From Transportation Equity to Accessibility Capability: A New Framework to Guide Transportation Planning for Older People

Paradigm Shift from Mobility to Accessibility

Accessibility is not a new concept. The word was first used in the early twentieth century by real estate companies and urban planners to link land values and the ease with which places could be reached using a location's transportation services (Levine 2020). In a review work, Levine (2020) states that accessibility can have either a normative or a positive meaning, and these are interrelated rather than mutually exclusive. From a normative perspective, accessibility is a concept which guides transportation and land use policies, suggesting that the performance of transportation projects should be judged by the accessibility, rather than the mobility, they offer. While accessibility refers to the possibility of reaching destinations, mobility refers to the ease with which such movement is accomplished, especially by automobile in the U.S. context (Levine and Garb 2002). From a positive perspective, accessibility is a measurement that describes the spatial patterns of interactions between transportation and land use, and it is widely used to predict how such patterns produce social and economic outcomes (Geurs and van Wee 2004; Lucas, Di Ciommo and Dupont-Kieffer 2019; Levine 2020). In a seminal work, Hansen (1959) defines accessibility as “the intensity of the possibility of interaction”. He proposes accessibility as a measurement for the distribution of residential and employment activities across urban development. Wachs and Kumagai (1973) further argue that physical accessibility is overlooked as an indicator of quality of life and access to various economic and social opportunities.

In planning and transportation literature, accessibility is commonly used to measure the extent to which the interaction of transportation and land use enables people to access various economic and social opportunities (Geurs and van Wee 2004). This paper will not reiterate the numerous measurements of accessibility that have been elaborated in previous reviews (Geurs and van Wee 2004; Siddiq and Taylor 2021). The simplest and perhaps one of the most widely used in planning practice is the cumulative opportunity approach, which measures the number of jobs and other opportunities available within a time threshold by certain travel modes, for example, the number of jobs available within a 30-min ride by transit.

Accessibility measurements distinguish themselves from mobility-based measurements, which prioritize congestion relief and travel time savings. Mobility-based measurements are widely applied in cost-benefit analysis to evaluate transportation projects, with the result that projects offering strategies that save more time gain more support in transportation development practice (Berechman 2009; Martens and Di Ciommo 2017). However, this approach has many limitations which contribute to vehicle-dependence and associated social and environmental problems. First, this approach is naïve about travelers’ responses to time saving. Empirical evidence demonstrates that when driving becomes more convenient, drivers may drive more in their spare time and worsen congestion (Crane 2000; Metz 2008). Second, this approach tends to overlook the needs of those who do not drive for economic, health, or other reasons (Martens and Di Ciommo 2017). As a result, it reinforces travel difficulties for those who do not have vehicles (Zhao and Kockelman 2002). Several studies have suggested that, in the U.S., access to a vehicle is more important than the proximity of a residential location to job opportunities for a low-income job seeker, even for one living in the inner city (Shen 2000a; Hess 2005; Grengs 2010). Third, relying on this approach may deter compact development. Some studies have found that neighborhoods with higher density, more diverse land use, and greater walkability are not related to less vehicle travel (Crane 2000) or transportation costs (Smart and Klein 2018). A recent study further concludes that a lack of time saving should not be considered a failure of compact land development (Yan 2021).

The mobility-based approach puts the cart before the horse and compounds environmental pollution, congestion, and social inequity. As travel is a derived demand, transportation scholars such as Jonathan Levine, Joseph Grengs, and Louis Merlin (Grengs et al. 2010; Levine et al. 2012; Merlin, Levine and Grengs 2018; Levine, Grengs and Merlin 2019) argue that planning transportation systems should focus on getting people to destinations rather than on movement per se.

In the digital era, connectivity to various information and communication technologies (ICTs) redefines accessibility. Levine et al. (2012) define accessibility as a combination of three interrelated elements: (a) mobility, the ability to move around; (b) proximity, the physical distance between origins and destinations; and (c) connectivity, the delivery of goods or services to locations using ICTs. Few studies have incorporated ICTs into accessibility measurements, the exception being Shen's, in which he incorporates access to telecommuting into accessibility measurements, and finds that telecommuting plays a more critical role than the location of jobs in the digital era (Shen 1999). In another article, Shen concludes that, in the digital era, low-skilled job seekers who lack access to telecommuting and vehicles have more disadvantages in accessing jobs than their high-skilled counterparts (Shen 1998).

