen from each overpass to distinctly illustrate its present condition and functions. A total of 32 specialists and academics in relevant disciplines were invited to complete surveys regarding numerous overpasses, utilizing online or offline methods, adhering to the basis of non-communication or in-person meetings among participants, with a total of 1120 surveys being handed out. Totally, 1118 out of the total responses were considered real, yielding a valid response rate of 99.8%. The principle of removing invalid questionnaires is as follows: (1) removing questionnaires that were filled out too quickly and (2) removing questionnaires with obvious regularity.

This study’s goal was explained to experts and academics prior to distributing the questionnaire to maintain the scientific integrity of this study. The questionnaire consisted of three sections: the first gathered personal information from the respondents, while the second clarified the significance of each indication, ensuring the respondents comprehended the cultural service indicators through written and verbal explanations. The last part evaluates the significance and content of cultural services. The evaluation set was divided into five levels: “excellent,” “good,” “fair,” “poor,” and “very poor,” with each level corresponding to quantitative values ranging from five to one. The levels were given to five questionnaire options sequentially.

2.2.4. Analysis of Reliability and Validity

The questionnaire data was analyzed for reliability and validity using SPSSAU (v23.0) software to assess the dependability of the data and the appropriateness of the design.

Questionnaire reliability analysis was employed to assess the consistency and dependability of the questionnaire data outcomes, while also indicating the stability and concentration of the data. The questionnaire data on the value of CES under the Chengdu overpass was analyzed using Cronbach’s reliability analysis [35]. A questionnaire is considered reliable if its alpha coefficient exceeds 0.6. The Cronbach’s alpha coefficient for this questionnaire was calculated to be 0.92, surpassing the threshold of 0.6. This indicates that the data collected for this study is highly reliable and can be utilized for subsequent analysis [36].

Validity analysis assesses the rationality and precision of the questionnaire, specifically measuring its level of validity. This work utilizes SPSSAU (v23.0) software and employs KMO value and Bartlett’s sphericity as validity criteria. A KMO value greater than 0.6 signifies the reliability of the questionnaire results and suggests that the data is eligible for extraction [37]. Bartlett’s sphericity test assesses the appropriateness of factor analysis, and a p-value of less than 0.05 indicates suitability. After analyzing the questionnaire, it was found that the KMO value was 0.891, which exceeds the threshold of 0.6. This indicates that the questionnaire has a high level of validity and is appropriate for collecting data. The Bartlett sphericity test yielded a p-value of 0.000, indicating that the data is appropriate for factor analysis [38].

2.2.5. Fuzzy Comprehensive Evaluation (FCE)

FCE utilizes fuzzy mathematics to quantitatively evaluate qualitative indicators [39]. To evaluate the value of the remaining space ecosystem cultural services under each overpass in Chengdu City, FCE [40] had to be used due to the qualitative nature of the CES indicators. This method will provide a total score for the value of these services. The subsequent steps are as follows:

(1)

Determine factor set. Establish the judgment set of the space under an overpass in Chengdu based on the scores of the CES questionnaire for the lost space under that overpass.

(2)

Determine a criterion for judgment. The evaluation level of the questionnaire is divided into five categories: “excellent,” “good,” “fair,” “poor,” and “very poor”.

(3)

Calculate the weight vector. The weight vector is created based on the weights of the indicators derived from the hierarchical analysis approach.

(4)

Create a fuzzy matrix. By standardizing the experts’ assessments of secondary indicators across five levels, the affiliation degree of each element on multiple levels may be determined. The fuzzy matrix R was calculated to determine the CES score in the lost spaces under a certain overpass in Chengdu City.

These steps were utilized to acquire the CES scores for the lost space under the Third Ring Road and 35 overpasses within the Third Ring Road in Chengdu City.

2.3. Applying AHP for SUO Evaluation

2.3.1. Establish a System of Indicators

We conducted the initial selection of ESQ indicators by summarizing the relevant literature and drawing on the evaluation system of linked urban public spaces [41]. Afterwards, the assessment indicator system was modified according to Chengdu City’s planning and design guidelines, incorporating principles of ecology, relaxation, enjoyment, and integrating art, culture, business, and economy to create an optimized system [42]. Finally, based on field research, the index system was enhanced to create the ESQ indicators system for the lost space under overpasses in Chengdu (

Table 4. Indicator system of ESQ evaluation.

