In a bid to promote sustainable development and environmental conservation, the UAE government introduced the UAE Vision 2021 National Agenda. This agenda encompasses plans to enhance air quality, preserve water resources, transition to clean energy, and implement green growth strategies [1,2]. As part of this initiative, H.H. Sheikh Dr. Sultan Bin Muhammad Al Qasimi, Ruler of Sharjah, unveiled the Sharjah Sustainable City (SSC) in 2020 (Figure 1) [3]. The SSC represents the first community in the region to offer its residents access to renewable energy storage solutions while adhering to the most stringent green economy and environmental sustainability standards [4].

Developed collaboratively by the Sharjah Investment and Development Authority (SHUROOQ) and Diamond Developers, this project boasts a budget of 2 billion AED (approximately 545 million USD) and spans across an area of 668,900 km2 (Figure 2) [5]. The mixed-use residential complex comprises 1120 villas, distributed over four phases. The commercial complex features retail and community facilities, such as restaurants, cafes, two mosques, green spaces, central sustainable domes for cultivating organic products, and educational institutions [6]. The first phase, completed in 2020, includes 280 townhouses, with options for 3, 4, and 5 bedrooms [7].

Sharjah’s proactive leadership in low-carbon green growth at the government level is complemented by the growing interest and discourse around low-carbon green cities, carbon-zero cities, or low-carbon energy-saving cities within academic circles, particularly in the fields of urban and regional planning [8,9,10]. The ‘low-carbon green cities’ concept focuses on reducing carbon dioxide (CO2) emissions, a primary contributor to global warming, while simultaneously enhancing sustainable urban functions [11,12]. Although this concept is somewhat abstract, the ideas of ‘zero-carbon cities’ and ‘energy-saving cities’ are more tangible [13]. A zero-carbon city aims to ultimately eliminate CO2 emissions, whereas an energy-saving city incorporates systems designed to conserve energy, even though a universally accepted definition for this concept is lacking [14,15].

As new urban planning concepts emerge and are discussed in the UAE, many Emirates endeavor to integrate these ideas into their cities [16]. Recently, several Emirates have proactively adopted low-carbon, energy-saving, or carbon-neutral cities, such as Masdar City [17]. Furthermore, various planning elements are being advocated to achieve urban objectives.

On the other hand, successfully implementing a new urban plan necessitates the establishment of the most suitable urban strategy (planning elements) tailored to the specific city or region, as urban conditions can differ significantly from one location to another. If the planning elements do not accurately reflect the urban conditions and identity, not only will it be difficult to achieve the intended goal, but it may also prove challenging to sustain continuous performance even if the goal is initially reached [18,19]. Thus, the selection of planning elements that align with the urban conditions and identity is of paramount importance [20].

This study seeks to investigate the urban planning elements and determine the appropriate priorities for Sharjah to become an energy-saving city, specifically identifying which planning elements should be prioritized. The findings of this research are anticipated to serve as primary data for implementing the SSC master plan (Figure 3) in Sharjah.

To accomplish the research objectives, a research process was devised, as depicted in Figure 4. The study began with a comprehensive review and organization of sustainable urban planning elements gleaned from previous research. These planning elements were then arranged hierarchically to facilitate priority-setting through a survey in Appendix A [21,22,23]. Urban planning experts, encompassing urban planners, architects, government officials, and researchers, were the target audience for the survey, which was conducted via email [24].

The analytic hierarchy process (AHP) was employed to analyze the priority of the planning elements, as it is a decision-making methodology capable of determining the relative importance of each element [25,26,27]. The AHP methodology is an analytical technique that utilizes pairwise comparisons between elements constituting the hierarchical structure of decision-making to derive differences in significance [28].

Previous studies concentrating on planning elements for energy-saving or low-carbon green cities can be divided into two categories: early studies conducted between 2010 and 2015, and more recent studies carried out between 2015 and 2021 [29]. Early studies primarily focused on energy-saving urban spatial structures. For example, Khanna et al. (2014) [30], Kii et al. (2014) [31], and Wang et al. (2014) [32] investigated transport energy-saving urban structures, while Liu et al. (2012) [33], Manfren et al. (2011) [34], and Zhang and Lin (2012) [35] proposed energy-saving plans and policies at the urban planning level.

