Identification of Local Accessibility Hubs and Leisure Amenities in Suburbanized Settlements: Case Study on the Suburban Zone of Prague

This paper focuses on the topological definition of the system of public spaces in suburbanized settlements. It identifies hubs with the best local accessibility within the system of public open spaces using the Space syntax method and analyses their leisure amenities. The topological investigation was performed on the example of the suburban zone of Prague, the immediate surroundings of which have been developing dramatically in recent decades. About 44 rapidly developing settlements in this area were included in the study and their system of public open spaces was analyzed using the Integration HH metric and local accessibility hubs (those with the highest Integration HH value) were identified. Subsequently, the placement of existing leisure amenities with respect to these accessibility hubs was evaluated. Only 32% of leisure amenities were located in the accessibility hubs, which indicates an unfulfilled potential of locally well-accessible places. At the same time, the placement of leisure amenities within new developments in areas difficult-to-access from other parts of the settlement poses a threat to the integration of the population from these new developments with those from other parts of the settlement. This paper offers solutions for preventing these issues, for identifying natural centers with the best accessibility, and proposes possible measures for mitigation of the identified problems.


Introduction
Research of the issues associated with the public open space (POS) has intensified in the last decades.With rapid urban expansion, POS is perceived as an essential part of settlements; hence, research in this field should lead to a better understanding and shaping of the public space and its optimization, which is expected to have a positive impact on its users as well as on the environment.

Public Open Space
Public open spaces reflect the culture of communities and entire settlements (Kratochvı´l, 2013).POS can be defined as a space accessible to everyone, regardless of their gender, age, race, ethnicity, or religion.Such spaces constitute valuable elements of every settlement (Kratochvı´l, 2015;S ˇteˇpa´nkova´& Kristia´nova´, 2012), as they play many roles in the life of community (Carmona et al., 2018), participate in forming urban structures, and ensure the permeability of the territory as well as the accessibility of individual parts of the environment (Gehl, 1987;Jones et al., 2007;Maier, 2012).Good permeability of the area for walking and cycling is an essential requirement for a quality residential environment (Carmona, 2019a(Carmona, , 2019b;;Maier, 2012;Prince's Foundation for the Built Environment, 2007).Pedestrian permeability reduces the burden of automobile traffic (Gehl, 1987); POS also play a crucial social and cultural role (Gehl, 1987(Gehl, , 2006(Gehl, , 2010;;Kaz´mierczak, 2013), and are important for the psychological perception of the environment.Streets, squares, parks, gardens and other POS also represent traditional meeting places (supporting mutual interaction of residents as well as interaction with residents from other parts of the settlement) (Jennings & Bamkole, 2019;Kaz´mierczak, 2013;Prince's Foundation for the Built Environment, 2007;Sugiyama et al., 2010;Vaughan, 2007) and facilitate daily communication, exchange of opinions and information (Gehl & Svarre, 2013;Huang, 2006;Jacobs, 1992;Jehlı´k, 2016;Marcus et al., 2016), as well as relaxation and recreation (Carmona, 2019b;Jones et al., 2007;Paul et al., 2020;Wolch et al., 2014).
It is important to note that besides the space itself, its content, such as objects (equipment) complementing the functional focus of the space (Carmona, 2019a;Carmona et al., 2018;Park et al., 2019;Thompson, 2002), and their availability for all residents and other space users (Barnett et al., 2017) are crucial for the POS function.

