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October 2018

Researchers develop computer model to regulate city traffic and ease gridlock

Two researchers in Pullman, Washington have developed a computer algorithm to regulate traffic flow in and around urban areas. The technology could help prevent gridlock and reduce travel times on congested city streets by nearly 30 percent.

The groundbreaking research, published in the August issue of Transportation Research Part C: Emerging Technologies, was led by led by Ali Hajbabaie Ph.D., assistant professor in the department of Civil and Environmental Engineering at Washington State University, and graduate student Rasool Mohebifard.

The computer model enables estimating the traffic needs for individual metering gates on city streets. The system is dynamic, meaning it is able to update the metering estimate based on increases or decreases in traffic.

Hajbabaie said researchers have developed solutions for city streets gridlock by determining how much traffic needed to be reduced overall in an urban grid, but there has been no way to determine how much of incoming traffic needed to be stopped at a given entry point.

The WSU researchers used mathematical techniques to optimize traffic flow, finding the optimal percentage of incoming traffic that should be stopped at each gate. With optimization, researchers have to maximize or minimize quantities while satisfying some necessary conditions, explained Hajbabaie.

Traffic metering technology to regulate traffic flows has been around for years, perhaps most notably for regulating freeway entrances in congested areas.

In developing their system to better manage traffic on city streets, the professor and student aimed to maximize the number of vehicles passing through a street grid while making sure it is not oversaturated, causing gridlock.

"The idea is that at a certain traffic volume, we're going to have gridlocks unless we can intelligently regulate flow of traffic into an urban street network," said Hajbabaie.

The researchers, whose work was funded by a grant from the U.S. Department of Transportation, have tested their model using traffic simulations on a computer and calibrated it with real world traffic data.

Dr. Hajbabaie joined WSU in 2014. His research focuses on developing data driven methodologies to improve operations, safety, and sustainability of current and next-generation transportation systems.