Since 2015, research on the derivation and importance of energy-saving planning elements has become more refined compared to earlier studies. Numerous researchers, such as Ying and Yue (2017) [36] and Deakin and Reid (2018) [37] have presented low-carbon, energy-saving urban planning elements and their significance. Furthermore, Topi et al. (2016) [38] sought to establish the concept of low-carbon, energy-saving urban planning and related planning standards, while Ruan et al. (2017) [39] conducted a survey of experts, similar to this study, and analyzed the results [40]. Additionally, Ghorbanzadeh et al. (2019) determined the importance of urban planning elements for experts using AHP [41], and Yildiz et al. (2019) carried out an AHP survey targeting urban planning experts to analyze the importance of low-carbon urban planning elements by city type [42]. Lee and Lim (2018) conducted an empirical examination of the relationship between compact cities and transportation energy consumption [43], and Fouad et al. (2020) performed a global study introducing significant zero-energy town policies [44].

While various planning elements have been proposed in recent research, selecting which elements should be applied at the local government level remains a challenging task [45,46,47]. This is because choosing appropriate planning elements is of paramount importance, requires substantial financial resources, and must account for the varying conditions of each local government [48]. Consequently, this study aims to utilize the hierarchical decision-making method (AHP), an analysis technique capable of deriving weights for each element, to identify the necessary planning elements for Sharjah using the SSC as a case study [49]. However, as previously noted, the importance of planning elements can vary depending on a city’s conditions. As such, this study assumes a case study character, where the approach takes into account Sharjah’s specific conditions.

To identify the major energy-saving urban planning elements from previous studies, Table 1 summarizes these planning elements as presented in earlier research. The most frequently proposed energy-saving urban planning elements in previous studies include green transportation-oriented urban management and nature-friendly park and green space creation (5 times each), followed by eco-friendly density management, waste and food waste reduction, and recycling system establishment, rainwater collection, and management system establishment, energy-efficient building plans, and greenway/green matrix establishment (4 times each).

Table 2 showcases the consolidation of similar sustainable energy-saving urban planning elements derived from Table 1. The planning elements were divided into five categories, specifically, spatial system, transportation system, environment/conservation/recycle, energy/building, and parks/green areas.

Within the spatial system sector, eco-friendly density management, mixed-use development induction, and enhancing accessibility (ensuring the adequacy of the neighborhood area) were included [50,51]. The transportation system sector comprised planning elements such as public transportation-oriented urban development, green transportation-oriented urban planning, and the introduction of new transportation methods [52,53]. The environment/conservation/recycle sector encompassed planning elements related to reducing trash and food waste, establishing a recycling system, constructing a low-carbon water supply system, implementing a greywater management system, and creating hydrophilic spaces for the water circulation system [54]. In the energy/building sector, the planning elements consist of using renewable energy, expanding cogeneration, and energy-efficient building design [55]. Finally, the park/green area sector incorporated planning elements such as creating nature-friendly parks and green spaces, promoting building greening (green roofs, green walls, and green artificial ground), and establishing accessible greenways and green matrices in residential areas [56].

This study utilizes the hierarchical decision-making method (AHP) to ascertain the priority of sustainable urban planning elements [57]. To apply the AHP, the hierarchical structure of evaluation elements must be established (Figure 5). In this study, the structure is composed of upper and lower criteria based on the types of sustainable urban planning elements presented in Table 2.