Target Layer	Criterion Layer	Indicator Layer
ESQ Indicator System for Lost Spaces under Chengdu Overpasses A1	Accessibility Level B1	Sidewalks C1
		Distance to Bus Stop C2
		Distance to Subway Platform C3
		Traffic Light C4
	Adjacent Locations B2	Distance to Residential Area C5
		Distance to Retailers C6
		Distance to Offices C7
	Space forms B3	Available Area Under the Overpass C8
		Mean Clearance Height of the Space Under the Overpass C9

).

2.3.2. Calculating and Ranking the Weight Values of ESQ Indicators

We designed the questionnaire based on the ESQ assessment technique for the lost spaces under overpasses in Chengdu and consulted 32 relevant experts and professionals. The initial section of the questionnaire focuses on personal information and explains the foundation of the indicators’ source and the scoring principle. The second stage involves elucidating the significance of each indicator. Following the collection of the questionnaire, the AHP was utilized, and the YAAHP software, version 10.1, was employed to calculate the weight of each indicator. The results of the calculation align with the process of determining the weights of the CES indicators discussed before. Once the computation was finished, the weight values and rankings were acquired (

Table 5. Weighting and ranking of ESQ indicators.

Target Level	Standardized Layer	Relative Weight	Indicator Layer	Relative Weight	Absolute Weight	Ranking
ESQ Evaluation System for Lost Spaces under Chengdu Overpasses A1	Accessibility Level B1	0.4905	Sidewalks C1	0.4595	0.2254	2
			Distance to Bus Stop C2	0.2008	0.0985	4
			Distance to Subway Platform C3	0.2008	0.0985	5
			Traffic Light C4	0.1389	0.0681	6
	Adjacent Locations B2	0.1976	Distance to Residential Area C5	0.7394	0.1461	3
			Distance to Retailers C6	0.1788	0.0353	8
			Distance to Offices C7	0.0818	0.0162	9
	Space forms B3	0.3119	Available Area under the Overpass C8	0.8571	0.2673	1
			Mean Clearance Height of the Space under the Overpass C9	0.1429	0.0446	7

).

2.3.3. Evaluation Set of ESQ Indicators

Based on the on-site research and the discussions with experts, a range of values for each indicator was established. Then, by the average segmentation approach, each indicator range was separated into five grades, which are “excellent,” “good,” “fair”, “poor”, and “very poor”, and assigned a value of 5–1.

Table 6. Criteria for evaluating the level of ESQ indicators.

	Excellent	Good	Fair	Poor	Very Poor
Sidewalks (n) C1	>15	11–15	6–10	1–5	0
Distance to Bus Stop (m) C2	<300	300–600	600–900	900–1200	>1200
Distance to Metro Station (m) C3	<300	300–600	600–900	900–1200	>1200
Traffic Light (n) C4	>3	3	2	1	0
Distance to Residential Area (m) C5	<300	300–600	600–900	900–1200	>1200
Distance to Retailers (m) C6	<300	300–600	600–900	900–1200	>1200
Distance to Offices (m) C7	<300	300–600	600–900	900–1200	>1200
Available Area under the Overpass (hm2) C8	>2	1.5–2	1–1.5	0.5–1	<0.5
Mean Clearance Height of the Space under the Overpass (m) C9	>6	5–6	4–5	3–4	<3

displays the rating criteria for each indicator of ESQ (Table 6).

2.3.4. Fuzzy Comprehensive Evaluation

After acquiring the weight values of the ESQ indicators for the lost space under the overpass using the Analytic Hierarchy Process (AHP) [32], the qualitative indicators were then quantitatively examined by employing the Fuzzy Comprehensive Evaluation (FCE) method, based on the standard evaluation set of ESQ indicators. The calculation procedure for FCE is in line with the FCE of CES discussed earlier. The ESQ scores of the lost space underneath each sample overpass were obtained using this method.

2.4. Screening with Two-Dimensional Quadrant Diagram

The average scores for the CES and ESQ of each overpass were determined based on the scores from two evaluation methods [43]. The coordinates of the origin are (0, 0). The x-axis coordinates are calculated by subtracting the mean value of the overpass from the ESQ score. This resulting number can also be referred to as the deviation of the ESQ score. The vertical coordinates (y-axis) are obtained by subtracting the mean value of the CES score, resulting in a value known as the deviation of the CES score. A positive score in one evaluation system indicates that the score is higher than the average, while a negative score indicates it is lower than the average. A two-dimensional quadrant diagram was then created using this data.

