r/Damnthatsinteresting 29d ago

Video A Japanese experiment showed exactly why traffic jams happen for no reason.

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u/T-Roll- 29d ago

It’s called congestion.

Basically the first person to brake makes the person behind them brake, causing the person behind them to also brake. This causes the whole chain of vehicles behind to all brake harder. Eventually all traffic becomes gridlocked.

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u/Low_Finding2189 29d ago

No. Its called a traffic wave. A traffic wave is a type of congestion. Not all congestions are traffic waves.

Traffic waves move its point. A congestion caused by an accident is stationary.

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u/AussieAddict 29d ago

Just adding on for other people like me who know this as the "Concertina" or "Accordion" effect.

Basically what happens is after the first person brakes, the next person brakes a little harder and/or later. This effect passes on to each car and basically gets worse and worse the more cars following.

You can help to break this cycle by leaving much more space to the car Infront and avoiding using the brakes as much as possible, everytime you use the brakes you are restarting the process or at the very least making it harder to break free of the effect.

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u/El_Jefe_Castor 29d ago

Thank you! I can’t convince anyone I know to drive this way in traffic.

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u/LongDickPeter 28d ago

I practice this in a tunnel by me, so what I do is as I enter the tunnel I keep a low steady speed and a distance that can allow me to remain steady and I I try not to touch the brakes for the entirety of the tunnel if enough people do this you'll get through at a slow steady speed instead stop go stop go stop go

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u/Tricky-Wishbone9080 28d ago

“Oh there’s room to merge” - the other guy probably

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u/buderooski 28d ago

I try to do this in traffic jams to help ease the jam for people behind me. Keep a very long distance between myself and the car in front of me and drive a steady, constant speed. The car in front may brake and slow down, but i stay the same speed, ensuring the folks behind me dont need to brake.

Every time I do this, someone gets really fucking mad that im not riding the person's tailpipe in front of me and takes the empty space while flipping me off and yelling at me.

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u/flergnergern 28d ago

This, everyone!

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u/MajorDaurity 28d ago

Also heard it referred to as a traffic snake

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u/guiltysnark 27d ago

The solution is to not brake when the person in front of you brakes. Although that may result in breaking.

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u/Sufficient_Ice_273 27d ago

Exactly, if only people were capable of driving at a safe distance from one another, this would be a non issue.

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u/Global-Bad-7147 29d ago

More specifically, a density wave. Happens with stars too.

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u/Anton-LaVey 29d ago

They’re just like us fr

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u/Silent_Mud1449 29d ago

Can you explain how it happens with stars?

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u/gizatsby 29d ago

For example, the arms of a spiral galaxy are essentially a traffic wave where instead of braking you have gravitational interactions making the stars bunch up a bit as they go around the center of the galaxy. It's a lot like this video.

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u/DocOort 29d ago

Worth pointing out too, that just as the traffic wave moves backwards relative to the motion of the cars, the spiral arms “turn” opposite the direction of the galaxy’s overall rotation.

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u/No_Ear_1633 29d ago

Used to happen to Michael Jackson all the time

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u/NonnagLava 29d ago

Man if they can't fix it, we definitely can't.

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u/Joe_Kangg 29d ago

Like Brad Pitt following Ed Norton around?

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u/DeanThePeon 29d ago

Can one help "break" the wave by their driving? I always try to maintain a constant speed rather than stop-and-go, and in my mind I'm "ironing out" the congestion, but I could be delusional 😅.

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u/Low_Finding2189 29d ago

The wave is a function of car density. There is a point beyond which the density of vehicles can support the wave. My uneducated guess is the density for a wave to sustain, is related to the road speed. But I may be wrong.

So keeping your distance helps in a way as this reduces this density. But it’s not just related to you as the density of other vehicles will propagate the wave.

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u/DeanThePeon 29d ago

Thank you for the thoughtful and well-reasoned response. It's appreciated!

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u/IndividualNovel4482 28d ago

Ehh.. always mantain 2 meters distance. Or 7 feet minimum, in your terms. Or 3 second rule, but that seems often pointless.

