Towards addressing transportation planning’s contradictions: The unified theory for transportation planning based on the capabilities approach

Abstract

This article proposes a unified theory for transportation planning based on the capabilities approach which helps reconcile three key contradictions with which transportation planning has not sufficiently grappled. Those contradictions include the following. First, should transportation planners focus on opportunities or outcomes? Second, is travel good or bad? Third, how can transportation deliver value in a polyrational world which faces challenges in balancing universalist principles (meaning that they apply everywhere) and local context? To address these contradictions, the proposed unified theory firstly includes nine core principles, builds on the work of Vecchio and Martens, and centers locally produced understandings of accessibility (here refined to the construct of freedom of access) as one of many capabilities necessary to live a life of dignity. Transportation planners’ key roles are to locally co-produce understandings of freedom of access as a capability—thereby bridging universalist ethical frameworks (ones which apply everywhere) into local circumstances through discourse ethics. Secondly, the proposed approach embraces the necessary linkages between freedom of access and transportation system use. Therefore, while travel is not of central interest, it is necessary to realize other capabilities. Third, the constructs of fertile functioning, corrosive disadvantage, and tragic dilemma enable transportation planners to uniquely co-produce (with residents and institutions) interpretations linking freedom of access-as-a-capability with transportation system use-as-a-functioning. Finally, the proposed unified approach reframes public involvement from project-specific initiatives toward a community-centered and domain-specific spatial ethics of transportation planning which revisits the changing meaning of freedom of access over time.

Introduction

Transportation planning suffers from three internal contradictions which, if left unaddressed, leave it as a weaker version of itself. First, it is unclear whether transportation planning should prioritize ethical perspectives based on expanding opportunities or based on achieving outcomes through utilitarianism. Second, it is unclear whether travel is a good thing which should be accommodated or whether travel is problematic and hence should be managed. Third, transportation planning struggles to navigate the application of universalist principles, such as travel demand forecasting, while considering the local context with its distinct histories, traumas, values, and ways of knowing. This article proposes a solution to these contradictions in the form of the unified theory of transportation planning based on the capabilities approach. This normative theory includes nine principles which establish a domain ethics which aligns transportation planning practice with Nussbaum and Sen’s capabilities approach (Nussbaum, 2011; Sen, 1993). This unified theory addresses these three contradictions, all the while building from the current state of practice involving utilitarianism, accessibility planning, and participatory planning in the context of a deliberative democracy.

Like other planning sub-disciplines, transportation planning perpetually navigates the balance between universalist ethical principles (in particular, consequentialism—i.e. based on outcomes) and relativistic principles which are highly localized, fragmented, and spatio-temporally situated. While universalist ethical principles are fundamental to a way of doing and being and are therefore designed to apply guidance in all contexts, localized contexts inherently have unique circumstances and histories. Transportation planning’s north star, its form of universalism, continues to be utilitarianism based on traffic engineering principles. Utilitarianism provides a framework to assess the relative benefits and costs of different policy actions based on diverse implications which are all scaled on a common metric: monetization. While other planning sub-disciplines have adopted other ethical frameworks more prominently over time (e.g. discourse ethics, distributive justice), transportation planning continues to lean heavily on utilitarianism, which promotes the greatest good for the greatest number.

Transportation planning needs to provide unique guidance and needs to advocate for its own north star, rather than continuing to cede moral authority to other transportation practice-disciplines, such as engineering, design, and policy studies. While transpor-tation planning’s interdisciplinary role in connecting/mediating/moderating between stakeholders and perspectives remains central to practice, it is unclear what unique role transportation planning plays in identifying competing aspirational visions which compete with those perspectives of other disciplines. This leaves it in a very postmodern space of moderating and/or interpreting the discourses of other actors without a pathway toward providing and legitimizing normative claims. Continuing to straddle utilitarianism and discourse ethics reduces transportation planning to a battle over what outcomes matter most (e.g. economics, sustainability, equity, etc.). This leaves transportation planning as an arbiter of power, rather than providing a clear role in defining a normative pathway toward action. This must change.

To set out a pathway toward that change, I propose the unified theory for transportation planning based on the capabilities approach in light of the three key contradictions in transportation planning. I first review a brief history of transportation planning and its underlying ethical principles. Next, I further develop the three contradictions before (in the section “Shifting transportation planning ethics using the capabilities approach”) I describe the capabilities approach, as defined by Nussbaum (2011) and building on Sen (1995). The capabilities approach is an alternative ethical framework to consider justice and fairness based on opportunities (capabilities) in a liberal democratic society. Past linkages between transportation planning and the capabilities approach are described. In the section “Principles for a unified theory of transportation planning based on the capabilities approach,” I build upon these and present the unified theory of transportation planning based on the capabilities approach. Finally, I identify key conclusions with respect to the implications of shifting toward the unified theory of transportation planning based on the capabilities approach.

Literature review

Humans have been building transportation infrastructure since the beginning of cities. But transportation planning motivations have changed over time and newer approaches have often been in response to older practices. Today transportation planning is on a precipice where its future is unclear. Below, a brief history of transportation planning is presented before key ethical and value-based contradictions in the practice are identified.

Transportation planning: A brief history

The first recognizable era of contemporary transportation planning was an essential component of early industrial-era town planning of the late 1800s and early 1900s and was not distinguished as a separate form of more general town planning. As the populations of cities such as New York, London, Vienna, and Chicago swelled, this brought problems of crowding, sanitation, horse carcasses and manure, mobility, housing, and disease. Despite radical social change, cities’ governance processes remained rooted in systems of graft and corruption which were poorly suited to address nascent social issues (Ackerman, 2005). In response, the Progressive Reform Movement proposed a comprehensive and expertise-driven app-roach to identifying and addressing urban ills across a range of policy domains (Ward, 2002).

