Morphology of Urban Villages in China: a Case Study of Dayuan Village in Guangzhou

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Article Morphology of Urban Villages in China: A Case Study of Dayuan Village in Guangzhou

Yuan Gao 1 , Sina Shahab 1,* and Negar Ahmadpoor 2

1 School of Geography and Planning, Cardiff University, Cardiff CF10 3WA, UK; [email protected] 2 School of Engineering and Built Environment, Anglia Ruskin University, Chelmsford CM1 1SQ, UK; [email protected] * Correspondence: shahabs@cardiff.ac.uk; Tel.: +44-0-29-2087-6092

Received: 31 March 2020; Accepted: 3 May 2020; Published: 7 May 2020

Abstract: Urban villages play an important role in providing affordable housing to urban migrants in Chinese cities. They are considered as supplementary to the dual rural-urban system in China. Of central importance to studying urban villages is how the morphology of these informal settlements affects urban life. It is essential for urban planners and designers to examine the morphology of urban villages. This paper, therefore, investigates the morphology of urban villages using the case study of Dayuan Village in Guangzhou, China. The morphology of this urban village is tested against four main elements of urban morphology: urban density, accessibility, functional mix, and urban interface. Our results revealed that the type of street within the urban village has considerable influence on accessibility, functional mix, and urban interface. Regarding urban density, our results show that buildings’ height is not influenced by the centrality of buildings nor land value; however, it is likely that it is affected by planning agreements between the village committee and the local government. Land coverage does not comply with the planning regulation for residential districts. Regarding accessibility analysis, the number of entrances to streets is influenced by the type of street under analysis. The distribution of different types of functional mix is also affected by the type of street within the urban village. The buildings with a mix of ‘live/visit’ are concentrated along the formal streets and primary inner streets. The mono-functional use of ‘live’ and the bi-functional mix of ‘live/work’ are mostly located in the secondary inner streets. Regarding urban interface, our results demonstrate that the formal streets have an interface with considerable porosity, and that this can contribute to the livelihood of the immediate area.

Keywords: urban morphology; urban village; informality; morphological elements

1. Introduction During the last few decades, China has experienced rapid urbanisation. This is characterised by large-scale urban expansion and considerable urban rural migration [1]. As a result, China’s informal settlements known as urban villages—villages inside urbanised areas—emerged and have become a common phenomenon, especially in the major cities such as Guangzhou, Shenzhen, Shanghai, and Beijing [2–4]. Urban villages are considered supplementary to the formal planning system [5] and everyday neighbourhoods that provide urban life for migrants without legal urban status [6]. Scholars reveal this contribution from socio-economic perspectives, arguing that urban villages help integrate the migrants into urban society [3,4] by providing aﬀordable housing and amenities [2,7–9]. However, the living conditions of urban villages do not often meet the standards of oﬃcial planning [10,11]. Moreover, the production and exchange of goods that occur in urban villages tend to transgress regulations and laws [12].

Urban Sci. 2020, 4, 23; doi:10.3390/urbansci4020023 www.mdpi.com/journal/urbansci Urban Sci. 2020, 4, 23 2 of 23

Research has revealed that the morphology of urban villages affects urban life at a micro scale. For example, literature has shown that the diversity of land use [5] and the dynamic of activities in the public realm [6,13,14] are affected by the morphology of urban villages. However, more research is needed to examine the relationship between the morphology and urban life in these villages. In order to address this gap, this paper investigates how spatial characteristics of urban villages from the perspective of urban morphology contribute to our understanding of the complex informality of these settlements. To this end, we use a framework that is in line with previous morphological studies in the context of formal and informal settlements [11–14]. According to this framework, the four key spatial elements that need to be taken into account in any morphological studies include density, accessibility, functional mix, and urban interface. Using the case study of Dayuan Village in Guangzhou, this paper aims to understand the key features of these four morphological elements and the underlying relationship between them. The results of this study demonstrate that this framework can be used to examine the urban morphology of informal settlement of urban villages in China. The framework can enable built environment professionals, such as architects, urban planners, and designers, to have a better understanding of how the incremental, self-organised space operates within urban villages. In this paper, we first discuss the typology, image, and informality of urban villages in China, as well as the literature on urban morphology in informal settlements. The paper goes on to present the utilised methodology, consisting of a case study approach and data collection and analysis methods. We then present the results of our analyses in terms of the four morphological elements of density, accessibility, functional mix, and urban interface, as well as their relations, in Dayuan Village in Guangzhou.

2. Literature Review

2.1. Urban Village: Typology, Image, Informality ‘Urban village’ is a translation from the Chinese term ‘chengzhongcun’, which literally means ‘the village embraced by the city’. After gaining attention among researchers in the 2000s [15], two terms (English translations) have been used in academic papers for referring to ‘chengzhongcun’: urban village [5,16–18] and village-in-the-city [19,20]. The former translation is more popular among scholars [15], while the latter refers to one particular type of urban village, those that are located in built-up urban areas and tend to have a higher degree of urbanisation. Considering the location of urban villages and whether they have farmland, Li [21] proposed a classification of urban villages as such: (a) centrally located villages with no farmland left; (b) suburban villages that have a small amount of farmland; and (c) peri-urban villages which still consist of large areas of farmland. Based on the location of urban villages, Wang, Wang and Wu [16] proposed a similar classification, dividing urban villages into three categories: (a) Chengzhongcun; villages located inside a city; (b) Chengbiancun; villages located at the edge of built-up areas; and (c) Chengwaicun; villages in suburban areas or industrial towns. The image of urban villages among scholars has experienced a change from negative and subjective to positive and objective [22]. In the 1990s and early 2000s, urban villages were considered as the dark side of urban development, and used to be referred to as ‘urban cancer’ in reference to their rapid and unregulated physical expansion. The ambiguous and ineffective regulations of rural land, which are rooted in the dual rural-urban system in China, have led to complex land rights, disordered construction, and a lack of infrastructure in urban villages. Considering their physical environment, which used to be characterised as ”dirty”, ”chaotic”, and ”deteriorated”, urban villages were perceived as a fertile ground for crime and fake products [23]. This image has been changing in recent years. Jingxiang and Wei [24] argued that the development of urban villages plays an irreplaceable role in alleviating the imbalance of China’s social structure and deprivation. In Futian district for example, 15 urban villages, occupying 390 hectares of land, house 572,100 migrants and 19,300 indigenous villagers (1515 persons per hectare) [25]. The existence of such highly dense areas reveals not only the Urban Sci. 2020, 4, 23 3 of 23 high demand for affordable housing, especially for migrants, but also the villagers’ pursuit for the maximisation of rental income [26]. With the success in assimilating migrant workers and indigenous villagers into urban life [5], urban villages can be considered as the third type of settlement following the urban and rural settlements in China. Urban villages also help to fill the gap of the dichotomy rural-urban system and diversified the social, economic, and spatial composition in China [16]. Urban villages have often been characterised as informal settlements. Compared with slums and squatter settlements, the informality of urban villages is somewhat more complicated. According to the dual rural-urban land system, the land of urban villages is formally owned by villagers either individually or collectively, but the land use, construction, and trading operate informally [23]. Village committees are the lowest level, yet an official part of the Chinese government structure. However, local governments have no jurisdiction in urban villages [27]. Indigenous family clans still play an important role in the governance of villages [28]. This complex nature of informality in urban villages enables villagers to construct their land and accommodate large numbers of migrants. This is because such informality provides space for villagers and migrants to transgress the state’s regulation in terms of formal urban planning, tenure, and construction [29].

2.2. Morphological Thinking in Informal Settlements Urban morphology is a critical issue to deal with the environment we inhabit. Helm and Robinson [30] simply deﬁned urban morphology as the pattern of land use within a town. Urban morphology is the study of human settlements in terms of their structure and the process of both formation and transformation [31]. Density, access, functional mix, and urban interface are considered as the four key elements of urban analysis in general and urban morphology in particular [32–35]. Understanding their relation is a critical condition for exploring the morphology of an informal settlement. This section reviews the deﬁnition and measurement of these morphological elements to inform the research methods of the present study.

2.2.1. Density The density of buildings is of central importance to urban morphology studies. Density of buildings is associated with different variables including building height, floor area ratio (FAR), and land coverage ratio. The number of floors of buildings is often used as a proxy for estimating building heights. FAR is the ratio of total floor areas to site areas, while land coverage is the ratio of footprints to site areas. FARs are often explicitly defined in urban planning and design guidelines [36]. Ahmadpoor and Shahab [37] explained urban density as one of the urban elements that form people’s spatial knowledge. Building density is measured either as gross density or net density [32,38]. Berghauser Pont and Haupt [39] proposed four levels in urban areas to illustrate the application of net and gross density: lot, island, fabric, and district levels. The lot level is the basic unit for market transactions [32]. Hence, it should be measured in net density. The island level is the combination of multiple adjacent lots and the public space around them. It can be measured with either net density or gross density [38]; net density is applied when only measuring the cluster of plots, while gross density is used when at least half of the adjacent streets are included. The fabric level is the combination of several adjacent islands. Since public space such as streets are included, this level uses a gross density. Finally, the district level is a broader urban area including various functions such as education, transport, parks, commercial, and residential. Planners often use gross density for the district level [32]. Given some important aspects of urban planning and design such as walkability and viability of public transport are not considered using net density [40], gross density is considered more appropriate when analysing urban morphology at large scales [40]. Urban Sci. 2020, 4, 23 4 of 23

2.2.2. Accessibility Accessibility concerns movement, connectivity, and permeability [34,41,42]. Movement ﬂows are physically structured by street networks [43] and include walking, cycling, public transports and vehicles. Zacharias, et al. [18] pointed out that movements consist of the ﬂows of people, goods, and vehicles. Connectivity can be considered as the extent to which two locations are easily connected. Southworth and Ben-Joseph [44] measured connectivity with the number of access points in a given area. This approach is a measure of connectivity between a study area and its environs rather than the inter-connectivity within an urban area [32]. Permeability is the result of small blocks which is argued by Jacobs [45] as one of the conditions for urban diversity. Marshall [46] described permeability as the extent to which an urban area is permeated by publicly accessible space. Permeability can be considered as the foundation for connectivity and ease of movement. Thus, measuring permeability is important in assessing accessibility. Berghauser Pont and Haupt [39] used network density to measure permeability. Network density is the ratio of the total length of streets to the area of an urban area. Knight and Marshall [47] used intersection density to analyse street network connectivity, referring to the number of intersections in a given urban area.

