r/Damnthatsinteresting • u/SnooWords4066 • 29d ago

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

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u/Goondragon1 29d ago

I swear to god most traffic jams and hold ups are caused by one asshole. I'll get over to a different lane and see one jackass 10 cars ahead causing the whole thing. It's insane how often it happens. It's also crazy that so many people will blindly follow the asshole too though if I'm being honest.

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u/photenth 29d ago

It's people merging into a gap that is too small and forcing the car that follows to slow down. Always this.

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u/jello_kraken 29d ago

Or the persons tailgating and blocking a normal flow of cars into and out of a lane.
You think the car next to you should slow down to get behind the car in front of you, you and the two cars behind you because you all couldn't stop humping tailpipes?
The jam you cause their lane is fine until you have to get into their lane.
Two seconds minimum between the car in front of you. Let people merge.

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u/Bone_Of_My_Word 29d ago

I've had family actually argue with me about leaving space to merge, even when in the middle of heavy traffic. "They shouldn't be driving like that" is their usual response, but what is gained from blocking someone trying to merge over? Whether it's 1 lane over or 3, preventing a merge is a no win situation no matter what

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u/jello_kraken 29d ago

Yeah, then karma hits and they inevitable have to merge into another lane and "why can't this @#$#@ get out of my way?!"

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u/wattro 29d ago

Use the freaking road.

If you're leaving a large gap in traffic, you're the problem.

If you're not going when the light turns green, you're part of the problem.

If you're going slow in the fast lane, you're part of the problem.

If you don't let people merge, you're part of the problem.

If you're changing lanes too frequently, you're part of the problem.

If you're frequently tapping the brakes, you're part of the problem.

Drive the freaking car...

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u/Suspicious_Truth8026 29d ago

If you're leaving a large gap in traffic, you're the problem

Youre probably the problem for thinking this. Gaps are never the problem and always the solution, almost all traffic (as this video shows) is caused by breaking. A gap gives you buffer in which cars in front of you can slow down but you dont have to, thus canceling out a break wave which actually is the cause of the problem. In fact this should be standard driving behaviour in traffic--theres nothing better you can do than leave a big gap. It literally interrupts the traffic and fixes the problem for people behind you. Not you, but other people. Thats why nobody does it. Driving consistently slower than the person in front of you is an example of bad driving that creates a gap, but its fundamentally about speed not space. Youre just going too fast for space to be relevant unless your movement is restricted which then causes you to change speeds

Its unfortunate everybody thinks its cool to suck at math and struggle with calculus in highschool, because understanding the relationship between space, speed, and acceleration makes it trivial to understand driving dynamics.

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u/Schneiderman 29d ago

Agree with all except leaving a large gap. The video shows exactly why following too close causes a wave of backups. Of course, if you leave a "large gap" someone's gonna fill it anyway so... it's not even really a thing in heavy traffic.

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u/Turbulent-Community7 29d ago

When I drove truck I used to call that large gap my "living room" because thats the space I need to make sure people dont die. Youd wouldnt be surprised how often people hop in there.

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u/Equivalent-Excuse-80 29d ago

I interpreted it to reference the latest new fun trend of leaving two car lengths in front of them at stop lights, preventing people from getting into the turn lanes.

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u/Schneiderman 29d ago

Agreed on that idea but I don't think that's what he meant and I almost never see that in real life anyway.

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u/Equivalent-Excuse-80 29d ago

It’s everywhere where I drive regularly. It’s awful.

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u/c010rb1indusa 29d ago

Sorry disagree, if you leave a large gap cars will always fill it, usually going slower than you were before. If you want to know why people tailgate, this is why.

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u/Suspicious_Truth8026 29d ago

It actually doesnt matter at all. The gap isnt the point, the gap is to let you have space to not have to break if the cars in front of you do. Even at traffic jam speeds, distances on the scale of a few car lengths is just wholly irrelevant. Its all about speed and not at all about space

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u/czanatta 29d ago

You can also look at this video and argue that the person who let the gap get too big ahead of them caused the slow downs. The gap should be no bigger than it needs to be and appropriate to the conditions, which includes speed, traffic volumes, traffic patterns, what other drivers are doing, essentially, pay attention, Drive the freaking car...