The two-dimensional quadrant diagram consists of four quadrants: Quadrant 1 (good external spatial quality and good ecosystem cultural services), Quadrant 2 (poor external spatial quality and good ecosystem cultural services), Quadrant 3 (poor external spatial quality and poor ecosystem cultural services), and Quadrant 4 (good external spatial quality and poor ecosystem cultural services). This study identified overpasses in the fourth quadrant that have high ESQ but require renewal of CES, as per the study objectives. Selected overpasses from the fourth quadrant had both ecological cultural services scores and external spatial quality scores that showed diversity from the mean and were chosen for the KANO model.

2.5. Quantifying the Requirements of the Residents—The KANO Model

The KANO model is a bivariate cognitive model created by Noriaki Kano, who is a renowned professor at the Tokyo Institute of Technology in Japan [44]. The KANO model’s results are derived from statistical analysis of user satisfaction levels with positive and negative aspects of a specific need. This analysis categorizes users’ actual needs and determines the degree of demand [45]. It can determine the optimal services to offer in different circumstances to best meet the genuine demands of people. This research introduces the KANO model to analyze the demand type and intensity for the CES in the lost space under the selected overpass. The questionnaire survey quantified the need for the lost space under the overpass, compares it with several demand indicators, and ranks the user’s demand in order of importance to guide the planning, design, and renewal of the SUO.

The KANO model consists of five categories of requirement types [46]. (1) Must-be requirements: Must-be requirements that are fundamental and have to be met. Customer satisfaction does not improve when it is supplied. Nevertheless, in the absence of supply, satisfaction decreases. (2) One-dimensional requirements: these requirements should be addressed with precedence. Customer satisfaction increases when it is supplied, but if not, it falls. (3) Attractive requirements: they should be met to the best of one’s capacity when possible. Satisfaction increases when such requirements are met. Yet, satisfaction does not decrease in the absence of supply. (4) Indifferent requirements: this requirement is dependent upon actual circumstances when conditions are constrained. Satisfaction will be mostly unaffected by its supply. (5) Reverse requirements: it should be minimized or avoided whenever possible. Providing it will result in a decrease in satisfaction instead [47].

2.5.1. The KANO Model’s Indicator System

The indicator set for the KANO model is derived from the CES indicator system mentioned before. Each indicator that is needed is classified into four types based on the guideline layer, totaling 11 indicators. The combination of these indicators forms the scale of the KANO model requirement indicators.

2.5.2. Questionnaire Design Based on the KANO Model

The KANO questionnaire is created based on the KANO model indicator system to assess the requirements of cultural service users in lost spaces under the city overpass [48]. The survey population consists of inhabitants living near the overpass, as they are the primary focus of this study’s humanized requirements. The questionnaire comprises two sections. The initial section comprises fundamental data on the survey participants, such as gender and age. Secondly, two positive and negative questions were created based on the KANO model for each cultural service indicator aspect and choices were provided for each question. The positive and negative questions contained positive and negative parts, respectively, where the positive aspect of asking residents about an indicator was how they felt about the space under the bridge having this function, while the negative aspect of the question was how they felt about the space under the bridge not having a certain function. Subsequently, the appropriate options were established for each question. The options were evaluated using a five-point Likert scale: “dislike, live with, neutral, must-be, like.” Based on 11 indicators, a questionnaire consisting of 22 positive and negative questions related to the KANO model was created. A total of 238 questionnaires were collected through paper and online surveys. Out of these, 226 were valid. The number of questionnaires collected was 10 times greater than the number of indicators, aligning with questionnaire design principles [49].

Reliability and validity tests were performed using SPSSAU software (v23.0). The Cronbach’s alpha coefficient of the questionnaire was standardized to a value of 0.875, which is above the threshold of 0.6. Furthermore, the questionnaire has a KMO value of 0.795, which falls within the acceptable range of 0.7–0.8, indicating that the data may be efficiently analyzed. Additionally, the p-value associated with Bartlett’s sphericity is 0.000, meeting the expected level. The reliability and validity of the questionnaire were up to standard.

2.5.3. Categorization and Ranking of Requirements

We classified the requirement attributes for each indicator according to the KANO Model’s Requirement Attribute Categorization Table, based on the responses to positive and negative questions.

Table 7. Comparison table for classification of requirements.

Functional (Presence) Question	Dysfunctional (Absence) Question
	Like	Must-Be	Neutral	Live with	Dislike
Like	Q	A	A	A	O
Must-be	R	I	I	I	M
Neutral	R	I	I	I	M
Live with	R	I	I	I	M
Dislike	R	R	R	R	Q

displays the KANO Model’s criteria for the classification of requirements (Table 7).

