A Theoretical Model for the Implementation of Social Sustainability in the Synthesis of Tourism, Disability Studies, and Special-Needs Education

: This paper deals with the study of disability science, special-needs education, and psychology of special needs in the context of tourism. It is rare to find a link between these research areas in the literature. Accessible tourism has attracted widespread research interest in recent dec-ades, but the number of studies focusing on tourism in the fields of disability studies, special-needs education, and psychology of special needs is very limited. Although there is growing literature on accessible tourism and related topics, the development of the research field is uneven, as most research focuses on specific subareas without considering the context of the whole spectrum of the topic. The interdisciplinary research aims to explore the situations of people with disabilities in terms of their participation in tourism. The data collected will be used to analyse the supply and demand side of tourism from a specific perspective. Among the external environmental impacts, the issue of sustainability will be highlighted, which will be addressed from a societal perspective by analysing the sustainable development goals (SDGs) related to the topic. The study includes a theoretical analysis through the processing of secondary sources, linking the fields of tourism, disability studies, special-needs education, and psychology of special needs, with the potential of social sustainability and the achievement of the SDGs. The paper presents a new model that illustrates the potential for achieving social sustainability from the supply and demand side of tourism. The model can be valuable, not only for those who want to extend their research into this new field, but also for tourism policy makers. The study also identifies key research questions on this topic that merit theoretical and empirical exploration in the future.


Introduction
Nowadays, sustainability is one of the most important areas of tourism research. Within the field of sustainable tourism, social sustainability, and responsibility are important research areas, alongside environmental and economic sustainability. Social sustainability has opened up new areas and concepts for researchers. The most frequently mentioned concept is sustainable tourism. It is based on the principle of sustainable development and seeks to reflect its application in tourism. Sustainable tourism addresses the issue of sustainability in the economic, environmental, and sociocultural spheres in a comprehensive way [1,2]. Responsible tourism [3] deals with the issue of social responsibility where sustainability has been defined as an end and responsibility as the means [4]. Several researchers emphasise ethical issues in justice tourism [5,6], and the ethical tourism [7] approach. They emphasise the importance of creating equal opportunities, taking into account human and social aspects.
The participation of people with disabilities in tourism is also a much studied area. This is where the concept of inclusive tourism comes into play. It explores the ways of involving people in the sector who are typically marginalised or excluded from tourism [8]. Accessible tourism puts into practice the possibility of creating equal opportunities [9]. Barrier-free tourism is for people with all abilities on an equal basis, making tourism services accessible and enjoyable to all, addressing the needs of those with physical, intellectual, and psychosocial disabilities as well [10].
In our study, we investigate the relationship between inclusive tourism and social sustainability by outlining a new model that illustrates the interrelationships and influencing factors.
The novelty of the research and the developed model explores a less researched area of tourism by synthesising the results of several disciplines: tourism, disability studies, as well as special-needs education. The aim of this niche research is to explore the situation of people with disabilities in terms of their participation in tourism. The data collected will be used to analyse the supply-and-demand side of tourism from a specific perspective. Among the external environmental impacts, the issue of sustainability will be highlighted, which will be addressed from a societal perspective by analysing the sustainable development goals (SDGs) related to the topic [11].
The study presents a new model by exploring secondary sources and using the results obtained from them. On the one hand, the secondary research is concerned with tourism, with a special emphasis on sustainability and the SDGs related to it. On the other hand, it explores the fields of disability studies, special-needs education, and the psychology of special needs, exploring the links between social sustainability, acceptance, and tourism.
Following the literature review, the research aims to develop a new model in which the relationships and the elements of each part are presented in detail. Then the specific aspects that support the participation of people with disabilities in tourism will be emphasised. In particular, the research will focus on the external environmental factors that affect the functioning of the model and influence its effective implementation. The paper presents the elements that point towards social sustainability but are not able to contribute to its achievement.
The importance of the study is to identify the specific factors that are necessary to meet the needs of the target group as fully as possible, thereby promoting their participation in tourism.
The aim of the study is to provide the theoretical background for empirical research that will enable an international study to be carried out in the future.

