1. Introduction
As an adverse effect of globalization and liberalization, inequality has been a core subject of academic inquiry in the fields of geography (e.g., [
1,
2,
3,
4]), development studies (e.g., [
5]), economics (e.g., [
6,
7]), environmental and urban studies (e.g., [
8,
9]), etc. It is a controversial problem which has caused long-lasting debates through the political, economic, or regional planning decision-making processes since the late 1980s [
1,
10]. As a key dimension of inequality, spatiality has triggered scholarly discussions, especially on its extent, dimension, consequence, and the policy [
1]. It facilitates multidisciplinary research branches, such as spatial inequality [
1], spatial justice [
11], spatial inequity [
12], environmental justice [
8], urban inequality [
4], urban justice [
13], and landscape justice [
14]. Throughout these subjects, the terms inequality, inequity, and injustice sometimes overlap and are not mutually exclusive. To establish the research scopes of these studies, it is necessary to identify the distinctions among them.
The definition of inequality is “difference in size, degree, circumstances, etc.; lack of equality”, which means it is potentially a neutral description of variation. The term injustice is defined as “an unfair act or an example of unfair treatment”, and inequity describes “a lack of fairness or justice” [
15]. In definitional terms, injustice and inequity are conceptually interchangeable, but they cannot be used interchangeably with inequality. For example, the differences in the distribution of retirement centers can exist without injustice. Inequality is explained by the difference in individual needs or choices, whereas inequity exists when some people in need do not have basic nursing service or lack the access to nursing centers while others have more. Even though differences and intersections of these three terms do exist in a definitional context, from a spatial perspective, they are not obviously distinguishable and tend to overlap slightly when describing the phenomena, mechanism, and consequence of unequal issues. For example, the uneven geographical distribution of parks and urban green spaces (e.g., [
16,
17]), unequal access to educational resources and medical services (e.g., [
18]), and unjust urban planning strategies and policies (e.g., [
19,
20]). Thus, this study refers to spatial inequality/injustice/inequity concurrently, with the intention to include a comprehensive overview.
As a predominant research subject, Urban Public Facility (abbreviated as “UPF”) refers to urban public services provided directly or indirectly by governments. UPF are the carriers of urban public services, which are related to the shaping of the urban environment and spatial structure as well as the normal operation of urban systems [
21,
22]. The uneven distribution and accessibility of UPFs leads to inequality for local residents to access public resources, marginalizing certain vulnerable communities and further increasing overall injustice and inequity [
22,
23,
24]. The research scope of UPF studies has expanded more recently, where some academics have focused on essential livelihood facilities, such as educational facilities and medical services [
25,
26,
27,
28], while others have focused on public services for higher-level needs including landscape and recreational facilities [
29,
30,
31]. Throughout previous studies, six main categories of UPF can be generated as: transportation facilities (e.g., transit stop, traffic network), healthcare facilities (e.g., clinic, hospital), educational facilities (e.g., primary school, high school), landscape spaces (e.g., urban green space, park, street trees), recreational facilities (e.g., sports hubs, play-space, libraries) and commercial facilities (e.g., retail shop, shopping center). Research on the spatial inequality/injustice/inequity found in UPFs is highly interdisciplinary and integrates social, political, and morphological concerns, which can be categorized into three approaches:
- (1)
Socio-demographic factors and the spatial inequality/injustice/inequity in UPFs: The corresponding research intends to explore the relationship between demographical characters and UPFs from a spatial perspective. For example, Sun et al. [
32] and Neutens et al. [
33] studied the correlations between income gap and the unequal supply of UPFs across different districts in urban areas. Recent research which has explored differences in the quality and quantity of educational facilities for migrant workers and local residents are explored by Wu et al. [
34]. Zeng et al. [
35] and Yang et al. [
36] showcased that marginalized communities living in affordable housing have a more limited level of access to UPFs than the other community members. Moreover, there are a few studies that link gender to spatial inequality and the ability to access UPFs. See Maroko et al. [
37] for a study that explores the spatial injustice that homeless women face when seeking Healthcare facilities. Moreover, a study exploring women’s bypassing behavior when seeking medical facilities in remote areas was conducted by Ocholla et al. [
38].
