The Fuse

MIT Study Shows Big Benefits of Autonomous Cars: No Traffic Lights and Congestion at Intersections

by Matt Piotrowski | April 01, 2016

It may be difficult to wrap your head around this, but some day, perhaps in our lifetimes, we will see intersections without traffic lights or stop signs. That may sound dangerous and mind-boggling at first, but if it one day becomes a reality, it would likely end up safer than the current system and allow for more mobility and more vehicles on the road to transport passengers.

Researchers at the Massachusetts Institute of Technology (MIT) have examined how autonomous vehicles will reshape traffic at intersections. As vehicles communicate with each other through sensors, they can remain a safe distance from each other but they do not have to completely stop before slithering through an intersection. See the video here for how “slot-based” intersections would operate through coordinated computer control and how vehicles would miss colliding with each other by just inches:

One benefit of such a structure is safety. By removing the driver from the equation, there’ll be no more crashes from motorists failing to brake correctly at intersections with either red lights or stop signs. The other positive: Since these vehicles, dubbed “slot cars,” won’t have to fully stop, traffic will flow a lot smoother, cutting down on transportation time and allowing for more vehicles on the street without congestion.

Slower is faster

The co-authors of the study, Carlo Ratti and Paulo Santi, say this type of system has the “slower is faster” effect. It cuts out bottlenecks and would allow vehicles to move faster in smaller clusters.

“The ‘slower is faster’ effect has been observed in many other contexts related to flow of entities, for instances pedestrians through a narrow space,” said Santi, a researcher in the SENSEable City Lab at MIT in a post by the school’s news office. “If you need to slow down the vehicles because there is a lot of traffic, you slow them down early in the road, so they approach the intersection at slow speed, but then when they cross, you use the best speed.”

Hindrances to cities without traffic lights

The idea of cities without traffic lights and constantly moving traffic appears fascinating, but while such a system would undoubtedly bring a number of positives, it also prompts a long list of questions. For one, since many traffic lights are close to one another, it is unclear what the knock-on effects throughout an entire urban network would be from changing just one intersection.

There’s also the complication of pedestrians and bicyclists. Solutions for this problem might include separate overpasses and underpasses for walkers and bikers.

Given that “slot-based” intersections are a long ways off from becoming realized, there’s time to figure out solutions to hindrances and build the proper infrastructure to accommodate these vehicles.

The benefits would be widespread and ultimately upend the today’s congested and unsafe driving environment. The advent of autonomous cars will increase demand from populations that currently don’t drive—the very old, the very young, the blind, certain other groups with disabilities—and is likely to boost travel overall with more convenient access to cars. Against that backdrop, cities will need a continuous flow of traffic. “Because the intersection is the crucial point, once you solve the intersection, it has a beneficial effect on the whole system,” said MIT’s Ratti.

topics: autonomous vehicle technology, autonomous vehicles, MIT, research, Traffic lights, Video