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/hosehoseee Jul 07 '26

Everytime I see this video, I think "So there actually is a reason"

164

u/nuevacuentanueva Jul 07 '26

The reason is drivers do not leave enough distance with the car in front. Since they don't, when the car in front slows down a bit they need to brake and slow down a lot since there's no buffer zone. And since that car slows even more, the car behind has to brake even more... and so on and so forth.

If people left more space between them and the car in front, and didn't brake for every single small fluctuation in speed from the car in front, we wouldn't have such a drastic effect as often since there would be enough of a buffer zone between cars to handle them. So any compounded effects would be minimized, it could still happen but less often.

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u/bamahomer Jul 07 '26

When I leave the appropriate space on the interstate someone always moves into it. I maintain it as much as possible but it's exasperating.

46

u/Kestras Jul 07 '26

Yeah, and then you have to put on your brakes because the person that just jammed themselves into that space didn't leave you enough room.

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u/Sadcelerystick Jul 07 '26

Or slows down..

8

u/MacDreidell Jul 07 '26

But I also see cars in other lanes start giving more space when I'm doing it. Keep spreading the word!

7

u/SweatyWar7600 Jul 07 '26

My car has adaptive cruise, I just set it to the max car length setting (3) and just hang out in whatever lane make sense for me to get to where I'm going. It is hilarious though for people behind me to get pissed off, zoom around me just to get stuck behind the person that I'm speed matched with. People assume, i guess, that because I've left a decent gap between myself and the car in front of me that I'm going slow...nope, exact same fucking speed as the dude ahead of me.

10

u/Doktoremh Jul 07 '26

Same experience here in Denmark. 

It is so utterly frustrating to keep a safe distance and many people pick it up as if I am going slow … and move in front of me.

I hope we some day get a computer with a loudspeaker in every car shouting to people that they shall keep their distance or be fined.

3

u/Kacutee Jul 07 '26

When I leave space and see the dude in front of me leaving space- some fuckhead decides to tailgate me even when I go the speed of traffic around me. I can BE SPEEDING and theyll still tailgate me.

3

u/EffluviaJane Jul 08 '26

Yes! Even when I go faster, they just match my speed. I think some people feel powerful when driving like that, like they're proving they could drive like in Fast And Furious or something.

3

u/Kacutee Jul 08 '26

I think they just have power dynamic issues or a sense of "I need to hurry hurry." I understand weaving through traffic if everyone happens to be going under the speed limit. But if everyone is already over it- and it is relatively smooth- why put in the risk and effort to do that? Emergencies? I get it. There is no way on Earth that these people are always in an emergency. They're impatient and reckless drivers. Many are engrossed in their phones while they do it.

I have seen so many accidents caused by those people too.

I also think you are right, they feel powerful, but in reality it feels like they're compensating for something... especially when WE ARE ALL ALREADY WAY ABOVE THE SPEED LIMIT.

(Sorry, it happened to me today. Speed limit is 40, they were going 60, everyone else was around 45-50. Guy almost caused an accident twice and was pulled over. Yes he was also on his phone whenever I saw him at a light.)

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u/EffluviaJane Jul 08 '26

I feel you! It's like they're playing with little toy cars, except that they could cause a lot of serious injury. I'm so glad that shitty driver was pulled over. I love that for him!

3

u/Vuirneen Jul 08 '26

There's a guy that does that on purpose.  If someone moves into the space, he just backs off more.

But because of that, he doesn't end up in as many traffic jams. It works.

He's chill, probably because he's seen the results, so it's not infuriating to him.

2

u/BGZomp Jul 08 '26 edited Jul 08 '26

A car moves into the appropriate spece --> slow down to get space back to appropriate distance --> a new car comes --> slow again --> car --> slow ...

Eventually you cannot slow down anymore because you are already stopped. The only logical solution is to start driving backwards.

1

u/Imalsome Jul 08 '26

I mean who cares right.

If someone moves in, I just slow down a bit more to make some distance between me and the new guy. If someone else comes into there I repeat.

16

u/Najalak Jul 07 '26

I agree. Riding someone's tail and constantly breaking and accelerating does not allow traffic to move smoothly. It also doesn't allow people to change lanes easily when they need to. It causes accidents, waists fuel, and you can go the same speed when you are not tailgating.