2.2.3. Functional Mix Functional mix is an essential condition for the intensity of urban life and social and economic vitality [45]. There is no consensus on the definition of functional mix. Taking the priority of activities into account, Jacobs [45] divided land uses into primary and secondary uses. The primary uses provide the possibility for the presence of secondary uses. Working or living are considered as primary uses, and secondary uses, such as shops in apartment blocks or cafes in business districts, take place to service them [48]. The functional mix can be considered as the mix of primary and secondary uses. Hoek [49] considered mixed-use as a combination of three urban uses: housing, working, and amenities. Dovey et al. [32] proposed a classification according to the purpose in which people go to a place. People live, work, or visit some kinds of facilities or amenities. Hence, the urban functions can be categorised into three primary groups: live, work, and visit. They argue that this framework includes overlapping classifications such as recreation, retail, entertainment, and community. There are different approaches to measure functional mix: entropy [50], destinations [51], mixed-use index [48,49], and the live/work/visit triangle [32].

(a) Entropy: entropy is a borrowed concept from physics which measures the degree to which different functions occur equally within a certain territory. The entropy-based measurements were developed by Cervero [52] and Frank et al. [50,53]. In their measurement of the functional mix, a score from 0 to 1 is calculated to describe the degree to which floor areas devoted to primary uses are equal within the 1-kilometer territory. The advantage of this measurement is that it not only reveals the proportion of different functions within a particular neighbourhood but also compares different neighbourhoods at the same scale [32]. (b) Destination: in the destination-based measurements, functions are treated differently since they have different levels of attraction [32]. For example, retail floorspaces attract more visitors than offices or apartments. Giles-Corti et al. [54] and Rundle et al. [55] used the degree of attractiveness of recreation and public transport. However, quantifying different levels of attractiveness is a complex task, since the attractiveness of the floor areas of different functions varies greatly. For example, within the same floor area, the shopping mall will attract much more visitors than apartment blocks. The key contribution of the destination-based approach is in recognising that different functions have various levels of attractiveness [32]. (c) Mixed-use index (MXI): Hoek developed MXI, which measures the ratio of different functions by calculating the floor areas. Based on this index, urban functions are categorised into housing, working, and amenities. The three primary uses are placed into a triangular model, which is a framework to measure the extent of mix within the three categories. The framework provides a Urban Sci. 2020, 4, 23 5 of 23

foundation for multi-scale analysis, ranging from individual buildings to neighbourhoods and districts in a city. (d) Live/work/visit triangle: drawing on the MXI, Dovey et al. [32] developed the live/work/visit triangle to analyse functional mix. Based on the purpose of people’s presence at a given place and given time, urban functions are divided into live, work, and visit. According to Dovey et al. [32], ‘visit’ is a better label compared to ‘amenities’ since the latter is a generic term and could overlap with housing and working. In the measurement of MXI, functional mix is calculated by the ﬂoor areas, and all the functions are treated equally. Since the category of live/work/visit is based on people’s behaviour, the live/work/visit triangle takes attractiveness into consideration in assessing the diﬀerence between the three primary uses. As places for work and visit are more attractive than residential districts, Dovey et al. [32] set a 1:2:5 ratio of live/work/visit as multiplier to ensure the evidence of calculation.

2.2.4. Urban Interface Urban interface is the threshold between private and public territories [34]. Dovey and Wood [56] defined urban interface as a transitional space, where private spaces plug into public realms. Carmona [57] considered urban interface as the area between public and private spaces that is physically demarked, but publicly accessible, such as street cafes and private pavement space. The importance of urban interface can be traced back to Jacobs’s argument [45] about the uses of street sidewalks in terms of safety and contact. The degree of liveliness of urban area is related to the ways how the edges of buildings in an area work [58]. Bobić[59] pointed out that the quality of the urban interface deeply affects urbanity and the character of spaces that people perceive. Gehl [60] classified urban interfaces into two categories of soft and hard edges. Hard edges are deficient in details and indoor/outdoor connections dramatically limit the activities in public spaces. Soft edges, which provide space for sitting or standing, facilitate social activities. Dovey and Wood [56] proposed a typology of urban interfaces, which considers four variables in terms of the physical characteristics of the edge of buildings: accessible/inaccessible, direct/setback, opaque/transparent, car/pedestrian. The typology consists of five types: impermeable/blank, direct opaque, direct transparent, pedestrian setback and car setback. Considering connectivity and proximity, Kamalipour [35] developed a typology of urban interfaces in informal settlements. Connectivity describes the extent to which the private space is connected to public realm. It is divided into three levels: impermeable, accessible, and porous. Although the extent of connectivity is a continuum, for the purpose of mapping, 50% of total length of interface is set as threshold [35]. An interface is defined as porous if more than half of the length is open to public space. Accessible interfaces are those interfaces that up to 50% of their total length are open. Proximity refers to the degree to which private spaces are close to public spaces. It includes two levels: adjacent and distant and 50 cm is set as the threshold. If the edge of buildings is more than half a meter away from public space, it is considered a distant interface. Based on the two variables, six types of interface are proposed: impermeable/adjacent, accessible/adjacent, porous/adjacent, impermeable/distant, accessible/distant, and porous/distant. Although the thresholds of the two variables (i.e., 50% and 50 cm) seem somewhat arbitrary, the typology provides a clear framework for a systematic analysis.

3. Methodology

3.1. Case Study of Dayuan, Guangzhou This research explores Dayuan Village, located in the Baiyun District of Guangzhou, China, as a case study. Case-study methodology is considered as a preferred approach when the focus of the research is on contemporary phenomena [61]. The use of a single case study method, which is common in the ﬁeld of urban planning and design [62,63], enables the researchers to develop a comprehensive and in-depth understanding of the case through studying it in detail. Exploring Dayuan Village is Urban Sci. 2020, 4, 23 6 of 23 interesting for various reasons. It is located in Guangzhou, that is one of the major cities in China, and is the manufacturing, commercial, and logistics hub of the Pearl River Delta. The rapid process of urban expansion in Guangzhou has created 138 urban villages, and Dayuan Village is the largest one at 25 square kilometres, accommodating 9500 original inhabitants and a further 138,000 people who moved to the village [64]. Dayuan Village is a suburban village and located in the north of the city centre. It is about 20 km away from the central business district of Guangzhou (Figure1). Traveling by public transport between Dayuan Village and the city centre takes one hour. For the micro-scale analysis of urban morphologies, Urban Sci. 2020, 4, x FOR PEER REVIEW 6 of 23 the present research selects one of the areas with the highest building and population densities in Dayuancorridors village. (i.e., Dayuan The location Road), of through the selected which area Dayuan is typical Village in relation is connected to major to the transport metropolitan corridors region (i.e., Dayuanof Guangzhou. Road), through which Dayuan Village is connected to the metropolitan region of Guangzhou.

FigureFigure 1.1. ((aa)) thethe locationlocation of the study area (left); ( b) the location location of of Dayuan Dayuan Village Village with with respect respect to to the the GuangzhouGuangzhou citycity centrecentre (top(top right);right); ((cc)) aa photophoto ofof thethe studystudy areaarea (bottom(bottom right).right).

TheThe land use of of Dayuan Dayuan Village Village reflects reﬂects the the characteristics characteristics of an of urbanising an urbanising village. village. Firstly, Firstly, the thevillage village still still maintains maintains a small a small amount amount of offarmland. farmland. Figure Figure 22 illustrates illustrates the the distribution distribution of maintained farmlandfarmland inin Dayuan Dayuan Village. Village. Secondly, Secondly, the landthe land of the of village the village is being is encroached being encroached by urban expansion.by urban Asexpansion. shown in As Figure shown2, a in formal Figure residential 2, a formal development residential has development taken place has in thetaken south place of Dayuanin the south Village. of TheDayuan transformation Village. The of transf buildingsormation to large of buildings size and to low-end large size warehouses and low-end embodies warehouses the development embodies the of labour-intensedevelopment industries.of labour-intense Hence, indu Dayuanstries. Village Hence, is a Dayuan typical suburban Village is village a typical of which suburban the urbanisation village of processwhich the is a urbanisationﬀected by urban process expansion is affected and by low-end urban industry.expansion and low-end industry. Dayuan Village is a typical Taobao village in Guangzhou [64]. ‘Taobao village’ is a concept describing the villages in which the development is driven by online shopping (Taobao is a large online shopping website in China). A village can be considered as a Taobao village when it reaches 10 million RMB in terms of the annual volume of e-business transactions or when it has over 100 active online stores [65]. According to Guangzhou Urban Planning & Design Survey Research Institute (GZPI), the number of active Taobao stores in Dayuan Village exceeds 3000, which makes Dayuan Village the largest Taobao village in Guangzhou [64]. Convenient transportation and adequate and well-equipped building space also provide a good foundation for Dayuan Village to develop into the largest and most representative Taobao village in Guangzhou. While Dayuan Village is an interesting case as discussed above, we do not claim that this village is representative of all urban villages in China. Urban villages

Figure 2. Map of Dayuan Village and the study area. Source: Tencent Map.

Dayuan Village is a typical Taobao village in Guangzhou [64]. ‘Taobao village’ is a concept describing the villages in which the development is driven by online shopping (Taobao is a large online shopping website in China). A village can be considered as a Taobao village when it reaches 10 million RMB in terms of the annual volume of e-business transactions or when it has over 100 active online stores [65]. According to Guangzhou Urban Planning & Design Survey Research Institute (GZPI), the number of active Taobao stores in Dayuan Village exceeds 3000, which makes Urban Sci. 2020, 4, x FOR PEER REVIEW 6 of 23 corridors (i.e., Dayuan Road), through which Dayuan Village is connected to the metropolitan region of Guangzhou.

Figure 1. (a) the location of the study area (left); (b) the location of Dayuan Village with respect to the Guangzhou city centre (top right); (c) a photo of the study area (bottom right).