- (2)
Governmental policies and economic activities referring to the spatial inequality/injustice/inequity in UPFs: Studies under this category showed a significant interest in investigating the underlying reasons of spatial inequality/injustice/inequity in the supplement of UPFs through governmental policies and economic activities. Chae et al. [
39] point out the negative effects of urban shrinkage on spatial inequality and showcased that urban economic shrinkage results in the unequal supplement of educational facilities, medical facilities, commercial facilities, and recreational facilities. Mobaraki et al. [
40] proved that the uneven redistribution of income and resources by the government may cause injustice in allocating UPFs. In addition, Habibov [
41] showed that, in areas where private healthcare is more common, people without healthcare subsidies would need to pay more for expenditures when seeking medical attention.
- (3)
The spatial allocation and distribution of UPFs: This category addressed the attributes and organization of UPFs from a spatial perspective, which mainly includes research that models the location-allocation of facilities, analyses the spatial layouts of UPFs, as well as the unequal accessibility of different UPFs caused by uneven urban development [
42,
43,
44,
45]. Lan et al. [
46] also reveal the uneven distribution of educational and medical facilities both in urban fringe and inner urban areas. Moreover, a recent study by Zhao et al. [
47] discusses differences in high and low-income districts in terms of the quantity of commercial and recreational facilities. Chen et al. [
48] explore the geographical concentration of high-quality medical facilities in a Chinese urban context and reveal its negative impact on tidal traffic phenomena.
As the evidence above points out, extensive attempts have been made to parse and understand how social differentiations, decision making processes, and spatial patterns act on the spatial inequality/injustice/inequity in UPFs. However, there is still a lack of detailed guidelines in terms of location-specific design strategies for more equitable opportunities to access and use UPFs. Therefore, the research hypothesis of this paper is that an analytical lens to understand and interpret the spatial inequality/injustice/inequity in UPFs from an ambiguous concept to detailed interventions is needed, with an aim to provide a systematic method and spatial perspective to recognize and unscramble spatial inequality problems in UPFs for the further research. To fill the gap, this research provides a comprehensive overview of the spatial inequality/injustice/inequity research in UPFs and develops a systematic framework to diagnose spatial problems of UPFs, translating them into design language and proposing empirical interventions in a local context.
2. Materials and Methods
To provide a systematic overview of the relationship between UPFs and different dimensions of inequality/injustice/inequity related to spatial distribution, configuration, or policymaking, the authors have collated and reviewed a vast quantity of relevant research. This was done in order to have a better understanding of how spatial inequality/injustice/inequity is rooted in UPFs and the subsequent reflection of inequality/injustice/inequity within the spatial guidelines of the design and planning process.
2.1. Material Collection
A literature review was conducted through the Web of Science database accessed in September 2021, which combined three groups of keywords. The first included terms of “inequality”, “equality”, “injustice”, “justice”, “inequity”, “equity” in order to collect all papers with direct or indirect relations with the fact of unfair and unequal situations. The second part was to distinguish the studies of UPFs, which contained terms of “facility”, “amenity”, and “public service”. Moreover, the search added “spatial” to identify research that discusses the inequality/injustice/inequity issues of UPFs from a spatial perspective. All three groups of keywords were combined with the Boolean operation “AND” to find precise matches. An integrated query string was shown as “TS = ((inequality* OR equality* OR injustice* OR justice* OR inequity* OR equity*) AND spatial* AND (“facility*” OR “amenity*” OR “public service*”))”. The dataset was restricted to English-written journal articles, books, book chapters, and conference papers, and a total of 284 papers were found, spanning from 1993 to 2021. Through the “duplicate removal” function in CiteSpace, 9 duplicates were removed from the search resulting in 275 articles.
After the data were gathered, abstracts were screened and analyzed for their relevance to the research objective. Contents of the retained papers had to meet at least one of the following criteria: (1) locational studies of UPFs; (2) efficiency and equity concerns of UPFs; (3) the usage of UPFs in local communities; (4) underlying reasons of the uneven allocation and accessibility of UPFs (e.g., urban planning process, cost and benefit concerns of the government); (5) methods to reconfigure UPFs for equal access. After the selection, a total of 64 papers were eventually included for further review.
