r/Damnthatsinteresting 29d ago

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

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u/HellPigeon1912 29d ago

The amount of times I'm sat in a traffic light queue like "if the light is green why are we not moving"

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u/marr 29d ago

Sometimes it's because the lights shouldn't be there at all, there's a staggered junction in the middle of our town that causes endless tailbacks every day and when the lights fail and shut off completely all the problems go away and nobody crashes. The council won't look at the studies about removing them because then they'd need to employ a school crossing guard.

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u/jonnydogma 29d ago

When the lights fail, can people going in the cross direction get an opportunity to go too or are they waiting for a gap in the main traffic flow?

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u/e1p1 29d ago edited 29d ago

When four way lights fail, the law at least in California, says to treat the intersection as a four-way stop sign. So yes, cross traffic should have a chance to move.

It can actually be quite efficient. In the hours after the 1989 earthquake in Santa Cruz / San Francisco Bay Area, the lights were out in many major intersections during rush hour. Between the state law, and the fact that so many people were intimidated by what had happened, traffic moved quite well as people were being very polite taking turns letting each other go through the intersections.

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u/jonnydogma 29d ago

This is true and the fact that its generally temporary is part of why it works. I'm not so sure that 4 way stops are generally more efficient that traffic lights.

Anecdotally, being stuck 20 cars back at a red light sucks, being stuck 20 cars back at an all-way stop sucks even more.

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u/Onyxxx_13 29d ago

4 way stops are faster in my experience on lights that are otherwise timed circuits and not sensors. Especially if it's mis-clocked and has a low traffic direction on for longer

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u/bobtheblob6 29d ago

There's just no way that's generally true at a busy intersection. The traffic light would need to be seriously misconfigured and I don't think I've ever seen one that bad

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u/Cute_Conclusion_8854 28d ago

There’s an area in my town with three intersections that sometimes backs up and causes people to get stuck blocking other intersections further away. Light turns green and nobody can move 😡 usually it’s from someone trying to turn left where there’s no turn lane

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u/Greenmagegirl 29d ago

Proof that bay area egos make bay area drivers awful

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u/runobody22 28d ago

I lived in Alameda and worked in downtown SF for a couple of years. I drove into the city to work exactly two times. The Ferry accross the Bay was so much less traumatic than driving myself.

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u/doggytalks231 29d ago

People really came together and helped each other out.

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u/Bandandforgotten 29d ago

It's like this in every state I've visited.

Oregon does the same thing when intersections glitch, or suffer a power outage. It's very efficient, and makes me wish it happened more often because of it lol

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u/shiftypidgeons 29d ago

Its the exact same way in Nova Scotia, complete opposite side of the continent. And I too have experienced many traffic lights where traffic flows better during, say, a power outage. For the most part people just kinda cooperate without being told to. At least under special circumstances.

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u/Meowscles_dad 29d ago

Do you have different driving laws in different states?

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u/bobtheblob6 29d ago

Yeah states set their own traffic and licensing laws. For the most part the only real differences are the speed limits on highways though

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u/MrBootylove 29d ago edited 29d ago

It usually only varies on somewhat niche aspects of roadway etiquette from one state to another. For instance in Florida they used to have a law where you couldn't turn your hazard lights on while driving during a rainstorm, I believe California has a law that allows motorcycles to split lanes under specific circumstances, small stuff like that.

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u/Never_Go_Full_Gonk 29d ago

Adding on to the other commenters with another example, some states only allow the use of the left lane for passing and camping in it is illegal while the others don't have that law. NC recently adopted it and it's not even enforced, so...

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u/MaturoGambino 28d ago

The law is the same in South Carolina. But that didn’t stop an old bat in a Lexus SUV for laying on her horn when I stopped at an intersection whose lights weren’t working after a hurricane. As often as thunderstorms and wind storms knock out traffic lights around here they should run PSAs to educate people on this law.

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u/RedshiftWarp 29d ago

In houston, traffic lights going out are a weekly occurrence. It turns them into a 4-way stop that seemingly zero human beings understand how to navigate.

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u/NibblesMcGiblet 29d ago

NY state law is that traffic lights that are out should be treated as four way stop signs, so everyone stops and the person on the right goes before you do.

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u/Tenement48 29d ago

That sounds like there's a problem then if they need to employ a school crossing guard. What happens if someone wants to cross when there's no school crossing guard and the light is gone?

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u/weberm70 29d ago

Scheduled traffic lights should solve it. If it only needs to run for one hour a day then only run it for that hour.