The land use of Dayuan Village reflects the characteristics of an urbanising village. Firstly, the village still maintains a small amount of farmland. Figure 2 illustrates the distribution of maintained Urbanfarmland Sci. 2020 in, 4,Dayuan 23 Village. Secondly, the land of the village is being encroached by urban7 of 23 expansion. As shown in Figure 2, a formal residential development has taken place in the south of Dayuan Village. The transformation of buildings to large size and low-end warehouses embodies the aredevelopment diverse, and of eachlabour-intense has its own indu uniquestries. characteristics. Hence, Dayuan This study,Village we is hope,a typical is an suburban endeavour village to spark of awhich debate the on urbanisation the morphology process of urbanis affected villages. by urban expansion and low-end industry.

Figure 2. Map of Dayuan Village and the studystudy area. Source: Tencent Map.

3.2. DataDayuan Collection Village Methods is a typical Taobao village in Guangzhou [64]. ‘Taobao village’ is a concept describingThe data the collection villages methodsin which utilised the development in this paper is consisted driven by of archivalonline shopping records and (Taobao visual recording.is a large Archivalonline shopping records includedwebsite in planning China). reports A village and can vector be considered base maps. as The a planningTaobao village reports when were it issued reaches by the10 million local planning RMB in authority terms of andthe Aliannual Research volume Institute, of e-business which focus transactions on the studies or when of Taobaoit has over villages. 100 Theactive quantitative online stores data [65]. such asAccording building storeys,to Guangzhou the area Urban of footprint Planning of individual & Design buildings, Survey theResearch length ofInstitute building (GZPI), façades, the andnumber thedistance of active of Taobao building stores setbacks in Dayuan were extractedVillage exceeds from the 3000, vector which base makes map. Visual recording was used to record the character of the site. Photographs were taken to illustrate the physical characteristics of buildings and the location and number of entrances. The building signboards captured in the photographs illustrate the function of each ﬂoor. Table1 summarises the collected data and data sources for each of the morphological elements. The photos were taken by the ﬁrst author between the 2nd and 7th of July 2019 at Dayuan Village, Guangzhou. The satellite images were extracted from Tencent Map. The vector base map was prepared by the Guangzhou Urban Planning & Design Survey Research Institute in 2019.

Table 1. Data resources for the morphological elements.

Elements Corresponding Data Data Resource Building storeys Density Vector base map Area of footprint of individual buildings Accessibility Location and number of entrances Photograph Building storeys Vector base map Functional mix Area of footprint of individual buildings Function of each ﬂoor photograph Length of building façade Vector base map Urban interface Distance of building setback Physical characteristics of buildings Photograph

3.3. Data Analysis Methods The data analysis methods consist of typological analysis, multi-scale analysis, and visual analysis of maps of density, accessibility, functional mix, and urban interface. Urban Sci. 2020, 4, 23 8 of 23

3.3.1. Typological Analysis Typological analysis is one of the main analysis approaches in the present research. Kelbaugh [66] argued that the typological analysis is a departure to discover spatial-related problems since types serve as abstractions rather than actual buildings. In the context of urban villages, where the physical form of buildings varies due to self-organised constructions, the typological analysis will help to reduce the disturbance of the greatly varied exterior of buildings. Proposed by Deleuze and Guattari [67] and Dovey [68], types can be considered as a diagram, which illustrates the relationships between diﬀerent objects. In the context of informal settlements, the typology can be considered as a diagrammatic way to study how the urban morphology works [69]. For the present study, typological analysis was applied to street, functional mix, and urban interface.

(a) Typology of street

According to the formality, width, and connectivity, the streets within and surrounding the Urban Sci. 2020, 4, x FOR PEER REVIEW 8 of 23 investigated area of Dayuan Village were categorised into the formal street, primary inner street, secondarysecondary inner inner street, street, and and laneway laneway (Figures (Figures 3 andand4 4).). TheThe formalformal streetstreet representsrepresents thethe streetstreet thatthat isis plannedplanned and and financed financed by the the government. government. The The formal formal street street has has higher higher traffic traffic capacities. capacities. The The primary primary andand secondary inner streets andand lanewayslaneways areare informally informally constructed constructed by by the the village. village. Their Their capacities capacities of ofvehicular vehicular tra ffitrafficc are lower,are lower, compared compared to the to formal the fo street.rmal Primarystreet. Primary inner streets inner are streets directly are connected directly connectedwith the formal with streetthe formal and are street wider and than are 6 m.wider The than secondary 6 m. The inner secondary streets are inner under streets 5.5 m. are The under laneways 5.5 m.are The the laneways narrowest are pathways, the narrowest accounting pathways, for 2–4 accounting m width. The for laneways2–4 m width. are linkedThe laneways to secondary are linked inner tostreets secondary and they inner have streets the lowestand they degree have of the connectivity. lowest degree of connectivity.

FigureFigure 3. 3. MapMap of of street street network. network.

Figure 4. Photos of different types of streets. Urban Sci. 2020, 4, x FOR PEER REVIEW 8 of 23

secondary inner street, and laneway (Figures 3 and 4). The formal street represents the street that is planned and financed by the government. The formal street has higher traffic capacities. The primary and secondary inner streets and laneways are informally constructed by the village. Their capacities of vehicular traffic are lower, compared to the formal street. Primary inner streets are directly connected with the formal street and are wider than 6 m. The secondary inner streets are under 5.5 m. The laneways are the narrowest pathways, accounting for 2–4 m width. The laneways are linked to secondary inner streets and they have the lowest degree of connectivity.

Urban Sci. 2020, 4, 23 9 of 23 Figure 3. Map of street network.

Urban Sci. 2020, 4, x FOR PEER REVIEW 9 of 23 Figure 4. Photos of diﬀerent types of streets. Figure 4. Photos of different types of streets. (b)TypologyTypology of urban of urban interface interface Drawing on the typology of urban interface in informal settlement proposed by Kamalipour [35], Drawingthe urban on theinterfaces typology were of grouped urban interface into six in categories: informal settlement‘impermeable/adjacent’, proposed by Kamalipour‘accessible/adjacent’, [35], the urban‘porous/adjacent’, interfaces were grouped‘impermeable/distant’, into six categories: ‘accessible/distant’, ‘impermeable/adjacent’, and ‘accessible‘porous/distant’/adjacent’, (Figure ‘porous 5). Imperm/adjacent’,eable ‘impermeable interfaces are/distant’, those ‘accessiblewithout any/distant’, entrance. and When ‘porous up/ distant’to half (Figureof the length5). Impermeable of the interface interfaces is open are thoseto public without space, any it entrance. was defined When as up accessible. to half of thePorous length interface of the interfacerequired ismore open tothan public 50% space, of itthe was total defined length as accessible. to be opened. Porous interface The threshold required more to thandistinguish 50% of theadjacent/distant total length to interface be opened. was The set threshold as 50 cm, to since distinguish such distance adjacent provides/distant interface a possibility was setto accommodate as 50 cm, since suchhome distance appliances provides and activities a possibility such to as accommodate sitting and socialising home appliances [34]. If and the activitiesedge of a such building as sitting is more and socialisingthan 50 cm [ away34]. If from the edge public of arealm, building it was is more considered than 50 a cm distant away interface. from public The realm, distance it was between considered public a distantspace and interface. adjacent The interfaces distance betweenwere under public half space a metre. and adjacent interfaces were under half a metre.

Figure 5. Samples of different diﬀerent types of interfaces.

(c) Typology of functional mix The typological analysis of functional mix was based on the typology proposed by Hoek [49] and Dovey et al. [32]. The uses were categorised into seven groups: ‘live’, ‘work’, ‘visit’, ‘live/work mix’, ‘live/visit mix’, ‘work/visit mix’ and ‘mix’. Live, work and visit are three types of mono- functional uses. Live is the use for housing. Work describes the space in which the number of employees outweighs that of visitors and visit is on the opposite. Live/work mix, live-/visit mix and visit/work mix are three types of bi-functional mix. According to Dovey et al. [32], live/work mix is about commute, live/visit mix is often related with lifestyles such as living and shopping in a given place and visit/work mix describes the way we shop, eat, and play in conjunction with work. Lastly, mix represents the space that mixes the three uses of live/work/visit.

3.3.2. Multi-Scale Analysis Drawing on the framework of multi-scale analysis proposed by Berghauser Pont and Haupt [39], the investigated area of Dayuan Village was analysed at the three levels of plot, island, and fabric. At the plot level, the unit of analysis is individual buildings. The island level constitutes adjacent plots and the public space around them. The shapes of islands are irregular due to the irregularity and high permeability of the layout of the investigated area. The size of an island is equal to the 80-to-90- m-wide block in the formal city, since the block width of 80–90 m enables accessibility, adaptability, and functional mix [70]. Several primary and secondary inner streets were chosen as the boundary of island. In the fabric level, the unit of analysis was the investigated area as a whole. As shown in Figure 6, the case study included 166 buildings and 10 islands. Urban Sci. 2020, 4, 23 10 of 23

The typological analysis of functional mix was based on the typology proposed by Hoek [49] and Dovey et al. [32]. The uses were categorised into seven groups: ‘live’, ‘work’, ‘visit’, ‘live/work mix’, ‘live/visit mix’, ‘work/visit mix’ and ‘mix’. Live, work and visit are three types of mono-functional uses. Live is the use for housing. Work describes the space in which the number of employees outweighs that of visitors and visit is on the opposite. Live/work mix, live-/visit mix and visit/work mix are three types of bi-functional mix. According to Dovey et al. [32], live/work mix is about commute, live/visit mix is often related with lifestyles such as living and shopping in a given place and visit/work mix describes the way we shop, eat, and play in conjunction with work. Lastly, mix represents the space that mixes the three uses of live/work/visit.

3.3.2. Multi-Scale Analysis Drawing on the framework of multi-scale analysis proposed by Berghauser Pont and Haupt [39], the investigated area of Dayuan Village was analysed at the three levels of plot, island, and fabric. At the plot level, the unit of analysis is individual buildings. The island level constitutes adjacent plots and the public space around them. The shapes of islands are irregular due to the irregularity and high permeability of the layout of the investigated area. The size of an island is equal to the 80-to-90-m-wide block in the formal city, since the block width of 80–90 m enables accessibility, adaptability, and functional mix [70]. Several primary and secondary inner streets were chosen as the boundary of island. In the fabric level, the unit of analysis was the investigated area as a whole. As shown in Figure6, theUrban case Sci. study 2020, included4, x FOR PEER 166 REVIEW buildings and 10 islands. 10 of 23

Figure 6. Boundaries of islands and fabric. Figure 6. Boundaries of islands and fabric. 3.3.3. Combination of Research Methods 3.3.3. Combination of Research Methods The analysis was undertaken in a sequential manner (Figure7). First, in the analysis of density, buildingThe heights analysis were was measured undertaken in di inﬀ aerent sequential scales. manner The relation (Figure between 7). First, the in distribution the analysis ofof buildingdensity, building heights were measured in different scales. The relation between the distribution of building heights and the types of streets was analysed. Second, the density of building entrances and their heights and the types of streets was analysed. Second, the density of building entrances and their relationship with the types of streets was analysed to illustrate the accessibility to buildings. Third, relationship with the types of streets was analysed to illustrate the accessibility to buildings. Third, the extent of functional mix was measured at multiple scales. Then the impact of the types of streets on the building functions was analysed. The combination of typological analysis of street and urban interface illustrate the impact of the formality of streets on the form of urban interface. Finally, the visual analysis was carried out to analyse the interrelation between the four spatial elements.

