May 19, 2021

The Meaning of Equity in Transportation

Content and discussions about equity in transportation have increased substantially in recent decades, but assessments of what does or does not constitute an equitable distribution of transportation costs and benefits have existed within the profession much longer. In a new paper published in Transportation Research Interdisciplinary Perspectives (TRIP), I along with Professors Don MacKenzie and Jessica Kaminsky explore the concept of equity and how it has been applied within transportation both explicitly and implicitly.

The primary definition of equity provided by Merriam-Webster is deceptively simple:

“justice according to natural law or right
specifically : freedom from bias or favoritism”

While the definition is short, it relies on an understanding of justice, and justice is a multifaceted concept explored within the field of philosophy. Philosophical theories of justice present arguments regarding how society should function; arguments and theories about equity are particularly concerned with how goods and resources should be distributed within society. In other words, theories of equity define the parameters of just distribution.

Much like a mathematical model, philosophical theories of equity utilize strings of logic built on underlying assumptions and constrained by limiting parameters. If applied properly (i.e. apply the logical structure completely to a scenario that meets the assumptions and constraints), the result should be a just distribution of goods and services; the result should be equitable. However, much like mathematical models, theories that are applied improperly cannot be expected to yield reasonable results.

While models can certainly be applied in scenarios where some assumptions and/or constraints are not met precisely (as we all know, data from the real-world is messy), it is still tremendously important to understand and take assumptions and constraints into account when identifying and specifying the best model to use. If a given scenario strays too far from the assumptions and constraints of one model, then the model cannot be reasonably applied; the logical structure of the model remains valid and robust, however it’s application would not yield a reasonable result for the scenario at hand. We argue that philosophical theories of equity parallel mathematical models in this regard and require similar levels of comprehension and consideration in order to be applied in ways that will yield reasonable results.

It is also important to recognize that different theories of equity may yield different, and potentially conflicting yet equally reasonable (depending on your perspective) results. It is therefore important to understand equity as a concept that generates a conceptual space in which multiple theories, analyses, and associated discourse are valid and necessary. Equity, especially in diverse, democratic contexts, does not have a single answer.

To explore the conceptual space generated by equity, we review various philosophical theories of equity that have been presented in the transportation literature. Journal articles, reports, and books are all included to capture the breadth of knowledge resources utilized by transportation researchers as well as practitioners. The works considered were predominantly written by and for a Western audience, therefore the theories presented were predominantly generated by Western philosophers.

These theories are explained and placed in conversation with one another within the article. Table 3.1 summarizes the theories and categorizes them by their assumptions and constraints and Table 3.2 provides transportation-based examples of each theory. This content serves as a resource for improved comprehension and application of theories of equity. Additionally, a table is used to illustrate which theories have been presented in the transportation literature and how some have been incompletely and/or imprecisely handled. Using the common language and definitions of the underlying philosophical theories, this contribution clarifies points of confusion within the existing body of transportation literature, among other things.

The article also presents the distinction between positive and normative forms of inquiry. This dichotomy was first established within the field of economics; positive assessments focus on the world as it is vs. normative assessments which focus on how the world ought to be. Figure 2.1 demonstrates how positive and normative assessments interact with and inform one another; ideally an informed normative assessment considers positive information and related assessments. Conversely, it is important to understand that positive analytical methods do not operate in a vacuum; they are rooted in and operationalize normative ideals. Given this understanding, equity is an inherently normative concept that is informed by positive analyses – distributional effects analyses in particular.

Business-as-usual methods tend to apply positive analytical methods without considering the normative theories that they operationalize, and certainly without considering the assumptions and constraints of said normative theories. Doing so does not remove these theories (such as equity) from the analysis, it simply obfuscates it. Take, for example, a Cost-Benefit Analysis (CBA). A CBA is a positive analysis that operationalizes a Utilitarian equity norm. As shown in Table 3.1, the Utilitarian theory of equity assumes an a-historical base case – this means that Utilitarianism does not account for contextual realities. Moreover, Utilitarianism is only concerned with the maximization of aggregate benefit – the outcome of this calculation is heavily influenced by which metrics are considered and, more importantly, which are omitted. As research has shown, this combination of a-historical assumptions and aggregate benefit maximization of some metrics (often limited and specified with limited intention) has led to outcomes that are deemed equitable under CBA (and, by extension, Utilitarianism), but inequitable under most other ethics.

The article discusses the CBA/Utilitarian relationship as well as other equity theories that are commonly implied in the transportation literature. Additionally, the article lays out the limitations of applying theories of equity that have been specified at the broad, societal level to the more-specific, disaggregate level of transportation infrastructure and services. While this article does not offer up its own transportation-specific equity ethic, it does present a range of theories that have been developed by other transportation scholars in recent years.

Transportation challenges are complex and nuanced, with any given project affecting the lives of many. As a result, transportation projects must be treated with careful ethical consideration. The recent push for equity within the field demonstrates a widespread recognition that such intentional consideration was not used in the past, but should be used now. This article is a resource to aid in this effort.