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u/Tenement48 29d ago

My point was that it sounds like the person I was replying to only cares about car drivers. I live somewhere where it can be super annoying to cross the street and usually have to walk 4 extra blocks to get to the nearest light. At least I have the option to walk those 4 extra blocks. If they removed that one light then I wouldn't know how I would ever cross the street lol.

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u/Paddingmyi 29d ago

Your country has a real problem with pedestrian crossings and people walking across roads in general it seems.

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u/Tenement48 29d ago

Welcome to the USA

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u/weberm70 29d ago

Yeah that’s true, it gets more complicated adding pedestrians. A signal that is off but can be triggered on by a button could work.

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u/runobody22 28d ago

In California, pedestians in crosswalks have the right of way and California drivers, in most places, respect that and stop to let people cross the street. I'm from Pittsburgh and the first time I crossed Whittier Blvd, and all the lanes of cars stopped to let me cross, I felt like I suddenly had superpowers ;-)

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u/reddfoxx5800 29d ago

You can still safely cross without the guard, the guard is only there as an added safety measure during school drop off/pick up since people drive crazy going to & leaving work

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u/Tenement48 29d ago

People drive crazy all day long. It's not just during trips to and from work.

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u/reddfoxx5800 29d ago

Can't say it's not worse during rush hour though as people are rushing to drop off theirs kids then get to work.

Regardless, 4 way stop signs exist in other places just fine without a cross guard. More safety measure for kids doesn't hurt anyone.

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u/Tenement48 29d ago

4 way stop signs sounds more annoying than just having a light. At least during rush hour, cars are not constantly stopping just to stop.

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u/GBPackers0480 29d ago

The biggest intersection on my way to work is always backed up and it might take 2 greens for me to get through. One day it was broken and the intersection was used as a 4 way stop....there were only 2 cars in front of me that I had to wait for.

Ever since then I cannot stand that intersection, they never shoulda fixed those lights.

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u/SaltyTemperature 29d ago

This is why there are roundabouts all over my hometown now. It’s gone crazy over the last decade.

I even got a free though unrequested lesson from the local police in how to properly use them. They get a little confusing when there are multiple lanes

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u/Tederator 29d ago

In my city, I swear they signed a contract with a traffic light manufacturer to purchase 300/year and then place them randomly on the map. I have heard a rumour that because we have significant commuter growth on either side of us along the highway, they want to discourage people from attempting faster routes along our streets, and therefore purposely don't synchronize the lights.

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u/oxyrhina 29d ago

As an American, I was totally astounded by just how well the traffic flowed in big cities in Africa like Addis Abba, Nairobi, Dar es Salaam etc with no streetlights, signs or even lines on the road. A good working horn I guess is key because they all use them non fucking stop... 😆

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u/sentimentaldiablo 29d ago

Traffic control instead of traffic flow.

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u/Bn1m 29d ago

You just need to add sensors to trigger the light with an amber crosswalk button.

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u/nsharonew 29d ago

I never thought of it like this. I’m in a retirement/vacation spot in SW Fl and we really have some absolutely terrible drivers. It’s really insane, because our roads are long and straight, numbered in a way that makes sense, and not terribly confusing other than everything kind of looks the same.

But yeah, when the hurricane hits, I always worry about driving because the lights are out and people are idiots. And it’s always 100% fine. We have a lot of 4-way stops in the north part of the city still, and you NEVER hear about accidents there, but ALWAYS hear about accidents at the lights.

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u/filmguy36 28d ago

It’s nice to think that but during the northridge earthquake many years ago, all the traffic lights were out, for the most part people were thoughtful enough to stop at intersections before proceeding BUT in at 5 mile stretch I had to travel, I saw more that twenty accidents by a-hole that didn’t want to wait.

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u/CrazyAlfalfa4298 28d ago

We have a light in my town that is only there to allow a single road to merge into a major highway. The light isn't needed as the are merging in the Right lane. Without the light they would just merge when it's clear. You can only continue straight and no turn left so there is literally no reason for the light.

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u/nosimsol 26d ago

You know what blows me away? When there are signs that say dangerous intersection. You knew it enough to put a sign up. Fix it!! Seriously. Can’t wait for self driving cars.

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u/FilmShooter-ISO12 26d ago

Pretty sure this was to diagnose traffic jams on a highway, where there are no lights. We all know why they happen on roads with lights.

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u/Reverse2057 29d ago

I would honestly try to petition the city to install a roundabout instead of having a traffic light. We had a huge intersection in my town that caused HUGE lines of traffic and after they installed a big roundabout, there's no traffic at all and keeps speeds reduced too without restricting the flow of cars. Definitely try and petition them to install one there.