Sustainability and the Sustainable Development Goals
According to the most widely accepted definition of sustainability, sustainable development "meets the needs of the present without compromising the ability of future generations to meet their own needs" [12]. Perhaps the most frequently cited 'definition' of sustainability is the one given in the 1987 UN Brundtland Report [13], which gives prominence to the social dimension. At the request of the UN Secretary-General, the World Commission on Environment and Development was established in 1983 under the leadership of Gro Harlem Brundtland, then Prime Minister of the Kingdom of Norway. The work of the commission resulted in the 1987 report, most often cited as the Brundtland Report. The document argues that in a finite world, infinite growth is unthinkable and that the viability of the existing economic model is, therefore, subject to physical and ecological limits. The idea of social justice, that all inhabitants of the Earth have the right to live in conditions of human dignity, is given considerable emphasis [13] as well.
A very common list talks about three pillars of sustainability: economic, social, and environmental ( Figure 1). When the term "triple bottom line" (TBL) was first coined, it was widely argued that businesses should measure social, environmental, and financial performance [14], i.e., that it is not a single financial indicator that matters, but all three factors together. TBL is also reflected in sustainable development strategies for tourism. Tourism organisations use this model to try to incorporate socially and environmentally sustainable development into their strategies in addition to economic sustainability [15].
One of the main objectives and activities of the United Nations since its creation has been to strengthen international development cooperation. As stated in the UN Charter (1945), the main objective of the organisation is to promote conditions for economic and social progress and development.
In September 2015, the 193 member states of the United Nations adopted a new integrated sustainable progress and development framework, the 2030 Agenda (officially known as Transforming our World: The 2030 Agenda for Sustainable Development), which sets out a vision for ending poverty, tackling inequality, and protecting the Earth's environment [16]. One of the main features of the new framework is that, unlike previous development cooperation plans, it adopts a broader approach to sustainable development programmes, setting goals and targets for each country and region. At the heart of the agenda are the sustainable development goals (SDGs), which apply to all nations, "leaving no one behind" in the achievements.
In total, the agenda contains 17 goals, 169 subgoals, and more than 230 indicators, which aim to measure and monitor multiple aspects of sustainable development up to 2030.

Disability-Related Sustainable Development Goals
The sustainable development goals include those related to persons with disabilities. Disability is referred to in various parts of the SDGs, for example, in the sections on education, growth and employment, inequality, accessibility of settlements, and data collection and monitoring of the SDGs.
Goal 4 focuses on access to inclusive, quality education and lifelong learning opportunities. It focuses on closing gender gaps in education and ensuring equal access to all levels of education and training for disadvantaged people, including people with disabilities.
Goal 8 is to achieve inclusive and sustainable economic growth, full and productive employment, and decent work for all. The goal is full and productive employment, decent work for all women and men, including people with disabilities, and equal pay for work of equal value.
Goal 10 is closely linked to this, which seeks to reduce inequalities within and between countries by strengthening and promoting the social, economic, and political inclusion of all, including people with disabilities.
Goal 11 aims to make cities and towns inclusive, safe, and sustainable. To achieve this goal, the aim is to provide access to safe, affordable, and sustainable transport systems for all, to improve road safety and public transport, with particular attention to the needs of vulnerable people, such as people with disabilities. Goal 17 emphasises that data collection and the monitoring and accountability of the SDGs are of key importance.

Tourism-Related Sustainable Development Goals
Tourism was the world's third largest export earning category (2019), accounting for 10% of the world's GDP and 28% of the services exported, and provided one in ten jobs worldwide [17]. Tourism can contribute directly or indirectly to all the SDGs [18]. In particular, it is included in Goals 8, 12, and 14, which relate to inclusive and sustainable economic growth, sustainable consumption, and production, and sustainable use of oceans and marine resources.

Disability and Sustainable Tourism
The link between disability and tourism is explicitly observed in two areas of the SDGs. Goal 8 concentrates on decent work, while Goal 12 focuses on responsible consumption and production. In addition, Goal 11 regarding sustainable cities is also crucial, as cities and metropolitan areas are important tourist destinations. The following objectives can contribute to social sustainability:

•
Job creation in the tourism sector can increase employment opportunities for people with disabilities; • Tools for monitoring sustainable tourism can help to measure the impact on people with disabilities, both as tourism workers and as tourists; • Cities are important tourist destinations for people with disabilities as they generally offer more accessible tourism opportunities than rural tourism [19].
In the relationship between tourism and disabilities, researchers very often approach the issue from the consumer side only, i.e., by looking at accessibility for tourists with different abilities and the inclusiveness of tourism. Several studies have examined issues related to physical ability, cognitive ability, and age [20,21]. In these studies, inclusive tourism is presented as a possible solution to accessibility [22,23] and as a way of meeting different special needs, thus acknowledging the rights to tourism [24]. In addition to consumers, Scheyvens & Biddulph also consider the opportunity on the service provider side [25], thus examining the role of persons with disabilities as owners, entrepreneurs, and employees. It can be argued that inclusive tourism aims to remove barriers for persons with disabilities [26] as the participation of persons with disabilities in tourism allows them to be integrated into society [27].
This research examines inclusive tourism from the perspective of social sustainability and addresses the opportunities for the inclusion of persons with disabilities on both the demand and supply side.

The Disabled Person
According to the World Health Organisation (WHO), around 15% of the world's population (1 billion people) have a disability [28]. According to 2020 data, in the United States of America, 26% of the adult population (61 million people) have a disability [29]. In the European Union, more than third of the population reported physical or sensory limitations, according to a 2019 figure. Of people aged 15 and over, 37% suffer from moderate or severe physical or sensory impairments [30]. It is difficult to give a comprehensive picture of the number of people with disabilities in the world based solely on statistical data, as analyses use different data, different approaches, and different definitions, and therefore, there is no accurate figure for the number of people with disabilities. The numbers vary considerably from research to research. One of the reasons for this is that it is difficult to find the borderline or the point at which the lack of development of abilities can be classified as an extreme, i.e., a "disability".
In 2001, the World Health Organization published a classification, International Functioning, Disability and Health (ICF), which assesses the functional capacity of the human body [18]. Its main aim is to provide a common language for classifying health status across disciplines and sectors. In describing an individual's condition, it defines functional capacity, i.e., it identifies bodily function, activity, and participation. It defines disability as the sum of physical impairment, activity disability, and participation limitation. In addition to physical impairment, the degree of activity disability, and the severity of social participation and life limitation in performing activities are also determinants [31].
However, regardless of the severity of the impairment, people with disabilities are autonomous, self-determining individuals who, as equal members of society, are entitled to the same access to social resources, education, training, and the labour market, new technologies, and consumer goods and services as their able-bodied counterparts [32].

Disability Studies
The emergence of disability studies began in the 1970s as a critical social science and social movement. "Disability is a sociocultural, personal, embodied physiological or psychological phenomenon. Disability studies prompt us to think about how we make sense of our bodies, minds, relationships, communities, and economic priorities in normal-or, if you like, normative-terms" [33].
The study pf disabilities is an interdisciplinary, transdisciplinary academic field that organizes the subject based on the knowledge and experiences of people with disabilities into a holistic, self-reconstructing network [34].
Disability studies is concerned with the discussion of concepts that promote the wellbeing of individuals in society. Among these, self-advocacy and supported decision-making are highlighted based on the relevance of the research. Persons with disabilities have the right to self-advocacy under the Convention on the Rights of Persons with Disabilities (CRPD) [35]. Empowerment is a process, whereby a person with a disability takes control of their own life and takes responsibility for their actions and choices. The internal factor in this process is when the individual is confident in their ability to make decisions, act, and solve problems. The external factor is that the person with a disability actually performs tasks, solves problematic situations, is able to apply the knowledge they learned in practice, and can learn new content [36]. Supported decision making, modelled on the human rights model, has become the subject of research under the CRPD. It should be incorporated into the legislation of the member states. It is difficult to implement, as it requires the social acceptance and inclusion of the two most affected disability groupspeople with intellectual disabilities and people with psychosocial disabilities-by reducing negative stereotypes and making them known [37].