Figure 7. The process of data analysis. Urban Sci. 2020, 4, x FOR PEER REVIEW 10 of 23

Figure 6. Boundaries of islands and fabric.

3.3.3. Combination of Research Methods The analysis was undertaken in a sequential manner (Figure 7). First, in the analysis of density, buildingUrban Sci. 2020 heights, 4, 23 were measured in different scales. The relation between the distribution of building11 of 23 heights and the types of streets was analysed. Second, the density of building entrances and their relationship with the types of streets was analysed to illustrate the accessibility to buildings. Third, the extent of functional mix was measured at multip multiplele scales. Then the impact of the types of streets on the building functions was analysed. The combinat combinationion of typological analysis of street and urban interface illustrateillustrate thethe impact impact of of the the formality formality of streetsof streets on theon formthe form of urban of urban interface. interface. Finally, Finally, the visual the visualanalysis analysis was carried was carried out to analyseout to analyse the interrelation the interrelation between between the four the spatial four spatial elements. elements.

Urban Sci. 2020, 4, x FOR PEER REVIEW Figure 7. TheThe process of data analysis. 11 of 23

4. Analysis Analysis 4.1. Urban Density 4.1. Urban Density 4.1.1. Plot Level 4.1.1. Plot Level The building height in the study area (166 buildings) ranges from one storey to 13 storeys, with an averageThe buildingbuilding heightheight ofin the 6.2 storeysstudy area (Figure (1668 buildings)). According ranges to Zacharias from one etstorey al. (2013), to 13 storeys, the average with anbuilding average height building of Shipai height Village of 6.2 storeys (a centrally (Figure located 8). According urban village to Zacharias in Guangzhou) et al. (2013), is 5.06the average storeys. buildingDayuan Villageheight isof locatedShipai Village in the suburban (a centrally area located while urban Shipai village Village in is closeGuangzhou) to the central is 5.06 businessstoreys. Dayuandistrict of Village Guangzhou. is located The in di theﬀerence suburban between area the wh averageile Shipai building Village height is close of theto the two central villages business is only districtone storey. of Guangzhou. It can be concluded The difference that the between centrality the av oferage the location building has height a limited of the eﬀ twoect onvillages the average is only onebuilding storey. height It can of be urban concluded villages. that the centrality of the location has a limited effect on the average building height of urban villages.

35% 30% 30% 25% 19% 20% 20% 17%

15% 10%

Percentage 10% 4% 5% 0% 1 to 2 3 to 4 5 to 6 7 to 8 9 to 10 Above 10 Building Height

Figure 8. PercentagePercentage of of different diﬀerent buildin buildingg heights—number of storeys.

Figure 9 compares the height of buildings with different types of street network, while Table 2 exhibits the average storey number of the buildings along each type of street. The buildings located in the proximity of secondary inner streets and laneways have the highest average height (6.6 and 6.5 storeys, respectively). However, they are just one storey higher than those that are located along formal streets and primary inner streets. We can consider that the type of street has a limited effect on the height of the buildings. It is often expected that the centrality of streets affects land value, and consequently, increases the height of buildings in central areas. However, in the studied urban village, the height of buildings does not show any correlation with land values. Urban Sci. 2020, 4, 23 12 of 23

Figure9 compares the height of buildings with di fferent types of street network, while Table2 exhibits the average storey number of the buildings along each type of street. The buildings located in the proximity of secondary inner streets and laneways have the highest average height (6.6 and 6.5 storeys, respectively). However, they are just one storey higher than those that are located along formal streets and primary inner streets. We can consider that the type of street has a limited effect on the height of the buildings. It is often expected that the centrality of streets affects land value, and consequently, increases the height of buildings in central areas. However, in the studied urban village,Urban Sci. the 2020 height, 4, x FOR of buildings PEER REVIEW does not show any correlation with land values. 12 of 23

Figure 9. Building heights located in different types of streets. Figure 9. Building heights located in different types of streets. This might be because: (a) the central areas of the village were developed when the land values This might be because: (a) the central areas of the village were developed when the land values were lower; (b) although the land values of the central areas increased over time, the construction were lower; (b) although the land values of the central areas increased over time, the construction expenses and the informal nature of these settlements were hindering factors in rebuilding or adding expenses and the informal nature of these settlements were hindering factors in rebuilding or adding more storeys to the existing central buildings; or (c) the building heights are the result of continuous more storeys to the existing central buildings; or (c) the building heights are the result of continuous coordination between villagers’ constructions and local planning regulations [20]. Table2 exhibits the coordination between villagers’ constructions and local planning regulations [20]. Table 2 exhibits average storey number of the investigated buildings and the proportion of different building heights. the average storey number of the investigated buildings and the proportion of different building Moreover, the analysis also illustrates that the centrality of the urban village, formality, and traffic heights. Moreover, the analysis also illustrates that the centrality of the urban village, formality, and capacity of the streets have limited impact on building height. traffic capacity of the streets have limited impact on building height. Table 2. Average building heights in each type of street. Table 2. Average building heights in each type of street. Type of Street Average Building Height Type of Street Average Building Height Formal street 5.4 Formal street 5.4 Primary inner street 5.5 SecondaryPrimary inner inner street street 5.56.6 SecondaryLaneway inner street 6.66.5 Laneway 6.5 4.1.2. Island Level 4.1.2. Island Level The investigated area was divided into 10 irregular sections at island level, of which the land coverageThe and investigated gross floor area ratiowas divided (gFAR) are into analysed. 10 irregular From sections the perspective at island of level, land coverage,of which mostthe land of thecoverage islands haveand gross a land floor coverage area ratio higher (gFAR) than 40.are Accordinganalysed. From to Guangzhou’s the perspective urban of planning land coverage, regulation most ofof formal the islands cities, thehave maximum a land coverage coverage higher of residential, than 40. commercial, According andto Guangzhou’s industrial land urban stays planning at 30%, regulation of formal cities, the maximum coverage of residential, commercial, and industrial land stays at 30%, 50%, and 45% respectively. Although it is difficult to compare the investigated area with the regulation of formal cities due to the function’s dynamic in the urban village, the incremental construction drives the land coverage to go far beyond the norms of the local planning authority of Guangzhou. In China’s land management system, the village’s land for housing is divided into plots and allocated to individual household according to population regardless of the consideration of public space [8]. Kochan [6] argued that there is no shortage of public space in urban villages since the definition of public space is extended to the places which facilitate chatting, sitting and other social and economic interactions, such as food markets, chess rooms, and other indoor spaces. However, Urban Sci. 2020, 4, 23 13 of 23 Urban Sci. 2020, 4, x FOR PEER REVIEW 13 of 23 the50%, high and land 45% coverage, respectively. which Although is common it is di ffiincult suburb to comparean and thecentrally investigated located area urban with villages the regulation in the southernof formal Chinese cities due cities, to the proves function’s the encroach dynamicment in the of urban publicly village, accessible the incremental outdoor space. construction drives the landFour coverage islands have to go gFAR far beyond higher the than norms 2.0, oftwo the islands local planninggo beyond authority 3.0, and of the Guangzhou. other two islands exceedIn 4.0. China’s These land figures management generally reach system, the the same village’s level as land the forgFAR housing in the is central divided business into plots district and ofallocated Guangzhou, to individual which is household2.7 [71]. Although according Dayuan to population Village is regardless a suburban of village, the consideration the gFAR of of the public ten islandsspace [8shows]. Kochan that the [6] arguedconstruction that theredensity is nois equal shortage to the of city public centre space of Guangzhou. in urban villages In a sense, since the the centralitydefinition of of village public spacehas a islimited extended influence to the places on the which density facilitate of space. chatting, Our analysis sitting and on otherland socialcoverage and andeconomic building interactions, height illustrates such as foodthat the markets, studied chess case rooms, reaches and high other construction indoor spaces. density, However, which the results high inland the coverage, encroachment which of is outdoor common public in suburban space. However, and centrally this located high density urban is villages merely in linked the southern to the geographicChinese cities, centrality proves or the the encroachment formality of the of publicly external accessible and internal outdoor street space.network. Four islands have gFAR higher than 2.0, two islands go beyond 3.0, and the other two islands 4.2.exceed Accessibility 4.0. These to Individual figures generally Buildings reach the same level as the gFAR in the central business district of Guangzhou,In the analysis which of accessibility, is 2.7 [71]. Although the density Dayuan of entrances Village is is analysed a suburban according village, to the different gFAR types of the often street islands network shows (Figure that the 10). construction Among the four density types is of equal streets, to the the city form centreal street of Guangzhou.has the highest In density a sense, ofthe entrances, centrality accounting of village has for a12.7 limited entrances influence per 100 on them, densityand there of is space. a big Ourgap analysisbetween onthe land figure coverage of the formaland building street with height those illustrates of the other that thethree studied informal case street reaches types high (Table construction 3). The density density, of which entrances results of primaryin the encroachment and secondary of inner outdoor streets public and space. laneways However, decreases this highrespectively density with is merely the decline linked of to the the connectivitygeographic centralitycompared or to the formal formality streets. of It the illustrate externals that and the internal density street of entrances network. is closely linked to the formality of the routes and the connectivity with the formally planned street. 4.2. Accessibility to Individual Buildings In the analysis of accessibility,Table the3. Density density of of entrances entrances by isstreet analysed type. according to different types of street network (Figure 10). Among the four types of streets, the formal street has the highest density of Type of Street Network Average Number of Entrances in Every 100 m entrances, accounting for 12.7 entrances per 100 m, and there is a big gap between the figure of the Formal street 12.7 formal street with those of the other three informal street types (Table3). The density of entrances Primary inner street 9.2 of primary and secondary inner streets and laneways decreases respectively with the decline of the Secondary inner street 8.5 connectivity compared to formal streets. It illustrates that the density of entrances is closely linked to Laneway 7.2 the formality of the routes and the connectivity with the formally planned street.