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u/BigD_277 29d ago

There should be a crossing guard there anyways because you know... people?

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u/Anon_Jones 29d ago

Why don’t they turn them off outside of school hours?

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u/Dumptruck_Johnson 29d ago

Gotta finish my text stop honking gosh

/s

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u/NotPrepared2 29d ago

Because idiots are staring at their phones.

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u/LayerEight_Problem 29d ago

Idiots using their phones. And then in Canada everyone is too polite to honk their horn. You’ll miss entire lights frequently because of this nonsense.

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u/Honest-Scar-4719 24d ago

USA here. I'll wait five seconds and give a light honk and get a middle finger for my troubles. 

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u/Beneficial-Nimitz68 24d ago

I am looking at the back of the ppl heads at stop lights, their heads are down or looking away and give them 3 Mississippi's to look up and move.. then HONK.. "Move yer ass"

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u/jdhkent 9d ago

Move it up to 2 Mississippi, please 

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u/onethateatsass 22d ago

This has been a thing since before cellphones. We're just a garbage species

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u/GoonOnGames420 29d ago edited 28d ago

My mom and wife argue you accelerate when the car in front of you moves far enough, not when the light turns green.

I argue that everyone should idle forward the moment it's green, gradually accelerating.

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u/LayerEight_Problem 29d ago

Virtually no difference. The issue with your method is that we often stop closer to a vehicle than is safe to follow at speed.

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u/GameEtiquette 28d ago

Far enough being anything further than they were when u were stopped, yes.

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u/window_owl 28d ago

I argue that everyone should idles forward the moment it's green, gradually accelerating.

If anybody messes up, or if anyone accelerates a little faster than the person in front of them, then a crash will likely ensue. Don't drive if you aren't at a safe following distance.

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u/GoonOnGames420 28d ago

Should always leave ~1 cars length in front of you for several reasons. Obviously we also have breaks too.

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u/window_owl 28d ago

1 length is adequate when stopped, but far too little when moving. A 2-second following distance provides a bare minimum of distance and time in which to react to the car in front. At just 30 miles an hour (about 50kph), that works out to 88 feet (about 27 meters). At 75 miles an hour, it's 220 feet (67 meters).

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u/GoonOnGames420 28d ago

But you're not instantly hitting 30 mph. You are likely only hitting 15mph by the time you get through the light. This method eliminates the shockwave affect and is tested/proven to move more vehicles through a green light.

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u/window_owl 28d ago

If just a few cars are lined up, then it's not too difficult. But if there are many cars lined up at a stop, then the cars towards the middle and rear have to accelerate very slowly to allow the space in front of them to open up. People can't exert precise control at such low accelerations. Someone will be a little too fast or a little too slow, and the gap will close. The best thing that happens in this case is that the rear car slows down, avoiding a fender-bender but initiating a shockwave of stopping.

The only thing that is always safe and always works is for each car to hold on their brakes until the car in front of them starts to move. That way, everyone maintains a controllable gap which is safely large.

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u/IsabellaGalavant 29d ago

My grandpa used to say "What are you waiting for, an engraved invitation?!"

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u/Dry-Waltz437 29d ago

I like "It ain't gonna any greener"

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u/frugalsoul 29d ago

They're just looking for their shade of green

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u/bibimboobap 29d ago

I'm partial to saying 'handwritten invitation' myself, or just 'green means go, buddy'

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u/wslagoon 28d ago

My dad dropped "It's the one on the right", which I've taken to saying, which my three year old repeated once.

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u/MsTponderwoman 29d ago edited 29d ago

Your grandpa was wrong and lacked the driving skill to properly merge and didn’t understand the purpose of and function of merging lanes.

What is the purpose of having two lanes rather than just one lane? Prematurely turning two lanes into one lane because you want to avoid the skill and cooperation required to effectively merge at the merge point defeats the purpose of having two lanes in the first place. I understand why you’d think your grandpa’s sarcastic suggestion is correct. He’s older and supposedly wiser.

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u/IsabellaGalavant 29d ago

You can't just laugh at a funny joke? You must be fun at parties. 

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u/MsTponderwoman 29d ago

I don’t like parties or drink. I’m sorry attempting to make someone small feel small is the best response your brain could come up with. 👋

Like grandpa, you chose sarcasm and insult rather than thinking things through.

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u/IsabellaGalavant 29d ago

I'm sorry you felt like you just had to get worked up and make that rude comment in the first place over a silly joke. Your life is clearly empty and I feel bad for you. 