Special-Needs Education and the Psychology of Special Needs
Psychology of special needs is concerned with the exploration and research of psychological phenomena related to disabilities and the application of the results of this research to practical work. It is an interdisciplinary field that has the closest links with psychology and special-needs education. It is the applied branch of psychology which "deals with the understanding of the personality of people (children and adults) with various impairments, disabilities and handicaps, with the exploration of the difficult socialisation path and the different cognitive development, with the psychological assistance of the conditions for their education, development, therapy and social integration" [38] (p. 616). It is a field of therapeutic pedagogy in the broader sense, which is a fruitful collaboration through shared goals, tasks, and theoretical foundations. Both disciplines take the axiom that 'we work with people, children, young people and adults, who, despite their various impairments, disabilities and handicaps, are human beings' [39] (p. 397) as a fundamental point. This approach also determines the use of language; we do not talk about the disabled or blind, but about a disabled person, a blind boy, or people with disabilities.
The role of special education in the present study is not to cure, but to provide the helping attitude and methodological knowledge that is involved in supporting the disabled person from childhood to the end of adulthood, from less severe injury to very severe disability, and from minor needs to significant limitations. "In a broader sense, special needs education is a complex human science and, through its sub-disciplines, it is intended to examine all the possible aspects and issues-anthropological, pedagogical, psychological, sociological, pathophysiological, etc.-associated with the phenomenon of disability, and can therefore be described and work as a multidisciplinary structure" [40] (p. 81).
In the study, disability is discussed in terms of the ICF definition, and it deals with persons with disabilities in terms of the discussed views of disability science, special needs education, and psychology of special needs.

Materials and Methods
By reviewing the literature and findings from various disciplines, a new model (Figure 2) was developed that takes social sustainability into account. The four major elements of the model are demand, supply, specific needs, and external environmental impacts.
Demand is represented by people with disabilities as potential tourists, whose participation depends on discretionary income, motivation, available leisure time, and degree of socialisation.
The tourism offer can be interpreted at three levels. On the one hand, the model shows tourism businesses that can meet the needs of consumers and, in the spirit of social sustainability, must be prepared to welcome people with disabilities. On the other hand, at the macro level, destinations should also have a strategy that takes into account the specific needs of this target group. The third level is the tourism sector, where the focus is on promoting cross-sectoral cooperation. By linking tourism and actors from other functional sectors (e.g., mobility providers), a socially sustainable offer can be developed [41].
The model also presents certain specific needs on the supply and demand side as important factors to be taken into account. These include specific infrastructure needs, additional, complementary services, adequate support staff, and supporting tools and technologies.
Changes in the external environment also have an impact on the functioning of the model, thus these have been highlighted as well. The social environment, as an external environmental factor that facilitates the acceptance of people with disabilities, includes the necessary sensitisation and education activities. Sustainability, as one of the most important trends and central themes of our time, is also included as an external environmental influence. Of the pillars of sustainability, social sustainability is the one to which the participation of people with disabilities in tourism is most closely linked. In examining the model, the SDGs related to this topic are examined first and foremost. The effects of the economic environment on both the demand and supply side can be decisive. The political and legal environment that provides the legal backdrop and governmental support for the issue under consideration will also be examined. A particular focus is on digitalisation, which today is bringing huge development and change in all areas of the economy and society.

Discussion
The new model developed in the previous section is presented in four main aspects. First, the necessary conditions to enable people with disabilities to participate in tourism are presented. Then, the elements of the supply side are examined. At last, the specific needs at the intersection of the supply and demand sides are described. It is also important to highlight the impact of external environmental factors on the functioning of the model.

Demand
Demand is a fundamental part of the tourism model [42,43], which defines the factors that are preconditions for consumers' participation in tourism.
The analysis is conducted with the view that tourism can contribute to a more successful social inclusion of people with disabilities by providing information on how tourism service providers can increasingly integrate people with disabilities into their customer base. Due to their impairments, disabled people are inherently unable to access tourism opportunities, but this is further complicated by barriers at the individual, social, and societal levels in addition to physical barriers. It is assumed that tourism has the potential for 'rehabilitation', which helps the disabled person to develop as an individual, to improve their quality of life, and to promote social acceptance through social interactions and communication. In the following, the demand-side factors that are necessary from the consumer side for the potential tourist to realize his/her trip-discretionary income, motivation, leisure, and socialization-will be examined.

Discretionary Income
Discretionary income is the part of income used freely. The potential tourist chooses to travel based on his/her discretionary income. The range of services is wide, with a choice of services based on price levels. The research would like to find answers to the question of on which areas of tourism (travel, theatre, hobbies, wellness) people with disabilities will spend their income or discretionary income.

