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On These MIT-Designed Streets, There Are No Traffic Lights, Or Need To Stop At All

The intersection looks like chaos, but it's really a perfectly timed work of art and technology.

  • <p>Researchers at MIT have come up with what they call a slot-based system for intersections, which means the intersection doesn't need any lights.</p>
  • <p>It relies on self-driving cars that can talk to a control point in the intersection, much like planes can talk to air-traffic tower.</p>
  • <p>The slot system allocates a timed "space" for each car, and a car can't enter the intersection until its slot is ready.</p>
  • 01 /03

    Researchers at MIT have come up with what they call a slot-based system for intersections, which means the intersection doesn't need any lights.

  • 02 /03

    It relies on self-driving cars that can talk to a control point in the intersection, much like planes can talk to air-traffic tower.

  • 03 /03

    The slot system allocates a timed "space" for each car, and a car can't enter the intersection until its slot is ready.

In Larry Niven and Jerry Pournelle's classic sci-fi novel The Mote in God's Eye, humans end up visiting an alien planet. One of the oddities of this new world is that the aliens cross the roads by striding out into full-speed traffic. They all trust each other so much that nobody panics or dashes. Traffic and pedestrians weave past each other.

That novel was first published in 1974, so perhaps the aliens have gotten cellphones since then, and mow their pedestrians down like we do back here on Earth. But MIT has a new system that could do away with traffic lights, and let cars and trucks slip past each other at intersections without stopping, just like those alien pedestrians.

Researchers at MIT, along with the Swiss Institute of Technology (ETHZ), and the Italian National Research Council (CNR), have come up with what they call a slot-based system, which relies on self-driving cars that can talk to a control point in the intersection, much like planes can talk to air-traffic tower.

"Traffic intersections are particularly complex spaces, because you have two flows of traffic competing for the same piece of real estate," says MIT Senseable City Lab's Professor Carlo Ratti.

The slot system allocates a timed "space" for each car, and a car can't enter the intersection until its slot is ready. In practice, this allows the intersection's brain to fine-tune the speed of every vehicle that enters it, letting them slip past each other, just like those aliens.

"A slot-based system moves the focus from the traffic flow level to the vehicle level," says Ratti. "Ultimately, it’s a much more efficient system, because vehicles will get to an intersection exactly when there is a slot available to them."

This system, say the engineers behind it, should lead to zero queueing at intersections. Traffic lights and other stop-start controls could be ditched altogether. Travel times, and also fuel consumption, would drop.

And this isn't just for highway junctions. The tech works even better in urban settings, or is at least even more useful, because it "can easily accommodate pedestrian and bicycle crossing with vehicular traffic." That's right. You can just wander across the street, through moving traffic, without getting hit.

The catch is that this needs self-driving cars to work. As soon as some moron who is actually driving his SUV hurtles through the intersection, while also slurping a coffee and sending a text, all safety bets are off. And we know from existing research that humans will take advantage of autonomous cars' politeness.

But the payoff in cities is so big that perhaps these intersections could encourage cities to hasten their bans on cars, or human-controlled cars at least. Or maybe only self-driving cars will be allowed on slot-controlled downtown roads, while human drivers are banished to the overpasses and expressways, away from vulnerable pedestrians?

All Images: MIT Senseable City Lab

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