Focus on new faculty: Soyoung (Sue) Ahn, filling the gaps in traffic research
When Soyoung (Sue) Ahn first became interested in transportation engineering as an undergraduate at the Ohio State University, she realized that it wasn’t the most well-developed field. This, and the variety of research areas within transportation engineering, lured her away from her initial undergraduate focus on structural engineering.
Now, as an associate professor of civil and environmental engineering at UW-Madison, Ahn is still trying to fill in some crucial gaps in how engineers and planners study and solve traffic problems.
Ahn has long experience with congested areas. She grew up in Seoul, South Korea, amid the massive city’s decades of rapid expansion. Before joining UW-Madison in July 2013, she spent seven years as a professor at Arizona State University in the sprawling Phoenix area, where one of her PhD students analyzed the area’s entire freeway network and its bottlenecks.
Much of Ahn’s research thus far has focused on non-steady traffic features. "What I mean is that when you're in congested traffic, you don't travel at 30 mph the whole time,” she says. “You go through stop-and-go cycles, and when there are freeway merges and diverges, you tend to see very turbulent flows around those areas."
In other words, what makes traffic jams so frustrating and mind-numbing is also what makes them so ripe for study. Ahn currently is working on National Science Foundation-funded research on driver behavior in congested traffic. "If you are stuck in congestion, how do you follow the car in front of you, or when you change lanes, how do you go about making that decision and executing the lane change, or if you are entering from an on-ramp, how to you enter into mainline traffic?” she says. “These may seem like microscopic details, but the reason they're important is that they affect how non-steady traffic arises and develops over time and space."
Ahn also is part of the UW-Madison Traffic Operations and Safety (TOPS) Laboratory, which partners with the Wisconsin Department of Transportation to develop practical transportation solutions. That close partnership, Ahn says, offers a strong opportunity for researchers to access detailed empirical traffic data. She is currently preparing to work with WisDOT on a study of how road-work zones affect the capacity of roads and the safety of drivers.
Like her colleagues at TOPS, Ahn sees great opportunity for civil engineers to work with state agencies and planners to make America’s roads safer and more efficient. Her long-term interests include studying how the use of variable speed limits—common in Europe, but still new to the United States—can help make roads more efficient. She also sees a need to improve traffic research on the whole, and to make a stronger connection with researchers interested in sustainability and climate change.
"I would like to relate these traffic phenomena to environmental issues and health issues,” she says. “When we think about traffic that's not smooth, it can also affect the air quality significantly."
On a pure research level, Ahn thinks her field still has great hurdles to overcome in the way it models traffic. "What I see lacking is that a lot of models are not really based on empirical observations,” she says.
She sees a disconnect between people who study passenger traffic and researchers who focus on freight traffic—when in reality, she says, you can’t realistically study one without factoring in the other. And with more thorough data, she hopes engineers can create simulations that don’t require prohibitive amounts of computing power. "What's important is to develop a relatively simple model with just key parameters that are physically very meaningful,” she says.
Fortunately, she sees great opportunity for collaboration at UW-Madison, with colleagues in areas ranging from the National Center for Freight and Infrastructure Research and Education (CFIRE) to the Nelson Institute for Environmental Studies. By building interdisciplinary connections—or even better connections within traffic research—Ahn believes civil engineers can create build a more holistic and reliable picture of how our transportation systems operate.