Motivation
Motivation is a psychological concept. It is determined by the psychological functions or psychological characteristics of the individual. In tourism, it is basically thought of as a motive for travelling. Research usually highlights physiological, sociocultural, and existential motives. These are based on the fact that persons are individuals who strive to maintain the biological balance of their body, to communicate well with their environment, to be active members of society, and to create existential opportunities through their work. The motives for travelling also have some inhibiting factors. Disability is also a factor that can make travelling impossible or difficult or be an obstacle of it. For people with disabilities, the achievement of physiological optimum may not be the starting point of motivation due to injuries, but tourism services can help to achieve a near optimal level. Health tourism can be an example of it. Furthermore, the communication difficulties of disabled persons can be a barrier to the existence of sociocultural motives in travel arrangements. Intensive development, maintenance, and nurturing of interactions provide an opportunity for this motivation. For people with disabilities, it can be of great help to use and learn as much as possible about barrier-free, easy-to-understand communication (e.g., sign language) to build interactions. Existential motivations are more narrowly expressed and are typical of people who travel a lot for work. However, as it is also a good opportunity to build a career (attending conferences, participating in sports competitions, touring, professional study trips), it is also an important motive for people with disabilities, in addition to helping with their specific needs.

Leisure
The trend that people have more and more leisure time is increasing. This general idea makes sense when the term leisure is defined. For every individual, leisure is a desirable component of life, but psychological approaches suggest that it is much harder to enjoy than work. It is mainly because to achieve quality experiences or a high quality of leisure time, one needs to invest "initial attentional capital" [43]. Leisure time makes sense in the context of work. Tourism provides the opportunity for individuals to spend the time they have left over from work in a rational, organized, and experiential way. The leisure industry creates a competitive opportunity to reach consumers.

Socialisation
Socialisation is the process of learning the specific rules of an environment, adapting to its customs, and integrating into society. The environment that socialises an individual to travel determines their travel habits. The primary socialising environment is the family. It plays a key role in enabling children to spend their leisure time as adults. If the parents travel, go on excursions, and attend cultural events with the disabled child, they will become an active tourist as an adult. Secondary (institutions) and tertiary (peer groups) socialisation environments have a similar effect on becoming a potential tourist.

Supply
According to the World Health Organisation (WHO), a significant proportion of the world's population has a disability [28]. A central part of a responsible and sustainable tourism policy should be to ensure that tourism facilities, products, and services are accessible to all. Accessibility is not just about human rights. It is also a business opportunity for destinations, companies, and the entire tourism sector to accommodate all visitors and thus increase their revenues.
As Figure 3 shows, the needs of people with disabilities must be taken into account at all levels of tourism supply. Accessibility of tourism also means that all people, regardless of whether they have a disability, can participate in it, including people with mobility, hearing, vision, cognitive, intellectual, and psychosocial disabilities, as well as people with temporary disabilities [44]. When considering the specific supply elements, the following factors should be taken into account, as recommended by the WTO [45]:

•
The tourism destination management organisation must set out its measures for the reception of disabled people in a strategy document, which includes the objectives and measures for accessible and available tourism. This can also help to ensure accurate and credible communication of accessible services; • The destination may also consider accessibility in terms of the urban and architectural environment. Providing parking, sidewalks, spaces, corridors within buildings, ramps, lifts, and proper design of access to wash facilities for people with disabilities will help to promote accessibility in tourism. Alternative modes of communication and signs (sign language, Braille, easy-to-understand communication) will make the reception area and its services more accessible; • For tourism service providers, such as hotels, restaurants, and event venues, the provision of accessible rooms, customer services, and the accommodation of assistants (e.g., guide dogs) is essential. Special care should be taken to provide accessible design (wash facilities) and equipment (e.g., menus) for the halls. Accessible conference rooms, equipment (e.g., voice induction loop), and services are also important factors; • Provide accessibility, information materials, and equipment, as well as training for customer service staff for tourist attractions, cultural events, and shopping in natural or cultural settings.
Sustainable product development for tourism accessible to people with disabilities should be based on the core values of the destination and serve as a philosophy [46]. Collaboration between service providers [47] is also an important factor in the design of tourism products, services, and environments.

Specific Needs
After examining the demand and supply side, it is important to present the specific needs in tourism, which the supply side should to take into account. Several research deal with the specific services that appear in the tourism sector [48,49], but they are based on the study of a single disability [50] or present specific supply elements in a destination. Furthermore, a review of the studies shows that in the field of tourism and disability, the majority of the research concerns the needs of people with physical disability, although a smaller number of studies also relate to other disability groups (visually impaired, intellectual disabilities) [51]. Table 1 summarises some of the research published so far by disability group.

