Experiment Shows Traffic 'Shock Waves' Cause Jams 642
Galactic_grub writes "Japanese researchers recently performed the first experimental demonstration of a phenomenon that causes a busy freeway to inexplicably grind to a halt. A team from Nagoya University in Japan had volunteers drive cars around a small circular track and monitored the way 'shockwaves' — caused when one driver brakes — are sent back to other cars, caused jams to occur. Drivers were asked to travel at 30 kmph but small fluctuations soon appeared, eventually causing several vehicles to stop completely. Understanding the phenomenon could help devise ways to avoid the problem. As one researcher comments: 'If they had set up an experiment with robots driving in a perfect circle, flow breakdown would not have occurred.'"
Brakes. Not breaks. (Score:5, Informative)
Re:Brakes. Not breaks. (Score:4, Funny)
Not that simple (Score:5, Insightful)
Once traffic reaches a point of saturation ANY change is flow will bring traffic to a halt. This includes things like a road feature that makes people accelerate, a merging or diverging ramp, or a hill or corner that allows people to see farther ahead inducing them to adjust their speed.
Any change in relative speed will at some point cause a person to slow down. If they are accelerating they will slow when they get close to the car in front. If they are slowing then that is obviously a slow down. Each car behind this change reacts to it after a delay. The longer the delay the more they have to react. People tend to react much slower then they normally would because very few drivers focus primarily on driving. They only use the minimum attention that is necessary. This just makes the problem worse. It only takes a few cars for a subtle adjustment to become a complete stop. The length of time each successive car is stopped will become longer and longer.
To make the problem worse the same 1 to 2 second delay in reaction applies to the acceleration of the vehicles after the slowdown/stop. Every fraction of a second that a person delays accelerating is adding to the stacking of the delay.
To look at another aspect of a slowdown...
If you have a smooth flow of traffic at a fixed speed you will have a certain number of cars passing a point on the road per minute. If you have a slowdown you will reduce the number of cars passing per minute. But the traffic was already at a capacity flow so the number of cars feeding into this situation continues unabated. It is obvious that the flow of traffic is done until the quantity of vehicles feeding into the situation is drastically slowed to less then the flow of traffic at the restriction. (In Orange County, CA that means waiting till after 6:30PM for a situation that started at 3:00PM.)
What can be done about this without building a vastly increased number of lanes? (The I-405 is already 14 lanes in central Orange County. Increasing it to 20+ lanes would cost billions and in 20 years when they are done we would need 30+ lanes...)
A big improvement could be made through driver training (Yeah right...). Teaching people how to merge can reduce the constant forced slowdown from cars merging onto a freeway at less then freeway speed. The correct speed to merge at is 5 to 10 MPH FASTER then the flow of traffic. A car won't accelerate quickly but it will slowdown quickly so you simply drive down the on ramp picking the hole in traffic you will merge into and brake into that hole matching speeds. This minimizes the disruption. "Freeway Meters" on an onramp actually make this problem worse on a freeway that is still flowing at a reasonable speed because they reduce the distance that a car has to accelerate insuring that they enter the roadway at a reduced speed causing traffic to slow down for them.
Teaching people to slowdown after they are on an offramp will also help reduce the disruption to traffic flow. Most drivers slow down a minimum of 10mph before the exit the roadway causing large backups for open free flowing offramps.
To reduce the effect of slowdowns you can teach people to look past the car in front of them and try to slowdown before the car in front of them, which can reduce the quantity of speed they have to scrub off. If they look ahead and start to accelerate earlier this will cause a similar improvement in reduction of traffic impediment.
(Truth is that you will never be able to teach people to change their driving habits because their cell phone, their coffee, and their daydreams are way more important then driving the 1-1/2 tons of steel they are sitting in.)
Re:Not that simple (Score:5, Informative)
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I've talked with the local head government transportation guy, and he said the term that they called this phenominon is the "accordian effect".
I think main motorways should be allowed to use the shoulders when traffic is backed up (w/o rumble strips). But you can get in some legal trouble if you do that today.