The KANO questionnaire categorizes the requirements of the residents of the lost space under the overpass, determining the category of each requirement but not the degree of satisfaction sensitivity of the respondents to each requirement. Hence, it is essential to further examine the sensitivity of satisfaction levels for each indicator in order to transition the KANO model from qualitative to quantitative analysis. The Better-Worse coefficient assesses the sensitivity of satisfaction for each indicator effectively [50]. It consists of the satisfaction coefficient “Better” and the dissatisfaction coefficient “Worse,” both ranging between 0 and 1 in absolute value. The higher the value of “better” approaching 1, the more rapidly satisfaction grows. Conversely, lower values of “Worse” typically indicate a negative impact on satisfaction, with closer values to -1 resulting in faster decreases in satisfaction. The Better-Worse coefficient is determined using a specific formula. The connection between requirements and satisfaction can be seen by creating a matrix of requirement qualities.

The KANO model prioritizes attributes in the following order [51]: Must-be Attributes > One-dimensional Attributes > Attractive Attributes > Indifferent Attributes. Prioritization within the same attribute is determined by the Better-Worse value.

3. Results

3.1. Result of the CES Evaluation System

Scores Result of FCE for CES

Out of the 35 overpasses, those with scores ranging from four to five are considered “excellent” for CES. There are three overpasses in this area: the Yongfeng Overpass (4.118), the Second Ring Road Fuqing Overpass (4.115), and the Yangxi Overpass (4.045). Overpasses with ratings of 3–4 are considered to have a “good” degree of cultural service, and there are a total of 18 overpasses falling within this category. Out of a total of 14 overpasses, the cultural services ratings for overpasses with scores of 2–3 are at a “fair” level.

Table 8. FCE scores for CES in 35 overpasses.

Ranking	Rating	Subject of Evaluation	Score
1	Excellent	Yongfeng Overpass	4.118 4.115
2		Second Ring Road Fuqing Overpass
3		Yangxi Overpass	4.045
4	Good	Shuangqiaozi Overpass	3.829
5		Rennan Overpass	3.559
6		Shiling Overpass	3.419
7		Renju Overpass	3.415
8		Jinniu Overpass	3.392
9		Tianfu Overpass	3.320
10		Jinjiang Overpass	3.288
11		Yingmenkou Overpass	3.213
12		Liuli Overpass	3.207
13		Supo Overpass	3.183
14		Shabanqiao Overpass	3.166
15		Shiyang Overpass	3.155
16		Chengyu Overpass	3.151
17		Hangtian Overpass	3.108
18		Guixi Overpass	3.069
19		Shulong Overpass	3.045
20		Caojin Overpass	3.026
21		Wuhou Overpass	3.012
22	Fair	Chengmian Overpass	2.974
23		Jiaozi Overpass	2.942
24		Beixing Overpass	2.894
25		Chuanzang Overpass	2.894
26		Fenghuang Overpass	2.832
27		Third Ring Road Yongfeng Overpass	2.755
28		Jinfenghuang Overpass	2.753
29		Chuanshan Overpass	2.649
30		Chengpeng Overpass	2.562
31		Longtan Overpass	2.482
32		Kehua Overpass	2.457
33		Jiaoda Overpass	2.417
34		Chengnan Overpass	2.405
35		Shuangnan Overpass	2.197

displays the individual FCE scores for the 35 overpasses (Table 8).

3.2. Result of the ESQ Evaluation System

Scores Result of FCE for ESQ

Overpasses with scores of 4–5 are considered “excellent” in terms of ESQ out of the 35 overpasses. There are four overpasses within this range: the Yongfeng overpass at 4.648, the Rennan overpass at 4.327, the Wuhou overpass at 4.275, and the Supo overpass at 4.177. The ESQ is considered “good” for overpasses with a score of 3–4, and there are 23 overpasses in this category. Overpasses with a rating of 2–3 are classified as “fair”, and there are a total of seven overpasses in this category. The ESQ is rated as “poor” for overpasses scoring 1–2, with the Chuanzang overpass (1.932) being the only overpass falling within this range.

Table 9. FCE scores for ESQ in 35 overpasses.

