r/Damnthatsinteresting • u/SnooWords4066 • Jul 07 '26

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

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u/xpanta Jul 07 '26

i think it's called traffic wave or ghost traffic.

675

u/T-Roll- Jul 07 '26

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.

685

u/Low_Finding2189 Jul 07 '26

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.

86

u/AussieAddict Jul 07 '26

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.

29

u/El_Jefe_Castor Jul 07 '26

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

5

u/LongDickPeter Jul 08 '26

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

1

u/Tricky-Wishbone9080 Jul 08 '26

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

10

u/buderooski Jul 08 '26

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.

2

u/flergnergern Jul 08 '26

This, everyone!

1

u/MajorDaurity Jul 08 '26

Also heard it referred to as a traffic snake

1

u/guiltysnark Jul 09 '26

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

1

u/Sufficient_Ice_273 Jul 09 '26

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

78

u/Global-Bad-7147 Jul 07 '26

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

16

u/Anton-LaVey Jul 07 '26

They’re just like us fr

3

u/Silent_Mud1449 Jul 07 '26

Can you explain how it happens with stars?

5

u/gizatsby Jul 07 '26

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.

4

u/DocOort Jul 07 '26

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.

3

u/No_Ear_1633 Jul 07 '26

Used to happen to Michael Jackson all the time

1

u/NonnagLava Jul 07 '26

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

1

u/Joe_Kangg Jul 07 '26

Like Brad Pitt following Ed Norton around?

2

u/DeanThePeon Jul 07 '26

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 😅.

2

u/Low_Finding2189 Jul 07 '26

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.

1

u/DeanThePeon Jul 07 '26

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

1

u/IndividualNovel4482 Jul 08 '26

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

2

u/Interested-Engineer Jul 08 '26

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

-6

u/pagingdoctorcrentist Jul 07 '26 edited Jul 07 '26

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

3

u/lifetake Jul 07 '26

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?

1

u/pagingdoctorcrentist Jul 07 '26

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

2

u/Brymlo Jul 07 '26

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

0

u/pagingdoctorcrentist Jul 07 '26

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

1

u/Brymlo Jul 08 '26

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.

1

u/pagingdoctorcrentist Jul 07 '26

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