Physical disabilities
This study explores how people with disabilities are represented in tourism promotional materials, specifically tourism brochures from the American Southeast [52]. The results of the research provide a basis for developing a strategy to improve sports tourism for people with disabilities [53].
Visual impairment The study examines the participation of visually impaired people in tourism activities through content analysis [54].
The study examines the challenges faced by visually impaired people when travelling and the positive emotional well-being generated by the journey [55]. Hearing impairment The research explores the experiences of hearing-impaired people with regard to travel and tourism services and experiences using the interview method [56].

Preston, M. (2016)
The study examines the travel motives of hearing-impaired people using the pushand-pull model of travel [57].
The study examines how to meet the needs of people with autism for a joyful tourist holiday. It also presents strategic suggestions that can help the travel agency in planning a tourist trip for customers with autism [59].  Of course, meeting special needs is an additional task for service providers that may require major investments and upgrades, but the target group can be reached with minimal investment. In fact, good results can be achieved by adapting existing infrastructure elements or by expanding communication tools and improving their content to meet special needs, and significant financial investment is not always necessary. As specific needs vary according to the type of disability, information on them can be collected in the future through specific research. The basic specific needs that can be identified for all types of disability in general are specific infrastructure, range of complementary services, support staff, accessible communication, and assistive technology.

Social Environment
Social responsibility must be taken into account by tourism enterprises. Several international conventions have been drawn to sensitise the social environment. Three of them, which are essentially designed to support efforts to promote a nondiscriminatory social environment, are highlighted in the research.
In 1993, the UN document "The Standard Rules on the Equalization of Opportunities for Persons with Disabilities" [62] identified social-awareness raising as one of the most important objectives. It was adopted with the aim that member states should take steps to increase society's awareness of the rights, capacities, needs, and potential contributions of persons with disabilities to the functioning of society. For example, information that is easily understandable to all members of society should be easily accessible to people with disabilities as well. In addition, member states should launch campaigns to deliver the message that disabled people are citizens with the same rights and responsibilities as others but who need support to reduce the disadvantages of their disability.
The UN Convention on the Rights of Persons with Disabilities [35] ensures that member states include in their laws that people with disabilities have the same rights as others. Article 30 § deals with participation in cultural life, recreation, leisure, and sporting activities. Countries recognise that persons with disabilities have the right to participate in leisure activities. State leaders should work to ensure that this is achieved without barriers.
The Madrid Declaration adopted in 2002 by European Union members, is concerned with disability issues and provides member states with an action plan to create a society free from discrimination. The basis for the implementation of this agenda is provided by legal measures, attitudinal changes, services to promote independent living, support for families and women with disabilities, as well as creating employment. This document also underlines the responsibility of member states to assess the legal framework in their countries for the implementation of these measures. It emphasises the importance of the joint efforts of local authorities, disabled people's organisations, employers, trade unions, the media, the school system, and disabled people themselves to achieve this goal [32].

Economic Environment
The driving force behind the functioning of the market-and the model-is the economic environment, where the economic policies of enterprises are at the microeconomic level and those of public organisations are at the macroeconomic level. The functioning of these also influences the feasibility of the model and the sustainability measures [43]. In addition to the social aspect of sustainable tourism development, economic sustainability, which aims to create value, plays a crucial role in the product development of inclusive tourism [46]. When considering the economic impact, it is worth looking at the results achieved by inclusive tourism.
In 2014, the European Union published [63] the largest and most comprehensive study on the economic impact of inclusive tourism and travel patterns, with the following findings for 2012: • Accessible tourism generated €786 billion, including indirect and induced contributions; • Accessible tourism generated a total economic contribution of €394 billion in terms of gross domestic product; • A total of 8,711,000 people were employed in the region to generate this economic output; • On average, 2.2 escorts travel with disabled persons; • Persons with disabilities and their companions contributed a total of €1,109,740 million to the gross domestic product.
Better accessibility could increase the total contribution by up to 40 percent and employ up to 12 million people. Available estimates suggest that the demand for accessible tourism is steadily increasing in the European Union, with a growth rate of 0.12 percent for people with disabilities [63].