Though accessibility measurements incorporating ICTs have been uncommon until recently (Siddiq and Taylor 2021), the trip generation effects of ICTs have been widely explored. Current findings lean towards the suggestion that ICTs and online activities increase daily travel for all purposes (Wang and Law 2007; Le Vine, Latinopoulos and Polak 2014; Kroesen and Handy 2015); for commuting (Mokhtarian 1991; Zhu 2012); for shopping (Farag et al. 2007; Cao 2012; Ding and Lu 2017); and for social trips (Kenyon 2010; Delbosc and Mokhtarian 2018); though not all researchers agree with this (Shi et al. 2019; Ozbilen, Wang and Akar 2021). Some studies further state that ICTs may make a small number of people's residential locations more flexible due to the redefinition of location accessibility that comes with connectivity to ICTs (Mokhtarian 1991; Shen 2000b).

Understanding Accessibility from an Equity Perspective

Martens and his colleagues (Martens 2012, 2017; Martens, Golub and Robinson 2012) combine Rawls’ justice theory and Walzer's theory of distributive justice to define transport equity. Based on Walzer's (Walzer 2010) sphere theory, they first argue that transportation is a unique social good and requires unique distributive principles. The fair distribution of accessibility resources requires both a market sphere and another redistribution sphere. Based on Rawls’ justice theory (Rawls 1999), Martens and his colleagues further argue that a fair distribution of accessibility needs a free market to satisfy diverse choices and public interventions to subsidize the disadvantaged.

Scholars have used the “sufficientarinism” theory to argue that distribution of accessibility should be considered equitable when everyone can get a minimum and acceptable level, a level that ensures basic social inclusion and participation (Lucas, van Wee and Maat 2016; Martens 2017). This has led to an emphasis on the importance of finding a “sufficiency” threshold (Karner et al. 2020; Martens, Singer and Cohen-Zada 2022; Ryan and Martens 2023). Based on the concept of environmental justice, Karner et al. (2020) have identified a spectrum of approaches, from state-led to community-led strategies, to identify “sufficiency” and achieve equity goals. However, sufficiency levels are sensitive to places and population groups. Several studies have suggested that when transit accessibility is sufficiently high, those with and without vehicles do not have significant differences in earnings (Smart and Klein 2020), or in activity participation (Allen and Farber 2020). However, defining sufficiency levels in practice involves contention among stakeholders and it is difficult to reach a consensus (Karner et al. 2017; Ryan and Martens 2023).

The capability approach provides a theoretical foundation for defining sufficiency in relation to accessibility. This approach (Sen 1981, 2011; Nussbaum and Sen 1993; Nussbaum 2011, 2013) looks at individual abilities in relation to disparities in people's freedom of choice in distributive outcomes. Nahmias-Biran, Martens and Shiftan (2017) argue that though the capability approach has not been explicitly applied in transportation research and practice, the level of accessibility for a person has been related to the fulfillment of individual capabilities. They further apply the activity-based model to predict the utility of using certain travel modes and arriving at various destinations (Nahmias-Biran, Martens and Shiftan 2017; Nahmias-Biran and Shiftan 2020). Karner et al. (2020) emphasize that the capability approach provides a straightforward theoretical foundation for estimating sufficiency level, as it focuses on what people can do, rather than what they have actually done. In a more recent paper, Vecchio and Martens (2021) develop a conceptual framework for understanding transportation equity using the capability approach. Their framework applies several key terms from the capability approach, including capability, functioning, resources, and conversion factors, to transportation research and practice. In their framework, accessibility is a capability which enables a person to engage in various activities and achieve goals such as securing their income, health, and nutrition. Functioning refers to when the required level of accessibility is achieved; resources are what directly and indirectly shape mobility and accessibility; and individual or spatial conversion factors, such as a person's household income or physical health, which facilitate or deter the transformation of resources into capability and functioning. These scholars further link accessibility as a capability, and actual accessibility as a functioning, to well-being. They also mention a key contribution to the success of measuring accessibility as capability: a comprehensive consideration of conversion factors.