System of Public Open Spaces
The basic element of a settlement is a street, which cannot be perceived as a separate component of the environment but always as a part of an interconnected, sophisticated and hierarchized network (Alexander, 1965;Lynch, 1984;Marshall, 2004).Streets form the basis of the system of public open spaces (SPOS), being linked to other streets, pavements, squares, parks, paths, centers, etc.The SPOS covering the entire settlement and surrounding open landscape results from long-term development, complex urbanization and landscape transformation processes, and a wide range of various influences (Marshall, 2004;Prince's Foundation for the Built Environment, 2007).
The creation and good accessibility of local POS centers from housing areas is an essential prerequisite for the development of a sustainable community of residents (Barner et al., 2010;Carmona et al., 2018;Maier, 2012;Marcus et al., 2016;Prince's Foundation for the Built Environment, 2007;Thompson, 2002).In addition to purely utilitarian operational and transport-technical functions (Hnilicˇka, 2013), POS and their entire system also play an essential social role (Carmona, 2019b;Gehl, 1987;Gehl & Svarre, 2013).Jacobs (1992) identified the presence of a dense network of streets and passages as a prerequisite for a living settlement.
This system can be seen as the principal structure supporting the entire settlement.The locally most integrated parts serve as places with the highest local potential of accessibility for inhabitants and users of the space (Hillier, 1999;Jones et al., 2007;Prince's Foundation for the Built Environment, 2007;Vaughan, 2007).Hereinafter, these places will be referred to as accessibility hubs.Conversely, the less accessible areas can become segregated.This may in turn lead to the formation of gentrified neighborhoods (Standl & Krupickaite, 2004), gated communities etc. (Blinnikov et al., 2006;Sy´kora, 2009), concentrating the rich, socially and spatially mobile people (Sy´kora, 2009).On the other hand, the opposite effect can be also observed in segregated areas, with poor or less mobile people concentrating here (Cagney et al., 2020;Robinson, 2011;Xu et al., 2019).To prevent this, the designs by architects, urban planners and land-use planners should aim to create a pleasant place for getting to know each other, forging contacts (Vaughan, 2007) and spending leisure time (RICS, 2016;Thompson, 2002).Such places should exploit their potential and create polyfunctional POS that support public life (Gehl, 1987).
Furthermore, SPOS should include a network of walking and cycling routes (Gehl, 1987;Gehl & Svarre, 2013) with the absence of cars (Lerman et al., 2014;Stoker et al., 2015), which should cooperate both with the modernist system of the suburban area (Marshall, 2004) and with the core (original) settlement (Barner et al., 2010).The importance of local open spaces cannot be underestimated; the same can be said about the perception of these spaces by residents and users (Dempsey & Burton, 2012).

Space Syntax
In the second half of the last century, Bill Hillier and Julienne Hanson developed the set of Space syntax methods, which builds on graph theory (Hillier & Hanson, 1984;Major & Dalton, 2018;Marcus et al., 2016), allowing the analysis of non-discursive properties of space configuration (Hillier, 2007).The method, which serves for socio-spatial analysis that can be applied on a wide range of examined paradigms (Hillier, 2007), is based on the assumption that socio-cultural processes are influenced by the organization of the structure where they occur (especially houses, streets, squares) (Conzen & Conzen, 2004;Karimi, 2018;Major & Dalton, 2018).It is necessary to note that this concerns not only close structures but also remote ones as the complex network must be considered (Karimi, 2018).This implies that the quality of the environment is determined by the mutual relationships of its elements rather than solely by the quality of separate elements (Hillier & Hanson, 1984;Hillier et al., 1987).Based on this knowledge, it is possible to predict the flows of people in a given environment with acceptable accuracy (Hillier, 2007).In other words, the spatial contexts contribute to the emergence of social solidarity or, vice versa, spatial segregation, social differences.The configuration theory (Hillier & Hanson, 1984) focuses exclusively on the geometry and arrangement of space.One of the basic geometric metrics is the so-called Hillier-Hanson Integration (abbreviated as Integration HH).Integration indicates the number of spaces in the system and the changes in direction needed in order to reach all other spaces within the entire system (Haq & Berhie, 2018;Hillier, 2007;Karimi, 2018;Penn et al., 1998).The maximum integration value in space then indicates the most integrated position, that is, the bestaccessible parts within the system.For example, in the case of a city and its street networks, the streets with the highest values are those with the best accessibility within the particular city.However, such streets (or, in general, places) do not necessarily indicate cultural or business centers but rather places of urban significance in the topological sense.
To support the significance of such natural local centers, it is important to place suitable leisure amenities in such spaces.This is especially important for the integration of the new population (both with the original population and within the new population itself) as the presence of suitably equipped POS in (or near) local accessibility hubs serves as a meeting place.
The main goal of this analysis was to assess whether the equipment of accessibility hubs of rapidly developing suburban areas of Prague supports the utilization of their potential; in other words, our research aimed to find out whether the accessibility hubs contain suitable furniture for leisure activities.

