McCormick School of Engineering, Northwestern University

Transportation Engineering

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Transportation is at a tipping point: with the nation’s infrastructure crumbling, urban and suburban traffic congestion overwhelming, and concerns over greenhouse gas emissions ever increasing, it’s clear the country can’t continue on the same path as it has been on for the past 60 years. Change — in this case, massive change — is always resisted: politically, culturally, and economically. But faculty members at the McCormick School keep pushing and creating new models and technologies for this necessary change.

Technology and Psychology

“Transportation is a particularly interesting area because it’s at the intersection of technology and people and the behavior of people,” says Joseph Schofer, professor of civil and environmental engineering. Schofer should know: for the past several decades he has studied the planning and management of transportation systems from the perspectives of policy, planning, design, and operations.

Schofer directs the Infrastructure Technology Institute, which develops strategies and tools to protect and improve the condition, capacity, and performance of the nation’s highway, railroad, and mass-transit infrastructure systems. A major research focal point for the center — one that has gotten more attention since the August 2007 bridge collapse in Minneapolis — is using sensors to measure the condition of a structure in real time. The institute currently has sensors on a bridge in Louisville, Kentucky, that transmit condition and performance data back to the lab at Northwestern.

Image of McCormick professor Pablo Durango-Cohen That’s where Pablo Durango-Cohen, associate professor of civil and environmental engineering, comes in. “The problem I tackle is how to process these data efficiently to obtain information and use them to decide what actions we’d like to take and when we should take them,” says Durango-Cohen, who has a background in industrial engineering. He is working on models to determine how to best synchronize infrastructure work — and how to finance it, as well.

“We are modeling interactions between governments and private agents who wish to invest and develop or take over infrastructure,” he says. “In the United States alone, we spend tens of billions of dollars a year on the maintenance of roads and bridges. There is a huge potential not only for direct savings but also indirect savings with greater mobility.”

Engineering a Better Decongestant

Besides the roadwork that results from infrastructure problems, one of the main complaints of drivers is congestion. How congestion happens is an area of interest for Yu Marco Nie, assistant professor of civil and environmental engineering, who researches traffic-flow theory and traffic simulation. Nie studies the mechanisms causing oscillations and gridlocks in urban traffic, and he has developed a traffic simulation platform that integrates a variety of traffic-flow models.

But unless overall demand decreases or available supply increases, congestion may ultimately be a matter of better managing existing facilities, including the communication of information to users. Existing variable message signs that are based on roadside sensors can tell drivers of current congestion, but they can’t predict future traffic problems, so they aren’t ideal. Hani Mahmassani, professor of civil and environmental engineering, William A. Patterson Distinguished Chair in Transportation, and director of the Transportation Center, is researching the use of real-time information — through wireless location and communication devices, vehicle sensors, and variable displays — to give drivers information about traffic in the area and enable system managers to operate their networks and distribution systems optimally.

If Cars Could Talk

Other faculty members, such as Fabian Bustamante, associate professor of electrical engineering and computer science, and Karen Smilowitz, associate professor of industrial engineering and management sciences and William A. Patterson Junior Professor in Transportation, are working on a project called C3, which stands for “car-to-car cooperation.” The project explores what would happen if vehicles had the ability to communicate with each other. In such a model, vehicles would be equipped with wireless communicators, GPS navigators, and digital maps so vehicles could exchange information about infrastructure, road conditions, and traffic. “This creates a wireless environment that is completely free of infrastructure,” Bustamante says. “It’s more resilient, dynamic, and scalable but also more complex than current approaches.”

Pricing Traffic Away

Another possible solution for congestion is so-called congestion pricing, or requiring vehicles to pay fees to drive in a certain area at a certain time. “We have developed methods that can predict traffic flows and set prices accordingly to prevent congestion proactively,” Mahmassani says. Considering the state of infrastructure funding, Schofer thinks more and more road systems will be financed this way.

“My prediction is that in another 10 years, you’re going to see that as a very common way to finance road systems,” says Schofer. “Charging for driving at a certain time is a fairer and more efficient way to collect revenue.”

Back Away From the Vehicle

Even if traffic is relieved via congestion pricing, it still leaves a major problem: pollution. The average car emits more than 11,000 pounds of carbon dioxide into the atmosphere each year. Long-term solutions will certainly involve using different sources of energy, but what can be done now?

Image of McCormick professor Hani Mahmassani Schofer and Durango-Cohen, along with Kimberly Gray, professor of civil and environmental engineering, are trying to assess the environmental impact of infrastructure and how it shifts demand to different modes of transport. They are working on a case study that looks at various Chicago neighborhoods to assess how greenhouse gas emissions and energy consumption relate to how close people live to mass transit. Mahmassani and his group have developed methodologies to analyze the European intermodal rail network to shift freight from trucks to rail to reduce environmental impact.

“The transportation sector is a major consumer of energy and a major polluter,” Mahmassani says. “Solutions to the global problem of pollution must address transportation issues. By making our systems less congested and more efficient, we tend to also make them more environmentally friendly.”

A Long-Term Commitment

To find solutions to these myriad problems, faculty members must not only study transportation and infrastructure but also sociology, economics, and political science. The base for these multifaceted studies is the Transportation Center, a leading interdisciplinary education and research center founded in 1954 that serves industry, government, and the public. “It was revolutionary when it was conceived,” says Mahmassani. “It is a very dynamic environment. We interact very closely with the transportation industry: our business advisory committee includes more than 75 different companies, including airlines, railroads, and shippers. It’s a source of real-world insights and problems that our faculty and students work on.”

Finding solutions to problems doesn’t matter if you aren’t working closely with both government and industry, Schofer says. “If you don’t work with the customer, then you’re distant from the problem. Grounding in reality is tremendously important for the quality of our research and the impact it produces.”

The Greater Good

Working with industry doesn’t always mean working with the Department of Transportation or industry bigwigs — it also means using transportation research to help nonprofits. Smilowitz has worked with both a local suburban library system and a local food bank to optimize how books and food are distributed. Besides having problems that they often lack the budget and knowledge to solve, these organizations have different needs than for-profit companies.

“With a nonprofit, the goals change,” Smilowitz says. “You can’t just take a commercial model and apply it, since maximizing profit and minimizing cost aren’t necessarily the goals.” Smilowitz and her colleagues have found the best way to distribute books in the budget-constrained library system and helped the food bank find the best way to pair up donors and recipients and how to best design delivery routes to serve people. “It’s great to work with organizations that need our help,” Smilowitz says.

It’s also a good lesson for students, who work with faculty on many transportation problems. Says Mahmassani: “Transportation engineers design solutions, and we teach students the skills to design solutions to problems like these.”