I also just think that cars don't scale well, and we just need a better way to get from point A to B.
Re:Not that simple (Score:5, Interesting)
What happens if there is a break down? You are back to three lanes of traffic, just like there would have been if you had never allowed driving on the hard shoulder in the first place. The rest of the time, you get an extra lane.
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You're not considering safety. Someone broken down on the side of the road most likely will be walking around the car, possibly changing a tire, making a phone call, or walking to the off-ramp. Traffic in the shoulder is a serious danger to that person. It would also make it more
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Re:Not that simple (Score:4, Funny)
Mercedes drivers are awful too, but has anyone noticed just how much of a wanker the average Audi driver seems to be these days? Many car buyers are fashion victims, and I think some of the "cooler"[1] BMW drivers are moving to Audis.... I don't think its a co-incidence that the newer Audis look more aggressive than the BMWs.
[1] shallower or wankerer
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It's not. This guy [eskimo.com] was an amateur looking at the problem a decade ago.
Geez, not THAT guy again. His observations on what causes that stuff are spot on, but his proposed solutions show a complete inability to understand the concept of scaling as it applies to traffic. He notes that by keeping a larger interval in front of him, the "wave" disappears. Well no shit. Doing that simulates a small pocket of uncongested freeway. This pocket is created at the (small) expense of the cars behind him. You can't have everyone leave a larger interval because that would require the road to be carrying fewer cars. The waves are caused by too many cars too close together. no amount of driving "tricks" is going to increase the car-to-car interval without actually reducing traffic density.
Commendable effort, but it's further proof of what my father (an engineer) has always said about engineers "Never ask an engineer to solve a problem outside his area of expertise. You'll get the most plausible sounding wrong answer you've ever heard."
To respond to your specific claim:
The goal is not traffic density (cars per mile of roadway, f'ex) but rather traffic throughput (cars per hour).
If you double following distance you reduce density by half*. If you were to continue at the same speed you'd also cut throughput by half. But if the extra following distance avoids propagating perturbations that would cause slowdowns your average speed m
Re:Not that simple (Score:5, Insightful)
I think what's new here is that it's been shown in an actual experiment using real cars, rather than just theorized or modeled in a computer.
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The problems with merging and so on would essentially evaporate if people dropped back a bit fr
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Right, I first learned about this from my GCSE Chemistry teacher in about 1986. He'd been in North Africa in the war, where supply convoys could easily be a couple of miles of a single line of traffic. Each jeep set off when it saw the one in front move, which meant that the ones at the back had to go hell-for-leather to catch up, only to realise that the ones at the front weren't going all that fast. There were regular ~100-jeep pile-ups until they instituted a sy
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Traffic jams leave ~1m between cars, almost at a standstill. That's a rate of one car per 5-10 seconds, at best. If they left 40m between cars and cruised at 100kph you'd get roughly three cars in the same time.
The faster and smoother emptying rate of the highway should actually empty the feeder roads faster than it would if everyone crammed on at once.
If more is better then too much is just right... (Score:4, Insightful)
It is pretty rare that anyone truly questions the vehicles that we buy today. People have accepted SUVs as the norm for driving around in the US for some reason. People will recite a number of reasons but in reality the only real reason is that they have become accepted as normal and 'cool'. It is just a change in peoples perception. If you had asked someone in the 1970s to select a 'people hauler' they would select a station wagon. It is lower to the ground making it safer to drive and is a much better layout for a vehicle. No one would have accepted a 70s Suburban, Blazer, or Bronco (even with a more luxurious interior) because of the perception, "That's a truck!"
This change of perception is actively damaging our country. Moving the increased mass of these vehicles around just plain costs energy and increases wear and tear on our roadways. If you are conscious of this and want to get a reduced mass commuter vehicle you are taking your life in your hands because of the battering ram reality of a large percentage of the vehicles.