Ranking	Rating	Subject of Evaluation	Score
1	Excellent	Yongfeng Overpass	4.648
2		Rennan Overpass	4.327
3		Wuhou Overpass	4.275
4		Supo Overpass	4.177
5	Good	Yangxi Overpass	3.979
6		Longtan Overpass	3.979
7		Chuanshan Overpass	3.830
8		Fuqing Second Ring Road Overpass	3.825
9		Renju Overpass	3.804
10		Hangtian Overpass	3.786
11		Jinniu Overpass	3.776
12		Chengmian Overpass	3.766
13		Shuangqiaozi Overpass	3.686
14		Jinfenghuang Overpass	3.622
15		Yingmenkou Overpass	3.621
16		Yongfeng Third Ring Road Overpass	3.531
17		Shiling Overpass	3.436
18		Liuli Overpass	3.420
19		Jiaozi Overpass	3.420
20		Shulong Overpass	3.384
21		Caojin Overpass	3.337
22		Chengyu Overpass	3.328
23		Guixi Overpass	3.312
24		Chengpeng Overpass	3.258
25		Shabanqiao Overpass	3.233
26		Kehua Overpass	3.222
27		Shiyang Overpass	3.214
28	Fair	Chengnan Overpass	2.941
29		Jinjiang Overpass	2.873
30		Shuangnan Overpass	2.862
31		Fenghuang Overpass	2.857
32		Tianfu Overpass	2.783
33		Jiaoda Overpass	2.555
34		Beixing Overpass	2.261
35	Poor	Chuanzang Overpass	1.932

lists the FCE scores for the ESQ of the 35 overpasses (Table 9).

3.3. Result of the Two-Dimensional Quadrant Diagram

This study screened overpasses in the fourth quadrant that had good ESQ but needed to be renewed in terms of CES based on their purpose. The overpasses in the fourth quadrant are the Longtan Overpass (0.543, −0.605), the Chengmian Overpass (0.330, −0.113), the Wuhou Overpass (0.839, −0.075), Third Ring Road Yongfeng Overpass (0.095, −0.332), the Jinfenghuang Overpass (0.186, −0.334), and the Chuanshan Overpass (0.394, −0.438). Figure 4 presents a two-dimensional quadrant diagram of the distribution of CES and ESQ scores for the 35 overpasses (Figure 4).

Among all the overpasses in the four quadrants, both the Longtan Overpass and the Wuhou Overpass deviate significantly from the origin. Nevertheless, the y-coordinate’s absolute value of the Wuhou Overpass is extremely low, suggesting limited capacity for the renewal of ecological cultural services. As a result, the Longtan Overpass was selected for the succeeding KANO model because it had bigger absolute values for both the x-coordinate and y-coordinate. The Longtan Overpass has a low y-coordinate value, indicating a lack of ecosystem cultural services. This suggests that there is ample room for regeneration and improvement in this area. Furthermore, the x-coordinate value of it suggests that it possesses favorable exterior spatial conditions. Overall, the Longtan Overpass has significant potential for renewal in every aspect, aligning with the study’s objectives. This is a crucial factor in selecting the Longtan Overpass.

3.4. Quantifying the Resident Requirements of the Longtan Overpass

When applying the KANO model to classify the 22 requirement elements, it was found that the ECS indicator system for the lost space under the Longtan Overpass in Chengdu City includes zero elements classified as must-be attributes and two elements classified as one-dimensional attributes, specifically Facade Landscape C6 and Natural Aesthetics C3. The attractive attributes include Humanistic Aesthetics C5, Physical Education and Sports C1, Geographical History C7, and Customs and Humanities C8. The indifferent attributes include Leisure and Recreation C2, Sense of Identity C11, Engineering Aesthetics C4, Inspiration C10, and Popular Science Products C9. There are no attributes that belong to the reverse requirement category (

Table 10. The KANO attributes and Better-Worse coefficient in the Longtan Overpass regarding CES indicators.

Function in the Longtan Overpass	KANO Attributes	Better Coefficient	Worse Coefficient
Facade Landscape C6	One-dimensional factors	65.85%	−58.54%
Natural Aesthetics C3	One-dimensional factors	65.00%	−57.50%
Humanistic Aesthetics C5	Attractive factors	70.00%	−27.50%
Physical Education and Sports C1	Attractive factors	67.50%	−25.00%
Geographical History C7	Attractive factors	65.00%	−27.50%
Customs and Humanities C8	Attractive factors	65.00%	−27.50%
Leisure and Recreation C2	Indifferent factors	52.63%	−28.95%
Sense of Identity C11	Indifferent factors	43.90%	−31.71%
Engineering Aesthetics C4	Indifferent factors	42.50%	−12.50%
Popular Science Products C9	Indifferent factors	39.02%	−17.07%
Inspiration C10	Indifferent factors	24.39%	−14.63%

).

Table 11. The KANO attributes and scores of CES indicators and corresponding weighting values.

