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What Are Traffic Waves and Why Do They Happen So Much?

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Re: What Are Traffic Waves and Why Do They Happen So Much?

#41

Post by greeneggs »

kokey wrote: post #6

I find this happens a lot more in some countries than others, and it's not down to levels of traffic on the road, it's down to driving habits. I think the UK has done well with driver education and variable speed limits to mitigate this, and zipper merging is the norm.

I wish California would put traffic mitigation into its high-school driver's education classes. Knowing the rules of the road and driving safely are important, but so is reducing traffic, and some simple information could save a lot of time in traffic jams.

Re: What Are Traffic Waves and Why Do They Happen So Much?

#42

Post by morley »

ninkendo wrote: post #40
mixmastamyk wrote: post #2

This reminds me of a piece on traffic I read quite a few years ago and might have been on reddit or even perhaps slashdot. I still follow its advice to this day when having to brave the 101. It discussed traffic waves and our reactions to them. The repeatable waves this article mentions come from (most of) the individual drivers driving faster than the capacity of the road to carry them all. So they bunch up at some…

How can you be sure the cars behind you aren't even more compressed than they otherwise would be if you're leaving so much space in front of you like that? One thing I hated about that article was that the author assumed he was doing such a great service for everyone by "smoothing out" the traffic waves by leaving a buffer, but he never really proved it; he just waved his hands and said that it looked like the cars b…

Whenever I see an article about traffic patterns, I inevitably see this exchange:

Person 1: You can fix traffic waves by smoothing!

Person 2: Smoothing traffic waves makes no sense!

It's frustrating. I don't know what to believe. Is there any peer-reviewed, simulation- and data-backed research that puts this issue to bed for good?

Re: What Are Traffic Waves and Why Do They Happen So Much?

#43

Post by mikeash »

leviathan wrote: post #26
vlasev wrote: post #9

Earlier quoted context omitted.

One problem of the "car idle" in terms of humans is that it takes almost constant attention to make sure you don't bump into the cars in front. Compare that to the speed-up/break/slow-down which allows time to relax. In my own driving I tend to have a more relaxed speed-up/slow-down cycle which is somewhere in-between the two modes you describe.

Not to mention that, in the country I live in, it is guaranteed that while you're idly rolling forward, some asshole will cut you off and take your place so that he can win that precious 2 seconds.

So let him. What's the harm? If he's gaining an insignificant amount of time, then you're losing an insignificant amount of time.

Re: What Are Traffic Waves and Why Do They Happen So Much?

#44

Post by knodi123 »

Does anyone else remember the scene in Mission Impossible 3, where tom cruise is hosting a dinner party full of guests who only know his fake cover identity as a statistician working on traffic waves for the department of transportation?

The movie portrays it as conversational kryptonite, where he briefly discusses traffic issues in order to weaponize boredom and get some people to leave him alone.

That part broke my suspension of disbelief, because I was like "Hey, why is everyone wandering away?!? I want to hear what Tom has to say about how to address the problem!"

Re: What Are Traffic Waves and Why Do They Happen So Much?

#45

Post by ninkendo »

morley wrote: post #42
ninkendo wrote: post #40

Earlier quoted context omitted.

How can you be sure the cars behind you aren't even more compressed than they otherwise would be if you're leaving so much space in front of you like that? One thing I hated about that article was that the author assumed he was doing such a great service for everyone by "smoothing out" the traffic waves by leaving a buffer, but he never really proved it; he just waved his hands and said that it looked like the cars b…

Whenever I see an article about traffic patterns, I inevitably see this exchange: Person 1: You can fix traffic waves by smoothing! Person 2: Smoothing traffic waves makes no sense! It's frustrating. I don't know what to believe. Is there any peer-reviewed, simulation- and data-backed research that puts this issue to bed for good?

I think the sad truth is that it doesn't matter how you drive, traffic is going to suck.

Given that everyone requires a safe lead time of (for example) 1-2 seconds, the more cars there are per mile of highway, the slower everyone must drive. (You can't drive 80 miles per hour bumper-to-bumper.) So if density is say, 50% (one carlength of open space per one car), you have to drive a speed such that a carlength is 1-2s, in other words 10-20mph.