FigureFigure 10. 10. EntrancesEntrances located located in in different diﬀerent types types of of streets. streets.

The formal street is financed, constructed, and managed by the local government of Baiyun District. It has better traffic capacity and public transport facilities, such as bus stops and metro stations. Therefore, the formal street has a better connectivity with the city centre. This connectivity Urban Sci. 2020, 4, 23 14 of 23

Table 3. Density of entrances by street type.

Type of Street Network Average Number of Entrances in Every 100 m Formal street 12.7 Primary inner street 9.2 Secondary inner street 8.5 Laneway 7.2

The formal street is financed, constructed, and managed by the local government of Baiyun District.Urban Sci. 2020 It has, 4, betterx FOR PEER traffi cREVIEW capacity and public transport facilities, such as bus stops and metro stations.14 of 23 Therefore, the formal street has a better connectivity with the city centre. This connectivity makes the formalmakes the streets formal the streets catchment the catchment of pedestrian of pedestrian flows, which flows, facilitates which thefacilitates emergence the emergence of shops along of shops the streets.along the In streets. the buildings In the adjacentbuildings to adjacent the formal to the streets, formal the streets, ground the floor ground is generally floor is divided generally into divided several independentinto several independent shops. The high shops. density The high of entrances density of of entrances the formal of streets the formal is rooted streets in theis rooted connectivity in the withconnectivity the formal with city the area. formal city area. In conclusion, although the spatial layout of the street network seems random and lacks a sense of hierarchy, thethe aboveabove analysisanalysis provesproves thatthat accessibilityaccessibility is notnot evenlyevenly distributed.distributed. The density of entrances decreasesdecreases withwith the the decline decline of of the the streets’ streets’ width, width, formality, formality, and and connectivity. connectivity. It proves It proves that that the formalitythe formality and connectivityand connectivity to formal to formal streets streets have an ha impactve an onimpact accessibility. on accessibility. The density The of density entrances of canentrances be considered can be considered as a variable as measuringa variable measuring the street hierarchy the street within hierarchy the urbanwithin village, the urban in addition village, toin streetaddition widths to street and widths connectivity and co tonnectivity the formal to streets. the formal streets.

4.3. Functional Mix

4.3.1. Plot-Level Analysis Figure 1111 illustratesillustrates the the proporti proportionon of ofthe the buildings buildings in each in each type typeof mix. of Among mix. Among the three the mono- three mono-functionalfunctional uses, the uses, buildings the buildings used for used housing for housingconstitute constitute the highest the proportion highest proportion at 33.7%, while at 33.7%, the whileproportions the proportions of the buildings of the buildings categorised categorised as visit or as visitwork or uses work are uses both are below both below5%. The 5%. buildings The buildings with withvisit/live visit /mixlive mixand andlive/wor live/workk mix mix account account for for25.9% 25.9% and and 27.1% 27.1% re respectively.spectively. The The proportion proportion of of the buildings mixing the three primaryprimary usesuses ofof visit,visit, livelive andand workwork isis thethe lowestlowest atat 3.6%.3.6%.

40.0% 33.7% 30.0% 25.9% 27.1%

20.0%

Percentage 10.0% 4.8% 4.8% 3.6% 0.0% visit live work visit-live mix live-work mix mix

Figure 11. Percentage of buildings in different diﬀerent types of functional mix.

Figure 12 compares the functional mix of the buildingsbuildings connected by different diﬀerent types of street network. Among Among the the buildings buildings located located in in the the formal formal street, street, only only two two types types of uses of uses are arefound: found: the themono-functional mono-functional use useof visit of visit and and the the bi-functional bi-functional mix mix of of live live and and visit. visit. The The latter latter has has the the highest share atat 86.7%.86.7%. In In the the buildings buildings adjacent adjacent to to the the primary primary inner inner street, street, the the blocks blocks with with a mix a mix of live of /live/visitvisit still makestill make up the up highest the highest proportion proportion of 48.4% of 48.4% while thewhile type the of type live/ workof live/work mix accounts mix accounts for 19.4%. for Besides, 19.4%. theBesides, buildings the buildings used for used work for account work account for 16.1%. for Within16.1%. Within the buildings the buildings connected connected by secondary by secondary inner streetsinner streets and laneways, and laneways, the mono-functional the mono-functional use of housinguse of housing accounts acco forunts the largest for the proportion largest proportion of 40.8% of 40.8% and 55.1%, respectively. The second highest is the live/work mix, accounting for 33.8% of the buildings located in the secondary inner streets and 30.6% of those located in the laneways. Urban Sci. 2020, 4, 23 15 of 23 and 55.1%, respectively. The second highest is the live/work mix, accounting for 33.8% of the buildings locatedUrban Sci. in 2020 the, 4 secondary, x FOR PEER inner REVIEW streets and 30.6% of those located in the laneways. 15 of 23

120.0%

100.0% 3.2% 4.2% 4.1% 8.2% 15.5% 80.0% 48.4% 30.6% 60.0% 33.8% 86.7% 2.0%

2.8% 40.0% 19.4% 55.1% 20.0% 16.1% 40.8%

13.3% 12.9% 0.0% Formal street Primary street Secondary street Laneway

Live Visit Work Live-work mix Live-visit mix Mix

FigureFigure 12.12. Functional mix mix of of buildings. buildings.

AccordingAccording toto thethe aboveabove analysis,analysis, the proportion of of the the buildings buildings with with a alive/visit live/visit mix mix declines declines withwith the the shift shift from from the the formalformal streetstreet toto thethe laneways.laneways. The shift shift of of the the street street types types suggests suggests a adecline decline ofof formality formality and and connectivity. connectivity. TheThe decreasedecrease in the pr proportionoportion of of the the live/visit live/visit mix mix is is connected connected to to the the reductionreduction of of the the formality formality and and connectivity connectivity of of the the street. street. The The proportional proportional decline decline of theof the buildings buildings with awith live/ visita live/visit mix can mix be can explained be explained from thefrom vertical the vertic arrangemental arrangement of functions. of functions. The The ground ground floor floor is used is forused retail for (e.g.,retail supermarkets,(e.g., supermarkets, restaurants, restaurants, and shops),and shops), while while the the upper upper floors floors are are generally generally used used for residentialfor residential units. units. These These buildings buildings are faced are faced to the to formal the formal street street and theand primary the primary inner inner streets streets due todue the requirementto the requirement for proximity for proximity to pedestrian to pedestrian flows. Figureflows. 13Figure illustrates 13 illustrates that within that within the buildings the buildings reached byreached the secondary by the secondary inner streets inner and streets laneways, and thelane mono-functionalways, the mono-functional use of live anduse bi-functionalof live and bi- mix offunctional live/work mix both of occupylive/work a shareboth o ofccupy over a one-third. share of over These one-third. buildings These are buildings located in are the located area where in the is distantarea where to the is formaldistant streetsto the formal and primary streets and inner primar streets.y inner This streets. implies This that implies the distribution that the distribution of housing andof housing live/work and mix live/work depends mix on depends the formality on the and formality the connectivity and the connectivity of streets. of streets. In the formal city, however, the places for work are often concentrated in the areas with a strong accessibility to transport facilities. The main difference between the distribution of spaces for work in formal and informal settlements stems from the specific content of ‘work’. For the present research, the spaces for work consists of industrial development of logistics and warehousing, which require large spaces, low rents, and vehicular accessibility. Due to the higher rents of the buildings in the proximity of the formal streets, the live/work mix use is pushed to the areas which are away from the formal and primary inner streets but provide vehicular accessibility.

Figure 13. Map of the functional mix. Urban Sci. 2020, 4, x FOR PEER REVIEW 15 of 23

120.0%

100.0% 3.2% 4.2% 4.1% 8.2% 15.5% 80.0% 48.4% 30.6% 60.0% 33.8% 86.7% 2.0%

2.8% 40.0% 19.4% 55.1% 20.0% 16.1% 40.8%

13.3% 12.9% 0.0% Formal street Primary street Secondary street Laneway

Live Visit Work Live-work mix Live-visit mix Mix

Figure 12. Functional mix of buildings.

According to the above analysis, the proportion of the buildings with a live/visit mix declines with the shift from the formal street to the laneways. The shift of the street types suggests a decline of formality and connectivity. The decrease in the proportion of the live/visit mix is connected to the reduction of the formality and connectivity of the street. The proportional decline of the buildings with a live/visit mix can be explained from the vertical arrangement of functions. The ground floor is used for retail (e.g., supermarkets, restaurants, and shops), while the upper floors are generally used for residential units. These buildings are faced to the formal street and the primary inner streets due to the requirement for proximity to pedestrian flows. Figure 13 illustrates that within the buildings reached by the secondary inner streets and laneways, the mono-functional use of live and bi- functional mix of live/work both occupy a share of over one-third. These buildings are located in the area where is distant to the formal streets and primary inner streets. This implies that the distribution Urban Sci. 2020, 4, 23 16 of 23 of housing and live/work mix depends on the formality and the connectivity of streets.

Urban Sci. 2020, 4, x FOR PEER REVIEW 16 of 23

In the formal city, however, the places for work are often concentrated in the areas with a strong accessibility to transport facilities. The main difference between the distribution of spaces for work in formal and informal settlements stems from the specific content of ‘work’. For the present research, the spaces for work consists of industrial development of logistics and warehousing, which require large spaces, low rents, and vehicular accessibility. Due to the higher rents of the buildings in the proximity of the formal streets, the live/work mix use is pushed to the areas which are away from the formal and primary inner streets but provide vehicular accessibility. FigureFigure 13. 13.Map Map of of the the functional functional mix. mix.

