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Self-Driving Cars: A Single Autonomous Vehicle Can Reduce Traffic Jams Around It

Self-driving cars will have a big effect on reducing traffic jams. In fact, according to a piece in the MIT Technology Review in May, just one autonomous car has a huge impact on alleviating traffic backups. Seems improbable, right?

Just as most traffic crashes are a result of human error (about 90 percent), a majority of traffic jams result from the way humans drive: erratically, illogically and emotionally. How often have you been in stop-and-go traffic on the freeway, straining to see if the culprit is an accident, breakdown or construction? Suddenly traffic begins to spread out and flow again. There was no construction or accident, just traffic moving erratically. It’s the human factor.

Phantom Traffic Jam

Demonstrations of phantom traffic jams stage several cars driving around in a circle, simulating moving traffic on a highway. Gradually, the circle of cars begins to sporadically slow, stop in places, and jam up. Why? One car brakes for no particular reason, setting off a chain reaction. As the following cars brake to compensate, things just grow worse. Soon, the entire circle spastically stops and starts in fits and jerks.

To the Rescue

Why are some experts convinced self-driving cars will all but eliminate traffic jams? Because researchers at the University of Illinois significantly reduced the amount of braking in a phantom traffic jam when they introduced just one autonomous vehicle (AV) into the mix of 20 cars. With that one AV added to the circle, the amount of braking behind it was reduced significantly. It reduced the standard deviation in speed of all the cars behind it by about 50 percent. Even more impressive was that sharp hits to the brakes were reduced from around nine per vehicle for every one kilometer driven to 2.5 or fewer brake hits. On some tests, the sharp brake hits were reduced to zero.

Lowering stress levels and saving time aren’t the only benefits. Research team calculations indicated that with the AV smoothing out the traffic flow, the fuel savings were as much as 40 percent when averaged across all the cars in the traffic flow.

What it means to you: The results achieved in the University of Illinois research weren’t even with a totally autonomous car. The research used a vehicle with features currently available on many new cars, such as adaptive cruise control. One can only imagine the traffic issues that could be solved once humans are out of the equation completely. It may be another decade or two before self-driving cars fill our roadways, but we should feel a positive impact well before then.

Russ Heaps
Russ Heaps is an author specializing in automotive, financial and travel news. For nearly 35 years he has covered the automotive industry for newspapers, magazines and internet websites. His resume includes The Palm Beach Post, Miami Herald, The Washington Times and numerous other daily newspapers through syndication. He edited Auto World magazine, and helped create and edit NOPI Street... Read More about Russ Heaps

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