2.2. Research Methods
In order to thoroughly understand the literature and establish targeted spatial principles and guidelines from a design and planning perspective, it is important to recognize which dimensions of inequality/injustice/inequity are discussed in this research, as well as the spatial issues that are indicated. To answer this question, the authors first grouped the selected literature by the type of UPFs, which are transportation facilities, healthcare facilities, educational facilities, landscape spaces, recreational facilities, and commercial facilities. Then, an in-depth review of the literature was conducted, and synthesizes the phenomena of spatial inequality/injustice/inequity into three core dimensions of environmental justice: distributional justice, procedural/participatory justice, and recognition justice [
49]. Distributional justice concerns the equal per capita distribution of resources; an equality and guaranteed standard of environmental quality for everyone (i.e., clean water, basic standard of air quality); and a guaranteed variation above the minimum based on personal choices and expressed personal preferences [
50]. Procedural/participatory justice ensures that those formulating the procedures should maintain elements of neutrality, and that stakeholders should be well represented in the process of decision-making [
51,
52,
53]. Recognition justice implies that people’s unique socio-cultural and local identities (i.e., immigrants, ethnicity, age, gender) are valued, respected, acknowledged, and that they experience fair treatment [
52,
54]. Based on these particular dimensions of inequality/injustice/inequity, spatial issues in UPFs, either from a distributional, procedural, or recognition perspective, could be explicitly discerned and summarized. As a step forward, evidenced-based empirical planning and design interventions related to spatial issues were proposed in order to promote an inclusive and equal urban environment.
Figure 1 shows the workflow of the methodology of this research.
4. Discussion
4.1. Empirical Interventions for Spatial Inequality Issues in UPFs
This research involved a comprehensive literature review of the spatial inequality/injustice/inequity research in UPFs, diagnose spatial problems of UPFs, translating them into design language, and proposing empirical interventions in a local context. As the results of this research point out, the spatial problems of UPFs can be summarized as the uneven distribution or coverage of UPFs, the disparity in the quality of UPFs, the failure of recognizing special preference and behavior of different social groups, and the failure of engaging adequate stakeholders in the decision-making process. From the urban planning perspective, proposed interventions can be mainly synthesize as: (a) planning integrated transportation network to improve the service radius of UPFs; (b) incorporating demographical analysis and observational research into the early planning process; (c) incorporating participatory approach into the early planning process; (d) boosting smaller scale community based UPFs in deprived areas; (e) raise the walkability of streets around UPFs. From the urban designing perspective, proposed interventions can be summarized as: (a) designing public spaces to fit in multiple types of smaller scale UPFs; (b) redesign vacant or abandoned spaces into new smaller scale UPFs; (c) supplementing urban features (i.e., urban trees, urban furniture) to raise the quality of UPFs; (d) boosting signage and guiding systems around UPFs. As for the UPF management perspective, interventions from the following aspects were proposed: (a) boosting long-term local engagement maintenance system; (b) encouraging local communities to host inclusive events and activities; (c) organizing free check-up and assessment services for people in need; (d) providing waiting facilities (i.e., waiting homes, resting spaces) for people who travel from a far distance.
The above interventions were generated based-on the specific spatial problems pointed out by previous literature. By doing so, this research established extensive knowledge-based design and planning interventions in terms of the equal distribution and configuration of UPFs for spatial designers and decision makers in future practices.
4.2. Analytical Framework for the Spatial Inequality in UPFs
As exemplified by this research, reviewing a vast amount of literature referring to the spatial inequality/injustice/inequity in UPFs holds the potential for both researchers and practitioners to understand the uneven allocation, distribution, and configuration of resources and services across areas and facilitate corresponding design and planning guidelines to achieve a more inclusive and equal urban environment. After extracting and synthesizing the findings, an analytical framework for diagnosing dimensions of inequality in UPFs, interpreting spatial attributes, and proposing location-specific interventions has been elaborated as follows.
As
Figure 2 shows, there are four layers that guide the interpretation and communication of the matter of UPF’s spatial inequality/injustice/inequity, which contains UPF type, dimension, spatial issue, and intervention. Different types of UPF have distinct contents and characteristics. To identify the scope and gain an explicit profile of the targeted UPF, it is important to absorb its sub-categories, components, attributes, and service radii (Layer 1). Dimensions of inequality/injustice/inequity are applied to analyze and categorize the detailed unequal phenomena of UPFs (Layer 2). Typically, distributional justice, participatory/procedural justice, and recognition justice are the three key dimensions, which respectively focuses on the morphological, political, and socio-demographical perspectives of the spatial inequality in UPFs [
49]. Then, inequality matters can be translated into spatial issues from a planning and design point of view, especially on the quantity, quality, and morphology of UPFs (Layer 3). To be specific, morphology refers to the spatial distribution and organization of UPFs; quantity indicates the numerical allocation of UPFs in a certain area; quality addresses the standard character of UPFs. In response to spatial issues, design-based and planning-based spatial interventions can be proposed primarily from the following aspects: (a) quantity complement; (b) quality improvement; (c) allocation and distribution of UPFs; (d) configuration of UPFs with other urban elements; € participatory strategy in the planning process; (e) recognition of specific demographic groups (Layer 4). This analytical framework displays a hierarchical process of understanding and interpreting the spatial inequality/injustice/inequity in UPFs from an ambiguous concept to detailed interventions. On the one hand, it supplements the body of knowledge, which enables spatial planners and urban designers to become more conscious about fundamental spatial inequality/injustice/inequity effects relevant to the optimization and design of UPFs. On the other hand, it provides a systematic method and spatial perspective to recognize and unscramble spatial inequality problems in UPFs for the further research.
