A systematisation of policies and programs focused on informal urban settlements: reviewing the cases of São Paulo, Luanda, and Istanbul

Urban growth, particularly in developing countries, has been impacted by the ﬁ nancial and institutional incapacity to provide a ﬀ ordable housing, leading to the development of large informal urban settlements. The support provided by international ﬁ nancial institutions, the growing economic capacity, and the interest from the real estate market have been responsible for the emergence of interventions, programs, and policies directed at informal urban settlements, with the goal to improve or replace them. This paper explores the modalities adopted for such upgrading projects in São Paulo, Luanda, and Istanbul. Using a categorization system, the research shows that the interventions in São Paulo are more concerned with keeping the residents in-situ , while the public authorities in Luanda and Istanbul show a preference for relocation and eradication of informal urban settlements, even though Luanda has recently shown a certain degree of change in its approach.


Introduction
According to UNFPA (2007) data, by the year 2008 over 50% of the world'sp o p u l ation was living in urban and metropolitan areas.That figure rose to 54% in 2014.This trend is expected to continue, and this number is predicted to reach 66% by 2050 ( a ni n c r e a s eo f2 .5b i l l i o np e o p l e )( U N ,2014).In 2012 a total of 863 million people lived in slums.This corresponds to one-third of the global urban population (United Nations 2014).
The growth of urban populations (as a result of rural migration and natural growth), also stimulated by economic and financial globalization, is especially visible in the Global South.Several countries, particularly in Asia and Africa, are still in the early stages of urban migration.Forecasts say that these two continents will be home to almost seven out of ten urban residents in the world by the year 2030 (Penrose et al. 2010;Turok and Borel-Saladin 2016) .B e c a u s eo ft h i st r e m e n d o u sp r e s s u r e ,u r b a nh o u s i n g problems and the informal solutions found until now remain a critical issue for the future of cities and metropoles (UN-Habitat 2003;Davis2006;Douglass 2000a).
The deregulated, and informal urban development is overwhelmingly important in many cities because of the area it occupies, its segregated location, and its share of the population (Kovacic, 2017).
As a result of economic, environmental, or political causes (acting alone or combined) (Mundia 2017), the question that arises is how to solve the problems in, as well as those caused by, these areas, as well as how to prevent new ones or their enlargement, since many of the reasons for their emergence remain active.
In the Global South, the perceived asymmetries between rural and urban spaces, reinforced by environmental problems and political instability, continue to be seen as one of the main justifications for the persistence of the rural exodus (Tacoli, McGranahan, and Satterthwaite 2015) and thus the continuous enlargement of Informal Urban Settlements (IUSs).
But if this pressure triggers the creation of IUSs, it is perhaps more useful to look at the present and future seeking to find logic and key elements in the political and urban approaches designed to face one of the biggest problems of the urban planet.
It is why it is urgent to contribute to adequate and timely responses in the form of policies and practices that could help change the supply-growth trajectories of informal dwellings in Latin America, Asian and African countries and improve living conditions in IUSs.For this reason, it is important to identify and systematise the current practices on the upgrading/ retrofitting of IUSs and to learn from their successful or unsuccessful experiences.We believe this reflection can help find new and more effective answers to this global problem.
This paper intends to contribute to the identification and analysis of the effects of programs and policies oriented to the IUSs, while trying to explain the main differences between them arising from the institutional and economic contexts in which they occur.
In this research, we explore three issues: 1.What are IUSs and how can they be characterized?2. What are the possible responses to this problem and how can we organize and systematise them? 3. How do these responses work in practice?
The methodology started by systematizing the approaches followed in informal urban areas, according to the analyzed bibliography.After selecting the three case studies and their solution´s strategies, it was possible to understand how each one fits in the systematization.A second focal point was the transformations, i.e., the responses of governments, academia, and development agencies, and how these are reflected in "ground actions," as argued by Younes and Simmons (2002).
Reports and other technical and scientific documents were used as generic sources, as can be seen in the bibliography presented throughout the text of the following sections and, in a more organized manner, in the "References" section.
The collection, analysis, and critical evaluation of the documentation related to the plans, policies, and projects that were in force in the three cities was an important part of the methodology.Short visits were made to each city and, based on some contacts initially established, it was possible to talk to planers, municipal and State Department of Housing experts (in the case of São Paulo), as well as researchers from the University of São Paulo (Brazil), Yıldız Technical University (Turkey), and University Agostinho Neto (Angola).In Istanbul and São Paulo, technical visits were made to IUSs in the company of academics and experts.This hybrid methodology, combining documentary, statistical and legal document collection, direct observation with site visit, and expert knowledge of local actors allowed the retrieval of information related to the different programs and policies and complement some of the analyses made in each of the cities.

Informal Urban Settlements: a global problem
An analysis of the global dynamics of population evolution shows that growth has been mostly concentrated in cities.This can be explained by a combination of natural growth and migrations from rural areas.Half of the world's population is already urban, and it is estimated that by 2050 the figure will rise to two-thirds, with most of this growth taking place in Asia and Africa (United Nations 2014; Penrose et al. 2010;Turok and Borel-Saladin 2016).
If this process is accompanied by sound economic development policies, it can be positive and contribute to a faster reduction of poverty on a global level and, at the same time, to increased productivity in rural areas.Rapid urban growth would seem, at the moment, to be a process that is disconnected from the development of the places where it occurs, contrary to what happened in other historical moments.Cohen (2004) shows that urban growth is more intense and visible in developing countries because they still have: i. rural to urban migration; ii.natural urban population increase; and iii. the reclassification of rural as urban areas.
Moreover, this sudden population growth presents a risk factor which may result in housing shortage problems and the associated challenges for social and territorial cohesion (Douglass 2000b).