Health and Transportation Among Older Americans

The ultimate goal of improving accessibility among older people is the promotion of better quality of life among them. Like the paradigm shift from mobility to accessibility, the relationship between aging and quality of life has evolved in the last half century. The most widely accepted paradigm in the middle of the twentieth century was the disengagement theory, which argued that the aging process involved a decline or withdrawal of social engagement when a person perceived a decreasing life space (Cumming and William 1961). However, the disengagement theory was criticized for its exclusion of the modifying effects of healthy lifestyles, such as healthy diet, physical activity, and social engagement (Havighurst 1963; Rowe and Kahn 1987, 1997). The successful aging model, developed after the disengagement theory, envisions an active and healthy later life for every older adult. Proposed by John Rowe and Robert Khan (Rowe and Kahn 1987, 1997), the model distinguishes a more optimistic outlook on aging, encompassing three dimensions: disease and disability avoidance; high cognitive and physical function; and engagement with life. This was a departure from the previous view of the aging process which was characterized by the acceptance of a decline in health and cognition for average older adults. Utilizing the successful aging model, gerontologists and public health scholars have centered their discussion on utilizing health and community interventions to prevent older adults from suffering the adverse effects of the aging process.

In vehicle-dependent countries, stopping driving is a key point for many older people's quality of life. Evidence shows that limiting, or completely giving up, driving negatively impacts older people's physical health, and their sense of autonomy and independence (Choi and DiNitto 2013; Curl et al. 2014; Dickerson et al. 2019). The longevity and health of today's older people have significantly improved as a result of improved living standards. A recent study has shown that older adults in more recent birth cohorts tend to stop driving later in life compared to those in older cohorts (Schouten et al. 2022b). However, as the statistics in the Introduction show, many older people still suffer from medical conditions limiting their driving abilities.

Residential patterns of older Americans further reinforce their reliance on vehicles for daily travel, adding to the health threats to those who have limited driving abilities but have to rely on driving for daily travel. As noted in early work in this area (Wachs 1979; Rosenbloom 1988), the number of older people who live in suburban and rural areas have increased since the 1960s and will continue in the future. This residential pattern requires changes in transportation services for older people, away from concentrating services in the center of cities. This trend has become even more pronounced since the massive Baby Boomer generation (those born between 1946 and 1964) has begun aging in suburbs and rural areas (Frey 2007).

The person-environment fit theory (Lawton and Simon 1968; Lawton and Nahemow 1973) offers a theoretical explanation of the relationship between residential location, transportation, and quality of life. Ideally, older adults should change their environment to fit their functional and cognitive abilities, so that they can engage in daily social activities, and maintain their quality of life. This perspective is well-known as the person-environment fit in gerontology. As a recent study shows, older people who live in denser and more walkable areas are more likely to give up driving earlier in life, all else being equal (Schouten et al. 2021). This finding reveals that those living in areas with a more compact and mixed use of land tend to have more choices as to where they go each day, and thus can reduce vehicle dependence. However, according to the National Household Travel Survey 2017 (Federal Highway Administration 2019), the mismatch between vehicle need and vehicle ownership among older people living in vehicle-dependent areas is evident: 11% of households consisting of people 55 and older living alone do not have a vehicle, and 80% of them live outside urban areas, including in suburbs, secondary cities, towns, and rural areas.

Additionally, some other social groups among older people may face even more travel difficulties – ones that prevent them from engaging in medical, social, or recreational activities. Studies have shown that African Americans (Park et al. 2010; Sikder and Pinjari 2012), those who live alone (Rosenbloom 1988, 2004), and those who live with low incomes (Nordbakke 2013) have lower daily trip frequency and travel shorter distances, due to a lack of social support, more complex health issues, and fewer alternative transportation choices. Rosenbloom (2004) further notes that widowed women, compared to their male counterparts, have fewer out-of-home trips, as widowed women are, on average, more advanced in age and have more medical issues than widowed men. A longitudinal study further shows that widowed women, compared to men, are more likely to live in zero-vehicle households or transition into zero-vehicle households (Li 2022).