But traffic distribution is not uniform, there's exits and entrances, and cars do occasionally need to change lanes. If traffic is going 10-20mph with 1 carlength of space between cars (steady state), and I change lanes, the guy I merged in front of now has to slow down more to leave more room, and this will cause a traffic wave behind him. What happens at an exit when half the cars change lanes? Standstill. No change in driving technique on anyone's part will help this.

I think the only times where the way you drive matters is when the density is kinda sorta high but still low enough for a safe following distance at reasonable speeds, at which point "smoothing out waves" becomes a common sense matter of "don't follow so close", which is effectively the same thing, and something everyone should be doing anyway when the density is low.

Re: What Are Traffic Waves and Why Do They Happen So Much?

#46

Post by [deleted] »

morley wrote: post #42
ninkendo wrote: post #40

Earlier quoted context omitted.

How can you be sure the cars behind you aren't even more compressed than they otherwise would be if you're leaving so much space in front of you like that? One thing I hated about that article was that the author assumed he was doing such a great service for everyone by "smoothing out" the traffic waves by leaving a buffer, but he never really proved it; he just waved his hands and said that it looked like the cars b…

Whenever I see an article about traffic patterns, I inevitably see this exchange: Person 1: You can fix traffic waves by smoothing! Person 2: Smoothing traffic waves makes no sense! It's frustrating. I don't know what to believe. Is there any peer-reviewed, simulation- and data-backed research that puts this issue to bed for good?

[deleted]

Re: What Are Traffic Waves and Why Do They Happen So Much?

#49

Post by bryondowd »

stormbrew wrote: post #8
orik wrote: post #7

Whenever the topic of self driving cars comes up in conversation I let people know I think self driving cars are going to solve a lot of our traffic woes. I'm not sure if a model exists yet for cars 'putting out' traffic waves, but I'm sure once we have self driving cars and they start talking to each other this is going to be of great interest. I'm hoping we can effectively 'micro' away some degree of congestion.

I think people overstate the degree to which self-driving cars will actively 'talk' to each other. And I actually think it's somewhat detrimental to advocating for self-driving cars, because the immediate thought is that communication acting as a channel for malware. And that's a fairly justified fear. In the end, I think most of the communication will just be in terms of the fact that self-driving cars interacting w…

I would think that active coordination could be beneficial, when not guaranteed. I'm sure most people have been in a situation where they are waving or gesturing with another driver to coordinate something in a friendly way. Maybe you need to move into their lane, so you point and make a questioning face. They nod as if they understand and make room for you. You move over.

They didn't need to back off, and in that case, you would have just waited for an opportunity to open up, or a friendlier driver to be next to you. Even if they nodded, but didn't back off, you'd just assume a mis-communication and not try to merge in.

So, self driving cars could do this on a much more regular and reliable basis, while still not relying on it or trusting one another. They broadcast that they want to get over, and if another car happens to get that signal and happens to be willing/able to comply, it opens a space. If the first car sees a space, it moves over, which is what it would have done anyway, regardless of whether the space is coincidental or intentional.

Could also be handy for determining right of way in edge cases where humans often get confused and play the you-go-no-I-guess-I'll-go-no-wait-now-he's-going game. Two computers might be playing the same game, but they can resolve it in a tiny fraction of a second. Of course, the flocking birds example works well here as well. If the rules are clear enough, the cars will just know who should go.

But yes, no matter what, a car couldn't trust what another will do, and should be prepared with an evasion strategy for every possibility, thus not doing anything that would leave it no way out if another car did something stupid or there was a mis-communication.

Re: What Are Traffic Waves and Why Do They Happen So Much?

#50

Post by zhte415 »

mixmastamyk wrote: post #2

This reminds me of a piece on traffic I read quite a few years ago and might have been on reddit or even perhaps slashdot. I still follow its advice to this day when having to brave the 101. It discussed traffic waves and our reactions to them. The repeatable waves this article mentions come from (most of) the individual drivers driving faster than the capacity of the road to carry them all. So they bunch up at some…

I think it was on Slashdot years and years ago. I can't find a link. I also remember the recommendation for spacing out and making it all better. Taxi drivers tend to do this (personal anecdote - others' taxis may differ).
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