The provision shortage of urban housing
These problems do not arise directly from population growth in cities.Indeed, studies show (Huchzermeyer and Karam 2006) that the negative consequences of this growth only occur if the relationships between the government, the private sector, and the population-in-need are dysfunctional.
An analysis of those relationships shows that the formal real estate markets are not easily accessible to the whole population (Buckley and Kalarickal 2005;Nassar and Elsayed 2017), due to issues on both the demand and the supply side: on the one hand, increasing inequality, low economic growth, low wages, informal/precarious employment, and difficult access to credit; and, on the other, real estate speculation, building costs, or operational problems in the real estate sector, creating a mismatch between demand and supply prices that make the functioning of markets and the formal provision of housing by the private sector close to impossible.Berner (2001) adds that public initiative housing production fails to adequately address the issue: "Social housing produced by the state is the other extreme.With the notable exception of Singapore, however, governments in developing countries have proved neither effective nor efficient as housing providers.Typically, immense expenditures for land and production yield negligible output, with the profit pocketed by speculators and poorly monitored contractors.To make things worse, most of the programmes suffer from huge targeting errors" (p.296).
With regard to the third aspect of these dysfunctional relationships, the government fails both in its regulatory role and as a provider, not only due to poor governance (technical shortcomings, financial incapacity, corruption, cronyism, etc.) but also on account of ideological issues that have an impact on the definition of priorities and strategies.The transformation of some metropolitan regions into world cities is a recognised main goal of a number of governments.We are thus in agreement with Douglass (2000b) when he argues that "mega-urban regions, international development corridors and transborder regions are part of what can be called a transnationalisation of territorial space through an accelerated urban transition organised into extensive spatial networks that transcend the nation-state in all forms of economic interaction.(. ..) the megaprojectshigh-rise business districts, global hub airports, super container ports, ultra-high-speed rail transit and expressways for trucking and car movementare manifestations in the built environment of the intensity of this urban restructuring associated with overt competition for world city status" (pp. 2321-2322).This commitment to the transformation or upgrading of mega urban regions into world/global cities requires huge investments in major infrastructure and events, diverting them from their application in housing, for example.

Informal Urban Settlements (IUSs): concepts, dynamics, and socio-spatial segregation
IUSs are, in a broad sense, the physical manifestation of the alternatives found by a vast and vulnerable population in response to the constraints on affordable housing supply.In the context of our research, IUSs do not necessarily have to be slums, although they are often considered as synonymous (Roy et al. 2017).The operational definition of a slum, as defined by the United Nations (UN-Habitat 2003), includes five criteria: (1) inadequate access to drinking water; (2) inadequate access to sanitation and other infrastructures; (3) poor structural quality of houses and location in hazardous areas; (4) overcrowding of housing units; and, finally, (5) ownership insecurity.At the same time, UN-Habitat recognises at least two different kinds of slums: "slums of hope: 'progressing' settlements, which are characterised by new, normally self-built structures, usually illegal (e.g., squatters) that are in, or have recently been through, a process of development, consolidation and improvement; and slums of despair: 'declining' neighbourhoods, in which environmental conditions and domestic services are undergoing a process of degeneration" (2003,11).
In the case of the "slums of hope," it is possible to find a range of situations where UN-Habitat criteria are applied in very distinct ways.One example is infrastructures, which can range from a total lack thereof to a reasonable supply; another is the structural conditions of buildings that can benefit from the quality of the materials used.There are even cases where self-building and land-tenure or housing insecurity occur, but where the lowincome population may still be socially well integrated in terms of holding formal jobs in the private or public sector.In some way, this explains why slums and informal urban settlements are seen as different (Silva and Farral, 2016).The conceptual confusion justifies the use herein of the IUS concept.
Whereas in the description of the main factors leading to the formation of IUSs, the focus was placed on the housing problem, it should be pointed out that the issue is a wider one and a reflection of urban development issues, with spatial segregation mirroring social segregation (Caldeira 1996;Lalloo 1998), becoming thus not just a symptom but a problem in itself.In this sense, it is possible to argue that the housing problem is both a cause and an effect of a socio-spatial problem, which is increasing "social immobility" (Boudon 1972;Ermisch 2008), and that the right to housing must be understood within a broader context of the "right to the city" as a decisive factor of change in the approach to interventions in IUSs.
Using this operational definition, we identified the dynamics present on a global level to understand, for example, that while the total population living in IUSs is increasing despite the decrease, in percentage, in relation to the urban population (De Vries 2003).It is also a known fact that the regions with the most people living in IUSs are sub-Saharan Africa, followed by Southeast Asia, which nevertheless presents a more rapid decline in the population living in IUSs (United Nations -DESA 2013a).Using the same indicator (population living in IUSs in relation to the total urban population) and comparing the three countries in this study, Turkey has the smallest proportion of urban residents in IUS (11.9%), followed by Brazil (22.3%) and then Angola with 55.5% (UNstats 2015).This is why Milbert (2010) argues that these areas are "part of the sum and substance of cities in the South" (p.300).