Challenges to Enhancing Older Americans’ Accessibility

Drawing on the concept of accessibility and the capability approach, it is possible to improve older people's accessibility in three ways: (1) subsidizing/assisting their mobility; (2) assisting them to live in/relocate to less car-dependent and more transit/walking-friendly neighborhoods; and (3) supporting their use of ICT. However, theoretical and empirical studies have shown that all three sets of strategies pose some challenges in practice.

The role played by different aspects of accessibility in the well-being of older adults is evident. Two literature reviews have found that scholars in planning, geography, gerontology, social work, and public health all tend to find that older adults who live in age-friendly communities with good access to various activity destinations (e.g., civic centers, parks, healthcare facilities, and restaurants and other commercial facilities), better walkability, more green spaces, and good access to other public transportation and active travel alternatives have a better quality of life, better physical and mental health, and experience less depression and loneliness (Li 2020; Lyu and Forsyth 2022). Neighborhoods with the above traits promote older adults’ daily interactions with neighbors and friends and encourage them to have more out-of-home activities, especially moderate-to-rigorous physical activities (Li 2020). In many circumstances, older adults can utilize ICTs to replace out-of-home activities, and research has found that ICT usage, especially exposure to the Internet, helps to make loneliness and depression less likely among older adults, increases their social interaction (Sum et al. 2008; Cotten et al. 2012; Cotten, Anderson and McCullough 2013) and their sense of independence and autonomy (Steele et al. 2009), and improves their physical health (Boekel et al. 2017).

Subsidizing or assisting older people's transportation services is the most direct way of improving these services’ accessibility. Several policy reviews (Rosenbloom 2009, 1988; Dickerson et al. 2019; Golant 2019; Li 2023b) show that federal policies relating to older people's transportation needs mainly focus on highway design and vehicle safety, based on the theory that most older people depend on vehicles for daily travel and can travel longer. For those who have limited ability to drive, or have ceased driving, services tend to prioritize on-demand paratransit, but these services are expensive to operate and fall short of supply in some suburban and most rural areas. All the research cited above has acknowledged the fragmentation of transportation services in the U.S., especially those funded by the Department of Transportation and the Department of Health and Human Services. As for other solutions, while some scholars (Rosenbloom 2009; Li 2023b) point to the need to change built environments and make them more age-friendly, others point to the importance of ICTs in replacing out-of-home travel for older people with travel difficulties (Golant 2019), to new transportation options such as ride-hailing services (Dickerson et al. 2019; Li 2023b), and to interagency collaboration on a more integrated transportation service supply (Wachs 1979; U.S. Government Accountability Office 2004; Li 2023b).

As concerns built environments, even though neighborhoods can be made denser and more walkable in the long run, persuading older people to relocate to such neighborhoods is not easy. Lawton and Simon (1968) contend, in their environmental docility theory, that environmental pressures influence older adults with fewer resources more than they influence those with greater resources. Golant (2011), proposes an emotion-based residential normalcy theory, drawn from social and environmental psychology and geography theories, in which he argues that many older adults have an attachment to place, and prioritize their positive perceptions of where they live over any objective mismatch between their living environment and their functional and cognitive status. This means that those who have fewer opportunities to change their lifestyle seek accommodative rather than assimilative approaches, overcoming any negative perspectives on their current environment. He further defines those who can access more coping strategies, especially those with active options to change their environment or daily activities, as more resilient (Golant 2015). Literature on the relocation of older people shows that relocation is not a common response to aging, with relocation rates decreasing as people age. Fewer than 10% of older Americans relocate from their homes; and of those who do relocate, many move to a place similar to their previous environment (Golant 1987; AARP 2018; Joint Center for Housing Studies of Harvard University 2019; Li, Hu and Guo 2022).

