MIT hopes to eliminate traffic lights

MIT hopes to eliminate traffic lights

Without stop lights, roadways could support twice as much traffic

As vehicles become more wirelessly connected, communicating with each other and the infrastructure around them, traffic lights may become an unecessary impediment in getting from A to B.

Instead of stopping for traffic lights, sensor-laden vehicles would communicate with each other and perform a kind of ballet around each other, according to a new study by MIT.

The study claims this kind of traffic-light-free transportation design, if it ever arrives, could allow twice as much traffic to use existing roads.

MIT vehicle-to-vehicle communication MIT

Vehicles are emerging today that 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 speed up traffic flow.

Vehicles are being built today, and hundreds of millions will be sold over the next decade, that enable vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2X) communication.

In the city of tomorrow, traffic lights will be replaced by intelligent intersections for controlling urban traffic, seamlessly knitting together flows of cars, pedestrians and bikers, researchers at MIT's Senseable City Lab said.

The study, Revisiting street intersections using slot-based systems, was published this week in the journal Plos One.

The study is based on mathematical modeling, through which researchers examined a scenario in which high-tech 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.

"An intersection is a difficult place, because you have two flows competing for the same piece of real estate," Carlo Ratti, director of the SENSEable City Lab in MIT's Department of Urban Studies and Planning, said in a statement.

Ratti, who co-authored the study, said a system with sophisticated technology and no traffic lights shifts control from the traffic-flow level to the vehicle level.

"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," he added.

The greater capacity of the system doesn't come from vehicles moving more quickly but by creating a more consistent flow at an optimal middle speed, at which automobiles can keep moving.

In just four years, most cars and trucks will be connected to the Internet, according to a report from Gartner Inc.

By 2020, 250 million cars will be "connected" through the expansion of high-bandwidth wireless network infrastructure, raising expectations for access to mobile content and better service from smartphones and tablets.

Opening a communication channel to allow wirelessly connected vehicle systems to share information with each other and with roadside infrastructure will make cooperative intelligent traffic systems possible, and pave the way for self-driving vehicles, Gartner said.

Cars will be able to report hazards and traffic conditions, select routes to avoid congestion, coordinate with traffic signals to optimize traffic flow and travel in platoons to minimize energy consumption, the research firm said.

At the Geneva International Motor Show this month, automobile electronics parts maker Harman announced a partnership with chip maker NXP through which it will demonstrate its “LIVS Connected Car Compute Platform.” The new V2X technology allows alerts to be delivered to vehicles from other cars and surrounding infrastructure, such as traffic lights and signage, to warn drivers about potentially hazardous traffic situations ahead.

The technology literally allows drivers to “see” around corners and through traffic obstacles by way of V2X powered alerts, delivering information from other cars and surrounding road infrastructure (such as traffic lights and signage) to alert drivers and their vehicles to road conditions ahead.

Even as the technology to create a connected vehicle infrastructure improves, MIT admits there's still much work to do before traffic lights can be eliminated. 

"In many cities, intersections with lights are often placed relatively close to each other. So how would the dynamics of traffic at one intersection propagate through a whole urban network of roads?" the study states.

"If you start from the intersection, this propagates to the city level," Ratti said. "Part of the work we're doing is studying that propagation."

Still, despite the complexities that might create, Ratti said the intersection-first theoretical approach to urban traffic will prove beneficial "because the intersection is the crucial point, once you solve the intersection, it has a beneficial effect on the whole system."

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