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An Engineer Beats The Physics Of Traffic


Ah, the road trip - one of the great American summer rituals. But sharing this great tradition with other road trippers can also be intensely frustrating. Perhaps you've found yourself wondering why traffic jams take so long to clear up or why they seem to last so much longer than a crash. Well, Bill Beaty is a research engineer at the University of Washington. He has a little advice about that.

BILL BEATY: If you're a little too close, so your reaction time is longer than the car ahead of you making changes - and everyone is this way, so basically tailgating - the traffic becomes unstable. So, any tiny, tiny motion - and not someone hitting the brakes - will be amplified as it goes along with the row of cars. Normally, if the spacing is large enough, those kinds of little fluctuations will die away.

MARTIN: So, you're saying that if we as individual drivers, if we actually resist the temptation to stop and go, speed up really quick, close the distance with the car in front of us, that that will actually keep traffic going?

BEATY: That's exactly it. So, if people don't rush ahead into the empty spaces, you can smooth out the waves. When I first found it accidentally, it was one classic place in Seattle where you can see about a mile and a half behind you.

MARTIN: Because of the hills and...

BEATY: Exactly. This is the 520 Floating Bridge. Huge number of traffic waves. It's just a two-lane highway. I could see the traffic waves in the headlights all in the other lanes. My lane was perfectly smooth as far as the eye could see off of the distance and, holy cow, one driver can smooth out the waves. What if you only had, like, one in 500 drivers doing this? There wouldn't be any stop and go driving.

MARTIN: Does everyone need to be doing this? I mean, you can't control the behavior of the other drivers around you, right?

BEATY: Oh, of course you can. You can control the behavior of everybody behind you, as long as it's fairly packed traffic.

MARTIN: Let me ask you this, though, Bill. I mean, is there larger life lesson in there about looking out for others, taking it slow, things will eventually work out?

BEATY: Exactly. Are you the type of person that, like, holds the doors for others? Or if you're a hiker, do you pick up others' trash or are you one of the people that leaves your trash all along? And the same thing is happening on the highway, except lots of ignorance, that people don't know that they're causing problems. Is it possible for one person to have any effect. 'Cause if you're completely powerless and frustrated, that's one kind of life to live on the highway. But if you know that you can have an effect, that transforms everything.

MARTIN: Bill Beaty is an electrical engineer at the University of Washington in Seattle. Thanks so much, Bill.

BEATY: Thanks much.


MARTIN: This is NPR News. Transcript provided by NPR, Copyright NPR.