The upper criteria were divided into five sectors: spatial system, transportation system, environment/conservation/recycle, energy/building, and park/green area sectors. Each upper criterion was further divided into lower criteria. For instance, the spatial system sector comprises three lower criteria: eco-friendly density management, inducing mixed-use development, and enhancing accessibility (securing the adequacy of the neighborhood area). The transportation system sector is divided into public transportation-oriented development, urban planning on green transportation (bicycles and pedestrian roads), and the introduction of new transportation (monorail, electric vehicles, etc.). The environment/conservation/recycle sector consists of three sub-criteria: reduction of trash and food waste and establishment of a recycling system, establishment of greywater management system, and creation of hydrophilic spaces for the water circulation system. The energy/building sector includes sub-criteria such as the use of renewable energy (solar power, geothermal heat, and wind power), expansion of cogeneration (energy and cooling supply), and energy-efficient building design (insulation and natural light). Finally, the lower criterion of the park/green area sector consists of the creation of low-carbon natural parks and green spaces, building greening (green roof, green walls, and green artificial ground), and establishment of accessible greenways and green matrix in residential areas. Figure 5 illustrates the hierarchical structure of the evaluation elements.

Evaluation techniques can be classified into two categories: uncorrected models and corrected models, used to assess alternative options. Uncorrected models share a common limitation, where the relative importance of the criteria must remain fixed, rendering them unsuitable for objectively reflecting the opinions of diverse expert groups [58,59]. This leads to a lack of clarity when selecting the optimal alternative, particularly in situations involving complex data [60].

The analytic hierarchy process (AHP) is a decision-making method that leverages mathematical and psychological principles to organize and evaluate complex decisions [61]. Developed by Thomas L. Saaty in the 1970s, AHP comprises three key components: the ultimate goal or problem to be solved, the possible alternatives, and the criteria for evaluating the alternatives [62]. By quantifying the criteria and alternative options, AHP provides a rational framework for making critical decisions that align with the overall goal [63].

During the decision-making process, stakeholders conduct pairwise comparisons of the importance of each criterion. For example, they might evaluate whether job benefits or a short commute is more crucial and by how much. AHP then converts these evaluations into numerical values that can be compared against all possible criteria [64]. This unique capability to quantify criteria and options distinguishes AHP from other decision-making techniques [65].

In the final step of the process, numerical priorities are calculated for each alternative option. These values reflect the most desirable solutions based on all stakeholders’ values [66].

The analytic hierarchy process (AHP) is especially useful for addressing complex problems with significant consequences. Its ability to quantify criteria and options that are typically difficult to measure using hard numbers sets it apart from other decision-making methods [67]. Instead of dictating the “correct” decision, AHP assists decision-makers in identifying the option that best aligns with their values and understanding of the issue at hand [68].

Involving all stakeholders in the decision-making process is crucial for achieving a comprehensive and well-rounded outcome. Different divisions or groups may prioritize criteria differently based on their unique perspectives and experiences [69]. By incorporating input from all relevant parties, AHP facilitates a more robust and inclusive decision-making process, leading to better overall results that take into account the diverse needs and preferences of the stakeholders involved.

The objective of this study was to establish the relative importance of various planning factors in creating a sustainable city, utilizing an expert survey. A total of 118 urban planning experts in the UAE participated in the study, including urban planners, architects, city planning officers, and researchers from both the public and private sectors [70]. Table 3 displays the distribution of these professionals: 42 urban planners (35.6% of total participants), 32 architects (27.1% of total participants), 18 city planning officers (15.3% of total participants), and 26 researchers, including university professors (22.0% of total participants).

Constructing a hierarchical structure: The planning elements, organized into five sectors (spatial system, transportation system, environment/conservation/recycle, energy/building, and parks/green areas), were structured hierarchically with upper and lower criteria based on the sustainable urban planning elements presented.

Pairwise comparison matrix: Participants conducted pairwise comparisons between elements (criteria) at each level of the hierarchy. They compared the relative importance of each pair of criteria within the same level of the hierarchy. Participants provided their judgment on a scale of 1 to 9, where 1 indicates equal importance, and 9 indicates an extreme difference in importance.

Calculating the local priority: After obtaining the pairwise comparison matrix, the local priority or weight of each criterion was calculated using the Eigenvalue method. This calculation process involves normalizing the matrix and determining the average of each row, which represents the local priority or weight for each criterion.