Methods
Various tools and methods can be used for mapping the region and proposing a framework for planning following the principles of sustainable development (Karimi, 2018).Due to the complexity of the issue of POS, only the essential element, that is, the physical space as such, was selected as the subject of the presented research.Hereinafter, by the term ''space'' we will mean the open space that allows an individual to access individual parts of the settlement by walking.For this reason, the Space syntax method, which analyses the space at the topological level, was chosen as a suitable tool (Figure 1).

Research Area
The suburban zone of Prague, the capital city of the Czech Republic was selected as the area for this case study.This suburban zone is the most dynamically developing territory within the Czech Republic, where the trend of formation and development of suburban areas has been particularly pronounced since the 1990s (Ourˇednı´cˇek, 2003(Ourˇednı´cˇek, , 2007;;Sy´kora, 2004;Sy´kora & Mulı´cˇek, 2014).There are many settlements in the suburban zone of the capital; for this study, only the rapidly developing ones were selected-a 100% increase both in the number of inhabitants and in the number of houses between 1991 and 2011, which indicates a suburbanization wave in the area, was chosen as the inclusion criterion (data were based on the national censuses).The population of these settlements is growing; hence, spatial planners, architects and local governments should react to this trend and design furniture for spending free time in public places that are easily accessible to the local community.This is especially important as the interaction between residents (both old and new) is crucial for establishing relationships and preventing social segregation.The form and equipment of local accessibility hubs (potential local centers) were investigated in particular in the newly created parts of the examined settlements.The equipment of the identified local accessibility hubs with such furniture was investigated by a field survey performed by the author.

Base Layers and Their Modification
Source data were provided by the State Administration of Land Surveying and Cadastre (C ˇU ´ZK, 2023).Two types of sources were used -cadastral maps with the space boundaries were used as the principal data source, which was further augmented with orthophoto map for the validation of the current real state.All streets and pedestrian paths in the settlements were used.At the same time, care was taken to avoid the problem of sensitivity to boundary conditions (Peltan, 2017;Ratti, 2004) that could affect the results.Therefore, the entire cadastral area of the given settlement unit was considered.As a result of the growth, some settlements merged and, therefore, needed to be considered as a single entity for local integration calculations.The POS recorded in the cadastral maps was verified using current orthophoto maps and were missing in the cadastral maps, the situation was amended to fit the current orthophoto maps (e.g., POS within development projects that might not have been recorded in the cadastral map, etc.).However, the evaluation of the SPOS was performed only on residential areas, which were affected by the dramatic building development and the associated rapid population growth.
In this paper, the term ''leisure amenities'' describes furniture elements for outdoor POS including benches, picnic tables or playgrounds, and outdoor fitness equipment.

Space Syntax Analysis
In this study, DepthMapX software was used for the topological analysis of the spatial structure of suburban areas.This software was proven effective for the analysis and topology evaluation of spatial relationships in the environment previously (Haq & Berhie, 2018;Karimi, 2018).Numerous techniques have been developed in Space syntax and, over time, more analysis tools are being added.The analysis presented in this study is limited to a single metric, namely Integration HH, which has proved to be relevant for the research of the movement of people.
The Integration HH metric calculated by the DepthMapX software can describe various levels of integration depending on the parameter r (radius).The presented study focused on local integration in the SPOS, which can be used to predict local scale movement of people (Penn et al., 1998) and, in particular, pedestrian movement (Lerman et al., 2014;Vaughan, 2007), which tends to cover shorter distances than movement by car (Hillier, 2007).For this reason, a relatively small radius parameter of r = 3 was chosen for analysis as it is particularly suitable for urban networks and for identifying local accessibility hubs within a SPOS (Greenberg et al., 2020;Hallowell & Baran, 2013;Hillier, 2007;Legeby, 2010;Omer & Zafrir-Reuven, 2010;Penn et al., 1998).
Subsequently, the software computed the Integration HH parameter for each SPOS segment in the area of interest and this calculated value was subsequently used for classification of the public spaces according to this parameter (see below).
The calculated Integration HH parameter was then used to classify the SPOS segments within each settlement into 10 bins.Segments in the 10th bin (the one with the highest Integration HH values) were considered local accessibility hubs in the respective settlement.