It is really time that we do something realistic about the mass of the vehicles on our roads. A general switch to smaller lightweight vehicles would massively reduce fuel expenditures, pollution, and the smaller size would help to reduce congestion. The solution to this is to change public perception, which will probably only come about by economic reasons. The price of gas will do part of it but taxing vehicles by weight will go a long way towards making it a more equitable situation. The lighter vehicles would be rewarded for their lessened impact on the roadway and the environment. More massive vehicles would pay for increased impact on the environment, wear to the roadway, and the increased risk they pose to lighter vehicles.
People talk about rail/mass transit as a solution to LA's transportation problems but usually it is people who haven't been here. This area is so spread out in all directions that it would take an indescribable quantity of money to build such a system. The land is insanely expensive and with the sprawling area you could spend a few years of our whole nation's federal budget to build such a system. It just won't work.
(That guy who stole the tank down in San Diego about 5 years ago is starting to look saner and saner...)
BTW - From trips to Europe: I love the mass transit! Munich has a rail, subway, tram, and bus system that is so good it is just fun to use it! For 15 euro you get a pass good for unlimited use of all of the above for a week! It is just amazingly convenient and cool.
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Re:Brakes. Not breaks. (Score:5, Interesting)
I wonder how much aggressive driving (someone speeding up to 90, and then cutting in front of you for seemingly no reason), contributes to breaking shock waves. I've seen it happen often enough where someone will make an unnecessary maneuver to get 30 feet ahead of traffic.
Re:Brakes. Not breaks. (Score:5, Insightful)
If police would enforce rules against driving too slowly (generally defined as being passed on the right (because if traffic is passing you on the right, then you need to get the fuck over)) as they do aggressive driving, the problem would be much less prevalent. Then, the faster moving traffic could pass the slower moving traffic, keep on going, and there wouldn't be any problems. Sadly, though, that's not the case in any metro-area I've dealt with. Instead, the jerkoff Sunday Driver creeping along at 50 in the passing lane just has to be dealt with, usually by getting around him in the right hand lane, then speeding up to 90 and cutting in front of him so you can pass the traffic on the right.
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the jerkoff Sunday Driver creeping along at 50 in the passing lane just has to be dealt with,
I could not agree more. These people seem to take pleasure in being a complete obstacle. For the life of me, I cannot understand why someone would willingly drive slowly in the left lane it's insane and definitely a major contributing factor to this problem.
If police would enforce rules against driving too slowly (generally defined as being passed on the right ...as they do aggressive driving, the problem would be much less prevalent.
While I agree, and I would like to see that enforced better, we should be careful about what we wish for. I just recently got an education (from an area police officer with ticket book in hand....$375 later) that passing on the right is ALSO
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as for why people go all the way to the left when they get on the high way. it's just a zombie driver mentality thing. They _THINK_ they're a "fast driver" and that lane is for them, or they think that by being in that lane they're allowed to go faster.
Some drivers just go one speed no matter what road they're on. For example: last year I needed to follow my aunt so
Re:Brakes. Not breaks. (Score:5, Interesting)
Maybe not, but there's something your highway authority can do about it: Adopt German rules. Passing on the right gets you a ticket; driving on the left without passing gets you a ticket.
Flipping someone off gets you a ticket too, but that's another issue.
rj
Re:Brakes. Not breaks. (Score:5, Insightful)
Of course if you are motivated by some other less honorable sentiments you will continue to act as you do and feel justified and prideful about it.
Also, be aware that there are varying circumstances that may cause someone to drive faster than you. Your statement that it is because of some dissolusioned consumer fantasy belies your presupposition that the people who drive faster than you are somehow inferior to you. Believing a lie and then becoming irrationally angry with you because you show them the truth of the world makes an easy straw man to flatten. However, consider that you might be stopping someone from reaching an important destination in an appointed time. Like the time my father was in the hospital. His respiratory doctor called me and said he was not breathing without assistance and that I had very little time to get there to see him before the DNR orders took effect. I was across town at work and had no idea if I was going to get to see my father alive ever again. I cannot tell you how frustrating it was to deal with people *just* *like* *you* as I made my way to see if my father was still alive, to talk to me one last time.