Global agents and their approaches for the IUS
For a chronological perspective of the kind of approaches developed for the IUSs, it is useful to analyze not only government practices but also the practices of the World Bank and UN-Habitat, as agencies with a global coverage and a significant impact in terms of their ability to advocate for and lead a change when it comes to technical practices.
Up until the 1970 s, government practices in developing countries were either merely negligent (UN-Habitat 2003) or, in some cases, aimed at eradication, expulsion, or resettlement in inadequate state housing developments.In the few cases in which the response to the housing deficit followed European examples (i.e., through the formal provision of social housing), the high cost of that approach, and the frequently associated corruption, meant that houses ended up being attributed to the middle classes and political clienteles, perverting the stated objectives (UN-Habitat 2003).
With the arrival of the 1970 s and the emergence of a stronger and more active civil society, IUSs began to be regarded as a persistent structural phenomenon, the previous approaches were recognised as failures, and the diversity of legal frameworks and local realities was acknowledged (UN-Habitat 2003).
The improvement projects for IUSs (slum upgrading) and land and services (sites and services) implemented in Senegal in 1972, marked the first fundamental change in the World Bank's housing policies (Pugh 1995).As a result, from that year until 1981, about 90% of the Bank's investment in housing would be in these kinds of projects (Spence, Annez, and Buckley 2009), marking a pivotal point and contributing to the forsaking of previous approaches made by many governments (Abbott 2002).In the same period, the United Nations organised the first conference on Human Settlements and Sustainable Development (Habitat I, Vancouver 1976), which laid the basis for the creation of the United Nations Human Settlements Programme: UN-Habitat.
By the early 1980 s, improvement of the physical environment was recognised as the core element of this new approach to the IUSs redevelopment process (Abbott 2002).Nevertheless, results failed to meet expectations: "sites and service schemes were later perceived to have failed, primarily because they did not provide a sustainable basis for housing delivery.In addition, there were later policy shifts (. ..)" (Abbott 2002, 306).
Following the appointment of a new president, the World Bank made significant changes to its policies.The focus was switched from IUSs improvement and sites and services projects to help property development financing institutions.Between 1992 and 2005, investment in IUSs improvement and sites and services projects decreased by 10% (Spence, Annez, and Buckley 2009).UN-Habitat followed this dominant philosophy between the mid-1980 s and the second Habitat conference in 1996.By adopting guidelines such as the "Global Strategy for Shelter to year 2000" in 1988, the agency encouraged governments to change the focus of their policies from house building and services provision to a broader approach including regulation and incentives for "greasing" the markets and increase the number of participants in the issues of housing for the poorest (UN-Habitat 2013b).
UN-Habitat currently advocates a holistic approach, and the most recent reports published by the agency on best practices highlight expressions such as "participatory slum improvement,"" city-wide slum upgrading," and "street-led slum upgrading."With these concepts, UN-Habitat places its emphasis on maximizing community participation; moving away from pilot projects to the implementation of IUS redevelopment programs in a city as one single planning unit; reinforcing the importance of the street as a public space and as the driver of the transformation of IUS; accepting the importance of sensible and participatory physical and social mapping; increasing ownership security of residents; ensuring services maintenance; and, last but not least, enabling incremental improvements in IUSs (Edward Miller (Ed.) 2012;MboupandWarah2013;UN-Habitat 2011, 2012).

Categorisation of IUS approaches
The approaches to IUS interventions were based on different perspectives to address the problem.Wekesa, Steyna, and Otieno (2011) identified 5 types: direct public housing; sites and service schemes; settlement upgrading; housing production and delivery modes; and reformulating building codes and standards.
Whilst it is possible to identify a chronological progression in terms of the most common and accepted practices recognised as "best practices," one can also find diverse approaches to IUSs.As part of our research, the diversity and complexity of the documented and analysed approaches (including those studied in this paper) suggests the advantage of building a categorisation system that works as a key to decoding and even interpreting those approaches as shown in Table 1: The relations between them, as well as complementary notes for some of the categories, can be seen in Figure 1, which gives us a categorisation system proposal: (a) The first factor to be taken into account when considering action on IUS is whether it is a preventive or interventional action (first level in Figure 1).Market regulation or the provision of housing is not really seen as direct approaches to IUS but have ag r e a ti n fluence on the issue of management as a whole and are not infrequently linked to actual interventions.In the preventive approach, market regulation issues are extensive and their enumeration here is not justifiable, but, as an example, any historical analysis of housing policies will show the impact of measures such as rentfreezing.The second factor is the provision of housing, including both finished housing units and other incremental building strategies such as assisted selfbuilding programs, building plots with pre-built infrastructures (sites and services) and plots with expandable basic housing units.(b) With respect to the interventional dimension, we considered significant elements present in one or more of the IUSs analysed.In this case, there are four main categories which can be applied on their own or in combination each other's (Anand and Rademacher 2011), depending on the fate of the target population in relation to their housing unit and in relation to their location in the city: (i) If the intervention involves the displacement of the population without a set destination, it is referred to as "eviction," and can be forced or induced.It is an induced eviction if, for example, the agent provides money so the people forced to move can find alternative housing by themselves; (ii) If the intervention involves displacement, but with the relocation set for elsewhere in the city, it is called ex-situ rehousing or relocation.This intervention usually involves the provision of new housing units.This can be further broken down into total/global or partial/specific if all or only part of the communities needs to be displaced; (iii) If the intervention involves eviction and rehousing within the same area of intervention or within walking distance, it is called in-situ rehousing (Anand and Rademacher 2011).This can be further broken down into total/global or partial/ specific.Global in-situ relocation applies to cases where a whole IUS is demolished in order to be rebuilt under an urban plan aimed at rehousing the respective resident population, and often providing housing for other people with greater purchasing power, as a means of helping finance the intervention.Specific in-situ rehousing happens when only a few people within the IUS are displaced for a particular reason (construction of a slope containing structure, environmental protection, installation of facilities, etc.) and rehoused in new housing units built in or near the same area; (iv) If an intervention does not involve displacement it is called redevelopment: the focus of the intervention is the improvement of existing housing units.Examples of such interventions are programs for the provision of building materials to residents at reduced prices.When the focus is the public space (e.g., infrastructure, services, equipment, etc.) it is called urban redevelopment.Also considered are Social and Economic Assistance components, including micro-credit and community organisation development programs, land regularisation, or any program designed to improve the ownership security of residents or to protect them from forced evictions.

