Motivations

In our increasingly interconnected urban environment, a vision of city as a space of flows has often materialized through network infrastructure, such as transportation systems for movements and social amenities for relationships. In urban planning, connectivity has become a normative goal, exemplified by programs such as USDOT’s “Reconnecting Communities,” which aim to remove dividing infrastructure, enhance community connectivity, and improve access through complete streets.

Yet, our understanding of urban infrastructure in the network systems is quite limited. Many highly connected infrastructures—especially those designed to serve high network flows—exhibit dual dynamics: they provide connectivity for certain populations, places, or types of flows while excluding others. Highways, for instance, often reinforce spatial and social segregation; railways frequently bisect informal settlements in the Global South; and airports facilitate regional passenger flows at the expense of local mobility. More localized examples highlight similar tensions: the demolition of a historic street in Guangzhou for a new subway station severed social connections, while the “shadows” cast by overhead train tracks in Chicago altered the surrounding urban fabric.

These tradeoffs and inequalities often remain hidden unless explicitly revealed or empirically examined. This challenge is further compounded by the lack of standardized methods to analyze, predict, and address the impacts of multi-network systems, particularly when these systems serve different and sometimes competing types of flows. Discussions of these impacts are often fragmented across disciplines, conflating social and land-use conflicts without addressing the unique dynamics of networks. Moreover, planning practices tend to optimize individual network systems in isolation, and funding structures seldom consider the costs imposed on alternative forms of connectivity.

Connectivity itself is deeply tied to power, with strong economic and efficiency incentives to further connect already well-served populations while marginalizing others. Addressing this imbalance requires a more holistic framework. My research seeks to unify these seemingly disparate planning issues by focusing on the nexus of networked connectivity, differential impacts, and cross-system dynamics. Through this lens, I aim to develop new methods and tools that not only reveal these hidden dynamics but also support more inclusive and equitable planning practices.

My work aims to advance the understanding of network duality—a concept I use to explore where, why, and when urban infrastructure becomes inclusive or exclusive for different populations, places, and types of flows. The primary methods I will employ include empirical studies and case analyses, often fused with network representation and analytics. I am open to investigating diverse types of urban infrastructure that can be conceptualized as supporting network connections and flows.

How can I learn more about Network Duality?

Network Duality is a new research theme that I am currently developing, so there are few examples online. Network Duality is not a “new” urban phenomenon, but rather, a new perspective to conceptualize, analyze, and contest issues around urban infrastructure. I also welcome a broad definition of the term “infrastructure” — it can be a piece of built environment, an organization, a practice, or a community of people!

Here are some relevant work:

• Liang’s PhD dissertation: Connectivity for whom and at what cost: contesting network infrastructure duality in urban planning (recommend to read Summary, Introduction, and Conclusion).
  • Case Study 1: Transforming Mobility Barriers to Connectivity: Examining the Impact of the AeroATL Greenway Plan in Reconnecting Communities around Aerotropolis Atlanta.
  • Case Study 2: A Network Lens on Social Costs: Demolishing a Historic Street for a New Subway Station.
  • Empirical Study 3: Where Does Social Infrastructure Exist Near Subway Stations? A Global Assessment Using OpenStreetMap Data
• Liang’s seminar talk at the Center for the Study of Complex Systems: Beyond Nodes and Edges: Integrating Spatial Contexts into Urban Network Science (recommend to start at 29:10; repeat some contents in the PhD dissertation)
• Network Duality Case Study Library (recommend to scan the QR code and read the case studies)

What proposals are desired?

You can come up with your own topic, or follow along with one of the inquires below. Please note that these are broad directions; you will need to submit a more SPECIFIC research question in your proposal.

One tip to start thinking about a specific research question is to map these thinkings to a specific type of network or network feature (e.g., killer intersection, highway, golf course, cloud server infrastructure, etc.). What urban infrastructure has deep connectivity implications or have contested debates due to its network features? Below are some starting points for thinking:

• What urban infrastructure would have a dual role in the local context and network space? While connectivity can bring growth and power to a location, it may also impose burdens on local communities. For instance, in one of my projects, I reveals that subway stations with high importance in the network do not always align with social infrastructure presence, with this disparity varying across 34 global cities.
• How would you represent, measure, or contest differential network impacts? Evaluating the impact of urban infrastructure often emphasizes system-level metrics (e.g., traffic reduction from a new road) while overlooking how these impacts are distributed among different populations, places, and flow types. Such inequalities can occur within a single network or across multiple interacting networks. For instance, a proposal accepted examined NYC Subway Network from the perspectives of ADA accessibility, comparing how the network would change, if only ADA stations are considered and how the flow-based experience is different for the population that needs such accessibility.
• How to capture interactions and competition among multiple network systems? Urban network systems often coexist, interact, trade off, or compete for resources and power, each operating with its own "pattern language" (or “semantic language). Translating benefits and costs across systems presents significant challenges. For instance, in A Network Lens on Social Costs: Demolishing a Historic Street for a New Subway Station, I compared the benefits and costs of subway infrastructure—measured as reduced travel distances in Origin-Destination data—with those of preserving a historic street, evaluated through metrics such as social ties and memories. These representations are inherently difficult to compare. Additionally, analyzing multi-network systems involves technical challenges, as data on interactions between systems is often limited or unavailable.

A different way to do the thought exercises is to think about a single case study or similarities across cases with the following questions:

• Is there a connectivity infrastructure in urban space that is casting shadows on other types of connectivity, other population, or other places?