Results
The presented research dealt with the analysis of accessibility of the SPOS in significantly suburbanized settlements (Figure 2) in the suburban zone of the capital of the Czech Republic (Sy´kora & Mulı´cˇek, 2009).Special attention was paid to the local centers of SPOS in each settlement (i.e., spaces that can be characterized as the most accessible to the communities of the given part of the settlement).Subsequently, it was determined whether such places offer suitable equipment.
Forty-four settlements were selected in the suburban zone of the capital (in the adjacent districts of Prague-West and Prague-East) using two aforementioned selection criteria (doubling the number of inhabitants and doubling the number of houses between 1991 and 2011).A total number of 168 places equipped with open space furniture were identified in these settlements, of which only 32% were located in the potential local hubs of these settlements.The remaining 68% of places with open space furniture were located outside the local accessibility hubs, regardless of whether in the original (46%) or newly created (54%) parts of the rapidly growing settlements.The places in the original part were usually created before the expansion and still serve as leisure spaces today.In most cases, they were not modified, even though the accessibility potential changed.In the case of the newly built parts of the settlements, these places are segregated spatially and were typically built as parts of the implemented development projects.In some cases, places for spending the free time were designed zone outside the residential zone to maximize the space for the housing construction.
Looking at the situation from the inverse perspective, the evaluation revealed that only 37% out of the 119 local accessibility hubs are equipped with elements for spending free time (25% are local accessibility hubs in the original parts and 12% in the newly created parts).
This reinforces the effects of spatial segregation, as the leisure equipment is often (namely, in 63% of cases) missing in well-accessible and well locally integrated places.
On the contrary, places with high potential-the local accessibility hubs-in the new residential areas are often represented only by streets with a 30 km/hr zone, without any street furniture.This follows from the design of the suburbs that neglects the pedestrian traffic and causes these areas to be suitable for car traffic only.In rare cases, the street was widened and planted with vegetation; in most cases, however, vegetation can be in such areas observed only on the private plots of land in the gardens of individual houses.
The results (Figure 3) further show that the quality and variety of the POS furniture in places that are currently equipped is often underestimated.In most cases, these places do not reflect the local culture, history, they are not places where works of art could be installed, and landmarks or central elements would be created.The potential of the SPOS and its partial POS is thus largely unmet.

Discussion
The presented research addressed the identification of the SPOS, its local centers, and the verification of whether the potential offered by these places is being exploited.The SPOS present in the settlement and creating conditions for recreational use, pedestrian and cycling permeability could be theoretically found in any settlement.
The analyzed suburban areas included comprehensive development projects of enormous scope as well as individual construction of family houses or smaller development projects.The former type is, according to S ˇveda & Pazu´r (2018), concentrated, and the latter named types are dispersed.Within the framework of comprehensive projects (in which, besides individual buildings, also streets and other POS were designed), the POS was usually solved locally well, with elements for leisure activities; on the other hand, the location of the equipped POS often neglected the complex aspect of the connection with the settlement as a whole.Besides, in rare cases, the public places were not located inside the residential area but in an adjacent area.Thus, one can only partially agree with the conclusions of Hnilicˇka and S ˇteˇpa´nkova´, who assume that areas of public greenery, parks and POS are absent in these areas (Hnilicˇka, 2012;S ˇteˇpa´nkova´& Kristia´nova´, 2012).According to the findings of this work, it is possible to agree with their assertion provided only small development projects are considered.Still, out of the total number of suburban places (irrespective of their size), the potentials of POS are not being realized, and conditions for building fullfledged local centers in suburbanized settlements are not *Due to the rapid growth, the equipment cannot be assessed yet in one location.The management of the street network and the location of buildings is already known, sometimes already implemented; however, the furnishing of POS is carried out only in the last phase of implementation.created.The majority of settlements contain fragmented areas.Each area is solved separately, without a comprehensive approach to the solution of POS as a part of the whole-settlement system.Leisure elements (if any) are often placed inside individual areas, which, in effect, have isolating consequences (as the number of entrances through the street network to suburban areas is lower than to others (Major & Dalton, 2018).Thus, the POS furniture is often not placed in the potential local accessibility hubs (high local integration) well connected to the system of the entire settlement.This is, in particular, true for the larger new developments, where the leisure amenities are typically placed in locations with difficult accessibility from other parts of the settlement.This turns such leisure amenities largely to ''private'' spaces accessible only to the inhabitants of the particular development, which prevents the interaction and integration of such population with that of the other parts of the settlement and supports segregation of the inhabitants of the area.From this perspective, we can consider such placement of leisure amenities as unsuitable for integration (even though the amenities may be widely used by locals).For this reason, we argue for planning the leisure amenities rather in areas that can be easily approached by population of the entire settlement, that is, in the local accessibility hubs.Saelens and Handy (2008) discussed the need for cities to require private developers to provide POS equipment.The results of this analysis indicate that while such projects can contribute to the development of SPOS, care should be taken by the authorities to support the placement of such POS in potential local centers that have the ability to integrate local communities.
As a settlement expands, its SPOS grows.Despite the growth occurring on the edge of the settlement, its consequences can be observed even in the center in terms of changing the local integration.It is, therefore, necessary to consider the dynamic process of changing the accessibility potential of its individual parts as the system grows.To prevent spatial segregation, such changes should be respected, and settlements adapted to them.