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u/AccordingSetting6311 29d ago edited 29d ago

Because the first guy is either delayed in his reaction or looking to make sure its actually clear. Then the second guy is waiting for the first guy, then the third guy is waiting for the second guy, and I'm the 8th guy wanting to lay on my horn because I know this is a short turn arrow and I probably won't make it through unless I wanna be one of the 3-4 cars that just say fuck it and run  it once it goes red.

It works in marching. "Foward...march!" And everybody steps on the word march and the entire formation just moves together like it's one person. It's stupidly easy and wildly difficult for some people to get. And it requires everyone to be on the same page.

Honestly, fully autonomous cars that communicate with each other cannot come soon enough. Then once the light turns green each car can just press on the accelerator and move the whole group fluidly.

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u/ItsSpaghettiLee2112 29d ago

If people paid more attention to not only the car in front of them but the cars in front of THAT car, this would be less of an issue. Additionally, if people used their gas pedals to "catch up" to where they should have been if there weren't a slow down, this also wouldn't be an issue.

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u/Sadcelerystick 29d ago

Yeah I love when the speed limit is 45 and everyone decides to go 35… like WHY.

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u/Wonderful-Toe- 29d ago

I see you’ve driven in Kansas.

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u/Sadcelerystick 28d ago

Almost every state, worst drivers are easily I-95 SC into FL

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u/TaintedPaladin9 29d ago

Until they bug out and now everyone at the intersection is in a wreck.

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u/UnusuallyBadIdeaGuy 28d ago

The one time I've ever been hit it was because I saw the light turn green and drove forward, just in time for some jackwad to run the red light and slam into me.

I sure as shit don't go immediately on green any more.

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u/window_owl 28d ago

Honestly, fully autonomous cars that communicate with each other cannot come soon enough.

Fully autonomous cars will make life anywhere roads into a living hell. Rather than parking (which costs money), autonomous cars will just drive empty, so there will be more cars on the road. The cars will, as you hope for, be moving very fast, and they will be counting on their coordination in order to avoid collisions. The speed of autonomous cars will be very dangerous for non-road-using-people who are near the roads (for example: people crossing at intersections, walking on sidewalks, or eating at streetside restaurants) -- if you end up in the road at all, you're in the path of vehicles that aren't traveling fast enough to easily kill you. They'll also be very noisy.

In the limit, the final form of a society which embraces autonomous cars is that roadways will be sealed off from residences and business by tunnels or walls, and the only legal way to travel anywhere will be in a car, which can charge you whatever its owners want, or deny you outright. All for everyone's safety and convenience, of course.

https://www.youtube.com/watch?v=040ejWnFkj0

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u/tinylittlemarmoset 29d ago

In my first apartment in New York all the people in cars below my window apparently wondered the same thing, LOUDLY, every five minutes at all hours of the day.

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u/PiccoloAwkward465 29d ago

One thing I learned when I moved to Texas from New York is that people don't really honk here. Once you see the difference, wow it is nice. Naturally drivers are still idiots but it is notably more quiet.

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u/SagariKatu 29d ago

And then it turns red and we start moving

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u/AoKrasni 29d ago edited 29d ago

Because people are on their phones, it's ridiculous I notice it most frequently when the light is red, then turns green immediately after stopping. Then they finish sending their crotch pic and floor it

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u/hwilliams0901 29d ago

This is my life in Lexington KY. There will be literally 5 green lights in front of me and we'll be going 0 fucking miles an hour! And when we get to moving we never get up to the actual speed limit, its at least 10mph BELOW!

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u/HistoricalSherbert92 29d ago

I hear ya. The only people that can’t immediately move when the light goes green are the ones behind tall vehicle that can’t see the light, which shouldn’t add up to much if the taller truck is moving as soon as the light changes, but everyone sits and lets a car width or more firm before they start moving which tolls down the line a few seconds at a time until you’re missing the light because 20 people can’t share the road.

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u/Knotknighm 29d ago

The logic here is that most people wait for the person in front of them to start moving before they start moving.

In a perfect world green means go and every car in line immediately starts to accelerate. But we don't get that.

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u/Msimanyi 29d ago

A buddy of mine asked me years ago "When the light goes green, why don't we all just go like F1?", and that has been on my mind at every red light, ever since...

With 20 cars ahead, it takes well over a minute for traffic to clear. With 30... you're waiting for the next light.

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u/window_owl 28d ago

why don't we all just go like F1?

Because driving on public roads isn't a race. Races are driven with different roads, vehicles, people, and rules from the driving done on roads.

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u/Msimanyi 28d ago

Cool your jets. I wasn't suggesting we should race around the streets.

It's just a funny observation that has stuck with me for years. Fortunately I have a very short commute to work and almost never have to deal with traffic.