The broader field of planning was explicitly comprehensive in nature by addressing multiple policy domains and types of outcomes simultaneously, including design and social policy. A central question of this era centered on shaping how individual actions relate to collective and public interests (Olmsted, 1914). Thus, transportation, housing, and design issues were all interrelated in their efforts to address broad outcomes including circulation, sanitation, and crowding (Bibbins, 1924). As exemplified in the work of Olmsted (1914), this loose adherence to an outcome-based ethical approach (also called consequentialism) trained planners based on a universalist outcome-based ethics but within the local context of specific cities and neighborhoods with nuanced and complex local histories. While crowding and congestion were broadly interpreted as problematic, the overall motivation to support mobility in cities was viewed as desirable.

The second era of transportation planning represents a response to mass automobility through which future transportation needs are estimated and accommodated by building out infrastructure and services. This approach is more commonly referred to as the “predict and provide” approach or transportation planning as a quasi-science (Brown, 2006), and is based on accommodating travel. The approach is based on utility theory, which posits that consumers choose options with characteristics which maximize the benefits relative to the costs of a given option (Lancaster, 1966). Thus, it focuses narrowly on testing preferred transportation infrastructure alternatives based on common metrics of estimated monetized benefits, including travel time reductions (Metz, 2008). This form of consequentialist ethics is termed utilitarianism and represents a universalist approach through which all costs and benefits are compared using the common metric of monetization. However, the approach’s narrow transportation policy guidance comes at the expense of other nuances, including benefits which cannot be monetized, other forms of knowledge, and different value systems (Brown, 2006).

Groundbreaking North American studies based on the predict and provide approach include the 1952 Detroit Metro Area Traffic Study and the Chicago Area Transportation Study (1956–1962), both led by J Douglas Carroll, Jr (McDonald, 1988). These pioneering studies established sampled household-level data collection of trip origins, destinations, and modes used as the standard for future four-step travel demand modeling. Boyce (1980) illustrates the strong influence of engineering on planning and the dismissive nature toward previous transportation planning eras, arguing that the field of transportation planning “begins” not with the Progressive Reform Era but in 1956 with the start of the Chicago Area Transportation Study based on the predict and provide approach.

In the third era of transportation planning, beginning in the 1960s and 1970s, the practice shifted toward travel demand management (TDM; Meyer, 2016) and a movement toward prioritizing the broader human and natural environments (Goodwin, 2012). The predict and provide approach was based on building capacity to accommodate demand. However, social and environmental pressures mounted in response to increasing automobility, gridlock, neighborhood bifurcation by highways, environmental consequences, and diminishing public coffers (Brown et al., 2023). In turn, this led toward broader ethical approaches being considered in transportation planning. These include discourse morality, through which public participation is emphasized, virtue ethics, through which other values such as environmentalism or social justice are prioritized, and different forms of consequentialism, through which broader outcomes are considered beyond utilitarianism. Examples include environmental and equity-based outcomes which have continued to be prominent motivators to redress the racist impacts of downtown freeways and histories of transit poverty (Geels et al., 2012).

Thus, this response represented a reaction to the predict and provide approach’s excesses, its environmental implications, and its social damages. The turn toward TDM reduced subsidies to auto users and increased alternatives to driving (Handy, 2023). Invariably, however, the broadening of ethical perspectives and values blunted the predict and provide approach’s singular, universal policy recommendations, leaving value questions to the local political process. Instead of transportation planners strictly occupying the space of planner as utilitarianist based on the predict and provide approach, this expanded the role of planners towards being power arbiters. Thus, planners are increasingly responsible for navigating power differences between different value systems, different processes, and different people who may inform policymaking through public participation.

The fourth era of transportation planning is the shift toward multimodalism, whereby options and usage of non-auto modes are embraced both as good outcomes and as valuable opportunities (Handy, 2023). Despite vast overlaps, these two forms of multimodalism stem from different ethical underpinnings: one from consequentialism (using non-auto modes to promote environmental and equitable outcomes) and one from a liberal conceptualization of virtue ethics focused on promoting opportunities and choice, rather than any specific outcomes. Multimodalism, as a response to the excesses of automobility, became a means of promoting transit, walking, cycling, and other modes as alternatives to driving and placed its focus on reducing the externalities of automobility, its consequences for social justice, and its environmental implications (Geels et al., 2012). In contrast, multimodalism in its liberal traditions of promoting opportunities focuses on giving transportation system users choices beyond auto dependency and on those choices being inherently valuable in and of themselves. Multimodalism thereby imposes a universalist approach, noting that auto use should be reduced and other modes should be encouraged (Handy, 2023). It therefore leaves planners squarely in the space of navigating power interests between different views of the good city.

Finally, the most nascent era is transportation planning as accessibility. Accessibility, the ease of reaching destinations, comprises both the ability to overcome space via mobility and the geography of prospective destinations through proximity (Levine, 2020). While the construct of accessibility has emerged since the early 20th century (Hurd, 1903), its development as a transportation planning performance metric started to emerge in the mid-20th century (Hansen, 1959; Wachs and Kumagai, 1973) before it received broader attention in the 1990s (Levine, 2020). Like with multimodalism, accessibility approaches employ multiple ethical lenses but their fundamental essence is about creating opportunity. Accessibility planning retains consequentialist motivations, through which accessibility is encouraged because of its positive implications for other outcomes (e.g. commute times, health, justice, etc.) which may be underprovided in the private market. Accessibility planning is based on virtue ethics, whereby accessibility is interpreted as a positive quasi-public good which should be enhanced as a matter of liberal philosophies of expanding opportunities and basic human rights and encouraging a more just society (Martens, 2017). Accessibility-oriented transportation planning is somewhat more agnostic with respect to whether travel is a good or a bad outcome, as it implicitly promotes trip taking as a means to engage in out-of-home activities. But it likewise favors built environments in which overly long trips are less necessary.