Indicator Name	Weighting Value	CES Indicator Scores	KANO Attributes
Facade Landscape C6	0.0222	3.000	One-dimensional factors
Engineering Aesthetics C4	0.0134	2.969	Indifferent factors
Natural Aesthetics C3	0.1397	2.906	One-dimensional factors
Leisure and Recreation C2	0.1228	2.594	Indifferent factors
Physical Education and Sports C1	0.3684	2.500	Attractive factors
Humanistic Aesthetics C5	0.0925	2.313	Attractive factors
Sense of Identity C11	0.0223	2.281	Indifferent factors
Customs and Humanities C8	0.0724	2.188	Attractive factors
Geographical History C7	0.0797	2.156	Attractive factors
Inspiration C10	0.0446	2.031	Indifferent factors
Popular Science Products C9	0.0220	2.031	Indifferent factors

lists the CES indicators scores for the Longtan Overpass along with their KANO attributes and evaluation scores (Table 11).

The priority principle of the KANO model establishes the following order [52]: Facade Landscape C6 > Natural Aesthetics C3 > Humanistic Aesthetics C5 > Physical Education and Sports C1 > Geographical History C7 > Customs and Humanities C8 > Leisure and Recreation C2 > Sense of Identity C11 > Engineering Aesthetics C4 > Popular Science Products C9 > Inspiration C10.

4. Discussion

4.1. Analysis of the Current Status and Reasons for Indicator Scores of SUO

By integrating the CES indicators scores of the Longtan Overpass with the KANO model’s categorization, it is evident that none of the indicators fall within the must-be requirement or reverse requirements category. This circumstance may be connected to the distinctive architecture of the overpass and its primary function.

Natural Aesthetics C3 and Facade Landscape C6, part of the one-dimensional requirements, suggest that including natural aesthetics and landscape designs in the SUO can improve inhabitants’ preferences. In the KANO model, one-dimensional factors indicate a positive correlation with satisfaction, while Natural Aesthetics C3 and Facade Landscape C6 are categorized as one-dimensional factors. Consequently, it can be concluded that the satisfaction of inhabitants adjacent to Longtan Overpass is positively connected with the scores of Natural Aesthetics C3 and Facade Landscape C6. KANO’s Better-Worse coefficient shows that the Better coefficient ranking for Facade Landscape C6 is first and Natural Aesthetics C3 is second, demonstrating that inhabitants exhibit greater sensitivity to their requirements for these two indicators compared to others. The higher score of the Facade Landscape C6 is nearer to one than that of the Natural Aesthetics C3, suggesting that resident satisfaction will increase more rapidly as the effect of Facade Landscape C6 is amplified. The CES score for Longtan Overpass reveals that the scores for Natural Aesthetics C3 and Facade Landscape C6 are within the range of 2–3 points, suggesting potential for enhancement in these two indicators. Nevertheless, they score highly on the overall indicators, meaning that while there remains potential for enhancement in the current natural aesthetics and facade landscape, they are more decorative than other indicators of the overpass. On-site research found that the greenery under the Longtan Overpass is abundant, with grass and green plants prevalent, leading to higher scores in natural aesthetics and facade landscape indicators compared to the overall CES score of the Longtan Overpass. The spatial landscape under the Longtan Overpass is uniform, mostly consisting of grasses and creepers, with limited plant diversity and inadequate plant structures. The lack of consideration for various landscape effects during seasonal changes results in a more desolate and monotonous natural view under the Longtan Overpass in fall and winter [53]. This contributes to the high ranking of natural aesthetics and facade landscape as indicators but the overall evaluation grade not being very high.

The requirements for Physical Education and Sports C1, Humanistic Aesthetics C5, Customs and Humanities C8, and Geographical History C7 belong to attractive factors, which are important for enhancing residents’ experiences in the SUO [30]. Improving these indicators can increase residents’ satisfaction. In the KANO model, attractive factors exceed user expectations, their provision significantly enhances user satisfaction, while their absence does not diminish it. According to KANO’s Better-Worse coefficient, Humanistic Aesthetics C5, Physical Education and Sports C1, Geographical History C7, Customs and Humans C8 rank third to sixth in order. This clearly reflects the sensitivity ranking of residents’ requests for these indicators. Among these indicators, enhancements in Humanistic Aesthetics C correlate with the most rapid increase in resident satisfaction rates at Longtan Overpass. The CES score for Longtan Overpass indicates that all indicators fall within the range of 2–2.5, defining them as fair. Among them, Geographical History C7 has the lowest score of 2.156, but residents’ Better-Worse coefficient value for this indicator ranks fifth among all indicators. This indicates that although the spatial representation of geographic history under Longtan Overpass is not very good at present, residents have a high demand for it, so it is important to focus on improving the representation of this indicator in the Longtan Overpass. Combined with the on-site research, it can be seen that the space under the Longtan overpass lacks sports venues and sports facilities as well as the embodiment of humanities and arts, Chengdu’s regional history, customs, and humanities. But these four indications are appealing to the residents and have the potential to be considered necessary by them [54], so they are categorized as attractive requirement traits.