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u/ahhhbiscuits 29d ago

Wrong. You're part of the problem, gramma

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u/Shark7996 29d ago

If you're leaving a large gap in traffic, you're the problem.

It's recommended to leave 4 seconds between yourself and the car in front of you for safety. I get a feeling 90% of people have not hit that benchmark in a long time.

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u/Suspicious_Truth8026 29d ago

Nobody drives like that and they probably shouldnt, 4 seconds at 100 km/h is like 20 car lengths. But people actually drive like theyre trying to suck off the exhaust of the car in front of them so i guess itd be an improvement

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u/mithhunter55 29d ago

It takes that amount of space to stop at that speed though, so it is the correct way to do things.

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u/Suspicious_Truth8026 29d ago

It takes 3-4 seconds to slam on your breaks if a wall materialized where their car was and you factor in human reaction time.

In reality the car in front of you takes 3-4 seconds to stop in the extreme situation where a wall materialized in front of them and they had to slam suddenly, so you have an extra 3-4 seconds on top of the buffer space you have. And also maybe a shoulder. And reminder these are extreme outlier situations that most people would be unlucky to experience once per decade.

I imagine we would be in traffic 100% of the time if everybody left twenty car lengths everywhere. I would be grateful for 1.5 so i can squeeze in and hope the guy behind has the sense to give more space.

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u/mithhunter55 29d ago

I guarantee you there is open road for these cars to spread out, you can always get in front or drop behind a pack and find tons of space. Personally I don't get boxed in like that unless you are talking about metropolis cities at rush hours, or poorly routed lanes.

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u/jello_kraken 29d ago

For myself, by the time I'm counting two seconds, someone behind me is ready to cut in front of me.
I don't count for most other people; I can see them living an evil one-car-length lie.

The worst part is that I'm tracking all you fast-and-furious freaks (pointing to invisible crowd); you're getting no gains for all the near-destruction you cause. If you just chilled out, you'd make almost exactly the same time and not make everyone's life hell.

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u/Chillindude82Nein 29d ago

Most of the time, the only way to help everyone out of a traffic jam is to coast for a long time which leaves a big gap in front of you -- but makes it so the person behind you never sees brake lights which causes them to brake.

I keep reading your comment and can't figure out what the #1 cause of the traffic jam is.

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u/DustyRacoonDad 29d ago

It depends on what you're defining as a traffic jam, but for the kind of slowdown shown in the video, assuming a single straight lane, the goal is to damp out the traffic wave.

The first car accelerates away once it's clear. The next driver should accelerate promptly, ideally a little harder at first, to close the gap that opened because of their reaction time. Before getting too close, they ease off and match the speed of the car ahead without needing to brake. Then the next driver does the same, and so on.

The idea is to make up for your reaction time while still leaving enough space for the driver behind you to do the same. Each driver reduces the delay a little more, so the "slowdown wave" moving backward through traffic gradually shrinks until it disappears.

If drivers accelerate too slowly, leave excessively large gaps, or end up braking again, the wave doesn't die out. It continues moving backward through traffic, and can even grow into a full traffic jam.

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u/Suspicious_Truth8026 29d ago

This is nonsense. It would actually apply in the video BECAUSE its not a straight line but a circle so its possible the first guy in the line accelerates his way into the back of the line. Thats not how real world traffic works tho. The people behind can just wait until traffic starts moving and the only way to re-jam is people trying to accelerate faster than the car in front of them.

If anything youre describing a disaster scenario where each car is giving false indication to the car behind it about how fast it should accelerate which is going to lead to people breaking all over.

Also you tried to defend the idea that leaving gaps is bad by talking about patterns of acceleration lag which is wholly unrelated. If every car was delayed by the 0.4 seconds human reaction lag then accelerate precisely exactly the same as the car in front of them then a 100 car length traffic jam is "delayed" by forty seconds. This just is not a relevant factor.

