Georgia Tech picked Sandy Springs as one of its four Georgia Smart grant winners for its pilot project to create a transit signal priority system for MARTA bus service to cut transit time for riders.

Sandy Springs will collaborate with MARTA and the city of Dunwoody on the Georgia Smart Communities Challenge project. Georgia Tech researchers Michael Hunter and Kari Watkins will work with the project team, the university announced in a release on Aug. 6.

The pilot project targets bus Route 5, which has high ridership between the Dunwoody MARTA Station and Buckhead’s Lindbergh Center MARTA Station via Hammond Drive and Roswell Road, said Dunwoody Public Works Director Michael Smith.

The project aims to cut how much time buses wait at red lights. That would reduce travel times for transit.

The project’s goal is to allow transit buses to talk to the traffic signals, said Michael P. Hunter, a professor of Transportation Systems Engineering and Smart Cities at Georgia Tech. He and Kari Watkins will evaluate the performance of the project.

“We are excited to work with Georgia Tech and in collaboration with MARTA and the city of Dunwoody in exploring opportunities to maximize current software to generate more efficiencies along our roadways, and at the same time enhance the benefits of using public transit,” said Sandy Springs Mayor Rusty Paul. “It’s a program with potential to provide benefits throughout the region.”

Sandy Springs will provide $25,000 in a local match to the grant, and another $15,000 comes through an in-kind contribution.

Dunwoody will participate through staff time and $11,000 to install equipment at two intersections in the city. Smith said they can use the equipment for emergency vehicle signal preemption also, which has done at a few other intersections in the city.

“We were pleased to partner with Sandy Springs and MARTA on this project because it fits perfectly with our goal of increasing connectivity,” said Dunwoody City Manager Eric Linton. “The Dunwoody MARTA Station is a key transportation asset, and this program builds upon the investments that Dunwoody has made in traffic technology.”

The project begins in September with the purchase of technology and modification of traffic signals. The project will go live from February to April 2021. Georgia Tech’s research team will evaluate the results through June 2021, followed by a public meeting in July. From the evaluation and other feedback, recommendations will be identified and an implementation plan to go beyond the pilot project will be developed.

The Georgia Smart project includes:

  •       $100,000 in grant funding to develop their pilot.
  •       Technical assistance and $50,000 in funding for Georgia Tech researchers.
  •       Access to a network of peer governments to share best practices.
  •       Access to a local, national, and international network of experts for advice on piloting a smart community.

Hunter said the project leverages a lot of emerging technology, including the connected vehicle, enabling the buses to communicate with the infrastructure. Current signal changing is handled passively, with vehicles driving over sensors or through observations via traffic cameras.

“The intersection determines what action it will take, but the technology allows the bus to request longer green lights (or shorter red lights if safely available) when the bus schedule is heavily impacted by traffic,” MARTA spokesperson Stephany Fisher said.

There are different types of signal switching capabilities, Hunter said. Ambulances and fire trucks use preemption, which gets immediate service to the signal so the emergency vehicle can get through the intersection. In the case of transit, it’s more about priority. A change still gets made to signaling, but it won’t be as drastic as might be seen with emergency vehicles.

“You don’t want to be disturbing other traffic flow when you are doing that. Everybody gets roughly the same amount of green time,” he said.

The transit buses will be a lower priority for signal changes than emergency vehicles.

“What you really want to be thinking about, it’s not just how many cars you can get through, but how many people can I get through?” Hunter said.

Large vehicles like buses take longer to get started once they’ve stopped. By limiting the number of times they have to stop, it helps other vehicles, too, Hunter said.

The role of Georgia Tech is to make an impartial evaluation of the system and see how it works, Hunter said. From the evaluation they will recommend what might be done in the future. And they can consider what the cost of the system is versus the benefits.

The project collaborators will have hardware challenges in making the system work. They need to get technology installed at traffic signal cabinets for each intersection, he said. And corresponding technology needs to be in the buses so they can talk to each other. 

They also will have operational challenges so they make sure they don’t penalize one piece of the traffic puzzle to help another. They’ll need to determine how priorities work and how the traffic lights would change in an efficient manner and stay safe, he said.

“MARTA has experimented with this technology in the past, but this project will pilot a newer approach that is less hardware-intensive and, if successful, could be more easily deployed in other corridors,” Fisher said. 

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