When it comes to perhaps the most promising way to improve accessibility in the digital era, the challenge of an age- or generation-based “digital divide” is well documented in the literature (Bonfadelli 2002; Choi and DiNitto 2013; Haight, Quan-Haase and Corbett 2014; Hill, Betts and Gardner 2015; Friemel 2016). A recent study shows that older people who have fewer shopping, social, and health trips tend to make less use of their online equivalents: online shopping, social media, and e-health applications (Li 2023a). The digital divide is also a barrier to older people benefitting from ride-hailing services: several recent studies have shown that older people who are regarded as disadvantaged in terms of transportation, including those with low incomes, those with low education levels, and those who live in rural areas, as mentioned before, also experience more barriers to adopting and using ride-hailing applications (Mitra, Bae and Ritchie 2019; Shirgaokar et al. 2021; Misra et al. 2022).

The Need to Develop a Model that Aids Understanding Older People's Accessibility Needs

As shown in the reviews cited above, planning and transportation engineering scholars, gerontologists, and practitioners have all acknowledged that addressing the transportation difficulties of disadvantaged older people requires reconsiderations of transportation systems, and of land use and digital technology. This perspective aligns with the mobility-proximity-connectivity triad of accessibility. However, no framework currently exists to help us engage with such a broad definition of accessibility needs among older people, to understand the determinants of those needs, and to find solutions to them.

In addition, transportation for older people is directly or indirectly connected to activity participation and quality of life. However, this perspective is only lightly considered in the accessibility literature, with a focus on activity participation (Lucas, van Wee and Maat 2016; Nahmias-Biran, Martens and Shiftan 2017; Allen and Farber 2020; Vecchio and Martens 2021). Considering the importance of health and quality of life among older people, the health and quality of life perspective deserves a more prominent role in literature.

Moreover, as scholars in different disciplines acknowledge (Dickerson et al. 2019; Li 2020), a comprehensive model based on theories and methods drawn from transportation studies, gerontology, and urban planning needs to focus on interventions that will address older people's transportation needs. The early-stage conceptual models for all disadvantaged groups (Vecchio and Martens 2021) are not sufficient to enable understanding of factors related to older people's transportation barriers. Nussbaum (2011) emphasizes the importance of individual capabilities interacting with the external environment, which she refers to as combined capabilities. A comprehensive model should include not only individual-level factors related to the life course, but also support or limitation factors at the household, community, local, and national levels.

A Health Capability Model and Its Implications for Creating Accessibility for Older Adults

In a paper published in 2010, public health scholar Jennifer Prah notes the limitations of the health equity theories then available: “none captures a fundamental reality: people seek good health and the ability to pursue it.” (Ruger 2010b, p. 41). Building on Sen's capability approach and Aristotle's theory of what constitutes flourishing in humans (Ruger 2010a), Prah argues that being healthy and having the ability to pursue health are critical to other economic, political, and social activities. This health capability framework consists of three elements: health capability, health functioning, and health agency. Prah notes that health capability “values health functioning and health agency as objects of social policy and change” (Ruger 2010b, p. 43); health functioning evaluates physical and mental health and the impacts of these on human flourishing; and health agency measures people's ability to achieve health status, which contributes to a desirable lifestyle (Ruger 2004, 2010a, 2010b). Her framework also provides an ethics framework to promote understanding of the determinants of health. In another paper, Ruger (2004) underscores the importance of identifying the individual, household, and community factors, and the various policies, that contribute to health outcomes and health agency, and she identifies the internal and external factors of health capability. Internal factors include biological and genetic predispositions; and external factors are those that endow people with various resources to pursue better health, including private and non-profit agencies, the federal and local government, and communities (Ruger 2010a). Scholars have applied this framework to help them understand health and political rights (Feldman et al. 2015), disability (Ruger and Mitra 2015), and addiction problems (Ruger and Zhang 2019).