Possible Steps for Improving the Situation
This paper demonstrates a method for the identification of places deserving special attention within the settlement.The use of a local integration analysis can help in the understanding of the issues associated with the new developments.This approach leads to the identification of places with the best accessibility from various parts of the settlement, which gives them the potential to act as spaces suitable for spending time and, therefore, for interaction and integration of the population of such developments (Carmona, 2019b;Jehlı´k, 2016).At the same time, these local accessibility hubs can be perceived as elements that mutually interact within the SPOS.The degree of accessibility (of local integration) provides a good basis for characterization and categorization of the particular places and for designing furniture suitable for their optimal function.
In the case of newly defined development areas, it is necessary to comprehensively assess the optimal connectivity of the newly proposed SPOS to the existing structure of these spaces (Barner et al., 2010).The creation of new links and roads forming the emerging street network in growing settlements is a dynamic process (Koohsari et al., 2019) and the planners should consider changes in accessibility potential (Dewaelheyns et al., 2014) not only of the new developments but also consider the effect on the older parts of the settlement.Hence, local centers equipped for spending leisure time should be primarily created in places that are best integrated into the SPOS and they should form a continuous network to avoid the creation of mutually isolated systems and to prevent spatial segregation.
Based on the results of the topological analysis and of the field survey performed within the study, it should be recommended that the following is considered by planners: Identification of local accessibility hubs should be performed in rapidly growing settlements; the method presented in this paper is suitable for this purpose New areas should be designed with knowledge of the characteristics of the original settlement, its street network and the location of existing local centers.This would facilitate designing of the new parts of the settlement in a comprehensive way (i.e., taking into account the modifications that should be performed in the original parts of the settlement).Street networks should be designed in a way supporting their use by different users, that is, facilitating motor transport, cycling, pedestrian transport.Streets on a local level should be seen as a social space and it is important to design the areas with their particular functions in mind (e.g., to support the formation of a zone suitable for community life by limiting the access of car traffic through such zone while making it sufficiently accessible).
Assessment of existing and design of new parts of SPOS should take into consideration the accessibility hubs.Newly designed amenities and POS furniture should be placed into or near such hubs in the residential areas.Adding greenery to such spaces has a positive impact on the well-being of the users (Matsuoka & Kaplan, 2008) and the air cleanliness of the area (Abbasi et al., 2016;Pham et al., 2013;Thompson, 2002).Where existing leisure amenities are placed in places with poorer accessibility from other parts of the settlement, we suggest that their prosegregation effect can be (at least partially) mitigated by construction of new leisure amenities in (or close to) local accessibility hubs.
SPOS are complex and must respond to new as well as existing conditions, requirements and demands of the residents.This is especially true in suburban settlements, the dynamic development of which takes place typically at the fringe of such settlements.In such areas, there is a particular need to create space for spending leisure time in order to offer opportunities to eliminate social isolation.