Case studies
In the previous section, a theoretical framework was presented, aimed at meeting the objectives set out in a global perspective, without addressing specific cases.The contents developed provide a basis that will be used to analyse the IUSs in the three cities described in the next sub-sections.Angola, Brazil, and Turkey, the countries where the analyzed cities are located, register different levels of development, but share significant problems in terms of poorly housed urban population.The urban population was, in 2018, over two-thirds of the total population (Angola 66%, Turkey 75%, and Brazil 87%) and in all of them it continues to increase (data.worldbank.org).
Rapid and large-scale urbanization (from the 60 s and 70 s of the last century in Brazil and Turkey and from 1980 to present in Angola) did not include housing and urban infrastructure in adequate conditions, leading to the generalization of self-built housing of very variable quality, on public and private land.
One should point out that Brazil and Turkey were ranked in 79th and 64th place, respectively, in the 2017 Human Development Report (UNDP 2018), corresponding to High Human Development in accordance with UNDP criteria while Angola occupied the 147th place (a Medium Human Development score).Their trajectories are also very different.While Turkey has climbed several places in the ranking (from 70th to 64th) between 2007 and 2017, Brazil and Angola have fallen from 55th place to 79th and 143th to 147th, respectively, in the same period.
In the last 5 years (2015-2020) all three countries have revealed persistent urban growth.Angola stands out, however, with a 4.32% growth vis-à-vis 2.04% from Turkey or 1.05% in Brazil (data.worldbank.org).This situation is not favorable to the reduction of the population living in slums which, to the contrary, could tend to increase.In 2014, the share of the urban population that lived in informal housing was 56% in Angola, 22% in Brazil, and 12% in Turkey.
This affinity in their urban path was also felt in the economic dimension.Since from 1995 to 2015 all these countries had moments of great brightness: Angola with 11 years of GDP above 5%, Turkey with 15 years, and Brazil with 5 years (data.worldbank.org).
These more or less extended episodes of economic dynamism were inducers of a renewed capacity (or at least the will) to look at the housing problem, triggering policies and programs to confront informal settlements, regardless of the political context specific to each country.This context, however, becomes more evident when it comes to understanding what kind of policies and projects have been adopted.
The three cases -São Paulo (Brazil), Luanda (Angola), and Istanbul (Turkey) -were selected because they are the main urban areas of their own countries, polarizing many of the problems related to informal urban areas, but each located in different geographies, thus underlining the universality of the problem and highlighting the diversity of approaches to their solution.
Our survey of interventions has focused on existing policies and programs since the beginning of the second decade of this century.
After the presentation of the case studies, a comparative analysis will be performed, applying the intervention categorisation system.

São Paulo, Brazil
The IUSs in São Paulo are located predominantly in outlying areas and are home to about 30% of the local population (SMDU 2012).During the years of strong demographic growth (from the 1950 s to 1980), such settlements occupied vacant land on the city's fringes, invading environmentally sensitive, often legally protected, areas, particularly in the north and the south of the city.Foregoing adequate infrastructures, they blindly occupied land that had considerable physical and environmental constraints, fragile land zones in hazardous areas with steep slopes or in flood plains, areas with contaminated soil, and areas near landfills or garbage dumps, among others.Environmental impacts are especially negative in terms of access to drinking water and the silting of watercourses.
The IUSs in São Paulo are categorised in the Municipal Housing Plan (PMH) (SEHAB 2012) as follows: a favela (coloured yellow in Figure 2)i sd e fined in the PMH as "occupation disregarding urban and building regulations in public or private zones, predominantly disorganised, with poor infrastructure, with buildings predominantly self-built and precarious, for low-income and socially vulnerable families";anúcleo urbanizado is "af o r m e r favela, now 100% covered by urban infrastructure networks built under different housing programmes, but still pending legal regularisation";acortiço (turquoise in Figure 2)i s "multi-family collective housing, consisting of one or more buildings on a single urban plot, divided into several apartments that are rented, sublet or let in any way; with several functions performed by the same apartment; with access to and common use of open spaces and sanitary facilities; with predominantly precarious road accesses and infrastructure, and overcrowded";aconjunto habitacional irregular is defined as a housing complex that "despite having been provided by the government, still lacks land, legal and registry regularisation";aloteamento irregular (orange in Figure 2)isa"settlement characterised by the existence of a developer and/or agent, whose type and morphology are defined by small land plots for single or multi-family use, that have been used and occupied without prior approval by the respective public authorities or, when approved or still in the approval process, were implemented in violation of the law or in violation of the approved project." The study of the interventions in São Paulo focused primarily on the work of the Municipal Housing Department (SEHAB), the main operational agent of housing policies in São Paulo and, as such, the main player in São Paulo IUSs.Of their work, it is particularly worth mentioning the creation of a support operational system known as HABISP, as well as three of the IUS intervention programmes that have had a significant impact (known as the "Programa de Requalificação de Cortiços,""Programa de Urbanização e Regularização Fundiária de Assentamentos," and "Programa Mananciais").Also of note, is the opening, by the SEHAB, of a tender programme for intervention projects aimed at supporting plural and comprehensive solutions: "Renova SP."