As discussed before, accessibility contributes to daily participation in activity and social inclusion, which contributes to human flourishing. The social impact of accessibility aligns well with health capability. For older adults in particular, gerontology literature has provided rich evidence of the impacts of accessibility on subjective well-being. Like health functioning, accessibility consists of several components, including mobility, land use, and technology use. Prah's framework highlights the critical role of shared governance among different actors in promoting health. From the cost-effectiveness and equity perspective, future transportation planning for older adults requires collaborative efforts from various departments.

Theorizing Accessibility Capability

Based on the health capability framework, transportation equity literature and the literature on older people's transportation needs, I propose the accessibility capability framework shown in Figure 1. In this section, I link the social justice and social gerontology theories to justify this framework. In the remaining text, I first offer an overview of the accessibility capability framework, then draw on theories in gerontology and transportation to answer three fundamental questions: What is the definition of accessibility for older adults? Why is it important? What are the determinants of older people's ability to pursue accessibility? Inspired by the health capability model and the transportation equity model developed by Vecchio and Martens (2021), this framework includes three interrelated parts: accessibility capability, accessibility functioning, and accessibility agency. The remaining text presents the definition of each part and details of the theoretical foundations for these.

OPEN IN VIEWER

Figure 1.

Accessibility capability.

Accessibility capability. Accessibility capability here refers to the ability to achieve accessibility that fulfills older adults’ need to engage in daily activities at a specific life stage. Accessibility, from a capability perspective, denotes people's access to, and ability to use mobility, proximity, and ICTs to fully involve themselves in daily employment, education, healthcare, and social and recreational activities, among others.

According to the health capability model and gerontology theories, a sufficient level of accessibility for older adults should reach a combination of mobility, proximity, and ICT usage which enables them to maintain a good quality of life and social well-being over their life course. This goal, which envisions an active and healthy later life for every older adult, aligns with the successful aging model proposed by John Rowe and Robert Khan (Rowe and Kahn 1987, 1997). To further operationalize accessibility capability, I expand the person-environment fit theory (Lawton and Simon 1968; Lawton and Nahemow 1973) and argue that a sufficient level of accessibility should reach a person-environment fit through a combination of mobility, proximity, and connectivity. A sufficient level of accessibility is one that supports people in their desired level of social activity in either a physical or a virtual way. The desired level varies from person to person and from place to place. For example, several studies have revealed that older adults’ needs and wants in terms of accessibility vary based on their residential locations and lifestyle (Wachs 1979; Dickerson et al. 2019).

Bearing in mind how needs vary, equity is achieved when every older adult has sufficient accessibility to enable them to attain person-environment fit. From the capability perspective, accessibility enables older adults to have multiple choices – the freedom to reach various employment, educational, healthcare, and social activity destinations. This level of accessibility helps the goal of successful aging, compensating for potentially declining health and social engagement over the life course. For example, a study shows that declining accessibility of job opportunities for older people predicts early retirement among them (Blumenberg et al. 2019). However, if those who have declining accessibility are able to access equal job opportunities through teleworking, their lower physical accessibility level can be compensated by ICTs. In this sense, accessibility can empower older adults with the resilience to actively combat environmental pressures that do not match their physical and cognitive needs over the life course (Golant 2015). This perspective differs from older adults’ passive coping strategy of accommodating themselves to their residential circumstances by taking a more positive emotional attitude to their residential built and social environment (Golant 2011).

Accessibility functioning. Consistent with the definition in the previous framework (Vecchio and Martens 2021), accessibility functioning here refers to the actual level of accessibility. The concept defines the actions, strategies, and behavior that older people employ to achieve a better accessibility outcome. As shown in Figure 1, based on previous work (Shen 1998; Geurs and van Wee 2004; Levine et al. 2012; Lucas, van Wee and Maat 2016; Vecchio and Martens 2021), accessibility in this framework includes the built environment, travel behavior, and virtual mobility. The first dimension, built environment, encompasses the available activity destinations and transportation choices in a neighborhood, city, or region. This dimension includes density and diversity of land use, and access to alternative transportation resources, e.g., public transit, pedestrian pathways, and bicycle lanes. The second dimension, travel behavior, includes private transportation resources, vehicle ownership, choice and usage of various transportation modes, and relevant costs. The last dimension, virtual mobility, is measured by access to the Internet, technology tools, and usage of ICTs. Accessibility functioning not only includes how many destinations an older person can access, or how many activities they can participate in, but also includes another dimension: how they feel about their daily travel experiences. For example, based on a mixed-methods study in Los Angeles, Loukaitou-Sideris, Wachs and Pinski (2019) conclude that although downtown Los Angeles is transit-rich, older people who use it witness many unpleasant features, such as crime, homelessness, deteriorating street environments, and heavy vehicle traffic.

