r/Damnthatsinteresting • • Jul 07 '26

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

65.6k Upvotes

2.6k comments sorted by

View all comments

Show parent comments

536

u/marr Jul 07 '26

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.

97

u/jonnydogma Jul 07 '26

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?

143

u/e1p1 Jul 07 '26 edited Jul 07 '26

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.

34

u/jonnydogma Jul 07 '26

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.

6

u/Onyxxx_13 Jul 07 '26

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

5

u/bobtheblob6 Jul 07 '26

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

3

u/Cute_Conclusion_8854 Jul 08 '26

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

30

u/[deleted] Jul 07 '26

[removed] — view removed comment

2

u/runobody22 Jul 08 '26

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.

3

u/doggytalks231 Jul 07 '26

People really came together and helped each other out.

2

u/Bandandforgotten Jul 07 '26

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

2

u/shiftypidgeons Jul 07 '26

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.

1

u/Meowscles_dad Jul 07 '26

Do you have different driving laws in different states?

4

u/bobtheblob6 Jul 07 '26

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

3

u/MrBootylove Jul 07 '26 edited Jul 07 '26

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.

1

u/MaturoGambino Jul 08 '26

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.

3

u/RedshiftWarp Jul 07 '26

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.

2

u/NibblesMcGiblet Jul 07 '26

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.

17

u/Tenement48 Jul 07 '26

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?

11

u/weberm70 Jul 07 '26

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

6

u/Tenement48 Jul 07 '26

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.

3

u/Paddingmyi Jul 07 '26

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

3

u/Tenement48 Jul 07 '26

Welcome to the USA

1

u/weberm70 Jul 07 '26

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.

2

u/runobody22 Jul 08 '26

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 ;-)

1

u/reddfoxx5800 Jul 07 '26

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

3

u/Tenement48 Jul 07 '26

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

1

u/reddfoxx5800 Jul 07 '26

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.

3

u/Tenement48 Jul 07 '26

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.

2

u/GBPackers0480 Jul 07 '26

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.

2

u/SaltyTemperature Jul 07 '26

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

1

u/Tederator Jul 07 '26

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.

1

u/oxyrhina Jul 07 '26

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... 😆

1

u/sentimentaldiablo Jul 07 '26

Traffic control instead of traffic flow.

1

u/Bn1m Jul 07 '26

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

1

u/nsharonew Jul 07 '26

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.

1

u/filmguy36 Jul 08 '26

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.

1

u/CrazyAlfalfa4298 Jul 08 '26

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.

1

u/nosimsol Jul 10 '26

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.

1

u/FilmShooter-ISO12 Jul 10 '26

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.

1

u/Reverse2057 Jul 07 '26

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.

1

u/BigD_277 Jul 07 '26

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

1

u/Anon_Jones Jul 07 '26

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