Accessibility planning, being newer, is still undergoing significant changes. More consequentialist-oriented accessibility planning strives to integrate utilitarianism with accessibility planning by generating monetized benefits from improvements in accessibility for evaluative purposes (El-Geneidy and Levinson, 2022; Geurs et al., 2010; Levine et al., 2017). Others note that, in planning practice, accessibility is used to inform the visioning process but is abandoned in the process of doing more detailed evaluations (Ferreira and Papa, 2020). Others still, including Vecchio and Martens (2021), argue that the construct of accessibility should be interpreted using the capabilities approach of Sen (1999) and Nussbaum (2011), a liberal and humanistic political philosophical view toward what justice might be. These efforts note the cross-sectoral nature of accessibility and the diversity in needs which can be considered by focusing on opportunities rather than strictly on outcomes. This understanding can significantly be enriched by further exploring how transportation planning can be informed by the capabilities approach, as discussed further below. Because accessibility planning is more nascent, it inherently represents a disruption to utilitarianist planning approaches and instead places planners at the center of power differences between the status quo of the practice and new opportunities.

Transportation planning’s key contradictions

Highly recognizable elements of contemporary transportation planning were refined as the predict and provide approach within the adjacent field of transportation engineering during the early 20th century. Today, this amorphous distinction between transportation planning and transportation engineering remains a challenge. Transportation planning, as a practice-discipline, has struggled to define its own north star as an alternative to either “transportation-planner-as-utilitarianist” or “transportation-planner-as-power-arbiter.” I focus on three key contradictions before describing a pathway toward addressing these using a new approach.

Contradiction 1: Opportunities or outcomes

First, transportation planning has struggled with the question as to whether it should focus on providing opportunities or on shaping outcomes. Using the typology of eras described above, two of the five eras focus primarily on outcomes. Those include the two earliest eras of transportation planning: (1) transportation as early town planning and (2) predict and provide. Both the TDM and environmental movements and the multimodalism era focus on both opportunities and outcomes. But while TDM and the environmental movement focus on opportunities to engage in processes through public engagement, multimodalism focuses on opportunities to have different modal options. Both focus on outcomes related to auto dependency and, particularly the TDM and environmental movement, on secondary social and environmental effects of transportation. Only the accessibility era focuses exclusively on opportunities. While outcomes are central to transportation planning’s origins, opportunities have more prominently featured in more recent transportation planning eras.

As a philosophical approach, a focus on outcomes grates with many western constitutions and could be construed as an alternative source of non-democratic political knowledge. Liberal western constitutions traditionally focus on rights and freedoms which are best interpreted as opportunities, rather than as outcomes. Accordingly, the state does not shape what people do but rather helps promote the social contract with possibilities from which individuals can choose how to realize their own conception of a good life.

But resolving the contradiction between opportunities and outcomes is not easy. For example, narrowly focusing on opportunities may preclude societies from achieving the travel behavior changes (which are outcomes) necessary to meaningfully address pollution and human-caused climate change. On the other hand, limiting transportation planning to a focus on outcomes may hamstring the field, requiring it to continue using the positivism of utilitarianism to promote a future, which runs the risk of closely mimicking and perpetuating limits and injustices embedded in the recent past—referred to by Healy (2002) as a form of “inertia and control.” Likewise, the challenge of focusing on outcomes leads to the question of what outcomes are desirable and which are not (see Contradiction 2 for further discussion). This challenge, again, leaves transportation planning in a polyrational space of mediating between different sources of value-based power.

Contradiction 2: Is travel a “good” or a “bad” thing?

A second key contradiction relates to the question of whether travel is “good” or “bad.” Different transportation planning approaches arrive at different conclusions with respect to this question—leading the broader goals of transportation planning to be unclear. On the one hand, transportation planning based on the predict and provide paradigm prioritizes accommodating future travel demand—making it explicit that travel is a good thing (Goodwin, 2012). Performance metrics which accompany this approach include a focus on travel time savings and congestion alleviation—both of which prioritize mobility. But there are additional caveats as to the conditions under which travel is “good,” including congestion, induced traffic, auto-based pollution, and transit crowding. In turn, this leads to the conclusion that while travel (i.e. trip/tour rates) is “good,” travel may be well suited to shorter auto-based trips and shifting those trips towards other modes. This vision of “many, short trips” (Mondschein and Taylor, 2017: 71) is a normative compromise between the perspectives of travel as “good” (many trips) and “bad” (but not too distant—especially in cars).

On the other hand, transportation planning based on the era of TDM and the environmental movement focuses on reducing or managing auto travel and its pernicious implications (Goodwin, 2012). This leads auto-based travel, in particular, to be interpreted as “bad.” Performance metrics which are aligned with this approach include vehicle-kilometers traveled (fewer is better) and mode share (lower auto mode share is better; Xi et al., 2020). Policy remedies include building out public transit, improving walking and cycling infrastructure, implementing road diets, and increasing the generalized cost of automobile use (Banister, 2008; Handy, 2023). But while the understanding of whether travel is “good” or “bad” requires significant nuance, performance metrics are blunt and the objectives to reduce vehicle-kilometers traveled or to increase transit mode share are both based on much simpler understandings of what the desired policy objectives are.

The issue of induced traffic represents one prominent example which illustrates the differences between interpreting travel as “good” or “bad.” While part of the induced traffic challenge is technical, the meaning and implications of induced travel are also a normative question (Cervero, 2002). Adherents to predict and provide may argue that induced traffic is good because it represents additional consumer surplus based on newly possible activity and travel patterns. In contrast, adherents to the TDM and environmental movement or multimodalist approaches would argue that induced traffic undermines the purported benefits advertised by supply-side investments. Instead, induced traffic is rarely taken into consideration in travel demand forecasts and it erodes travel time savings, one of the biggest monetized benefits of transport projects. Further challenges on induced traffic emerge from the question as to whether public transit infrastructure capacity may also induce additional traffic (Taylor, 2002).

But while reducing auto dependence is laudable, it is far from clear to this author that shifting completely toward performance metrics related to vehicle-kilometers traveled represents the most fundamental social goal toward which transportation planning aspires and it, paradoxically, even implies a need for less transportation investment. For an interesting recent discussion of this, please see Manville (2024). But while this line of reasoning has led to significant investments in alternative modes, the political will to increase the burden of auto use has been very low. This is partly because the private and social benefits of automobility have been enormous and, over the decades, automobility has been baked into the DNA of western society’s many visions of the “good life.”

