Estimating traffic today for better roads tomorrow

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Traffic in the city at night

Since 1963, the Committee on Traffic Flow Theory and Characteristics of the Transportation Research Board has been promoting the development, validation, and dissemination of research on traffic flow theory and characteristics. Each year the committee awards the prestigious Greenshields Prize to one paper that demonstrates the spirit of the award’s namesake, Bruce D. Greenshields, basing sound theory on rigorous empirical analysis. The 2017 recipients for the Greenshields Prize were none other than civil and environmental engineering’s (CEE) own Sean Qian, and Qian’s former doctoral student Yiming Gu, who is currently a Senior Research Engineer at the United Technologies Research Center. They received the award for their paper titled Traffic State Estimation for Urban Road Networks Using a Link Queue Model.

Traffic State Estimation (TSE) is the process by which engineers take data from multiple sources and use it to draw inferences about a number of traffic variables, such as speed, density, and flow on roads where no sensors are deployed. The focus of the Greenshields prize is to bring ideas off of the paper and into the real world. “If the theory is just a theory, it’s very hard to use,” explains Qian. “We’re trying to translate theory into practice.”

Most attempts at TSE within road networks have focused on highway networks as opposed to urban networks, due to the limited number of on-ramps, off-ramps, and exits on highways. This smaller pool of data makes it easier to compute accurate estimates in a reasonable time period. However, in this research, Qian’s sights were set a little higher; his goal was to glean accurate estimates for an urban network.