4.3.2.4.3.2. Multi-Scale Multi-Scale Analysis Analysis TheThe multi-scale multi-scale analysis comparescompares thethe extent extent of of the the mix mix at theat the three three levels levels of plot, of plot, island island and fabric.and fabric.As shown As shown in Figure in Figure 14, ﬁve 14, islands five islands reach areach mix ofa mix three of primary three primary uses, and uses, two and islands two islands provide provide a mix of alive mix andof live work. and At work. the fabricAt the level, fabric the level, investigated the investigated area has area a balanced has a balanced ternary ternary mix, which mix, implieswhich impliesthat the that three the primary three primary uses share uses a similar share proportion.a similar proportion. The investigated The investigated village provides village diverse provides uses diversewithin auses walkable within scale. a walkable It also supportsscale. It thealso argument supports ofthe Hao, argument et al. [5 ]of that Hao, the urbanisinget al. [5] that villages the urbanisingtend to have villages a high tend diversity to have of a land high uses. diversity of land uses.

FigureFigure 14. 14. Live/visit/workLive/visit/work triangle triangle at at three three levels. levels. 4.4. Urban Interface 4.4. Urban Interface Figure 15 shows the proportion of the length of diﬀerent urban interfaces. In the four types of Figure 15 shows the proportion of the length of different urban interfaces. In the four types of streets, the proportion of each type of interface varies signiﬁcantly. First, in the formal street there streets, the proportion of each type of interface varies significantly. First, in the formal street there are are only two types of urban interfaces: adjacent/porous and distant/porous. The latter accounts for only two types of urban interfaces: adjacent/porous and distant/porous. The latter accounts for a large a large proportion of 90.6%. Second, in the primary inner streets, although the diverse types of proportion of 90.6%. Second, in the primary inner streets, although the diverse types of interfaces interfaces emerge, the distant/porous interface still constitutes 65.5% of the total length, which is much emerge, the distant/porous interface still constitutes 65.5% of the total length, which is much higher higher than the other four types. Third, in the laneways, the adjacent/impermeable interface makes than the other four types. Third, in the laneways, the adjacent/impermeable interface makes up 60.4% up 60.4% of the total length. The second-highest proportion of adjacent/accessible interface is much of the total length. The second-highest proportion of adjacent/accessible interface is much lower, accounting for 16%. By contrast, the gap between the six types of interfaces in the secondary inner streets is not as significant as those in the formal streets, primary inner streets and laneways. The adjacent/impermeable interface constitutes 24.6% of the total length while the adjacent/accessible and adjacent/porous interfaces account for 22.2% and 19.9% respectively. Figure 15 exhibits the trend of how these two variables change. In terms of the connectivity, with the shift from formal streets to laneways, the proportion of porous interface decreases whilst the proportion of impermeable interface raises, and the proportion of accessible interfaces is relatively stable (about 20%). In terms of proximity, the proportion of distant interfaces decreases from formal street to laneway, while the proportion of adjacent interface rises. This trend is also revealed by spatial distribution. As shown in Figure 16, the distant and porous interface is mainly located along the formal and primary inner street, while the secondary inner streets and laneways are embraced by the adjacent and impermeable interfaces. Urban Sci. 2020, 4, 23 17 of 23

Urban Sci. 2020, 4, x FOR PEER REVIEW 17 of 23 lower,Urban Sci. accounting 2020, 4, x FOR for PEER 16%. REVIEW By contrast, the gap between the six types of interfaces in the secondary17 of 23 innerAs streets discussed is not asabove, signiﬁcant the four as thosetypes inof the streets formal are streets, formulated primary based inner on streets the formality and laneways. and As discussed above, the four types of streets are formulated based on the formality and Theconnectivity adjacent/ impermeableto the formal interface street. The constitutes shift from 24.6% the of formal the total street length to whilethe laneway the adjacent suggests/accessible the connectivity to the formal street. The shift from the formal street to the laneway suggests the andreduction adjacent of /formalityporous interfaces and connectivity account forwith 22.2% the form andal 19.9% street. respectively. Therefore, the proportion of different reduction of formality and connectivity with the formal street. Therefore, the proportion of different types of interface illustrates the way in which the street’s formality and connectivity affect the typesFigure of interface 15 exhibits illustrates the trend the of way how in these which two the variables street’s change. formality In terms and connectivity of the connectivity, affect the with physical form of the interface in the urban village. The porous of interfaces occur in the street with thephysical shift from form formalof the interface streets to in laneways, the urban thevillage. proportion The porous of porous of interfaces interface occur decreases in the street whilst with the intense formality and connectivity. proportionintense formality of impermeable and connectivity. interface raises, and the proportion of accessible interfaces is relatively It has been argued that porous forms of interface facilitate the interaction between public and stableIt (about has been 20%). argued In terms that of porous proximity, forms the of proportioninterface facilitate of distant the interfacesinteraction decreases between frompublic formal and private space [56], and the distant interface provides more semi-public or semi-private space, which streetprivate to laneway,space [56], while and thethe proportiondistant interface of adjacent provides interface more semi-public rises. This trend or semi-private is also revealed space, by which spatial benefits the social activity in outdoor spaces [60]. This is the point where the formality of street, the distribution.benefits the Associal shown activity in Figure in outdoor 16, the spaces distant [60]. and This porous is the interface point where is mainly the locatedformality along of street, the formal the form of interface, and street-life intensity can be connected. Through affecting the physical form of andform primary of interface, inner street,and street-life while the intensity secondary can inner be connected. streets and Through laneways affecting are embraced the physical by the form adjacent of the interface, the formality of streets has the capacity to facilitate street-life intensity in urban villages. andthe impermeableinterface, the formality interfaces. of streets has the capacity to facilitate street-life intensity in urban villages.

120.0% 120.0% 100.0% 100.0% 80.0% 80.0% 60.0% 60.0% 40.0% 40.0% 20.0% 20.0% 0.0% 0.0% Formal street Primary inner street Secondary inner street Laneway Formal street Primary inner street Secondary inner street Laneway Adjacent/Impermeable Adjacent/Accessibale Adjacent/Porous Adjacent/Impermeable Adjacent/Accessibale Adjacent/Porous Distant/Impermeable Distant/Accessible Distant/Porous Distant/Impermeable Distant/Accessible Distant/Porous

Figure 15. Percentage of the length of different types of interfaces. FigureFigure 15.15. PercentagePercentage of the length of of different diﬀerent types types of of interfaces. interfaces.

Figure 16. Different types of interfaces in the studied area. FigureFigure 16. 16. Different Different typestypes ofof interfacesinterfaces inin thethe studiedstudied area. As discussed above, the four types of streets are formulated based on the formality and connectivity 4.5.4.5. The The Relationship Relationship between between Density, Density, Accessi Accessibility,bility, FunctionalFunctional Mix,Mix, andand UrbanUrban InterfaceInterface to the formal street. The shift from the formal street to the laneway suggests the reduction of formality TheThe relationsrelations betweenbetween density,density, accessibility,accessibility, functionalfunctional mix,mix, andand interface at island level are analysedanalysed using using the the maps. maps. Two Two islands islands that that areare locatedlocated nextnext toto thethe formalformal street are chosen as samples Urban Sci. 2020, 4, 23 18 of 23 and connectivity with the formal street. Therefore, the proportion of different types of interface illustrates the way in which the street’s formality and connectivity affect the physical form of the interface in the urban village. The porous of interfaces occur in the street with intense formality and connectivity. It has been argued that porous forms of interface facilitate the interaction between public and private space [56], and the distant interface provides more semi-public or semi-private space, which benefits the social activity in outdoor spaces [60]. This is the point where the formality of street, the form of interface, and street-life intensity can be connected. Through affecting the physical form of the interface, the formality of streets has the capacity to facilitate street-life intensity in urban villages.

4.5. The Relationship between Density, Accessibility, Functional Mix, and Urban Interface

UrbanThe Sci. 2020 relations, 4, x FOR between PEER REVIEW density, accessibility, functional mix, and interface at island level18 of are 23 analysed using the maps. Two islands that are located next to the formal street are chosen as samples (Figure(Figure 17 17).). FigureFigure 1818 highlightshighlights thethe highhigh densitydensity ofof entrancesentrances inin thethe twotwo islands.islands. ThereThere isis anan averageaverage ofof 20.520.5 entrancesentrances inin everyevery 100100 m.m. TheThe reasonreason whywhy thesethese buildingsbuildings havehave aa higherhigher densitydensity ofof entrancesentrances isis linkedlinked toto thethe functionalfunctional mixmix ofof architecturalarchitectural infill.infill. TheThe buildingsbuildings inin thesethese areasareas generallygenerally havehave aa verticalvertical mixmix ofof livelive/work,/work, livelive/visit,/visit, oror livelive/work/visi/work/visit.t. The Theground groundfloor floor isis divideddivided toto provideprovide separateseparate entrancesentrances forfor didifferentfferent functions.functions. ForFor example,example, inin thethe buildingsbuildings withwith aa livelive/work/work mix,mix, oneone entranceentrance isis forfor thethe apartmentsapartments onon upperupper floorsfloors andand thethe otherother entrance entrance is is for for stores stores on on ground ground floors. floors.

FigureFigure 17.17. LocationLocation ofof thethe investigatedinvestigated islands.islands.

TheThe densitydensity ofof entrancesentrances alsoalso increasesincreases thethe porosityporosity ofof urbanurban interfaces,interfaces, whilstwhilst improvingimproving thethe exchangeexchange betweenbetween thethe publicpublic andand privateprivate spaces.spaces. TheThe formform ofof thesethese interfacesinterfaces isis eithereither porousporous/distant/distant oror porousporous/adjacent./adjacent. TheThe porousporous/distant/distant interfaceinterface isis oftenoften foundfound onon thethe groundground ﬂoorfloor ofof thethe buildingsbuildings withwith aa livelive/visit/visit mix.mix. TheThe transitionaltransitional spacespace inin frontfront ofof thesethese buildingsbuildings isis semi-publicsemi-public equippedequipped withwith movablemovable chairs,chairs, inin whichwhich peoplepeople cancan sit,sit, rest,rest, andand talk.talk. TheThe buildingbuilding withwith aa livelive/work/work mixmix tendstends toto havehave aa porousporous/adjacent/adjacent interface.interface. AsAs thethe logisticlogistic industryindustry isis aa keykey driverdriver inin thethe developmentdevelopment ofof thethe village,village, thethe building building function function of of ‘work’ ‘work’ is is mainly mainly referred referred to to the the use use by by the the warehouses warehouses or theor the oﬃ officesces of logisticof logistic companies. companies. Since Since moving moving goods goods requires requires reducing reducing the distance the distance between between indoor and indoor outdoor and spaces,outdoor the spaces, buildings the buildings with a live with/work a mixlive/work are rarely mix confrontedare rarely confronted with a transitional with a transitional space. The spacesspace. inThe front spaces of these in front buildings of these arebuildings often used are often as car used parking as car toparking facilitate to facilitate loading loading and unloading and unloading goods. Ingoods. conclusion, In conclusion, in the studied in the area,studied the area, functional the func mixtional of buildings mix of buildings increases theincreases density the of density entrances of andentrances thus improves and thus theimproves porosity the of porosity the urban of interfaces.the urban interfaces.

