By Siddarth Vodnala, Voiland College of Engineering and Architecture

Washington State University researchers have developed a computer model to better manage traffic and prevent gridlock in urban areas. Their metering system, using a computer algorithm, can reduce travel times on congested city streets by nearly 30 percent.

The researchers, led by Ali Hajbabaie, assistant professor in the department of Civil and Environmental Engineering, and graduate student Rasool Mohebifard, have published their work in the August issue of Transportation Research Part C: Emerging Technologies.

The average American commuter wastes 42 hours a year and nearly $1,000 stuck in traffic, according to a 2015 study from the Auto Insurance Center, an insurance information website. In large cities like New York City and Los Angeles commuters spend nearly 100 hours a year in traffic congestion, according to INRIX, a transportation analytics company.

Traffic metering to regulate the traffic flow has been around for a long time. Transportation agencies often use the technology to regulate freeway entrances in congested areas.

For city streets traffic, scientists came up with solutions for gridlock by finding out how much traffic needed to be reduced overall in an urban grid. But there was no way to determine how much of incoming traffic needed to be stopped at a given entry point, said Hajbabaie.

The WSU research, for the first time, has developed a computer algorithm that estimates the traffic needs for individual metering gates on city streets. The system is also dynamic, meaning it is able to update the metering estimate based on an increase or decrease in traffic.

“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.

They 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. Hajbabaie and Mohebifard aimed to maximize the number of vehicles passing through a street grid while making sure it is not oversaturated, causing gridlock.

The researchers are now developing computer programs that will identify optimal locations for installing meters in urban areas to prevent gridlock.

They have tested their model using traffic simulations on a computer and calibrated it with real world traffic data. Their research was funded by a grant from the U.S. Department of Transportation.

Hajbabaie points to a computer screen while discussing a new traffic metering system with Mohebifard.
Rasool Mohebifard (left) and Ali Hajbabaie (right) have developed a computer model that can reduce travel times on congested city streets by nearly 30 percent.