HABISP, the prioritization of interventions and integrated action
HABISP allows for the aggregation and geo-referencing of all relevant information, be it physical, social, economic, legal, or geographic, making it possible to cross-reference data from various agents with a view to generating important databases for the formulation, implementation, and monitoring of housing programmes.Using registration data and identification of the IUS perimeter based on aerial photography, files were created with details on the number of households, land ownership, urban integration, infrastructure networks, safety data (fire risk, structural risks), sanitary units, health conditions, and other relevant information.Subsequently, with the Prioritization Intervention System, indexes are generated from the data collected, characterizing the precariousness of a given settlement, where the weight for each criterion depends on the housing programme.These indexes are incidence of geotechnical risk in the area, degree of implementation of infrastructure networks, São Paulo index of social vulnerability (IPVS) and health index.

Cortiços redevelopment programme
The "cortiços" redevelopment programme has been applied in buildings in the neighbourhoods of Sé and Mooca in the centre of São Paulo since 2005.This programme "aims at renovating multi-family houses, providing minimum conditions of sanitation, ventilation, lighting, and physical and legal certainty, (. ..) in accordance with the parameters established in the Moura Law (Municipal Law 10,928/91)."Under this law, any owners of encortiçados (a slum tenement building) who do not improve them in accordance with minimum conditions of health and safety, are subject to penalties and may have the property "sealed" by the local authorities.Basically, as mentioned above, the Moura Law defines what "cortiços" are and the minimum health conditions expected for them.Besides this incentive component for the redevelopment of cortiços, other measures are in place, such as regularisation of rental contracts, housing programmes aimed at reducing the density of cortiços and social work programmes.To make the programme operational, SEHAB coordinated with the local authorities and the CDHU which, through the "Programa de Atualização de Cortiços" financed by the BID (PAC-BID), delivers housing for families who have to be relocated (SEHAB/Habi 2008).

Urbanisation and regularisation of favelas programme (PURFA)
This programme resulted from the merger of the programmes for "the upgrading of favelas, regularisation of settlements, and regularisation of municipal public areas" (SEHAB 2012, 119) which had been implemented until 2009, including those applied to housing projects promoted by SEHAB, CDHU, or COHAB.PURFA is mainly involved in: the urban redevelopment of IUSs, the timely construction of new housing units to re-house residents that have to be relocated, and the regularisation in land registry terms of preexisting developments.It is based, as much as possible, on the assumption of residents remaining in their homes.Several of the projects studied included, for example, the consolidation of slopes with the creation of public spaces and the introduction of facilities.Another example is the protection of a watercourse with the creation of a park and new houses.

"Mananciais" programme
This programme continues and expands what was implemented in Guarapiranga between 1992 and 2000, an environmental requalification of the IUSs located in the environmental protection zones of the Guarapiranga and Billings reservoirs, the main sources of drinking water for the metropolitan region of São Paulo, promoting not only an improvement in the quality of life of the urban population but also of all the inhabitants of the region.The "Mananciais" programme has basically the same components and objectives as PURFA, but specifically targets IUSs located in clearly designated macro-areas of environmental protection, which is reflected in its priorities and concrete actions.
3.1.5."Renova SP" tender programme The 2011 "Renova SP" tender programme was of particular importance, even though it was nothing more than an operational tool for already existing programmes, because it was autonomous in a way that it opened doors to a plurality of alternatives for intervention projects in the IUSs of São Paulo.It supported a competition featuring proposals for the 22 "Perímetros de Ação Integrada" (Integrated Action Perimeters) prioritised in the Municipal Housing Plan.The guidelines were very detailed but not restrictive in terms of the diversity of architectural solutions.The project evaluation tool provided a scientific and specific approach to project assessment by the jury, in addition to providing transparency in the selection process and assisting participants as a working tool.The anonymity of participants was guaranteed by using a digital system, contributing to the efficiency of the process (Barda and França 2011).