Sustainability
Sustainability and the adoption of the sustainable development goals (SDGs) can help to promote social sustainability by the inclusion of people with disabilities in tourism. To achieve the goals, the tourism sector should promote opportunities for people with disabilities: • Through employment and entrepreneurship within the tourism sector; • As consumers and users of tourism products and services.
The main areas where intervention is needed to achieve the SDGs in relation to sustainable, inclusive tourism are: • Improving accessibility of public transport, spaces, and places for people with disabilities; • Promoting the participation of persons with disabilities as economic operators and consumers in tourism [19].

Digitalisation
Digitalisation, i.e., the use of digital technologies, is also gaining ground in tourism. In the new model, digitalisation mainly affects the supply side by making services more accessible. Digitalisation can facilitate sustainable product development, making tourism accessible to people with disabilities and thus, contributing to social sustainability [46]. Digitalisation is taking place in all areas of tourism, including tourism companies and destinations [64].

Political Environment
One of the most important external environmental factors is the political environment, as the government can intervene in the process on both the demand and supply side through ideology, legislation, and the institutional setup [43]. The political environment influences the model outlined above, primarily through regulation. Issues of economic well-being, social equity, ethical principles of justice, inclusion, and equity can only be addressed through mechanisms of public or sectoral governance (facilitation, regulation, monitoring, education and training, incentives, rewards, etc.) to achieve the SDGs [65]. For example, they can promote the participation of disabled people in tourism through discounts and other forms of assistance. On the supply side, political power can require infrastructure to meet specific needs and other support measures. Several researchers also use the term "ethic of care" [6]. The term refers to that part of ethics which may be institutionalised in the social or welfare sector of public activity, but which usually relies on voluntary arrangements between families, friends, and neighbours [66]. In the case of disadvantaged groups in particular, it is worth looking at the issues of fairness, equity, and justice [67]. In some research, the terms ethical tourism and justice tourism are also used alongside the term ethic of care [6]. Political actors have a key role to play in addressing and ceasing inequities and damages [68], which are also noticeable in the tourism sector. The issue of social sustainability and responsibility in tourism is highly dependent on the political environment. The model is supported if the objective of tourism policy is to achieve accessible and available tourism. The dominant role of the policy environment is visible from the fact that other environmental elements are highly dependent on it.

Legal Environment
Legislation ensures that the disadvantages of people with disabilities are mitigated, that they are given equal opportunities, and that society's attitudes are shaped. People with disabilities are equal members of society and can only enjoy the rights and opportunities that are available to all with continuing difficulties. The primary aim of the laws and regulations on the rights of people with disabilities and to ensure their equal opportunities is to reduce disadvantages by guaranteeing rights, to define the means of enforcing rights, and to regulate complex rehabilitation. All this is done in order to promote equal opportunities for people with disabilities, their independent living, and their active participation in social life.

Conclusions
In the study, a theoretical analysis was carried out using secondary sources, linking the fields of tourism, disability studies, special needs education and psychology of special needs with the potential for social sustainability and the achievement of the SDGs.
In the field of tourism research, we find analyses on travel by people with disabilities, but in these research, disability studies, special-needs education, and psychology of special needs are less relevant.
Using the results of the secondary research, a theoretical model was developed that illustrates the possibility of achieving social sustainability, both from the supply and demand side of tourism.
The demand is represented by people with disabilities as potential tourists in the model. The research addresses their specific needs with the help of knowledge from the field of disability studies and special education.
In examining the supply side, the research found that there are good practices that point towards social sustainability, but they are not able to facilitate its achievement. The analysis of the internal factors was complemented by the external environmental elements that influence the functioning of the model. Our research will be continued by analysing the situation and mapping the supply of the tourism market internationally. Subsequently, we will investigate the application of our theoretical model in practice through empirical research. The results of the theoretical research will enable further evidence-based studies. In line with the principles of social sustainability, we want to conduct our research in a participatory way using easy-tounderstand communication. Participatory research is based on the CRPD [35] principle of "nothing about us without us." It implies that a person with a disability is present in all parts of the empirical research. As a participatory researcher, they are present as a competent expert who has an independent, informed opinion on issues that affect their own life and the lives of their peers [69]. This approach also promotes social inclusion in academic work.
In the future, we plan to develop and present a practical implementation of the specific needs of social sustainability in relation to persons with disabilities (e.g., development of information brochures with accessible communication, satisfaction questionnaires prepared with a participative approach, and a list of suggestions for accessible infrastructure for all disability groups).