Ditch Traffic Lights In Favour Of Connected Cars, Say Researchers

Twice as much traffic could use our roads if we ditched traffic lights in favour of cars that communicate with each other at junctions.

A study co-authored by MIT researchers, based on mathematical modeling, claims this kind of traffic-light-free transportation design would keep traffic moving smoothly as our roads become ever-busier.


Researchers examined a scenario in which vehicles use sensors to remain at a safe distance from each other as they move through a four-way intersection. By removing the waits caused by traffic lights, these so-called Slot-based Intersections (SIs) speed up traffic flow.

Carlo Ratti, director of the SENSEable City Lab in MIT’s Department of Urban Studies and Planning, and a co-author of the study, said: “An intersection is a difficult place, because you have two flows competing for the same piece of real estate.”

But a system with sophisticated technology and no traffic lights moves control from the traffic flow level to the vehicle level, he explained, adding: “Doing that, you can create a system that is much more efficient, because then you can make sure the vehicles get to the intersection exactly when they have a slot.”

Paolo Santi, a researcher in the SENSEable City Lab who is a member of the Italian National Research Council and another co-author of the study, noted that the greater capacity of the system does not stem from vehicles moving more quickly.

Instead, it comes from developing a more consistent flow at an optimal middle speed, at which cars can stay on-the-go.

Santi said: “You want the car to use the intersection for the shortest possible time.”

The theory is bound to work, according the researchers, because of what they call the ‘slower is faster’ effect.

Such an effect occurs, for example, when passengers board an airplane. The passengers tend to move faster if they are in smaller clusters that keep going steadily, rather than a scenario in which everyone crowds around the entrance, creating a giant bottleneck.

Santi added: “The ‘slower is faster’ effect has been observed in many other contexts related to flow of entities, for instances pedestrians through a narrow space.”

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Duncan Macrae

Duncan MacRae is former editor and now a contributor to TechWeekEurope. He previously edited Computer Business Review's print/digital magazines and CBR Online, as well as Arabian Computer News in the UAE.

View Comments

  • Having been a car driver for more years than I care to remember, I believe that traffic would move much more freely if many of the traffic light systems were removed. Yes, maybe "connected cars" would be a good idea, but most drivers are already connected by our existing senses. Anybody who has driven through a normally congested, traffic light controlled, junction must have seen, as I have, traffic flowing much faster than normal when the lights have failed. Furthermore, I have never seen an accident created by traffic light failure.

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