4.3. Limitations
To have a comprehensive understanding of the spatial inequality/injustice/inequity referring to UPFs from a design perspective, this research incorporates a systematic review of a large amount of relevant literature, provides an analytical framework to identify spatial issues behind the unequal status, and proposes pragmatic interventions, which are of fundamental importance for planning and design practices. However, it still has limitations in the research scope and content which can be further explored in future studies.
(1) The material collection stage of this study used the terms “facility*”, “amenity*”, and “public service*” to collect papers that focus on the facilities that are the direct carriers of public services, which are related to the shaping of the urban environment and spatial structure. However, there are studies that align with this paper’s research goal but did not use these terms to label themselves. For example, He et al. [
78,
79] studied the impact of urban heat on population migration and indicated guidance for potential cooling systems and heat prevention facilities. Such studies also presented findings that generate interventions from the perspective of urban planning, design, and management that respond to spatial inequality/inequity/injustice in UPFs.
(2) The selected literature in this study takes an expert approach as the basis which mainly focuses on measuring and describing the spatial inequality/injustice/inequity of UPFs based on the distribution and configuration of spatial elements and relevant socio-geographic factors. However, this does not exclude nor dismiss the importance of grasping the spatial inequality in UPFs from the user’s perspective. Studies that explored the individual’s perception of fairness or people’s evaluation through the use of public amenities also should be included, in order unearth an integrated understanding of the spatial inequality/injustice/inequity in UPFs.
(3) Most of the planning and design guidelines proposed in this study are tangible urban structures, yet there are interventions without constructive forms from a financial or political perspective, such as different types of subsidies offered by the government (e.g., providing traffic allowance can improve travelling preference and the accessibility to other UPFs) as well as flexible regulations (e.g., extra opening hour of certain government sectors for the public). These intangible interventions also have direct or indirect impacts on improving equal urban environment from a spatial perspective.
(4) This study synthesized and discerned specific spatial problems from previous research that investigated spatial inequality/inequity/injustice issues in UPFs. Though most papers studied spatial inequality/inequity/injustice issues in UPFs with locational-based research methods and their findings and suggestions refer to a specific location (i.e., Shanghai, Montreal, Santiago), this research did not comparatively study the literature from the perspective of similar or different locations. Therefore, in a future step of this research, the common rounds and divergence of studies that are based in the same locations can be analyzed with the aim to propose more targeted and location-specific interventions.
(5) This study respectively investigated the unequal status of different types of UPFs. However, the interplay between UPFs is lacking attention. For example, the allocation of educational facilities has a significant influence on attracting small-scale commercial and recreational facilities [
47]. These approaches can be considered by spatial practitioners in order to guide the future development of UPFs as a system.
5. Conclusions
The unequal allocation, distribution, and configuration of UPFs would cause significant inequality in providing resources and services to the local residents, marginalizing vulnerable communities and finally resulting in overall injustice/inequity. Though extensive studies have explored the relationship between spatial inequality/injustice/inequity and UPFs, they did not provide niche targeting guidelines in a practical way to develop an equal and inclusive urban environment. To fill the gap, this paper has conducted a systematic framework for reviewing the existing evidence and interlinked spatial inequality/injustice/inequity to UPFs from a planning and design perspective. Based on the analysis of the potential literature, six types of UPFs (i.e., transportation facilities, healthcare facilities, educational facilities, landscape spaces, recreational facilities and commercial facilities) have been analyzed and synthesized through the three dimensions of environmental justice (i.e., distributional justice, participatory/procedural justice, recognition justice) with the intention to translate specific spatial issues into design and planning interventions. The output of this research contributes to: (a) establishing extensive knowledge-based design and planning interventions in terms of equal distribution and configuration of UPFs for spatial designers and decision makers in future practices; (b) providing an integrated framework which combines academic approaches with practical implementations, in order to analyze, interpret, and communicate the spatial inequality/injustice/inequity in UPFs from a spatial perspective.