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Make it make sense (media.piefed.world)
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[-] socsa@piefed.social 96 points 1 month ago

Hey I studied this in grad school for a bit, and it really is just "someone does some dumb shit which leads to a cascading wave of additional people doing dumb shit which propagates backwards for miles." Basically when the offered load is getting close to the maximum load, all it takes is one person aggressively changing lanes to throw that section of highway into gridlock, and it will remain that way until the total integrated traffic flux across that incident boundary again falls below the critical offered load inflection point.

Basically, pick a lane and just stay in it. Maintain proper following distance. Counterintuitively, the following distance should be for the speed you want to drive, so even in traffic it should be like 5+ car lengths even though you are going slow. This is because it reduces the offered load, and once that number falls below the critical point, speeds will increase again. Bumper to bumper traffic basically prevents that from happening because it dampens the ability for a "speedup" wave to propagate.

Of course this is all impossible for humans. All it takes is a few idiots to throw off the balance.

[-] Takios@discuss.tchncs.de 50 points 1 month ago

so even in traffic it should be like 5+ car lengths even though you are going slow.

Other drivers: "It's free real estate"

[-] Corn@lemmy.ml 5 points 1 month ago* (last edited 1 month ago)

Secret is to play the game next to a semi. Some semis kinda do it too by engine braking as they see the wave approaching instead of waiting until theyre close to even slow

[-] LemmyZed@lemmy.ca 25 points 1 month ago

So basically: 1. Put people in public transport away from the steering wheel, 2) scale back cars use.

[-] SereneSadie@lemmy.myserv.one 3 points 1 month ago

Go back to fuckcars with the rhetoric.

[-] JargonWagon@lemmy.world 5 points 1 month ago

Yep! All it takes is one person braking, and then the person behind braking, then the person behind them, and eith each braking the overall speed slows down more and more. It creates a wave of traffic. The wave passes through. The starting point I think moves back further and further.

I think about it a lot while I sit in traffic.

[-] N0t_Legal_Advice@lemmy.today 4 points 1 month ago

There was a really interesting MythBusters episode where they essentially replicate what you're talking about. Albeit with an "n" of 1 or 2 and a very small scale, but still interesting.

[-] thejoker954@lemmy.world 2 points 1 month ago

Sad thing is its more than just a few idiots.

The idiots are the majority. So stupidly self absorbed they constantly screw themselves over trying to "get theirs".

[-] ftbd@feddit.org 2 points 1 month ago

"Pick a lane and stay in it" leads to slow drivers blocking the left lane, no?

[-] seralth@lemmy.world 10 points 1 month ago

You have demonstrated why fundamentally humans suck at driving and this problem is unsolvable.

Not because you asked the question but because it's not intuitive why.

So long as this has to be explained to anyone it can't be solved.

[-] ftbd@feddit.org 3 points 1 month ago

I'm genuinely curious: are there adverse effects to an arrangement where the right lane is used by large trucks going 90-100 kph, middle lanes used for normal traffic going 120-130 kph and the left lane kept open for faster traffic? As far as I understand, these issues arise when cars go back and forth between lanes all the time, or when cars go slower than the ones behind them without an open lane to overtake them. If you pick a lane and stay in it, you might cause the second issue

[-] socsa@piefed.social 7 points 1 month ago

From a purely traffic load perspective, the whole "fast lane" thing doesn't make a huge difference, and the aggressive obsession with it is actually a big part of the psychology which creates traffic in the first place. Traffic capacity is generally optimized when everyone is traveling close to the same speed and has enough following distance to safely maintain that speed, which is why speed limits are set for the slowest road users. Just in general, speed does not increase road capacity beyond a certain fairly low limit because it requires dramatically increased following distance, or in the absence of such responsible behavior, it massively increases the frequency of traffic disruption.

The worst case is a few people traveling much faster than the slowest road users, as these few users both take up more space, and cause more disruption. The "fast lane" concept is rooted firmly in an unfortunate behavioral reality and has basically no real scientific basis beyond that. Even if you had perfect robot drivers with perfect reaction time and the ability to see far ahead of themselves, the critical capacity speed only increases slightly because the maximum stoping distance is still limited by rubber and asphalt.

[-] BJ_and_the_bear@lemmy.world 2 points 1 month ago

I’m a little confused about the mechanism of the speeders causing the disruption. Is it because when they cut in front of someone closely, it causes the driver to hit the brakes to make more room, thus triggering the chain reaction?

[-] Mr_Dr_Oink@lemmy.world 2 points 1 month ago

Thats a big part of it, yeah. Theres lots of really good comments about it in this thread.

this post was submitted on 28 Aug 2025
754 points (100.0% liked)

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