Luanda, Angola
The term musseque is used to describe many of the informal settlements in Luanda and, although there is no consensus on its definition, it does fit the UN definition of slum.The etymological roots of the word are in Kimbundo, a dialect spoken in the area of Luanda, in which it means red sand/earth (DWA & CEHS, 2005).According to Pepetela (1990), the first musseques appeared on land with that type of soil.Some musseques are located in risk areas: drainage areas, steep embankments, depressions with natural water, etc. (Raposo & Salvador, 2007).As many of them are built on clay soils, in addition to the usual problems in IUS, they are affected by poor drainage of rainwater, leading to stagnant pools of water which aggravate health issues (increased ease of propagation of flies, worms, mosquitoes, and bacteria).
A research programme on the standards of informal settlements and urban poverty conducted by the NGO, Development Workshop Angola (DWA), identified several typologies that allow for characterisation of the urban morphology (DWA, D. W. A., & CEHS, C. for E. & H. S 2005).The following can be included in the IUS category: "bairros populares"; "musseques antigos"; "musseques ordenados"; "musseques em transição"; and "musseques periféricos." Towards the end of the colonial period, "bairros populares" (low-income working-class neighbourhoods) was built by the state or by public companies (orange in Figure 2), modelled on the "townships" of South Africa (DWA 2011;Cain,Daly,andRobson2002;Cain2007).Built on a large scale by construction companies, their level of infrastructure and services was limited.The construction of these neighbourhoods ceased after Angola became independent, and the subsequent deterioration of services has blurred the differences between "bairros populares" and "musseques" (DWA,D.W.A.,&CEHS,C.forE.&H.S2005).
The "musseques antigos" (old musseques, highlighted in green in Figure 3) are those that already existed before independence.In 1975, they were home to more than half the population of Luanda, a share that's been reduced to about 40% today.They first expanded to unoccupied areas and then underwent a densification process when horizontal expansion became impossible (DWA 2011).These musseques had slowly expanded over the centuries and had reached considerable sizes by the late colonial era.Their The "musseques ordenados" (ordered musseques, coloured blue in Figure 2)r e s u l t e d from the informal extension of urbanised areas along roads and service corridors, and were legalised by the colonial administration, a practice that ceased in the post-colonial period, leading to a certain trend towards densification and the occupation of roads and areas reserved for services.Many of the approximately 478,000 inhabitants of these neighbourhoods are reluctant to refer to their areas of residence as musseques (DWA 2011).
The musseques antigos, which reached saturation levels in terms of population density a few decades ago, began growing upwards as residents turned their ground-level dwellings into cement buildings with two or three floors, thus making the areas "musseques em Transição" (musseques in transition, deep pink in Figure 3), where roughly 623,000 inhabitants live today (DWA 2011;Cain, Daly, and Robson 2002;Cain 2007).Several of these musseques are undergoing a process of "gentrification" (Rodrigues and Frias 2016), as some poorer households sell their properties and migrate to the urban periphery.
Angolans who sought refuge in the capital, fleeing from the dangerous and unstable rural areas during the civil war, began overcrowding the musseques antigos.Refugees in the same circumstances that arrived later were forced to find cheap land on the urban periphery, giving rise to the musseques periféricos (peripheral musseques, light brown in Figure 3), where most of the population growth is now concentrated and that already held 1.24 million people in 2011(DWA 2011).

"Novas Centralidades" urban expansion and rehousing projects
The "New Centralities" correspond to the answer given to the objective established in the Housing Development Law (Law 3.07, 2007), where it is required that "(. ..) the definition and execution of Housing Policy should respect (. ..) the promotion of housing poles developed with the necessary public services, basic sanitation and urban planning."This legal orientation was, in turn, the natural sequence of what was established in the Constitution of the Republic of Angola (versions of 1975Angola (versions of , 1992Angola (versions of , and 2010)), which in its article 85º makes clear that "Every citizen has the right to housing and quality of life "(2010 version).
Having concluded the appropriate legal framework in 2007 with the new Housing Development Law, it was also necessary to combine the political and economic contexts to face the problem of urban and residential informality.And the appropriate context arose with the pre-election period of the 2008 presidential elections and the soaring oil price between 2005 and 2008.
As an electoral promise of the party in government (MPLA) came the proposal of the "Project for a million houses" recognizing the shortage of affordable housing for the majority of the population derived from the demographic and social pressure that experienced by the country's main urban centers (Pitcher and Moorman 2015;Cardoso2016).
With the election of the new Government, this proposal was formalized in the National Urbanism and Housing Program 2009-2012(PNUH, 2009-2012).From the proposed construction of one million houses, and due in part to the global financial crisis that arose in 2008 and the drop in the price of oil, only 115,000 houses would be the direct responsibility of the Government.120,000 houses would be built by the private sector, 80,000 by cooperatives and the remaining 685,000 by means of self-construction processes.
In Luanda, as in other Angolan cities, the process of construction of these new dwellings took place in new housing poles as determined by the Housing Development Law, and the centralities of Kilamba-Kiaxi, Zango, or Cacuaco are very good examples of that initiative (Buire 2014;Rodrigues and Frias 2016; Cardoso 2016).

PDGCSR -Master plan for Cazenga, Sambizanga, and Rangel
The "Plano Director Geral de Cazenga, Sambizanga e Rangel" (Master Plan for Cazenga, Sambizanga, and Rangel) aims to provide formal housing with infrastructure and public services to about 3 million residents.The drawing up of the detailed urban development plans is the responsibility of the Technical Office for the Urban Redevelopment of Cazenga e Sambizanga (GTRUCS 2012).In short, the plan identifies "compromised areas" and areas "for urban regeneration," which make up the bulk of its work, and proposes to eradicate IUSs and replace them with new housing.The plan was elaborated on the assumption that part of the area would be allocated to "social housing" to rehouse the current residents.