Contradiction 3: Universal principles or local context

A third contradiction within transportation planning is that while policy initiatives require localized participatory processes rooted in discourse ethics (e.g. most environmental review processes and most long-range regional transportation planning processes), the practice-discipline continues to rely on a universalist ethical framework rooted in utilitarianism, a universalist ethic. While this paper manuscript reflects primarily upon the North American policy context, this contradiction occurs everywhere. While the professional roots of transportation planning are based on the universalism of rationality and utilitarianism, the values of different communities are locally situated and are often based on ways of knowing which are unique to the history of a specific population group, city, or neighborhood.

Local understandings of “good” policy are on full display in the planning processes for many projects and compete with the universalized ethics of utilitarianism. While transportation engineers and travel demand forecasters frequently generate complex alternatives analyses, localized concerns often highlight very different values, including privacy or repairing past trauma, which cannot feature in travel demand forecasting. This represents a difference in how the very benefits of transportation investment are even conceptualized. Examples of these disconnects between universal principles and local context are diverse. One example from Philadelphia, Pennsylvania is the Chinatown Stitch, a proposed highway cap over the Vine Street Expressway, where there are two interesting components of this universalist–local disconnect. On the one hand, the Vine Street Expressway bifurcated the historic Chinatown neighborhood in the early 1990s based on utilitarianist rationales surrounding mobility benefits relative to costs—while the local Chinatown neighborhood’s local cultural role was discounted by economic appraisals (Philadelphia Chinatown Development Corporation, 2017). On the other hand, the recent planning initiatives to build a highway cap over the expressway have been locally rationalized to reconnect this important cultural neighborhood—while traffic capacity analyses were needed to establish the project need and secure state and federal funding (City of Philadelphia, 2023). In other words, even when this project was oriented toward advancing locally specific needs, it needed to be framed in universalist terms to secure funding.

This question of whose perspectives count is important. Insofar as technical planning processes focus primarily on value using a hedonic approach through utilitarianism, this has significant limiting implications for policy. But insofar as transportation investments long outlive the planners, builders, and citizens that inform their construction, how well do norms and values which are embedded in physical infrastructure relate to changing circumstances? While this is clearly a bidirectional relationship, the potential for mismatch between human values and the built environment’s physically embedded values warrants special attention. Utilitarianism, by definition, focuses much more on functionality than on form and the associated social production of meaning through design. This may miss important elements of localized identity, trauma/recovery, or culture that warrant special attention.

When there is real power asymmetry, communities may not be able to advocate for their own welfare, as illustrated by the Vine Street Expressway example above. This is particularly the case when communities have faced significant trauma, which reflects responses to disturbing circumstances which leave individuals and/or communities unable to carry on based on desired functionings (Schroeder et al., 2021). Trauma can lead individuals to internalize the harshness of their own conditions, leaving them with challenges in imagining alternative ways of being (Maté and Maté, 2023). The challenges therein speak toward engaging in planning over long time horizons—thereby not leading universalism to a subservient role but leaving it as a possible avenue to give voice to local needs. This then becomes a possibility for continuous planning, rather than interpreting planning as a one-time intervention (McClymont, 2019; Vuksanovic-Macura et al., 2020).

This nexus between universal principles and local context presents both challenges and opportunities. On the one hand, too much universalist power (e.g. interpreting utilitarianism too literally) has led to the traumas of urban renewal and urban freeways. A host of case studies on highways being rationalized based on utilitarianism to bifurcate and destroy neighborhoods of color can be found in Reft et al. (2023), including the examples in West Montgomery, Alabama (I-65 and I-85), Milwaukee, Wisconsin (I-94, I-794, and I-43), and West Baltimore, Maryland (US-40). On the other hand, prioritizing local context and identity over universalist principles of liberal democracies with urban co-habitation of a diverse citizenry can lead to tribalism and populism (Fainstein, 2011). Such examples are perhaps easiest to see in transportation planning through the practice of Not in My Back Yard (NIMBYism), a movement which has successfully leveraged the environmental review process to stop or slow projects (Klein and Thompson, 2025). Specific examples of NIMBY impacts on transportation projects include reactions to circulator buses in Tempe, Arizona (Weitz, 2008), or broad NIMBY efforts which have created transit deserts in New Orleans, Baltimore, and Chicago (Jones Allen, 2017). The very exercise of maintaining this balance in liberal democracies based on federalism is itself an exercise in building and maintaining the spirit of the city—the physical embodiment of present and future human values and spirits that connect people (McClymont, 2019).

Implications

But bridging these universalist–local spaces does not rely on more deliberate public engagement with and procedurally fairer implementation of the predict and provide approach in the service of utilitarianism. This leads to a categorical impasse with respect to reconciling other ways of knowing, different understandings of what outcomes are good, and navigating the opportunity–outcome contradiction with all of its democratic and political implications. More broadly, the predict and provide, TDM and environmental movement, and the multimodalist approaches diverge with respect to the conditions under which travel is “good” or “bad,” leading the very foundation of outcome-oriented ethics to falter under the weight of expectations within a pluralist liberal democracy. Even alternative outcome-based forms of ethics, such as Rawls’ (Beyazit, 2011), suffer from this ambiguity with respect to what primary goods (outcomes) matter most and how to integrate philosophy into a practice-discipline, such as transportation planning. There needs to be a new way.

Shifting transportation planning ethics using the capabilities approach

There is significant promise to address the three major internal contradictions in transportation planning by shifting away from an ethics of utilitarianism. Instead, this new direction would orient transportation planning practice around the capabilities approach—see Nussbaum (2011) and Sen (1995). First the capabilities approach is described before it is applied to transportation planning. While others have considered the capabilities approach with respect to transportation planning applications (Hananel and Berechman, 2016; Vecchio and Martens, 2021), these efforts are only beginning and there are opportunities to go further toward this end.

