Smart Intersections Could Help Autonomous Car Traffic

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Autonomous vehicles have been sold as an answer to congestion problems. While coordinating vehicles on the road through sensors and artificial intelligence might help, it won’t be enough without a supporting infrastructure. A smart intersection could help alleviate the parking lot atmosphere of city streets by increasing flow of traffic and street capacity.

  • Autonomous vehicles hold the promise of reducing congestion on city streets.
  • Without the proper infrastructure, self-driving in unlikely to reach its potential.
  • Smart intersections could reduce congestion while doubling road capacity.

TrafficCornell researchers came up with a model for a smart intersection for platooning autonomous vehicles that could make gridlock a thing of the past. (Photo: Getty Images)

Intersections the problem

Self-driving cars can potentially move faster and don’t need as much space in-between on the road. But what happens when the streets have to handle an influx of autonomous vehicles? Fitting more vehicles on the road could bring us right back to the original problem: gridlock.

As reported by the Cornell Chronicle, researchers at the university examined how intersections could play an important role in optimizing road capacity, minimizing accidents and keeping traffic flowing.

“If you have all these autonomous cars on the road, you’ll see that our roads and our intersections could become the limiting factor,” said Oliver Gao, professor of civil and environmental engineering and senior author of “Optimal Traffic Control at Smart Intersections: Automated Network Fundamental Diagram.”

The researchers developed a model whereby groups of autonomous cars, known as platoons, pass through one-way intersections without stopping. A microsimulation resulted in increasing vehicle capacity on city streets by up to 138% when compared to the conventional traffic signal. That’s doubling the number of cars on the road, while speeding up travel time!

Although the model is based only on autonomous vehicles on the road, Gao and his team are working on a model that will include both autonomous and human piloted vehicles.

The Texas A&M Transportation Institute provides a great explanation of platooning and its benefits. (Video: YouTube)

Platoon power

According to the article, most traffic modeling assumes autonomous vehicles will move in platoons, groups traveling in the same direction, for greater efficiency. When there’s a need for a change of direction, the vehicles can disengage from one platoon and join another. Hyundai recently demonstrated platooning with autonomous trucks.

One of the primary variables considered in the Cornell researchers’ model was determining “optimal traffic configuration”, meaning the number of cars traveling in each platoon approaching intersections. Since mathematical errors associated with this coordination can cause operational failures or accidents, researchers developed a formula that takes into account the probability of failures. The model therefore factors in that probability and adds a compensating time gap between crossing platoons.

“By coordinating the platoon size and the gap length between cars and platoons, we can maximize the flow and capacity,” Gao said. What this translates to in practical terms is that platoons can go through intersections not monitored by a traffic signal without stopping.

Traffic signals at intersections would operate differently than they do now. “Instead of having a fixed green or red light at the intersection, these cycles can be adjusted dynamically,” Gao said. “And this control can be adjusted to allow for platoons of cars to pass.” It’s quite possible that as smart technology advances, we might even be able to retire the traffic signal to historic memory.


For autonomous cars to reach their full potential, infrastructure must be in place to support them.

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