Figure 18. Maps of (a) urban interfaces, (b) building height, (c) entrance, and (d) functional mix. Urban Sci. 2020, 4, x FOR PEER REVIEW 18 of 23

(Figure 17). Figure 18 highlights the high density of entrances in the two islands. There is an average of 20.5 entrances in every 100 m. The reason why these buildings have a higher density of entrances is linked to the functional mix of architectural infill. The buildings in these areas generally have a vertical mix of live/work, live/visit, or live/work/visit. The ground floor is divided to provide separate entrances for different functions. For example, in the buildings with a live/work mix, one entrance is for the apartments on upper floors and the other entrance is for stores on ground floors.

Figure 17. Location of the investigated islands.

The density of entrances also increases the porosity of urban interfaces, whilst improving the exchange between the public and private spaces. The form of these interfaces is either porous/distant or porous/adjacent. The porous/distant interface is often found on the ground floor of the buildings with a live/visit mix. The transitional space in front of these buildings is semi-public equipped with movable chairs, in which people can sit, rest, and talk. The building with a live/work mix tends to have a porous/adjacent interface. As the logistic industry is a key driver in the development of the village, the building function of ‘work’ is mainly referred to the use by the warehouses or the offices of logistic companies. Since moving goods requires reducing the distance between indoor and outdoor spaces, the buildings with a live/work mix are rarely confronted with a transitional space. The spaces in front of these buildings are often used as car parking to facilitate loading and unloading Urbangoods. Sci. 2020 In, 4conclusion,, 23 in the studied area, the functional mix of buildings increases the density19 of 23 of entrances and thus improves the porosity of the urban interfaces.

FigureFigure 18. 18.Maps Maps of of (a) ( urbana) urban interfaces, interfaces, (b )(b building) building height, height, (c) ( entrance,c) entrance, and and (d )( functionald) functional mix. mix. 5. Summary and Conclusions This research aimed to develop a better understanding of the ways in which the informal settlements of urban villages operate in terms of urban morphology. Our analysis showed that three elements of urban morphology (i.e., accessibility, functional mix, and the urban interface) are moderated by centrality of the streets or street types (i.e., formal street, primary inner-street, secondary inner-street, and laneway), but the only element that has not been affected by these types is urban density. Regarding urban density, the average building height of the investigated area is higher than those located in the central villages-in-the-city in Guangzhou. This demonstrates that centrality has potentially limited influence on building density of the urban village. Moreover, the heights of buildings are not directly influenced by land value. However, they can be associated with landowners’ economic power and depend on the agreement between the village committee and local government. The land coverage ratio in this village also exceeds the planning regulation on residential districts. The gFAR of the investigated area reaches the same level as the central business district (CBD) of Guangzhou. The great land coverage ratio and gFAR leads to the encroachment of public spaces in an urban village. The density of entrances was found to be aligned with the type of streets (i.e., formal street, primary inner-street, secondary inner-street, and laneway). By transitioning street types from laneway to formal streets, the number of streets was increasing. Regarding functional mix, within the investigated area, the mono-functional use of ‘live’ and bi-functional mix of ‘live/visit’ and ‘live/work’ constitute a large proportion of the total number of buildings. The distribution of different types of functional mix is moderated by typology of streets. The buildings with a mix of ‘live/visit’ are concentrated along formal streets and primary inner streets which have the highest connectivity to the formal streets. The mono-functional use of ‘live’ and the bi-functional mix of ‘live/work’ are found to be accommodated in secondary inner street and laneways. At the scale of 80–90-m-wide blocks, five blocks mix the three primary uses of ‘live’, ‘visit’, and ‘work’. Two blocks are bi-functional of ‘live/work’ mix and ‘live/visit’ mix, and only three blocks are mono-functional. Regarding urban interface, the proportion of different types of interface varies between the four types of streets. Only two types of interface are found in the buildings along formal streets: adjacent/porous and distant/porous with the latter constituting a large proportion, whereas five types of interface are found in primary inner streets (adjacent/porous, adjacent/impermeable, distant/porous, distant/accessible, distant/impermeable), distant/porous still Urban Sci. 2020, 4, 23 20 of 23 accounts for the highest proportion. There are six types of interface in secondary streets, and the proportional gap between them is narrow. Three interfaces of adjacent/porous, adjacent/impermeable, and adjacent/accessible have a small proportion, about 20%, while the other three types of distant interfaces are all below 15%. At last, the laneway is mostly constituted of adjacent/impermeable interfaces. Therefore, formal streets often have an interface with considerable porosity and weak proximity. This can contribute to the livelihood of streets. Our analyses also show that the porosity of interface and the density of building entrance are linked to the functional mix. The buildings with a mix of live/work or live/visit often have several separate entrances for different functions, which increases the density of entrances and the porosity of the interface, and thus provides opportunities for the interaction between public and private spaces. This paper suggests that the framework, which has been tested in this paper to evaluate the urban morphology of the Dayuan urban village, can be used to inform how to apply this framework to the morphological study of other urban villages. The proposed framework consists of urban density, accessibility, functional mix, and the urban interface. Despite its fair level of analytical generalisability, this research is limited to the study of a single case study of a suburban village. Similarly, there are several approaches to analysing urban morphology, and each approach has its own limitations including the approach that has been utilized in this study. We suggest that the study of urban morphology in different types of urban villages, using different approaches, would be a fruitful and helpful area for further research. Such studies can reveal the differences between the morphology of different urban villages, whilst developing a better understanding of the effects of formal cities on the development of these settlements.

Author Contributions: Conceptualization, Y.G. and S.S.; investigation, Y.G.; writing—original draft preparation, Y.G., S.S., and N.A.; writing—review and editing; Y.G., S.S., and N.A.; visualization, Y.G.; supervision, S.S.; funding acquisition, N.A. All authors have read and agree to the published version of the manuscript. Funding: This research has been supported by Anglia Ruskin University’s Research and Innovation Development Office (RIDO). Conflicts of Interest: The authors declare no conflict of interest.

References

1. Liu, Y.; He, S.; Wu, F.; Webster, C. Urban villages under China’s rapid urbanization: Unregulated assets and transitional neighbourhoods. Habitat Int. 2010, 34, 135–144. [CrossRef] 2. Li, L.H.; Lin, J.; Li, X.; Wu, F. Redevelopment of urban village in China—A step towards an eﬀective urban policy? A case study of Liede village in Guangzhou. Habitat Int. 2014, 43, 299–308. [CrossRef] 3. Yu, L.; Xie, B.; Chan, E.H. How does the built environment inﬂuence public transit choice in urban villages in China? Sustainability 2019, 11, 148. [CrossRef] 4. Zeng, H.; Yu, X.; Zhang, J. Urban village demolition, migrant workers’ rental costs and housing choices: Evidence from Hangzhou, China. Cities 2019, 94, 70–79. [CrossRef] 5. Hao, P.; Geertman, S.; Hooimeijer, P.; Sliuzas, R. The Land-Use Diversity in Urban Villages in Shenzhen. Environ. Plan A 2012, 44, 2742–2764. [CrossRef] 6. Kochan, D. Placing the Urban Village: A Spatial Perspective on the Development Process of Urban Villages in Contemporary China: PLACING THE URBAN VILLAGE. Int. J. Urban Reg. 2015, 39, 927–947. [CrossRef] 7. Bach, J. “They Come in Peasants and Leave Citizens”: Urban Villages and the Making of Shenzhen, China. Cult. Anthropol. J. Soc. Cult. Anthropol. 2010, 25, 421–448. 8. Hao, P.; Sliuzas, R.; Geertman, S. The development and redevelopment of urban villages in Shenzhen. Habitat Int. 2011, 35, 214–224. [CrossRef] 9. Lin, Y.; De Meulder, B. A conceptual framework for the strategic urban project approach for the sustainable redevelopment of “villages in the city” in Guangzhou. Habitat Int. 2012, 36, 380–387. [CrossRef] 10. Wu, F. Housing in Chinese Urban Villages: The Dwellers, Conditions and Tenancy Informality. Hous. Stud. 2016, 31, 852–870. [CrossRef] Urban Sci. 2020, 4, 23 21 of 23