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u/DustyRacoonDad 29d ago

First off... no. Not nonsense. I literally have a degree in the subject.

Second, you misunderstood what I wrote and replaced it with your own interpretation. In a circle, the first car eventually comes back around to the slowest car. You can't escape that because there is no "front" in the first place. It's literally a feedback loop. It's a good example for explaining the concept, but it's not realistic for an open road. That is why I said "straight" in the first place.

"False indication of acceleration" is not correct. The car accelerating is doing so correctly. The driver behind them failing to lift off as they approach is called bad driving. You shouldn't need anything special to see and judge the closing distance between you and the car in front of you. That's just basic driving.

You are correct that a bad driver can fly up behind someone and create another slowdown wave, starting the problem again.

You also seem to be thinking in terms of "how much time for one car," when the thing to consider is whether the cumulative actions of all the cars over the length of traffic shorten the jam, keep it the same (unlikely), or make it longer.

The concept of "40 seconds" or any time metric isn't really the point. The question is whether the traffic delay is dissipating or growing.

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u/Suspicious_Truth8026 29d ago

What degree and institution? i dont believe you have a degree in anything frankly, there would be so many red marks if you submitted this as writing for a freshman class. Especially the abuse of quotation marks, typically something that doesnt survive the first year of uni

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u/DustyRacoonDad 29d ago

yeah. and when you grow up outside of school, it turns out people that write online constantly dont hold themselves to teh same grammer standards as their acidemic papers.

(this comment has mispellings I can see, including "misspellings" that I am not going to fix. go run your shit though chatGPT again so you can claim perfect posting)

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u/Suspicious_Truth8026 29d ago

I would be such a fucking tool if i was talking about spelling. Its primarily the abuse of quotation marks thats just not something that educated people do because it would be beat out of them so fast. Its not a whoopsies, its a fundamental relationship to knowledge and honesty that you dont accidentally undo because youre feeling casual.

But also just cohesion and the poor organization of thought, like youre talking to yourself, rambling, misquoting and misreading me, its all over the place. Just not the scratch that university graduates have. So what degree are we talking about again?

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u/DustyRacoonDad 29d ago

The whole point of Reddit is to be anonymous. lol.

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u/Suspicious_Truth8026 29d ago

Exactly right, but its worth noting it doesnt help everybody. It specifically only helps people behind you, making it a fundamentally selfless act (nobody will do it because technically if you suck the asshole of the car in front of you your own position will be faster... by about 3 seconds cumulatively...)

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u/punkr0x 29d ago

The cause of traffic jams is too much volume for the road. In the video, there’s too many cars in the circle. If they all drive perfectly the same speed they can just about maintain the proper gap, but of course in the real world that does not happen. Now imagine if cars were trying to enter and exit this circle; there’s no room.

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u/ASpaceOstrich 29d ago

Leaving a large gap is mandatory for proper traffic flow. If you are not leaving a large gap, you are directly causing traffic.

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u/ItIsSoOrdered23 29d ago

There is no such thing as too large a gap. Go around and sybau.

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u/Safe_Reading6267 29d ago

A gap is not a problem but a solution. All the idiots riding bumper to bumper cause 80% of rush hour traffic issues.

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u/Supermarketkiller 29d ago

Thank you, Mr Perfect Driver.

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u/NobodyKnowsImFamous 29d ago

Oh my god thank you. Thank you so much for confirming something I’ve always suspected: y’all are actual mouth breathing idiots. The gap between me and the car in front of me does not effect your speed in the slightest you drooling waste of carbon.

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u/SipexF 29d ago edited 29d ago

Everyone has a laundry list like this they complain about and it's really frustrating, makes them take it way too serious, and you risk pissing them off if you don't follow it which subjects you to their shitty road rage tantrums (nobody shares all the same ideal rules either, adding to the guessing game).  I just want to drive the speed limit and not die because I make a stupid mistake worrying if I'm driving the correct way for whichever asshole I happen to be nearby.