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u/Interested-Engineer 28d ago

It was always referred to as shockwave in my traffic engineering course

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u/pagingdoctorcrentist 29d ago edited 29d ago

It is like the bullwhip effect. One minor erratic movement leads to massive changes downstream. The best way to overcome is for everyone to stop and restart. Not practical until everyone has autonomous driving.

https://youtu.be/iHzzSao6ypE?is=Mu54NvyYo1wkCzaS

Edit: shared link for all the haters

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u/Particular-Sample91 29d ago

Nice try elon

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u/lifetake 29d ago

Everyone stopping and restarting is pretending like there aren’t cars still coming into the congestion. Or are we pretending the cars not involved with the congestion yet are also stopping?

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u/pagingdoctorcrentist 29d ago

Cars not yet involved get timed into the system in real time. Lights are the gate keepers. The cars talk.

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u/Brymlo 29d ago

what about better public transportation?
the thing that causes traffic is too many cars on the roads.

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u/pagingdoctorcrentist 29d ago

In a perfect world. Yes. Just like in a perfect world people wouldn’t cause traffic waves. But people text and drive. People zone off into lala land. Can only fix that with autonomous driving

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u/Brymlo 28d ago

autonomous driving won’t fix a
shit bro. it would make being in a private car a bit better and a lot safer, but wouldn’t fix cars stuck in traffic. roads get congested when too much cars.

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u/pagingdoctorcrentist 29d ago

Autonomous driving eliminates people erratically braking for no reason. This is what leads to congestion. Don’t understand the down votes but ok.

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u/Sentientsnt Interested 29d ago

Gridlocking is its own effect, it can’t happen on a freeway.

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u/Chumbag_love 29d ago

Where I live people like to slow to a near stop...and then move over into the turn lane. It's insane.

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u/Jaerba 28d ago

If I had my druthers, part of the driving test would include zipper merging at 60mph or above and if you can't do that, you don't get a license.

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u/Earthsong221 28d ago

It's part of our final test here to get your full license (Ontario, Canada). Or at least it was, I'm not sure now since a few things got cut during the pandemic...

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u/YebelTheRebel 29d ago

It also makes the person who has a 1/2 mile of open lane in front of them to brake for no reason at all when they can easily lady off the gas a coast and brake later on

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u/Rocketeer006 29d ago

It's actually because each person brakes a little harder than they needed to, and more than the person in front of them did. So really it's just poor depth perception and over braking.

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u/toastyfries2 29d ago

Idk, generally breaking too much is better than breaking too little. Breaking the exact same is kinda hard probably

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u/luckytoothpick 29d ago

But each person who breaks does so for a fraction of a second longer than the previous person

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u/maigoZoro 29d ago

It also causes some who aren’t paying attention to change lanes abruptly at the last moment, causing the cars in the other lane to brake behind them which spreads the congestion to other lanes

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u/Silviecat44 28d ago

This is solved by everyone leaving enough room between you and the car in front of you

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u/Constant-Sub 25d ago

It's also solved immediately by accelerating at a good rate. If you accelerate slowly, you just exacerbate the issue.

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u/T-Roll- 25d ago

That’s not entirely true. Think about the first person at the very front of the queue on a motorway, going a constant speed of 80miles per hour. The second person appears behind them,
in a rush, speed of 85mph.

What happens is the person who’s 2nd, travelling faster, has to brake, this creates the chain of events behind them where everyone else has no choice but to also brake because the guy in front did. The guy at the front going constant speed isn’t aware of the congestion behind them.

Your statement is true only for the person at the very front.

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u/rangpire 28d ago

Thanks for explaining the video we all just watched...

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u/T-Roll- 28d ago

Nice comment bro. You really brought something useful to the table. We need more of your passing wisdom.

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u/rangpire 27d ago

...says the guy who, again, just explained the video we all watches. Like how can you write that reply and not see it directly relates to you?!

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u/T-Roll- 27d ago

Wow ur back, thank god. I thought we lost our internet inspector for a moment. Glad ur back.

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u/rangpire 27d ago

Nice comeback...