What Are Traffic Waves and Why Do They Happen So Much? (opens in new tab)

Yes, that must have been it. I don't remember anything about the look of the page, but his tone seems very familiar.

> How can you be sure the cars behind you aren't even more compressed

Because, uh, you don't drive slow.

You drive at the average speed of traffic. Not slow. To smooth out the traffic waves, you don't come to a halt, and neither do you rush forward. "Average speed:" that's when it's not fast, and also it's not slow.

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Myth: if you have an empty gap, you must be a slow driver!!

Debunked: yes, genuinely slow drivers have big gaps ahead, but those gaps are continuously growing. If a clot of cars is going just 1/2MPH slower than average, then the gap increases rapidly: growing a half mile for each driving hour. If that clot of cars was 5MPH slow, then in just ten minutes the gap would increase by over four thousand ft.

But on the other hand, a constant-sized gap does not decrease your speed. Whether you're 6" from the car ahead, or 6ft, or 600ft, your gap has a constant size, and you're moving at the same speed as traffic ahead.

Slow drivers do make empty gaps, but empty gaps aren't any proof of slow driving.

Heh, so maniacal aggressive tailgating doesn't actually get you to your destination any faster? AMAZING! Who'd have thought!

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?

The way I do it, I eventually catch up to the car in front of me. Not having the data to pick the perfect, average speed, I err faster so that the traffic behind me isn't, on average, going significantly slower than traffic in front of me. Note that waves behind you are the only waves affected. All you're doing is thinning out the medium so they don't propagate efficiently. The end goal is keeping actual speed close to average speed; spacing is a means to an end.

Someone posted the link, and noticed the part where he saw behind him. TL;DR: When driving downhill into a valley, you can see for miles behind you out the rear window.

Also, I didn't say that smoothing the waves increased road capacity, though improving merging may help a bit. Rather, the reduction of stop/go is to everyone's benefit.

In the city things are largely the same, people here tend to speed to the next red light, but it doesn't help.

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.

California is the worst about this and if that's where you live may be giving you a false impression of the US as a whole. It's probably because in California, 18-wheelers are required to stick to the right lane and have a lower speed limit (55 instead of 65). That's not true in most other states.

I, too, have noticed that people here tend to just pick a lane (usually the left one to avoid trucks) and stick to it no matter the speed they're going. However, my experience in the other two states I've lived in (Florida, Indiana) and the other 35+ states I've visited, is that most people in the US know that the left lane is for passing and are somewhat more considerate about this.

Drivers have trouble merging in all 50 states, though. Half the people merge as soon as possible, thinking it's more polite to merge sooner rather than later (or just not wanting to fight for an opening or get angry looks from people who believe merging early is better), and half the people merge as late as possible, attempting to do the zipper merge which is actually the most efficient means of merging and what everyone should do.

I was taught this and practice it regularly.

I think it's an attitude thing. As often as I see drivers in my area blowing through red lights and pulling other ridiculous or dangerous stunts every single day, I can only imagine it's due to a lack of care or respect on the drivers' part.

Just a note - not sure if it is the case but the downvotes are likely due to your use of 'retarded'. Outside of the US, using it in a negative context as you have here is considered offensive.

Right - that needs to be fixed. Besides the graphical issue, the lane changing is instantaneous, which is not realistic.

The worst I've seen has been in Johannesburg in South Africa, where automatic transmission is rare. I used to refer to it as concertina traffic before I knew it was called a traffic wave, and the concertina is a popular instrument in South Africa amongst the ancestors of the people who are usually responsible for these waves.

The last time I counted, I have driven in 12 different countries. I found this certainly happens a lot in South Africa and a bit in various parts of Spain and Ireland. It seems to happen a lot less in the UK and Portugal.

While I largely agree, I think that some layer of _untrusted_ communication could be beneficial. Think along the lines of how turn signals & honking can benefit humans. Similar types of information could be conveyed more precisely "over the air", even if it was not presumed to be perfect (i.e. just likes human's signals aren't and a smart car isn't going to trust someone's turn signal, but it might react to it). Examples of this could be 1) relayed traffic ahead (more time to break smoothly) 2) lane switching plans (cars can coordinate such that it reduces slow downs & conflicts) etc. This is very similar to how network layer algorithms behave (i.e. TCP can hint to slow down, but you don't have to listen).

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.

I expect in the short run we'll see different tribes of self-driving cars - say Google vs. Uber - who will actively communicate cooperatively with their in-group, but actually compete against the out-group, depending upon whether or not their host companies decide to cooperate or not.

In the long run, I expect cars to become smart enough to be self-owning, in which case it's every car for himself.

And that's assuming error free communications, near latency free communications and non-congestion as well as perfect hardware.

Is 'no signal' the same as 'no other cars' or 'broken radio(s)'?

Self driving cars have all the elements of a distributed computing system only now it's moving at a pretty good clip and lives are at stake. 'Move fast and break something' is very bad advice and 99.999% uptime is not going to cut it.

Hard enough to get autonomous (pun not intended) systems right, much harder to make systems that communicate between vehicles right. The best way would be to not rely on inter-vehicle communication but to only work with the signals that the car can pick up from the environment.

At least that data will be somewhat trustworthy because you have some idea about the integrity of the system.

I hope that self-driving cars will broadcast their intentions, so other cars can use that to get a better prediction of where the car will be. But the broadcast processing definitely needs to be done carefully: the data may be corrupted or malicious, so the receiver needs to carefully process it to avoid crashing (software or vehicle), and also check it against the picture of reality it gets from its sensors.

If the vehicle in front of you tells you it will accelerate, you shouldn't accelerate too, unless you can verify the acceleration and that it's safe for you to do so.

I heard a few years back (no source) that when they model traffic they can design systems that work perfectly, its human error (not hitting the gas fast enough after a green light, changing lanes to often, 18 wheelers getting in the far left lane to turn right) that make the models break down.

I'm aware of CA splitting -- it's not been adopted yet elsewhere in the US. It's too bad that you had to experience someone who was "swerving in and out" and not the majority of riders who would split sensibly and safely.

Lane splitting is only supposed to occur below a certain speed; splitting above that number would be a violation, of course.

Take a look at Europe to see how easily splitting can be integrated, for both driver and rider. It absolutely does reduce congestion: bikes move smoothly to the front and away, freeing space.

American drivers just aren't educated to realize this because negative stereotypes about motorcycles are so prevalent in the US, and the many positive benefits of riding aren't presented as options here.

Okay, but on-the-fly time calculations aren't exactly optimal. It's much easier to establish a lower limit on distance.