The capabilities approach

The capabilities approach represents a model for thinking about social justice based on a focus on opportunities rather than outcomes and it is rooted in liberal democratic thought (van Burgsteden et al., 2024). It considers that humans aspire to a diversity of outcomes in seeking the good life and centers individuals as ends in and of themselves, rather than as means toward alternative socially constructed ends. It focuses on substantial freedoms and represents a direct response to the dominant ethical frameworks of utilitarianism and Rawls’ theory of distributive justice (Sen, 1993). Both of these can be critiqued as being overly focused on outcomes and primary goods and hence inclining toward being patronizing with respect to public policy approaches. Based on Sen’s (1993) original conception, the capabilities approach instead highlights humans as being the goal in and of themselves with respect to both their “beings” and their “doings.”

The benchmark of a life of dignity and minimal flourishing is explicit and central in the capabilities approach. Nussbaum argues that central capabilities, of which she defines 10, need to be explicit even while the minimum thresholds which are necessary to live a life of dignity may be further developed relative to Nussbaum’s (2011) base recommendations through local political processes or by professionals in effective governance contexts (Sen, 2009).

The capabilities approach explicitly embeds the yin and yang of localism and universalism in several ways. First, it provides a singular north star or approach through which localized circumstances can be interpreted. For example, the capability to engage in practical reason is fundamental as a universalist aspiration but the precise understanding of this idea in practice (i.e. education) can be defined based on localized circumstances by political, public, and professional actors. Second, the capabilities approach acknowledges the diversity of individual capabilities (e.g. physical, mental, emotional) as well as the role of the social environment (e.g. education, health, etc.). For example, Nussbaum emphasizes the totality of combined capabilities as comprising the sum of internal capabilities (related to the individual) as well as the social/political/economic environment in which they act. The approach thus explicitly considers the individual–collective ethical issues which pervade planning practice.

While the capabilities approach focuses on freedoms and opportunities which are inherently valuable, the approach does not ignore outcomes. According to Nussbaum (2011), functionings are the “active realization of one or more capabilities.” Insofar that capabilities are meaningless if they are never acted upon (e.g. building an outstanding transit system would be pointless if nobody used it), it is critical to understand functioning as an outgrowth of capabilities even if capabilities remain more important. The foundational idea of “dignity” prioritizes “policy choices that protect and support agency, rather than choices that infantilize people and treat them as passive recipients of benefit” (Nussbaum, 2011: 30).

Nussbaum (2011) argues that 10 central capabilities are so foundational to what it means to live a life of dignity and to pursue a minimally flourishing life that these capabilities should not be subject to the same context-specific political processes as other policy decisions. Both Nussbaum and Sen argue that a minimum threshold of these capabilities is needed, but the details of their implementation should be refined subject to the specifics of different political contexts. Such a threshold would align the capabilities approach with sufficientarianism, which argues that all should have enough, not that all should have equal amounts (Karner et al., 2024; Vecchio and Martens, 2021). Nussbaum argues that these capabilities are irreducibly heterogenous—meaning that one cannot be traded for another without compromising the very foundation of the ingredients necessary for a dignified life. Those 10 capabilities include the following (Nussbaum, 2011: 33–34):

• (1) Life

• (2) Bodily health

• (3) Bodily integrity

• (4) Senses, imagination, and thought

• (5) Emotions

• (6) Practical reason

• (7) Affiliation

• (8) Other species

• (9) Play

• (10) Control over one’s environment

Of these 10, the construct of bodily integrity is most relevant to transportation planning, as it includes “being able to move freely from place to place” (Nussbaum, 2011: 33).

There are key constructs which emerge from the capabilities approach which are relevant when considering transportation planning’s three internal contradictions. Those constructs include resources, conversion factors, tragic choices and tragic dilemmas, fertile functionings, corrosive disadvantages, and capability certainty. Several of these are further developed and applied by Vecchio and Martens (2021) as well as by van Burgsteden et al. (2024) to the context of transportation planning.

Contradiction 1—first, the capabilities approach prioritizes opportunities (capabilities) over outcomes (functionings). It holds that each individual is an end in and of themselves and therefore is more consistent with liberal democratic thought than the utilitarianism that pervades contemporary transportation planning. This is not to say that outcomes do not matter (they do, as discussed below). In turn, this shifts the collective action conversation from the task of redistributing benefits toward the work of ensuring a basic threshold level of opportunities.

Contradiction 2—second, with respect to the question of valuing travel (is it good or bad?), the capabilities provide useful terms which can guide this conversation. One term is the notion of a tragic choice, a result where an individual would be faced with the need to make trade-offs between two or more capabilities. Such tragic dilemmas relate to but are not equivalent to the economic notion of externalities—whereby one choice has indirect external consequences. In such circumstances, based on the capabilities approach, the needed remedy is not to monetize the costs and benefits of tradeoffs but instead to engage in collective action to preclude the necessity of facing tragic dilemmas in the first place. A good example can be illustrated by focusing on tragic dilemmas related to accessibility (related to Nussbaum’s third capability of bodily integrity) and bodily health (the second capability). In this example, neighborhoods may face the tragic dilemma as to whether individuals should have a sufficient level of accessibility which may only be achieved by using highly polluting and dangerous cars over long distances or whether the community may be safe from dangerous air pollution and excess automobile crashes. Such a tragic choice illustrates that capabilities are related to both individual and collective choices.

Wolff and De-Shalit (2007) build on Nussbaum and Sen’s work, arguing that a fertile functioning is a particular type of functioning (or capability) that promotes other capabilities. In the case of transportation, one may argue that having accessibility is positive, but that the very act of traveling can be a fertile functioning (an outcome) which confers new capabilities (e.g. for education, employment, etc.). Conversely to the notion of fertile functioning is the notion of a corrosive disadvantage, whereby not having access to a particular capability may degrade other opportunities.

