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Team receives NSF grant to study carpooling in cities

4/26/2021 2:31:39 PM

Lewis Lehe
Lewis Lehe

How to encourage and improve carpooling in cities is the focus of a new collaborative project by researchers from CEE at Illinois and Penn State, thanks to support from the National Science Foundation. Assistant professor Lewis Lehe is leading the University of Illinois team, which is receiving a $200,000 grant for the work.

The goal of the project is to more clearly understand how people’s travel choices are interrelated, Lehe said.

“If many more people were to carpool, then it would be easier for each person to carpool,” Lehe said. “Governments and businesses know this and thus have been encouraging various kinds of carpooling. For example, in Chicago there is a lighter tax on pooled ride-hail trips than on solo trips. But it is easier to think about these efforts when there exists a clear theory and vocabulary to describe how choices are interrelated.”

The project will explore the dynamics of carpooling considering that an individual’s choice to use a carpooling service depends on how many others choose to do so as well. The research will model new mechanisms of positive feedback in a range of settings, validate these results using data from public agencies and private firms, and leverage this information for improved control of pooled transportation systems.

The knowledge obtained can be used to develop and refine pricing, taxation and other policy strategies that can both promote pooling and reduce urban traffic congestion. Improving carpool options can also improve environmental outcomes, by reducing vehicle travel, and social equity, by providing reasonable travel times to those who cannot buy or drive a car but who do not live close to convenient transit options.

The research will specifically focus on two mechanisms of positive feedback in carpooling. The first is hyperdemand, whereby the share of people choosing to carpool both depends on and affects traffic congestion. The second are matching externalities, whereby the quality of matches among carpoolers increases as more choose to carpool.

The research will break new ground by bringing to bear tools from dynamical systems, search/matching theory and network-level traffic relations to build a robust theory of carpooling. To validate the theory, the research team will use empirical data collected from open data sources and industry partners.

“We are grateful to our industry partner, Scoop,” Lehe said. “Scoop has recently provided us with a great dataset that confirms some predictions we made from theory.”

Case studies of real policies to promote carpooling will inform the research and provide an evidence base for future work. The research activities will provide a new paradigm for modeling carpooling services and ride-hailing systems that will have significant impacts for the next generation of urban transportation systems.