Accessibility agency denotes the ability to pursue accessibility, and includes demographic and socioeconomic factors, family and community support, and federal and local policies related to three accessibility elements: the built environment, transportation services, and technology. Accessibility agency encompasses resources and conversion factors which determine the level of transportation and daily mobility as identified in the framework of Vecchio and Martens (2021). Some factors not only facilitate older people's transportation, but also influence their access to other resources, especially those related to residential location and technology. For example, a recent study shows that African American older people, compared to their non-African American counterparts, have both fewer shopping trips and lower online shopping frequency (Li 2023a). Like the health capability model (Ruger 2010b), this capability also highlights the importance of the family, community, and policy support, all of which can improve older people's accessibility. Additionally, as accessibility agency can transform into accessibility functioning and agency, support should not only involve transportation services, but also include efforts to help older people gain more options in housing and access to technology.

Implications for Urban Planning

This proposed framework has several implications for urban planning research and practice. First, it suggests that improving accessibility for older people needs efforts beyond transportation services. In the digital era, as previous studies have shown (Shen 1998, 1999; Cao 2012; Li 2023a), transportation disadvantages and a lack of access to digital devices often go hand in hand. Transportation programs and policies should pay special attention to those who have difficulty accessing and using technology, as well as private and public transportation, and those who have difficulty driving or owning cars but live in car-dependent areas where neither technology access nor alternative transportation means are readily available. From the accessibility perspective, mitigating travel inequity among older people necessitates paying attention to three areas of accessibility: transportation, land use/urban design, and technology. Policies or community support aiming to promote technology usage among older adults, along with land use and housing initiatives seeking to improve the convenience of accessing various activity destinations and transportation options, can compensate for travel difficulties among those with limitations that make it difficult or impossible for them to use vehicles. In addition, efforts aiming to support more than one dimension of transportation, such as providing more responsive on-demand transportation services using technology and creating transit- and walking-friendly neighborhoods affordable for people of all ages, are helpful for improving accessibility levels for older people.

Second, this study provides a theoretical foundation for interagency collaboration on improving accessibility for older people; although interagency collaboration and coordination, especially among urban planning, transportation, and social services for older people, pose a critical challenge. The accessibility capability framework links different domains of accessibility with person-environment fit and successful aging. More specifically, accessibility, which encompasses the proximity of daily activity destinations, the ability to travel around, and the availability of technology to promote participation in daily activities, should be raised to a level that will maintain older people's quality of life over the life course. This health perspective embraces the goals and missions of all the agencies serving older people. Transportation planners can partner with social service providers and non-profit agencies that better understand older adults’ residential, transportation, and technology needs to advance policy designs for older adults. Involving different stakeholders with a common goal is also the first step to reaching a consensus about what is a sufficient level of accessibility for different groups of older people.

Finally, this framework questions the current provision of transportation support for older adults based on their medical conditions and age. Increasing age and developing medical conditions add accessibility challenges to those who already have difficulties in daily travel and technology usage, e.g., older women living alone, older adults with low incomes, and those living in rural areas. Those whose wealth and resources are sufficient to ensure their existing environment continues to offer them accessibility find that increasing years, and even medical conditions, do not preclude their desired lifestyle. However, those who lack such resources are faced with the challenge of compensating for a decline in mobility by moving to a more suitable place or using new technologies (Li, Hu and Guo 2022; Schouten, Blumenberg and Wachs 2022a). In contemporary U.S. society, this is the challenge faced by many older workers with low incomes who, if they cannot compensate for a decline in mobility, may be forced to leave their jobs early.