Contradiction 3—third, with respect to considering how universalist and relativistic local processes intersect, the capabilities approach provides several means to bridge this linkage. First, it provides a specific universalist goalpost from which local contexts can work to create their own more nuanced aspirational capabilities or identify deficiencies therein. Second, a key part of the capabilities approach also surrounds capability certainty—leading one to look towards how capabilities are institutionalized over the longer term and how capabilities are collectively ensured (Wolff and De-Shalit, 2007). Third, insofar that both the social and individual availability of resources creates a means to realize capabilities, the capabilities approach provides a vocabulary to explore both physical and non-physical goods and services which are available to individuals to realize capabilities (Vecchio and Martens, 2021). Examples of resources may include both physical elements, such as transportation systems, and non-physical elements, such as information. Fourth, conversion factors affect the translation of resources into capabilities (Nambiar, 2013), leading to both individual and collective action challenges (Vecchio and Martens, 2021). There are multiple potential conversion factors which may affect accessibility for better or worse. First, insofar that accessibility comprises the ability to use transit, the availability of good transit services (a collective action challenge) may be insufficient alone. Instead, publicly provided education programs related to transit use (another collective action) may help as a conversion factor. Likewise, individual self-education using publicly available information (a combination of individual and collective action) may help as a conversion factor. Second, if a prospective transit rider’s lack of a cell phone and/or data services precludes a fare payment option and/or precludes access to sufficiently timely or detailed itinerary or connection details, the cell phone services may serve as a barrier to transit access—leading to the need for alternative information sources or payment methods as conversion factors. Third, the chauffeuring of dependent children (e.g. taking children to/from childcare or school) may impede the conversion of transit services into realized accessibility given the additional physical and psychological burden of traveling with dependents. Fourth, authors have confirmed that race continues to play a role as an impeding conversion factor, whereby even if transportation services (e.g. taxi services) should be the same, they are not due to racism (Brown, 2023).

Transportation planning and the capabilities approach

Based on past scholarly work on applying the capabilities approach to transportation planning, there are several broad implications. First, the most fundamental implication is that the construct of accessibility would become the central capability and a normative goal in transportation planning. This would cast transportation policy which supports sufficient accessibility as one means of furthering human rights and freedoms (Vecchio and Martens, 2021; van Burgsteden et al., 2024). However, within transportation scholarship that discusses the capabilities approach, Stanley (2023) disagrees. Instead of casting accessibility (the ease of reaching destinations) as a capability, he argues that it is mobility (the ease of movement) which should be interpreted as this capability, as it leaves the question of where to travel up to individuals. Like most other scholars contributing toward this debate, I am reluctant to endorse this interpretation largely for two reasons. For one, mobility is one way to foster activity participation but, given sociotechnological changes, such as telework and social media, focusing more explicitly on accessibility is crucial as it considers activity participation most broadly. For another, mobility is a universalist construct that is based in physics and therefore interprets a rational order for very different contexts, thereby further problematizing the universalist–local context contradiction. Instead, the social construct of accessibility is more meaningful than the metaphysical construct of mobility.

Second, another implication is that the adoption of accessibility as a capability implies the need to empirically measure and evaluate accessibility in transportation planning. This thereby solidifies one top-down evaluative approach which has already percolated into transportation planning research and (to a lesser extent) practice (Vecchio and Martens, 2021). Third, integrating the capabilities approach shifts transportation planning to focus on conversion factors: the potential for individuals to turn resources into capabilities (Xu et al., 2024) or functionings (Deka, 2022). This is a critical change from contemporary practice and represents a bottom-up planning approach which would necessarily be more qualitative and participatory (Vecchio and Martens, 2021). For example, many metrics of accessibility highlight the distribution of transit services, bike lanes, and pedestrian facilities. But understanding barriers to those facilities providing real access benefits (in other words, understanding conversion factors) frequently requires qualitative ways of knowing. One example relates to disability, whereby individuals may not experience accessibility benefits from walking or cycling infrastructure which is designed based on ableist expectations. Finally, it is expected that integrating the capabilities approach would reframe social justice as a more central element of transportation policy relative to economic rationales (Hananel and Berechman, 2016).

Several studies have identified possible ethical shifts that the capabilities approach would bring to transportation planning—most notably the shift from utilitarianism toward accessibility (i.e. sufficientarianism; Vecchio and Martens, 2021). Others have focused on very specific elements of how accessibility can be quantitatively modeled and considered for project assessment (Azmoodeh et al., 2023; Beyazit, 2011; Nahmias-Biran and Shiftan, 2020) despite uncertainty as to how effective it can be in project prioritization (Beyazit, 2011). In one of the earliest engagements with how the capabilities approach may be integrated in transportation decision making, Hananel and Berechman (2016) argue that it would shift from an approach of alternatives assessment toward identifying key capabilities and functionings, defining minimum standards, and ultimately designing projects considering these goals. However, these studies miss several features of Nussbaum’s capabilities approach which represent more consequential changes and which better bridge transportation planning’s contradictions between top-down utilitarianism and the bottom-up requirements for public engagement. Toward making that leap, this study proposes orienting transportation planning around the capabilities approach based on nine domain-specific principles which would lead transportation planning to strengthen its role as a spatial ethics.

Principles for a unified theory of transportation planning based on the capabilities approach

Using the capabilities approach, as defined by Nussbaum (2011), I propose the following principles to move transportation planning beyond its current contradictions. This enables a unified theory which does not completely abandon the approaches of utilitarianism, accessibility, or public engagement. Instead, it adapts key components of these ethical frameworks toward establishing a model of transportation planning based on liberal democratic principles oriented toward human dignity and flourishing.

While others have considered the possible implications of the capabilities approach on transportation planning (Vecchio and Martens, 2021), these nine proposed principles crucially address the three key transportation planning contradictions and they integrate different ethical frameworks. The principles prioritize opportunities (freedom of access) while recognizing the importance of outcomes (Principle 1), are explicit that trip taking is good (Principle 4), and provide a universalist benchmark (freedom of access) that is locally determined through public engagement and co-planning (Principles 2). The principles directly address cumulative and secondary social, fiscal, and environmental consequences of transportation based on a human rights approach rather than only based on utilitarianism (Principles 3, 5, 6, 7). Moreover, the principles address the longer-term stability of service expectations (Principle 8) while emphasizing the need for continuous planning using different ways of knowing (Principle 9). The nine principles are discussed in turn.