11. Lai, Y.; Tang, B. Institutional barriers to redevelopment of urban villages in China: A transaction cost perspective. Land Use Policy 2016, 58, 482–490. [CrossRef] 12. Tang, W.-S.; Chung, H. Rural–urban transition in China: Illegal land use and construction. Asia Pac. Viewp. 2002, 43, 43–62. [CrossRef] 13. Song, H.; Pan, M.; Chen, Y. Nightlife and public spaces in urban villages: A case study of the Pearl River Delta in China. Habitat Int. 2016, 57, 187–204. [CrossRef] 14. Ralphs, E.; Shahab, S.; Ahmadoor, N. Access to Small Airports and the Impact on Regional Growth in the UK. Curr. Urban Stud. 2020, 8, 24–56. [CrossRef] 15. Altrock, U.; Schoon, S. The Governance of Urban Upgrading in Southern China: The Example of Urbanized Villages. disP-Plan. Rev. 2011, 47, 37–48. 16. Wang, Y.P.; Wang, Y.; Wu, J. Urbanization and Informal Development in China: Urban Villages in Shenzhen. Int. J. Urban Reg. Res. 2009, 33, 957–973. [CrossRef] 17. Wu, F.; Zhang, F.; Webster, C. Informality and the Development and Demolition of Urban Villages in the Chinese Peri-urban Area. Urban Stud. 2013, 50, 1919–1934. [CrossRef] 18. Zacharias, J.; Hu, Y.; Huang, Q.L. Morphology and Spatial Dynamics of Urban Villages in Guangzhou’s CBD. Urban Stud. Res. 2013, 2013, 958738. [CrossRef] 19. Chung, H. Building an image of Villages-in-the-City: A Clarification of China’s Distinct Urban Spaces: Debates and Developments. Int. J. Urban Reg. Res. 2010, 34, 421–437. [CrossRef] 20. Al, S.; Shan, P.C.H.; Juhre, C.; Valin, I.; Wang, C. Villages in the City: A Guide to South China’s Informal Settlements; Hong Kong University Press: Hong Kong, China, 2014; Volume 1, ISBN 988-8208-23-3. 21. Li, L. A Study on the Formation and Reform Mechanism of Village-in-the-city in Guangzhou City; Sun Yat-Sen University: Guangzhou, China, 2001. 22. Pan, C.; Wei, Y. A Review on Urban Village Research and Planning Policy Recommendations. In Proceedings of the Urban Planning Forum; Urban Planning Forum: Shanghai, China, 2009; Volume 2. 23. Zhang, L.; Zhao, S.X.B.; Tian, J.P. Self-help in housing and chengzhongcun in China’s urbanization. Int. J. Urban Reg. Res. 2003, 27, 912–937. [CrossRef] 24. Zhang, J.; Zhao, W. City village in dual-system environment: Development and significance. City Plan. Rev. 2007, 31, 63–66. 25. Shenzhen Urban Planning Bureau Shenzhen Shi Chengzhongcun (jiucun) gaizhao zhongtiguihua gangyao (2005–2010). In Master Plan of Urban Village Redevelopment 2005–2010; Urban Planning & Design Institute of Shenzhen: Shenzhen, China, 2005. 26. Li, P. Great change: The end of villages—Study of the village in the city. Soc. Sci. China 2002, 1, 168–179. 27. Van Oostrum, M. Urbanizing villages: Informal morphologies in Shenzhen’s urban periphery. J. Urban Des. 2018, 23, 732–748. [CrossRef] 28. Sanders, P.S.; Guaralda, M.; Carroli, L. (Eds.) Urban Form at the Edge: Proceedings from ISUF2013; ISUF/QUT School of Design: Brisbane, QLD, Australia, 2016; Volume 2. 29. Dovey, K. Informalising Architecture: The Challenge of Informal Settlements. Archit. Des. 2013, 83, 82–89. [CrossRef] 30. Helm, J.; Robinson, A. GCSE Geography for AQA Specification B; Heinemann Educationa: Portsmouth, NH, USA, 2002; ISBN 978-0-435-35358-2. 31. Kropf, K. The Handbook of Urban Morphology; John Wiley & Sons: Hoboken, NJ, USA, 2018; ISBN 1-118-74769-0. 32. Dovey, K.; Pafka, E.; Ristic, M. Mapping Urbanities: Morphologies, Flows, Possibilities; Taylor & Francis: Oxfordshire, UK, 2017; ISBN 978-1-315-30915-6. 33. Dovey, K. Informal urbanism and complex adaptive assemblage. Int. Dev. Plan. Rev. 2012, 34, 349–368. [CrossRef] 34. Kamalipour, H. Urban morphologies in informal settlements: A case study. Contour J. 2016, 1, 1–10. 35. Kamalipour, H. Mapping Urban Interfaces: A Typology of Public/Private Interfaces in Informal Settlements. Spaces Flows Int. J. Urban Extra Urban Stud. 2017, 8.[CrossRef] 36. Cheng, V. Understanding density and high density. In Designing High-Density Cities; Routledge: Abingdon, UK, 2009; pp. 37–51. 37. Ahmadpoor, N.; Shahab, S. Spatial Knowledge Acquisition in the Process of Navigation: A Review. Curr. Urban Stud. 2019, 7, 1–19. [CrossRef] Urban Sci. 2020, 4, 23 22 of 23

38. Boyko, C.T.; Cooper, R. Clarifying and re-conceptualising density. Prog. Plan. 2011, 76, 1–61. [CrossRef] 39. Berghauser Pont, M.Y.; Haupt, P.A. Space, Density and Urban Form; TU Delft: Delft, The Netherlands, 2009. 40. Rudlin, D.; Falk, N. Sustainable Urban Neighbourhood; Routledge: Abingdon, UK, 2010; ISBN 0-08-093954-6. 41. Ahmadpoor, N.; Smith, A. Spatial knowledge acquisition and mobile maps: The role of environmental legibility. Cities. Available online: http://hdl.handle.net/10026.1/15463 (accessed on 20 March 2020). 42. Ahmadpoor, N.; Heath, T. Data and GPS systems: Comparing navigation and landmark knowledge between GPS users and non-GPS users. In Data, Architecture and the Experience of Place; Karandinou, A., Ed.; Routledge: London, UK, 2018. 43. Hillier, B. Space Is the Machine: A Configurational Theory of Architecture; Cambridge University Press: Cambridge, UK, 1998; ISBN 978-0-521-64528-7. 44. Southworth, M.; Ben-Joseph, E. Streets and the Shaping of Towns and Cities; Island Press: Washington, DC, USA, 2013; ISBN 1-61091-109-1. 45. Jacobs, J. The Death and Life of Great American Cities 1961; Vintage: New York, NY, USA, 1992. 46. Marshall, S. Streets and Patterns; Taylor & Francis: Oxfordshire, UK, 2004; ISBN 978-0-203-58939-7. 47. Knight, P.L.; Marshall, W.E. The metrics of street network connectivity: Their inconsistencies. J. Urban. Int. Res. Placemak. Urban Sustain. 2015, 8, 241–259. [CrossRef] 48. Van den Hoek, J.W. The MXI (Mixed-use Index) as tool for urban planning and analysis. In Corporations and Cities: Envsioning Corporate Real Estate in the Urban Future, Brussels, Belgium. Find in Text; TU Delft: Delft, The Netherlands, 2008. 49. Van den Hoek, J. The Mixed Use Index (MXI) as Planning Tool for (New) Towns in the 21st Century. In New Towns 21st Century: The Planned vs, the Unplanned City; Provoost, M., Ed.; Sun Publishers: Pawcatuck, CT, USA, 2009. 50. Frank, L.D.; Sallis, J.F.; Conway, T.L.; Chapman, J.E.; Saelens, B.E.; Bachman, W. Many pathways from land use to health: Associations between neighborhood walkability and active transportation, body mass index, and air quality. J. Am. Plan. Assoc. 2006, 72, 75–87. [CrossRef] 51. Moudon, A.V.; Lee, C.; Cheadle, A.D.; Garvin, C.; Johnson, D.; Schmid, T.L.; Weathers, R.D.; Lin, L. Operational definitions of walkable neighborhood: Theoretical and empirical insights. J. Phys. Act. Health 2006, 3, S99–S117. [CrossRef] 52. Cervero, R. America’s Suburban Centers: The Land Sse-Transportation Link, 1st ed.; Routledge: London, UK, 2018. 53. Frank, L.D.; Schmid, T.L.; Sallis, J.F.; Chapman, J.; Saelens, B.E. Linking objectively measured physical activity with objectively measured urban form: Findings from SMARTRAQ. Am. J. Prev. Med. 2005, 28, 117–125. [CrossRef][PubMed] 54. Giles-Corti, B.; Macintyre, S.; Clarkson, J.P.; Pikora, T.; Donovan, R.J. Environmental and Lifestyle Factors Associated with Overweight and Obesity in Perth, Australia. Am. J. Health Promot. 2003, 18, 93–102. [CrossRef][PubMed] 55. Rundle, A.; Roux, A.V.D.; Freeman, L.M.; Miller, D.; Neckerman, K.M.; Weiss, C.C. The Urban Built Environment and Obesity in New York City: A Multilevel Analysis. Am. J. Health Promot. 2007, 21, 326–334. [CrossRef][PubMed] 56. Dovey, K.; Wood, S. Public/private urban interfaces: Type, adaptation, assemblage. J. Urban. Int. Res. Placemak. Urban Sustain. 2015, 8, 1–16. [CrossRef] 57. Carmona, M. Contemporary Public Space, Part Two: Classification. J. Urban Des. 2010, 15, 157–173. [CrossRef] 58. Alexander, C. A Pattern Language: Towns, Buildings, Construction; Oxford University Press: Oxford, UK, 1977; ISBN 0-19-972653-1. 59. Bobić,M. Between the Edges: Street-Building Transition as Urbanity Interface; Thoth Publishers: Thoth Uitgeverij, The Netherlands, 2004; ISBN 90-6868-364-0. 60. Gehl, J. Life between Buildings: Using Public Space; Island Press: Washington, DC, USA, 2011; ISBN 1-61091-023-0. 61. Hollweck, T.; Robert, K.Y. Case Study Research Design and Methods, 5th ed.; Sage: Thousand Oaks, CA, USA, 2014. 62. Shahab, S.; Viallon, F.-X. A Transaction-cost Analysis of Swiss Land Improvement Syndicates. Town Plan. Rev. 2019, 90, 545–565. [CrossRef] Urban Sci. 2020, 4, 23 23 of 23

63. Shahab, S.; Viallon, F.-X. Swiss Land Improvement Syndicates: ‘Impure’ Coasian Solutions? Plan. Theory 2020. [CrossRef] 64. Guangzhou Urban Planning & Design Survey Research Institute (GZPI). Research on the Development Mechanism of Taobao Village in Guangzhou; GZPI: Guangzhou, China, 2019. 65. Ali Research Research Report of Taobao Village in China; Ali Research: Hangzhou, China, 2014. 66. Kelbaugh, D. Typology—An architecture of limits. Archit. Theory Rev. 1996, 1, 33–52. [CrossRef] 67. Guattari, F.; Deleuze, G. A Thousand Plateaus: Capitalism and Schizophrenia; Athlone Press London: London, UK, 2000; ISBN 1-283-19553-4. 68. Dovey,K. Becoming Places: Urbanism/Architecture/Identity/Power; Routledge: Abingdon, UK, 2009; ISBN 1-134-11736-1. 69. Kamalipour, H.; Peimani, N. Assemblage thinking and the city: Implications for urban studies. Curr. Urban Stud. 2015, 3, 402–408. [CrossRef] 70. Yeang, L.D. Urban design compendium. In English Partnerships/Housing Corporation, London; National Regeneration Agency: London, UK, 2000. 71. Guangzhou Urban Planning & Design Survey Research Institute (GZPI). Report of the Urban Deisgn of Gangzhou International Finance City; GZPI: Guangzhou, China, 2012.

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