Road Traffic Safety

Self-Driving Cars Can Eliminate Start-and-Stop Traffic Jams

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Sure, a shining future where every car on the road is self-driving sounds great. But won't there be problems in the transition, when human drivers have to share the road with robot drivers? A 2017 study says no. Not only that, but researchers found that it would take a mere five percent of cars being automated to improve traffic on even the most crowded freeways. And like the best stories involving the relationship between man and machine, this one involves both state-of-the-art innovation as well as human psychology—it was funded by the National Science Foundation's Cyber-Physical Systems program, after all.

What Causes Stop-and-Start Traffic Jams?

Phantom traffic jams are phenomena in which one person in a line of cars slows down slightly for some reason, forcing the person behind them to slow down slightly, forcing the person behind them to slow down, and so on. This causes a ripple effect that can result in long start-and-stop traffic jams, despite the fact that there's nothing actually obstructing the road ahead. As Seattle engineer William Beaty explained to the Wall Street Journal, just a few diligent drivers are enough to prevent a traffic jam by keeping a steady speed and allowing large gaps to form in front of their cars, rather than speeding up to fill every gap. While it seems counterintuitive, catching up with the car ahead makes you slow down faster, causing ripples and waves of congested traffic—thus the title of Beaty's website, trafficwaves.org.

But still, even consciously attempting to keep a steady pace results in traffic jams, as showcased by this video from a study published in the New Journal of Physics in 2008. While a handful of diligent drivers may speed traffic up here and there, humans aren't perfect—and that's where self-driving technology would come into play.

Faster Traffic And Better Fuel Efficiency

A collaborative study from a multidisciplinary team of researchers has shown that traffic where only five percent of vehicles are automated and precisely controlled so that they're evenly dispersed among their fellow drivers would completely eliminate stop-and-start traffic jams. The study also found that it could reduce fuel consumption by a whopping 40 percent. Engineering At Illinois explains what this might mean for the future: "Just as fixed traffic sensors have been replaced by crowd-sourced GPS data in many navigation systems, the use of self-driving cars is poised to replace classical freeway traffic control concepts like variable speed limits."

The study shows that not only will a few autonomous vehicles on a road full of humans not wreak havoc, but they may actually make our roads more pleasant to drive on. Of course, five percent of traffic is a lot of self-driving cars. But as William Beaty pointed out, one diligent driver can have a big impact. Until we reach that bright future, perhaps simply more diligence on the part of a handful of human drivers can have us driving smoother in the meantime. Hey, we can dream.

Watch And Learn: Our Favorite Content About The Science Of Traffic Jams

Field Test from the NSF Autonomous Vehicle Study

What Causes Traffic Jams?

Share the knowledge!

Key Facts In This Video

  1. In New York City and Los Angeles, commuters spend up to three weeks per year stuck in traffic. 00:18

  2. The real culprit of traffic jams is the sudden fluctuation in driving speed. 00:32

  3. Traffic jams can be prevented with wider lanes and better-synchronized traffic signals. 01:24

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