Principle 1: Freedom of access matters most

The goal of transportation planning should be to expand and ensure that sufficient opportunities to access destinations using the transportation–land use system are available. Sufficient thresholds should be set for individuals to live a life of dignity and of flourishing based on their broader capabilities and unique understandings of the good life. The construct of accessibility, as a descriptive measure and as a normative objective, is central to bodily integrity as one of Nussbaum’s 10 central capabilities. Some discussions about “accessibility” have been based on a specific political conceptualization and urbanist agenda (Cervero, 1997; Cervero et al., 1999; Levine, 2020), so I propose to use the term “freedom of access” rather than accessibility. My use of a different term also has another motivation, though. While the capacity to define and value accessibility is more ambiguous, freedom of access differs in that while this represents a universalist aspiration, freedom of access must be co-produced in a local political context. This opens the door for freedom of access to be co-created with planners in different political contexts through a liberal tradition based on local considerations of this universalist aspirational construct. The term entrenches the universalist meaning of “the ease of accessing destinations” but includes the proviso that this be considered based on locally situated norms with respect to a minimum threshold level of freedom of access. Likewise, using the term freedom of access attributes agency to the individual to be able to realize and make use of this capability on their own terms.

Some may critique my willingness to encourage the nuances within freedom of access to be locally determined. However, such critiques may ignore the diversity of political orientations which affect transportation planning and the baggage that planners as universalists (whether as progressive urbanists, as conservatives, or otherwise) bring to planning discussions with local communities. Similar concerns to mine can be seen in the work of Martens (2017), who argues that accessibility needs to be locally defined through participatory planning.

I would be remiss in not commenting on how freedom of access should be considered based on contemporary transportation technologies and urban form typologies. While all contexts are different, I see the following three as being relevant in all contemporary urban areas. First, considering the role of automobiles is critical both because such a significant share of urban travel occurs by car and because the lack of automobile access among significant segments of the population precludes car-based mobility alone serving as the minimum threshold for freedom of access. Second, and consequently, bus transit is expected to play a very central role in providing base levels of freedom of access considering that this is the lowest-cost public transit mode and bus use is potentially available to the largest swath of the population—regardless of auto ownership. Third, it is critical to carefully consider active travel (walking, cycling, etc.) as one of the most ancient modes with benefits for bodily and spiritual health and other capabilities. The nuances of these normative claims, including with respect to new mobility technologies and shared mobility, are subject to transportation planners’ acts of contextually co-producing freedom of access through public engagement.

Principle 2: Transportation planners need to co-define freedom of access and sufficient minimum thresholds thereof through continuous public engagement with communities within their political contexts

It is the job of transportation planners to discursively define freedom of access and what a sufficient threshold is. The co-production of freedom of access should be continuous in nature through sustained locally contextualized deliberative democratic processes. Regular reassessment through public engagement is important considering broader social and environmental changes. From a research perspective, this represents an explicit epistemology of post-positivism and co-learning where there is a non-fixity of meaning and a non-fixity of being (McClymont, 2019).

This places transportation planners not in the role of mediating/facilitating between different actors in a broad competition over power but in privileged positions in interpreting the universalist aspiration of freedom of access and co-creating its interpretation and implementation for specific local contexts. Without a more muscular, universalist (rather than relativistic) definition of freedom of access, the danger is that local political processes could erode this capability and leave it meaningless.

Principle 3: Transportation–land use system resources matter, but conversion factors matter more as objects of policy action

Transportation planners should engage in policy which provides transportation services and land use patterns as public resources, but the sheer availability of these resources is not what matters most. Instead, what is most important for transportation planners are conversion factors: the ability to translate these resources into freedom of access and other capabilities. Relevant resources include, but are not limited to, the physical transportation network and its operation; mobility technologies such as cars, buses, trains, etc.; the physical built environment and land use patterns; and information. In contrast, conversion of resources into capabilities is even more complex and depends on understanding household characteristics, individual characteristics, ethnicity and identity, social norms and attitudes, and institutions and rules. For example, even exceptional transit services may not enhance the accessibility of an individual if the transit system is unsafe.

The critical role of conversion factors, by extension, means that transportation planners need to focus not only on physical infrastructure and policy interventions but also on affective and socially produced motivations that constrain freedom of access. This endeavor is inherently both quantitative (from a top-down approach) and qualitative (from a bottom-up approach; Vecchio and Martens, 2021). While quantitative guidance will provide indications of tendencies, qualitative guidance is critical to identify who is not realizing central threshold levels of capabilities due to the absence of resources, the inability to convert those resources into capabilities, or the insufficiency of other central capabilities.

Principle 4: Trip taking is good

Transportation planners should interpret travel, in terms of trip taking, as a positive functioning which emerges at least partly from freedom of access. Consequently, one may expect individuals with high levels of accessibility to take more trips. Trip taking can have both positive and negative implications for broader capabilities. On the one hand, trip taking can be a fertile functioning by supporting other capabilities and functionings, including health care, nourishment, shelter, and activity participation. On the other hand, transportation planners need to ensure that insufficient freedom of access and lack of travel (i.e. mobility exclusion) do not function as corrosive disadvantages, whereby other capabilities and functionings are detrimentally impacted. This also means that it is relevant to understand when travel leads to a tragic dilemma (see Principle 5)—for example, when needing to accept a long commute as a trade-off to access shelter can have consequent impacts on social affiliation, play, and bodily health.

Principle 5: Transportation planners should eliminate tragic dilemmas

Transportation planners should focus on eliminating tragic dilemmas—whereby individuals or societies may need to trade off one central capability for another. This principle means that transportation planners need to think comprehensively across policy domains about the threshold levels for all central capabilities, how these are further specified based on the local political context, and how different capabilities impact one another. Sufficient freedom of access, for example, should not be traded off against sufficient shelter or against threats related to climate change. By extension, insofar as key risks (e.g. energy insecurity, global warming, etc.) are threats to capability security, shaping transportation planning and policy to both reduce and respond to those risks is critical.

