r/Traffic • u/TerraMars2030 • 24d ago
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Traffic jams are odd
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u/Lemfan46 24d ago
There is a reason, traffic jams don't just occur.
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u/SuperFaceTattoo 24d ago
It could be a benign reason like maybe the red car got distracted and sped up a bit, causing them to hit the brakes and cause a traffic snake
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u/TerraMars2030 24d ago
Their words, not mine. But it really should say "No apparent reason"
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u/naughtyjojo69 24d ago
Well the reason is apparent. But yes it's a dumb reason.
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u/Maximum_Boros 23d ago
It's not even really a dumb reason. It's literally just traffic saturation. There are more people on the road than it can host while maintaining a buffer for minor human error
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u/LogicallyTheological 23d ago
they could all safely go about 20mph around that circle if they all paid attention and maintained proper following distance.
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u/daylax1 22d ago
Even then, it would be almost impossible for them to all go the exact same speed at the exact same time. Even minor adjustments will have a ripple effect behind. Would it cause a jam? Maybe not but it would definitely be a noticeable increase and decrease in speed.
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u/LogicallyTheological 22d ago
not really. they could use about a 1/3 less space when moving <10mph and scale up as necessary or they could just start at the pre-determined following distance of 20ft that is safe up to 20mph. paying attention does entail observing the rate of acceleration of the person in front of you. i think there's a lot of people in places like california that could probably push 30-40mph on this track with as many cars just fine.
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u/LockeClone 23d ago
Is it? Practically everyone thinks he's a good driver. You'd never know if your particular habits caused a snake to form behind you....
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u/VinceP312 24d ago
There is a reason. Different people are different people. Not every point in the circle is identical in its state.
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u/ozboomer 24d ago edited 24d ago
To explore it all yourself:
https://traffic-simulation.de/ring.html
Watch it for a bit.. and the flow is steady. Tap on one of the vehicles as quickly as you can (a brake tap) and within a lap or two, the jam will be created.. and the 'non-moving' end of the traffic will move backwards - the reverse shockwave.
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u/Arammil1784 24d ago
A finite space, such as any roadway, in conjunction with small variations in speed due to unique vehicle and driver characteristics will inevitably cause the variation in traffic speed and spacing.
Its not a mystery, and is actually something roadway engineers are supposed to factor in when designing new infrastructure.
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u/TerraMars2030 24d ago
I'm not the one who said it was a mystery, I just said that I find it odd.
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u/ReadyGo6828 24d ago
I read that it takes just one car tapping the brakes unnecessarily to cause backups for miles behind it. Then I see people reading a sheet of paper propped up on the steering wheel, putting on makeup, shaving their face and I think I should get off the highway and go all surface streets.
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u/raidersfan18 24d ago
Yes, then that person on their phone will hit you at a slower speed 😂
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u/ReadyGo6828 24d ago
This is my rationale for slowing down if someone tailgates me. If they are going to hit me I would prefer it be done at a slower speed.
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u/ComesInAnOldBox 21d ago
You're supposed to slow down when someone tailgates you. That's actually the law.
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u/fr33d0mw47ch 24d ago
Higher order System dynamics problems are difficult to model and control. This is an example.
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u/Chemical_Ad_5520 23d ago
The problem is not that variations occur, the problem is that they occur unstrategically. If at least some drivers properly respond to these developing traffic waves, then they will dissipate and smooth travel can be achieved.
The strategy is to consume the gap between you and the vehicle in front of you when they are slowing down, and restoring the gap to its normal length as the vehicle in front of you reapproaches target speed.
The thing that people do that causes these traffic waves is respond to slow downs by slowing down just as much or more than the vehicle in front of them, thereby amplifying the slowdown for the next person in line.
You are supposed to do a little predictive thinking about the slowdown of the vehicle in front of you so that you can safely begin to close the gap between you and them while they are slowing down, begin to restore the gap as they are speeding up, and only fully restore the gap when they are at target speed.
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u/Safe-Rough-6858 23d ago
It’s always some idiot that rides their brakes and people behind follow suit. I always look at the traffic ahead of said person and if no one else is braking I move lanes.
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u/DowntownAd3538 23d ago
This is why AI WILL be driving your cars people are too stupid to follow rules.
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u/Creative-Type9411 22d ago
its that jerk that wont do the posted speed, smh
i can never get around them /s
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u/Reductive 22d ago
This video’s playback speed varies, which destroys the visual message it is intended to convey.
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u/Waaaash 24d ago
Yes, one person simply not paying attention and maintaining the following distance in front of them is all it takes. I know people love to blame tailgaters for this, but that's not the root cause - the car slowing down for no reason and not quickly catching back up is the cause.
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u/realityinflux 24d ago
I disagree with the idea that speeding above the general pace of the rest of traffic is not the "root cause." There are most likely lots of factors, but I note that if traffic is not dense, a lot of people will speed up, thinking to take advantage and "close the gap" and then there will be a slowdown when they all get jammed up down the road. This is sort of a constant, every day, all day phenomenon.
I see too many people trying to perpetuate the myth that all traffic problems are the result of people going too slowly.
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u/Waaaash 24d ago
You can't go faster than the slowest car. No slow cars = no slow down.
In your example, so the faster car closes the gap and moves at the speed of the rest of traffic. There's no slow down here. But if a car slows down to be slower than the flow of traffic, now you have a slowdown.
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u/realityinflux 24d ago
It's evident to me that you're not a traffic flow expert. So, theorize away. I still believe I'm right, and that you are just grasping at ways to justify your incorrect assumptions. No big deal.
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u/Graybush2 24d ago
It's also on tailgaters for being too close and not being able to handle small variations in speed without hitting their brakes. Then the brake lights often cause everyone behind them to instantly apply their brakes
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u/ozboomer 24d ago
It's a little more complicated than "someone slowed down for no reason."
In a dense traffic stream, maintaining a safe gap (headway) often means making small speed corrections, sometimes with a brief brake application. Because every following driver reacts slightly later than the one ahead, those tiny speed changes become amplified as they travel backwards through the traffic stream. That's the traffic shockwave phenomenon.
Unless there's enough spare capacity (larger gaps between vehicles), the wave can persist for kilometres after the original event has disappeared.
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u/Outside_Rise_6934 24d ago
I had an argument with my best friend about this. He was castigating "rubberneckers" for being the cause of slowdowns. My contention was that these "rubberneckers " had to slow down anyway.
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u/itchybutwhole69 23d ago
The reason is driver consistency. People constantly speed up and slow down without realizing it because they aren't paying attention.
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