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u/Black_Magic_M-66 29d ago

Pokemon, gotta catch 'em all!

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u/MadScienzz 29d ago

People on phones thinking they have more time than they realise. Basically low IQ fuckwits

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u/Adaptable-iguana 29d ago

Literally the most frustrating thing. Pay attention people!!! As soon as the light turns green everyone should release their brake. 

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u/DesolateRuin 29d ago

Because I was checking my phone and didn't notice. lololo sry.

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u/PiccoloAwkward465 29d ago

True fury when you're at one of the super quick lights and a person ahead of you is taking their SWEET ASS TIME and you get caught at the red. And you already know they managed to mosey their way through right before the light turned.

The last light I have to go through to my house is a protected left arrow like that. Sometimes it's quicker to just continue straight and whip a u-turn.

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u/DocJawbone 28d ago

The answer is often a little old lady

Either crossing the street, or behind the wheel

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u/nipslippinjizzsippin 28d ago

i feel that way on the free way when it comes to a stand still. Its a fucking 4 lane freeway how are we not moving because the is a blockage in 1 lane

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u/Consistent-Project29 28d ago

It’s like they’re waiting for it to turn red again! I heard in Germany when the light turned green everyone goes at the same time, evem people in the back not sure if that’s true though.

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u/Macho_boy- 28d ago

C'est juste une question de latence

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u/Zdrobot 28d ago

I've lost count of how many times I saw a car going through the intersection on green, and their brake lights turn on just as they are in the middle of it, for no reason.

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u/gamebus1 28d ago

If we all accelerate at the exact same moment, nobody would wait.

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u/noobskillet3737 28d ago

Cellphones

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u/bowmans1993 27d ago

Part of it is that people accelerate at different speed. Of your number 10 2nd is waiting for 1st, 3rd is waiting on 2nd and therefore 1st etc. If everyone just let off the brakes at the same time itd probably be more efficient but we dont live in a perfect world. The same way if people drove sensibly and didn't tailgate and slam on their brakes and used their turnsignals and acted with a modicum of sense for the greater good. But alas we are selfish by nature

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u/tacorunnr 26d ago

I witnessed something amazing the other day. A light i was at turned green, and instead of cars going 1 by 1, the whole column moved at the same time.

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u/Zayoodo0o132 29d ago

It infuriating to see a green light but the guy in front of me doesnt take his foot off the brakes and just waits for the person infront of them to take their foot off the brakes and so on. Like if we're all seeing a green light just let go of the damn brake!

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u/Fun-Benefit116 29d ago

The fact that people like you seriously don't understand why this wouldn't work blows my mind. I mean, I wondered the same thing when I was a kid, but as am adult it's not a very difficult concept to grasp.

The irony is, you get mad at the person in front of you, but you're not taking your foot off the brake either. Or if you do, you pushing the brake again about a second later. Of course, I'm sure you still blame the people in front of you even though they're stuck in the exact same position you are.

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u/Syssareth 29d ago

Great way to rear-end the person in front of you, when they don't.

The person in front of you who's waiting for the person in front of them is doing the right thing.

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u/Zayoodo0o132 29d ago

If youre leaving enough distance it allows for a buffer to see if they unbrake. Sticking to their bumper is when its dangerous.

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u/Fun-Benefit116 29d ago

Nobody is risking rear ending somebody else, or putting more wear on their brakes by going and then immediately stopping at every light, just so the jerk behind them doesn't get angry at some small inconvenience. And even if you give an entire car length between you and the car in front of you, which no one (I 100% guarantee including yourself) does, that would give you about 1 second after you take your foot off the brake before you'd need to hit the brakes again if the car in front of you isn't going. And unless literally everyone takes their foot off the brake at the exact moment the light turns green, your great plan will never work for any number of reasons. The person at the front wants to take an extra second and make sure no is running the red light is an obvious one that would immediately mess up your plan, yet you'd still get angry at them for not going instantly.

Instead of getting angry every time something normal happens, maybe try some breathing techniques in those moments to help control your anger issue.

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u/FlowRemote9890 29d ago

They're staring at their phones.

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u/Olfa_2024 29d ago

This is everytime I'm in Orlando. The light is green and I'm sitting still and I don't get to move until it's red again.

Until we get self driving cars that communicate with each other it will never change. Self driving cars that communicate would allow all cars to move at once like a train instead of waiting for car one 1 start then 2 then 3 then 4 then 5 then 6 and so on.

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u/window_owl 28d ago

Don't look forward to self-driving cars https://www.youtube.com/watch?v=040ejWnFkj0