Calculating the global priority: The global priority or weight of each criterion was calculated by multiplying the local priority of each criterion in the hierarchy by its parent criterion’s local priority. The results were then added up for each element at the same level of the hierarchy. This calculation helps in determining the overall importance of each planning element in the context of the final goal.

Consistency check: To ensure the reliability of the AHP analysis, a consistency check was performed by calculating the consistency ratio (CR). The CR is the ratio of the consistency index (CI) to the random consistency index (RI), where CI is calculated using the largest eigenvalue of the pairwise comparison matrix, and RI is the average consistency index of randomly generated pairwise comparison matrices for a given matrix size. A CR value less than or equal to 0.1 indicates an acceptable level of consistency in the pairwise comparisons.

The present study employed the AHP using expert survey data to calculate the importance of each of the five upper criteria and 15 lower criteria presented in Figure 5. The results of the analysis are presented in Figure 6, where the importance of each of the five upper criteria was assessed. The consistency index (CI) was 0.00533, indicating the reliability of the analysis [71]. A CI value of 0 in AHP analysis indicates complete consistency in pairwise comparison by the respondent [72,73,74], while a value of 0.1 or more indicates inconsistency, requiring a re-examination.

In Figure 7, the results of calculating the importance of sustainable urban planning elements (lower criteria) for each sector are presented. The analysis yielded a consistency index (CI) of 0.00037 for the spatial system sector, 0.02 for the transportation system sector, 0.01 for the environment/conservation/recycle sector, 0.04 for the energy/building sector, and 0.02 for the park/green area sector, indicating reliable results for all lower criteria (CI less than 0.1).

Regarding the spatial system sector in Figure 7A, the inducing mixed-use development planning factor had the highest relative importance at 0.361, followed by enhancing accessibility (securing the adequacy of the neighborhood area) at 0.331. Meanwhile, eco-friendly density management had the lowest relative importance at 0.311.

In the transportation system sector in Figure 7B, the public transportation-oriented development planning factor had the highest importance at 0.407, followed by urban planning on green transportation (bicycles and pedestrian roads) at 0.365, and the introduction of new transportation (monorail, electric Vehicle, etc.) at 0.228.

For the environment/conservation/recycle sector in Figure 7C, the reduction of trash and food waste and the establishment of a recycling system had the highest relative importance at 0.531, whereas the establishment of the greywater management system was 0.263 and the creation of hydrophilic for the water circulation system was relatively low at 0.208.

In the energy/building sector in Figure 7D, energy-efficient building design (insulation and natural light) had the highest importance at 0.464, followed by use renewable energy (solar power, geothermal heat, and wind power) at 0.392, while the expansion of cogeneration (energy and cooling supply) had the lowest importance at 0.147.

Lastly, among the planning factors in the park/green area sector in Figure 7E, the creation of low-carbon natural parks and green spaces had the highest relative importance at 0.388, followed by building greening (green roof, green walls, and green artificial ground) at 0.316, and the establishment of accessible greenways and green matrix in residential areas at 0.296.

The results of the relative importance of individual planning elements for SSC, considering the importance of upper and lower criteria simultaneously, are shown in Figure 8. The CI for the analysis results was 0.01, indicating a reliable outcome.

Broaden stakeholder input: Incorporate diverse perspectives from residents, policymakers, and other stakeholders, in addition to urban planning experts. This will provide a more comprehensive and nuanced understanding of the priorities and needs of an energy-saving city.

Examine different urban contexts: Investigate the applicability of the identified planning factors across various urban settings with unique socio-economic, cultural, and environmental conditions. This will help identify context-specific priorities and strategies for different urban environments.

Employ qualitative methodologies: Utilize qualitative research methods, such as case studies or interviews, to capture the complexities and interdependencies of various planning elements. This will provide a deeper understanding of the underlying processes, challenges, and opportunities in implementing energy-saving urban planning initiatives.

Investigate the importance of greenways and water-friendly spaces: Explore factors contributing to the relatively low importance of these planning elements in the current study compared to previous research. Identify ways to better integrate these elements into the overall planning and development of energy-saving cities.