The attributes of Engineering Aesthetics C4, Leisure and Recreation C2, Sense of Identity C11, Inspiration C10, and Popular Science Products C9 categorized as indifferent factors exert minimal influence on inhabitants’ daily life and do not substantially alter their overall views [55]. The Longtan Overpass obtained an overall CES score, with Engineering Aesthetics C4 and Leisure and Recreation C2 ranking second and fourth and scoring 2.969 and 2.594, respectively, signifying its good performance. Unexpectedly, KANO’s Better-Worse coefficient categorizes Leisure and Recreation C2 as indifferent factors, signifying a lack of substantial desire for this indicator among users. From this, it can be seen that the leisure and entertainment facilities in the space under Longtan Overpass are not significantly attractive to residents. When updating the Longtan Overpass in the future, more resources can be reserved in terms of leisure and entertainment facilities, leaving more resources for the indicators that are somewhat attractive to residents as mentioned above. On-site research indicates that the result may be attributed to the unique physical construction and geographical position of the space under Longtan Overpass, resulting in limited connectedness, diminished safety, and higher noise levels in that place. This diminishes inhabitants’ demand for leisure and entertainment activities in the space under the overpass [56].

4.2. Discussion of Research Questions

What is the present condition of overpasses in Chengdu in relation to research question 1? How should it be assessed? This study capitalizes on the similarities between the SUO and other urban public spaces, which led to the selection of CES to value the non-material elements of SUO. The ESQ assessment is introduced to enhance the value assessment of the material parts of the SUO. The average value of the two-dimensional scores of the SUO in Chengdu is between three and four, indicating an overall status quo state of relatively good quality.

Regarding Research Question 2, are all current overpasses in Chengdu suitable for renewal in their current state? If not, what is the appropriate method for selecting them? The analysis of 35 overpasses following question 1 revealed that the cultural service value and ESQ of overpasses in Chengdu are varied, with some displaying high quality in both aspects while others lack accessibility. Consequentially, not all existing overpasses in Chengdu city are suitable for renewal. This study uses a two-dimensional quadrant diagram to display the distribution of overpasses in two evaluation dimensions. Overpasses with weak cultural service value but good physical conditions (good ESQ) are chosen for renewal.

Research Question 3 examines ways to incorporate humanized standards to direct the renewal process for eligible overpasses after screening. Before addressing humanized requirements, it is essential to identify the specific types of requirements individuals have and their scope. The KANO model with these two functions was used in this study to quantify the indicators. This study utilized the KANO model with these two functions to administer a questionnaire survey and measure each CES indicator in the lost space under the overpass [57]. The KANO model results indicate the significance and level of importance of each indicator, highlighting which elements of the space should be either renovated or retained. This information can enhance the satisfaction and utilization rates of the SUO. The results indicate that Natural Aesthetics C3 and Facade Landscape C6 are one-dimensional attributes that strongly attract people and are positively correlated with people’s satisfaction. This finding aligns with that of previous studies. Urban designers can boost the sustainability of the SUO by focusing on developing its attractiveness in these directions with increased efforts. This study’s results diverge from prior research by identifying five variables associated with indifferent requirement attributes, which encompass Leisure and Recreation C2. It demonstrates that the presence or absence of enhancements does not significantly impact resident satisfaction. However, past research has indicated a connection between the rest and leisure aspects of urban public places and inhabitants’ experiential perceptions [58]. The varied findings of this study can be attributed to the unique characteristics of the SUO, which set it apart from other urban public places due to its distinctive geographic location and intricate transit infrastructure. The results contribute to existing research on urban space and people’s contentment, expanding the investigation into various types of satisfaction within urban spaces.