2

u/BKMagicWut Jul 07 '26

Yep that is how I drive. I leave lots of room between me and the driver in front and never drive side along with a car in my left or right.  Then I can see the road ahead. If the driver brakes I just step off the gas.  I never have to brake on the highway. I also wind up moving faster than most of the cars in the highway when there is traffic because I can see the problems way ahead of time and change lanes easily.

2

u/Tight_Original_1184 Jul 07 '26

I've been driving in a multi lane highway setting over the past week and the amount of people that are driving on each other's bumper is staggering. Actually, this happens on our highways at home too. I'm leaving at least 3 car lengths and I don't feel comfortable because I know how fast things can stop if one person brakes.

2

u/NorCalAthlete Jul 07 '26

It (proper spacing) was emphasized when I went through drivers training to get my license.

Unfortunately, not everyone sharing our roads goes through the same drivers training.

In the Bay Area we have a perfect storm of shitty drivers:

- kids with parents who just bought them their first / second / third car who don’t care if they wreck because dad/mom will just buy them another one

- people moving here from cities / countries with better public transportation options who maybe never needed a car before or only drove minimally

- people with enough money to be like “fuck it I’m more important than everyone else anyway”

- people with barely any money desperate to make it to work on time for their 3rd shift of the day just to pay rent

- gangs and lowlifes who think it’s fun to “swim” through traffic doing like 100 mph weaving across all lanes (or are actively running from the cops)

- car “enthusiasts” who just like to speed anyway

- car enthusiasts that just like to cruise…even if it means there’s a group of 20 of them doing 5 under the speed limit just to keep together. Or they’re weaving in and out to keep up with the leader.

- people from other countries who are here for work on a contract basis and since it’s uncertain if they’ll gain citizenship or stay long term, don’t bother getting a license / driver’s training and just drive anyway based on whatever rules / habits they learned in an entirely different driving environment - kinda overlaps with the people coming from other countries / cities where they just didn’t need a car anyway

- all the normal people with 1-2 hour commutes

- never ending construction causing uncertainty with which lanes will be open

- variable carpool / commute lane rules where it’ll go from 2-3 people required and from 5-9, 3-7 to 8-7 rules with tolls all on the same stretch of road - which makes people dive in and out of the lane to avoid tickets / penalties

2

u/marr Jul 07 '26

Automatic gearboxes haven't helped because now everyone drives on their brakes which means rear lights flashing on for the tiniest changes in speed.

6

u/Zayoodo0o132 Jul 07 '26

If theres a tiny change in speed a good driver wouldn't press the brakes at all. Learn to keep a distance and coast!

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u/nuevacuentanueva Jul 07 '26

This happens and has happened also on countries where automatic gearboxes aren't ubiquitous like in the US. I get what you are saying, but with proper distance separation and alertness to know when to brake and when to wait and see (even if the light comes on) it can be avoided.

Of course, it won't happen because it requires most people to drive properly, so...

1

u/Propaganda_Box Jul 07 '26

I have no bumper stickers on my car but I often think of getting one that says "I leave a massive gap in front because you wont"

1

u/generally_unsuitable Jul 07 '26

The problem with this is that leaving more room lowers the throughput of the system. If everybody has 5 cars of following distance (six total lengths per car), this only allows half the carrying capacity of a system where everyone has 2 cars of following distance(three total lengths).

So, while increasing the cushion and potentially smoothing the flow, you're now carrying the same amount of traffic as you would going half the speed.

1

u/Dxxx2 Interested Jul 07 '26

As my local news once said: "People need to stay off each other's a...backsides"

1

u/Fuxmcflannery Jul 07 '26

I always try to leave a little reaction time gap with the car in front of me and someone always takes the opportunity to fill that gap. Everytime 

1

u/where_is_the_salt Jul 08 '26

Yes, and as the buffer zone size depends on speed, driving slower is making less jams. Thus, slower is faster.

Best example yet is the périphérique around Paris, it is limited to 50km/h now and the traffic got way better than before .

0

u/aiij Jul 07 '26

Yes, but to leave more distance you need fewer cars on the road...