Development workshop Angola
The work of the Development Workshop Angola, the first NGO to operate in the country (it began in 1981), is particularly noteworthy.Although they do not deal directly with housing, they manage a number of programmes aiming at providing urban services and support to residents of IUSs.
In 1999, DWA joined three other NGOs in a programme, funded by the UK Department for International Development (DFID), to combat poverty in the province of Luanda (LUPP -Luanda Urban Poverty Programme).DWA has implemented projects that including the provision of basic services: water supply, private and public sanitation, waste collection, and community nurseries; in finance: micro-credit, savings accounts, consumer cooperatives, and business development services (BDS); in civic participation: community organisation and participative planning at the municipal and communal levels; in research: studies based on surveys, studies using GIS, and scientific publications (Cain, Daly, and Robson 2002;Cain 2007).

Istanbul, Turkey
The modern history of Istanbul is marked by the rapid growth of its population, housed, in large part, in illegal housing.The gecekondus can be considered as IUSs because they either were (a) built on public land belonging to the treasury department; (b) built on the private property of third parties; or (c) built without building and land occupancy permits (Baharoglu and Leitmann 1998).Baharoglu (1996) shows how certain political and economic events, either with external (such as the oil crisis of 1970) or internal causes, affected the real estate marketespecially for small investorsmaking it swing between formality and informality, and blurring the respective boundaries.
From its origins as a technical term, gecekondu evolved, in colloquial language, to come to mean a specific typology of self-built house and settlement, emerging during the industrialisation and rural migration period between 1945 and 1985."Gece" means "night" and "kondu" means "to settle," resulting in "settling at night" (Esen 2009;Eroglu-Hawksworth 2017).The first waves of immigrants built their own homes on illegally occupied landliterally overnight, with the help of family and countrymen (Baharoglu 1996).The term has evolved to include other informal settlements and building typologies.Its use denotes a prevailing spontaneous action during this first wave of mass migration, providing housing while conventional processes or government initiatives failed (Esen 2009).The houses were built without the usual infrastructure (water supply, sewage, roads, electricity, telephone, drainage, waste collection, transportation . ..) and the residents received lower quality services, informally or at higher prices (Baharoglu and Leitmann 1998) and organised communally and in networks for the distribution of goods and services (Esen 2009;Eroglu-Hawksworth 2017).
After several waves of amnesties and with the gradual installation of infrastructures by the government in the gecekondus, these IUSs were progressively consolidated and integrated into the city.Figure 4 The study of the interventions in Istanbul focused exclusively on the work of the Housing Development Administration (TOKI) -an agency under the supervision of the presidency.It is safe to say that all interventions in IUSs result directly or indirectly from its operations.The interventions studied were grouped according to the legal basis used for themwhich can be considered analogous to a programmeand for each group some paradigmatic neighbourhood interventions (Güven 2017) were characterised: Sulukule and Tarlabasi in the first group and Tepeüstü, Ayazma, and Basıbüyük in the second, as described below.

"Urban renewal" and "Preservation of historical and cultural property"
The interventions in the neighbourhoods of Sulukule and Tarlabasi were mainly based on the application of Law 5366, which was passed in 2005, and gives TOKI and municipalities the power to carry out renovation projects, not only in areas considered run down or degraded but also in historic urban sites, as is the case for these two neighbourhoods.The most important section of this law establishes the right to execute "urgent expropriations," an approach that until then had only been used in cases of natural disasters or for national defense purposes (Turkun 2015).This right, designed to protect degraded historical and cultural heritage through renovation and reutilisation, has been used as a form of pressure in early negotiations to ensure the cooperation of property owners (AGFE, 2009).
The intervention consisted basically of the eviction of residents and partial eradication of the IUSs (in the case of Tarlabasi), or total eradication (in the case of Sulukule), and the subsequent construction of new housing that is, normally, beyond the means of the displaced population."Urban renewal" and "threat of natural disasters" interventions in the districts of Tepeüstü, Ayazma, and Basıbüyük were based on Law 5393, which was also passed in 2005 and allowed for the classification of "urban renewal" areas in order to "take measures against the risk of earthquakes and to protect the historical and cultural heritage." In the specific cases of the above districts, as they were peripheral neighbourhoods of reduced real estate value, the argument used was that of safety.This argument was to be further strengthened by Law 5998, which was passed in 2010 and defined obstacles to the defence in the court of the rights of residents, and Law 6306 (the law on the classification of disaster risk areas), which followed in 2011 and gave the new Ministry of Urbanization and Environment, along with the Housing Development Administration (TOKI), full authority in decisions on urban renewal.The government was thus given a carte blanche to implement, through TOKI, renovation projects throughout the country, using the "risk" argument.
This made it impossible to halt renovation projects in the courts (Turkun 2015).The owners of property in "risk areas" found themselves forced to sell the land to the city or demolish their homes at their own cost (Cavusoglu, Strutz, Bekmen, & Akça, 2014).These interventions resulted in the removal of the poorest population groups from the areas of renewal.The neighbourhoods had complex ownership structures and, although the de jure property rights remained intact after redevelopment, the de facto residents who did not have legal property titles were evicted and moved to other areas (Turk and Altes 2014).