Limitations
Besides integration (accessibility), several other parameters can be considered for characterizing the SPOS and its individual parts (e.g., intelligibility, connectivity (Cervero et al., 2009;Hillier, 2007;Jiang & Claramunt, 2004;Porta et al., 2006;Shen & Karimi, 2016;Zielstra & Hochmair, 2011).When identifying the system and its local centers, other criteria should ideally also be considered, such as the population density, the age structure of the population, proximity to other functional areas, stops of public transport etc.However, in the specific environment of the suburban developments, which is relatively homogenous both topologically and socially (Hnilicˇka, 2012;Ourˇednı´cˇek, 2015), the focus of this study was on facilitating the integration of the new inhabitants both within the new population and with the original population.For this purpose, the accessibility of local POS facilitating the mutual interaction of the two populations was chosen as the most suitable metric sufficient for simple analysis.
The radius could have been also adjusted for analysis of individual settlements to possibly yield better results.However, this approach was not adopted as (i) the analyzed settlements were relatively homogeneous and (ii) the suitability of radius r = 3 for settlements has been demonstrated before, as mentioned in the Introduction.Of course, in other contexts, another radius value could be more fitting.

Conclusion
This paper provides a synthesis of information about the SPOS from topological analysis and field survey and shows how to identify their local accessibility hubs for creating local centers.The findings of the case study reveal the untapped potential of SPOS in the accessibility hubs in suburban settlements in the Czech Republic.
Unsuitable cumulation pedestrian and car traffic was found in the analyzed suburban areas, which is due to the modernist approach to street network implementation in developments (Marshall, 2004) and the design of these areas with priority given to car traffic.
The potential of well-integrated hubs is exploited by a small number of local centers that include elements for leisure and local community meetings.The structures of the newly created areas are mostly insufficiently connected with the original settlement (the new and original areas share mostly only a few streets).This makes a kind of ''structural lumps'' (Hillier, 2007) in the street structure, in which natural human movement is severely limited.From this, it is possible to conclude that the integration aspect of the new development is largely neglected by planners.
In other cases, a utilitarian solution of the street network (i.e., only a road and a sidewalk, without any public amenities) can be found.The untapped potential of easily accessible places in such areas (and, in particular, on the borders between the ''new'' and ''original'' areas) is obvious.At the same time, quality POS are completely missing in many new areas with a low degree of integration.
On the other hand, POS for spending leisure time are relatively frequently created in the original parts of the settlements.If this is combined with the lack of suitable amenities in the new developments, these facilities can be overloaded.Hence, it is necessary to keep the track of the shifting accessibility potentials occurring as a result of the settlement growth and plan the local amenities accordingly (ideally, on sites well accessible for inhabitants of both the new and old parts of the settlement, ideally on or near the borders to support the integration).
Topological analysis of the street network of suburban settlements proved to be a suitable way of identification of the accessibility hubs, which can help architects and urban planners.A design that takes the potential of this system into account can help prevent the effects of spatial and social segregation.
Topological analysis is not the only tool for examining the possibilities of SPOS in settlements from the perspective of integration.However, the identification of local accessibility hubs based on topology offers an interesting insight into the issue and can be used as an initial survey or aid in retrospective verification of whether or not the well-accessible parts of the SPOS have been equipped.

Figure 3 .
Figure 3.An example of a suburbanized settlement Velke ´Pr ˇı ´lepy: On the left, we can see the street network depicted by a color scale of accessibility, with the brightest color indicating the POS with lowest accessibility and darkest lines representing the streets with the highest potential of local accessibility.The bright polygons delimit the places that were created after 1989.On the right, we can see places that have been identified as places for spending free time (white cross in the black circle).Places representing local accessibility hubs with high potential for accessibility are mostly unused.Most leisure amenities are, despite the availability of accessibility hubs, located rather in the new developments in places with low accessibility from other parts of the settlement, which supports segregation.