# Why Ants Handle Traffic Better Than You Do

Jan 19, 2015
Originally published on June 24, 2015 10:52 am

Could studying ants reveal clues to reducing highway traffic jams? Physicist Apoorva Nagar at the Indian Institute of Space Science and Technology thinks the answer is yes.

Nagar says he got interested in the topic when he came across a study by German and Indian researchers showing that ants running along a path were able to maintain a steady speed even when there were a large number of ants on the path.

Nagar says there are three main reasons ants don't jam up. No. 1, ants don't have egos. They don't show off by zooming past people.

"The second thing is, they do not mind a few accidents or collisions," say Nagar. So unless there's a serious pileup, they just keep going.

The third reason, he says, is that ants seem to get more disciplined when paths get crowded, running in straighter lines and varying their speed less. They're less likely to make unexpected moves in this sort of heavy traffic. It's the kind of steady control you see when a computer, rather than a human, is controlling a car. There's less variability unless it's absolutely called for.

Nagar felt this kind of behavior could be explained by something called the Langevin equation, an equation physicists use when describing the movement of liquids, or how individual atoms behave in a lattice.

And what, you ask, is the Langevin equation? I wasn't entirely sure, so I turned to Thomas D. Donnelly, a physics professor at Harvey Mudd College. "This is basically a reworking of Newton's famous F=MA equation," Donnelly told me — force equals mass times acceleration.

"So it's all Newton," Donnelly says, "but they're using a special description of the forces which includes a random component."

I'm not going to say any more about that, but a thorough explanation of the Langevin equation, for those who are interested, can be found here. The bottom line is, when Nagar made a mathematical model of the ant traffic patterns using the Langevin equation, and compared what his model predicted with what experiments with ants running in a line showed, it "seemed to fit very well with the experiment," Nagar says.

So he wrote up his results, which will be published in an upcoming issue of the journal Physical Review E. Nagar collaborated on his research with Dr. Debasish Chaudhuri of the Indian Institute of Technology Hyderabad.

Nagar is not sure how relevant his model will be for human traffic engineers. After all, he agrees that allowing cars to bump into each other at 60 mph may be a nonstarter, although greater discipline and less ego may help keep traffic flowing smoothly.

There's one other tiny problem. Nagar is a physicist, not an ant man. I've talked with ant researchers who say that, for at least some species of ants, one will overtake another on the ant highway. And when the volume of ants is high enough, ants do jam up.

I suppose you could solve that latter problem by building more ant highways.

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STEVE INSKEEP, HOST:

Throughout this program, many NPR stations are adding local traffic reports for you, and we want you to have the fullest possible information, so NPR science correspondent Joe Palca now has an ant traffic report.

JOE PALCA, BYLINE: Good morning, everyone. Looks like another no-hassle day on the ant highways. Traffic is moving smoothly on Jungle Route 17 near the split. Ants are traveling at speed coming in on 95 through the savanna, heavy volume but no slowdowns on Parkside Drive near the picnic basket.

Now, you may have noticed something a little surprising about this traffic report - no traffic jams. Physicist Apoorva Nagar at the Indian Institute of Space Science and Technology says it turns out, for the most part, ants don't have traffic jams. Nagar wanted to know why that was and whether human traffic engineers could learn a thing or two from ants about how to avoid jams. I reached Nagar via Skype in his office in Kerala, India. He says there are basically three reasons ants don't jam up when running together in a single direction. Number one, ants don't have egos. They don't show off by zooming past slowpokes.

APOORVA NAGAR: They do not want to overtake each other.

PALCA: No aggressive drivers on an ant highway.

NAGAR: The second thing is that they do not mind a few accidents or collisions.

PALCA: So unless there's a serious pileup, they just keep going. And the third reason?

NAGAR: Ants seem to get more disciplined as the density increases.

PALCA: More discipline means no rubbernecking or distracted driving. Nagar felt this kind of behavior could be explained by something called the Langevin equation, an equation physicists use when describing the movement of liquids or how individual atoms behave in a lattice. I wasn't entirely familiar with the Langevin equation, so I turned to Thomas Donnelly, a physics professor at Harvey Mudd College.

THOMAS DONNELLY: This is basically a reworking of Newton's famous F=MA equation.

PALCA: Oh, yes, of course. Force equals mass times acceleration.

DONNELLY: So it's all Newton, but they're using a sort of special description of the forces, which includes a random component.

PALCA: OK, I think that's as far as I'm going to go in explaining that. But the bottom line is when Nagar made a mathematical model of the ants' traffic patterns using the Langevin equation and compared what his model predicted with what experiments with ants running in a line showed...

NAGAR: And they sort of seemed to fit very well with the experiment.

PALCA: So he wrote up his results, and they will appear in an upcoming issue of the journal Physical Review E. Nagar is not sure how relevant his model will be for human traffic engineers. After all, he agrees allowing cars to bump into each other at 60 miles an hour may be a nonstarter. Although greater discipline and less ego should help keep traffic flowing smoothly.

There's one other tiny problem. Nagar is a physicist, not an ant man. I've talked with ant researchers who say when the volume of ants is high enough, ants do jam up. But I suppose you could solve that problem by building more ant highways. Joe Palca, NPR News.

INSKEEP: Traffic is traffic, no matter how small. This ant traffic report comes to us from Joe Palca's project Joe's Big Idea which we hear on MORNING EDITION from NPR News. Transcript provided by NPR, Copyright NPR.