4.3. Renewal Strategy Based on the Humanized Requirements

Improving and satisfying Natural Aesthetics C3 and Facade Landscape C6 were emphasized as essential one-dimensional attributes [56]. These indicators’ scores are ranked higher, and low shrubs and flowers can be introduced while maintaining the existing plant landscape to prevent obstructing traffic sight lines. Seasonal changes will be taken into account to create a distinctive autumn environment on the flyover by using autumn foliage or colorful foliage species in the bordering region between the overpass and the residential neighborhood. The Longtan overpass has dense columns of creepers, but the scenery appears monotonous. To enrich the facade landscape and improve the facade landscape of the SUO, we can mix it with Chengdu cultural murals or wall carvings to increase diversity and beauty.

Physical Education and Sports C1, Natural Aesthetics C3, Humanistic Aesthetics C5, Customs and Humanities C8, and Geographical History C7 are attractive attributes that should be fulfilled to the best of one’s capacity when possible [59]. The space under the Longtan Overpass is inadequate for athletic activities. Installing table tennis tables and basketball courts could lure residents to use them, hence increasing the use rate of the SUO. The space under the Longtan Overpass lacks any humanistic art representation from an aesthetic perspective. The space under the overpass features mostly consistent green foliage. Enhancing the representation of painting and sculpture on the piers and walls is achievable. Customs and humanities can be integrated with sketches, paintings, and other components to incorporate Chengdu tea culture, mahjong, and panda themes, enhancing the intimacy of the location under the overpass [60]. We can learn from the Supo Overpass and Jinniu Overpass to depict the culture and folklore of Chengdu through paintings and sketches. Geographical history can be effectively represented by aligning regional culture with the current terrain. Furthermore, it can be integrated with drawings to create an entertaining representation of local culture. We can also learn from the Renju Overpass, which combines the famous local culture with leisure and recreational facilities. This deepens the activities and enhances the entertainment and participation in the culture shown at the SUO.

Engineering Aesthetics C4, Leisure and Recreation C2, Sense of Identity C11, Inspiration C10, and Popular Science Products C9 are considered indifferent attributes. When resources are limited, it is important to evaluate whether to include these requirements based on the specific circumstances. But the KANO theory proposes that public requirements follow a specific progression: I→A→O→M [61]. Hence, indifferent attributes must not be disregarded entirely. It is essential to monitor and comprehend the evolution of these traits and implement appropriate actions as needed.

4.4. Differences and Similarities in Research Methods

First of all, the two assessment methods developed in this work are more refined than the prior spatial evaluation systems. The spatial quality distribution of each overpass is clearly illustrated using a two-dimensional quadrant diagram. The ESQ assessment system and the non-material CES evaluation system introduced work together to address the limitations of prior studies that relied on a single evaluation system [59]. This paper’s research method can be applied to renew various types of lost space or even urban public spaces due to the similarity between the lost space under the overpass and other urban public space. Our research broadens the range of CES that may be assessed based on earlier ones and offers a reference for evaluating space quality in various sorts of lost spaces across the city. Furthermore, creating a two-dimensional quadrant diagram helps to identify areas for improvement and offers suggestions for prioritizing tasks. It quantifies and visualizes the screening process, unlike the qualitative screening method. The tight relationship between people’s requirement and urban public space means that the design of urban space is closely linked to human necessities [62]. Therefore, the KANO methodology chosen for this study enhances communication between the SUO and individuals, and it is flexible for revitalizing different urban areas that necessitate human involvement. This study’s methodology integrates and innovates past urban space regeneration methodologies, with implications of renewal for different types of lost space and even other public space.

5. Conclusions

This study applies two evaluation models and combines the results to identify which dimensional quadrant diagram to assess the overpasses and then applies the KANO model to determine the specific requirements of the population for the chosen overpasses. This study selected a total of six overpasses that met the purpose of this study, and the Longtan overpass was chosen and classified based on CES indicators using the KANO model of residents’ requirements. We found a positive correlation between the satisfaction of residents living near the Longtan Overpass and the natural aesthetics and facade landscape of the SUO. Improving cultural service indicators like Physical Education and Sports C1, Humanistic Aesthetics C5, Customs and Humanities C8, and Geographical History C7 could enhance the appeal of the SUO. This study’s results clearly demonstrate the feasibility of evaluating the current worth of lost space under urban overpasses using the CES approach. And it provides a quantitative evaluation of lost space, addressing a previous research gap. Simultaneously, examining the space under overpasses to analyze the CES of urban public areas can enhance the evaluation framework for CES values [63]. Furthermore, this study offers suggestions for the hierarchical screening of similar public spaces inside urban areas. Not only that, this study utilizes the KANO Model to evaluate CES indicators of the space from various viewpoints, aiming to integrate humanized elements [64] into the design and provide practical insights for developing specific strategies.