Principle 6: Transportation planners must conduct fiscal impact assessments and benefit–cost analyses for major investments

Based on the need to eliminate tragic dilemmas, transportation planners must conduct both fiscal impact assessments for all programs and benefit–cost assessments for all megaprojects. This is needed to ensure that the long-term economic base and fiscal capacity can support all central capabilities and can ensure capability security. Benefit–cost ratios should be set as minimum targets for implementation (e.g. no lower than 1.2) rather than as a tool to set project prioritization. While Landis’s (2022) definition of megaprojects as exceeding costs of US$1 billion may be a helpful benchmark, the definition should be locally determined before considering any individual project. For example, projects well under the US$1 billion threshold could still have an outsized impact on smaller municipalities’ broader fiscal capacities.

Principle 7: Transportation project prioritization should be comprehensive, should consider irreducible central capabilities, focusing on freedom of access, and should focus on ensuring sufficiency before expanding central capabilities

Project prioritization processes should be conducted based on local understandings of freedom of access, other central capabilities, minimum thresholds, and the priority placed on achieving those minimum thresholds. This approach does not prioritize equality in freedom of access and does not consider the distribution of primary goods (contrary to Rawls). It only considers that redistribution (e.g. through public taxation and/or programs) may be necessary to achieve the minimum thresholds for the central capabilities. Instead, it prioritizes first achieving sufficiency in and secondarily expanding capabilities. By extension, the comprehensive nature of the capabilities approach also means that if a sufficient level of freedom of access is available and other policy barriers relating to the central capabilities are of more fundamental concern (e.g. education, public health), new investments in transportation planning would need to cede to other priorities, so as not to create a tragic dilemma.

Principle 8: Transportation planners need to ensure capability security in freedom of access when maintaining, operating, and building out systems

Given that transportation–land use systems outlive those who co-plan them, long-term priority should be given to their maintenance and the consistency of base levels of freedom of access, rather than new capital projects. Instead, new investments and services should start through operational interventions first before capital investment whenever possible. This approach can explicitly be embedded in policies related to transportation funding and finance. This principle is informed by the need not just for capabilities but also for capability security over longer time periods.

Principle 9: The exercise of refining locally determined expectations for freedom of access needs to rely on diverse ways of producing knowledge while considering the spirit of the city

While more traditional participatory planning processes are still expected to play a role, part of co-producing local understandings of freedom of access is more akin to the process of creating Jean Jacques Rousseau’s social contract and producing a sense of the spirit of the city (Cavaglieri, 1947) or “spirit of the times” (Friedmann, 2008: 248). Preindustrial transportation infrastructure played a key role in building the spirit of the city (Cavaglieri, 1947) and creating a sense of awe—that is, that one is part of something greater than oneself. This process is more spiritual than rational, has origins in both conservative (Kotkin, 2001) and progressive traditions (Batty, 2022; McClymont, 2019), relies on different means of social engagement, and will need planners to consider non-planning ways of knowing. Notably, transportation planners will need to rely on the habits of their daily lived experience in learning about and shaping the spirit of their cities—thereby changing transportation planners’ understandings of expertise and authority.

Conclusion

Shifting contemporary transportation planning toward the unified theory of transportation planning based on the capabilities approach is possible. Some of these principles are already embedded in practice in different places and to different degrees. Professional practices change over time and the need for transportation planning to continuously reinvent itself is not an indictment of the present or past, but rather an acknowledgment that the world continuously changes and that transportation planners can enhance their role over time in shaping future cities. Nevertheless, the proposed focus on freedom of access, as a locally produced capability, is a significant change with respect to the existing state of practice which focuses on use (outcomes) based on a utilitarianist ethic—even when paired with public participation based on discourse ethics. This shift implies more qualitative approaches; it implies the need to very carefully (and locally) understand the linkages between transportation–land use systems (resources), freedom of access (capabilities), and travel and activity participation (functionings), and the barriers to strengthening these linkages over time. Most fundamentally, it implies a humanist approach, whereby the notion of freedom of access is further refined based on local circumstances through a continuous co-creation process between transportation planners and the public while comprehensively considering other capabilities and their interactions.

Transportation planning, by and large, faces the awkward task of navigating inertia in utilitarianism while also needing to fulfill public involvement responsibilities based on discourse ethics. This creates an ethical conundrum. By shifting toward the capabilities approach, as proposed here, the possibility of competing interests is not eliminated, but these contradictions can be interpreted using a unified framework and applied in local political contexts. Both the political right and left may critique my willingness to stand with Nussbaum’s 10 central capabilities and my willingness to propose a universalist approach toward navigating these tensions by centering transportation planning on the construct of freedom of access. However, insofar as a liberal democratic society based on human freedoms and rights is desirable, explicitly centering transportation policy on an approach based in human rights, rather than more rigidly on outcomes, is crucial. Some globally scaled challenges, such as pollution and human-caused climate change, are collective action problems for which motivating public actions is challenging based on utilitarianism. The proposed unified theory of transportation planning based on the capabilities approach casts such issues as most fundamentally being related to human rights rather than paternalism.

Some communities may conceptualize a minimum threshold of freedom of access in very different ways. The progressive city of Freiburg, Germany embeds bicycle access throughout the city. Large urban centers embed multimodalism with strong normative expectations of transit in their policy. For example, the Toronto Transit Commission has a coverage requirement that 90% of residents be no more than 400 meters or a five-minute walk from the base transit network during all-day, every-day service periods (Toronto Transit Commission, 2024). The more conservative city-region of Houston pairs support for automobility with a local and regional bus rapid transit system (Cervero, 1998). Likewise, rural areas face very different challenges with respect to implementing policies based on local fiscal and policy capacity constraints. This leads freedom of access to necessarily be locally refined, leading transportation planning to become a form of spatial ethics based on local context.