Results and discussion
In this section, the characteristics of the interventions in each of case studies are analysed and what distinguishes them is highlighted.The categorisation system proposed previously will be used for this purpose.Figure 5 presents a summary of the results.
Considering the first level of the developed system, the cases studied will be grouped by interventional dimension, in accordance with the research focus on direct interventions in existing IUSs.There are two exceptions to this: (1) the "Novas Centralidades" in Luanda, where new housing is built with the aim of alleviating the housing deficit, and does not serve the purpose of removing residents from specific IUSs; and (2) the case of the "Programa de Requalificação de Cortiços" because it is a housing redevelopment programme implemented via the imposition of legal obligations on the owners, which can also be considered a market regulation initiative.In the interventional dimension, under the Ex-situ Rehousing category, i.e. in the second level of the system, one group stands out, made up of the TOKI interventions in Istanbul (urban renewal) and the "Novas Centralidades" in Luanda, both of which are aimed at eradicating existing IUSs and relocating the residents in new housing in other areas of the cities (almost always on the periphery).
A second group worthy of highlight is made up of the "Programa de Urbanização e Regularização de Favelas," the "Programa Mananciais" and the "Renova SP," which are somewhere between Redevelopment or Upgrading and In-situ Rehousing.These programmes are based on keeping in the residents where they are, placing the emphasis on the redevelopment of the urban space (infrastructure, accesses, and facilities) as well as on land use regulation.However, in almost all interventions there is the need to evict some people in order to contain slopes, protect watercourses, etc.In those cases, residents are relocated to housing built within the boundaries of the IUS that is the object of intervention or, if that is not possible, in the immediate vicinity.
In addition to these two groups, there are other cases that fall into distinct categories: (i) the "Programa de Requalificação de Cortiços," whilst it can be classified as a market regulation initiative, as described above, is essentially a Housing Upgrading programme aimed at improving the health conditions of housing without the eviction of residents; (ii) the "Master Plan for Cazenga, Sambizanga and Rangel" (PDGCSR), which calls for the total eradication of the IUSs within the plan boundaries, but provides for the resettlement of the population in social housing to be built in the same area, and therefore can be classified as Global or Total In-situ Rehousing; (iii) the various actions of the Development Workshop Angola, which are diverse in nature but can, in general, be classified as Urban Redevelopmentas in the case of the installation of public fountainsor as Social and Economic Assistance, as in the case of micro-credit provision.
In general, it is observed that intervention in IUSs is almost always framed in the context of housing policies.However, whilst it is understood that assistance to residents of IUSs depends on sectoral policies, the study also shows that housing policies focus too much on the housing itself and may not always be in line with the sentiments of the resident population.In such cases, these policies may be counterproductive to attain the main objective, which is to improve the quality of life of residents (if that really is the objective).

Conclusions
The analysis of the case studies and the programs and strategies directed to these urban areas benefited through the use of our proposed IUS approaches categorization system.Two large groups stand out as unique from the categorization regarding types of intervention: 1) the intervention of SEHAB in São Paulo, and 2) the "Novas Centralidades" program and the TOKI interventions in Luanda and Istanbul, respectively.
It was noted that the work of SEHAB reflects the principles expressed in the Plano Municipal de Habitação regarding minimum displacement of inhabitants and emphasis on land regulation and urban qualification.To the contrary, in both Istanbul and in Luanda, the option was to dislodge and displace the population, which may suggest that the choice of this strategy depends not so much on the technical and financial conditions to ensure successas they are very distinct from each otherbut perhaps more on the ideological assumptions and the political environment that motivate this choice.
A weak institutional framework, when it comes to resisting the influences of economic interests (domestic or foreign), might be prone to initiatives that feed socio-spatial segregation and the eradication of IUS.Citizen involvement seems important to be able to create and apply the planning instruments that embody conditions of inclusion and social justice (as in the case of the Brazilian examples of IPTU, Outorga Onerosa, ZEIS, among others).
On the other hand, the adequacy of the strategies of prevention/intervention in IUS depends on the context and the economic and demographical dynamics.If the expected growth of IUS is high then the strategies should put emphasis on tackling inequalities while, at the same time, accommodating the IUS growth through realistic planning, that minimizes the negative aspects of informality and facilitates future interventions and the progressive improvement of these areas.If stabilization or reduction of the factors that lead to the creation of IUS is expected, it would be more sensible to plan with emphasis on the transformation of existingIUSorevenoneradicatingthem,iftherights and freedom of choice of the residents can be protected, and there is no segregation nor discrimination by the government.
Quality of life is influenced by several factors, and each person attributes different priorities.The importance of housing is not transversal in this equation.Nor can this concern be assigned to a whole class, as if it was a single entity.Consequently, a policy that imposes a change in order to improve the quality of life runs the risk of spending resources to solve a problempoor housingand creating a greater onesegregationthus becoming not only ineffective but counterproductive.
If it is true that in the course of this research the advantages of not relocating people stood out, it should be noted that the issue in question here is not so much that of looking at these intervention strategies as the only valid solutionsas the balance of pros and cons depends on the context.What is argued here is the possibility of looking at interventions in IUS as an opportunity for the governments to counter the socio-spatial segregation, and for ensuring the fundamental right to housing, but on the wider context of guaranteeing the right to full fruition of the City and full Citizenship.
The interventions in IUS, because they are typically state-led, reveal an enormous instability and uncertainty in their implementation, both in the form of programmes and actions and in their continuity.The main reason is the financial instability in some of these countries, which are highly dependent on natural resources or the supply of cheap labour.In both casespolitical and/or financial instabilityit leads to the inconsequence of interventions in IUS and, at the same time, the formation of the idea in communities of eternally incomplete/unfinished processes.
central location, close to employment opportunities and utilities, made them desirable areas to live in (DWA, D. W. A., & CEHS, C. for E. & H. S 2005).

Figure 5 .
Figure 5. Overview of case study categorisation.

Table 1 .
Types of approaches to IUSs.