But hey, one thing I have learned is that people act as they feel they must. Compelled is a good word. People who drive faster than me, I move over for them. People who drive slower than me, I just wait till I can pass them. Understanding that they have their own internal motivations that I probably do not understand makes it easier to live and let live. When I catch myself assigning characteristics, thoughts, and motivations to people driving near me I just take a deep breath and realize that I don't know why they are doing what they are doing and it is best to work cooperatively with people, even if I have never met them.
Ambulances are slow (Score:3, Insightful)
If you'll re-read the post you're responding to, you'll see he didn't care about the "casual speeder." He was criticising the maniacs who drive as much as 50% over the speed limit. Not to be insensitive, but if you were driving like that, you're doing exactly what he was criticising and risking others' lives in the process. If you were driving responsibly (although not legally) in your haste to get to the hospital, chill out. He doesn't care. Nor do I or most other people.
Even ambulances with sirens and lights operating don't drive that fast, because the risk of seriously hurting or killing someone else is too great compared to the benefit gained from time saved.
No, ambulances with lights and sirens don't drive that fast because they recognize that they're driving very slow heavy diesel trucks not meant to accelerate, brake, OR handle, and that most of their time savings therefore come from safely negotiating intersections without stopping and waiting in traffic. If they have to spend a long time on the highway there is a problem anyway, as their base is too far from the people they need to serve.
Ambulance drivers are smart enough to realize it's unsafe to drive
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If you're in the left lane, and just keeping pace with traffic in the right lane, and there is somebody behind you, you should try to move over for them when safe to do so.
It is just courtesy. I have all the patience in the world for somebody who passes somebody else slower than I might. I get really annoyed when two cars drive in side-by-side formation for 5 miles. As long as you're passing I don't care what you
Re:Brakes. Not breaks. (Score:5, Insightful)
I try to stay far enough behind the car ahead of me so that when he brakes, I merely have to remove my foot from the accelerator so I don't convert my kinetic energy to heat. Of course, some dipshit always sees the three car length hole in the thirty mph traffic (you're supposed to maintain 1 car length for every 10mph anyway but none of the fucktards in Springfield do) and fills it in.
If people maintained a reaonable distance (the 1 car lenhgth for each 10 mph) you wouldn't have this effect, or if it occurred it wouldn't be so bad.
Every time you touch your brake for any reason whatever you throw fuel away as waste heat.
<jk>(global warming comes from the hot air blowing out of the world's capitols)</jk>
-mcgrew
Re:Brakes. Not breaks. (Score:5, Insightful)
And yes. Tailgating certainly is a HUGE problem. What's most astonishing to me is how many people shrug it off as no big deal or even justify their own tailgating behavior by saying something like: "Well, it's much worse and more dangerous to be driving slow on the freeway." This is of course utter nonsense. Tailgating is insanely dangerous, leads to a huge number of accidents, and in my mind is the equivalent of pulling a knife on someone for taking too long getting their wallet out at the grocery store.
(I would love to see widespread police crackdowns on tailgating, but I'm guessing it's just easier to prove speeding in court so that's where the tickets go. Anyone know if that's it?)
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Re:Brakes. Not breaks. (Score:5, Insightful)
Another interesting aspect of the problem is how many people who aren't these kind of habitual tailgaters will become tailgaters when speeds drop, e.g., on exit ramps. They maintain a safe distance until the speed gets down to 50 or 40mph. Then it's as if they forget that much past 30mph is fatal crash territory, and they plant themselves one foot off the next car.
I think the root cause for all this is a lack of respect for how potentially dangerous driving is in general. You won't find large numbers of gun owners who play with guns like toys (though they're out there), but you can find plenty of people who treat driving with all the care and attention they put into watching TV. There just isn't enough respect for driving. If there were, accident rates would plummet. I'm just going to hold out hope for a day when reckless driving is rare.
Re:Brakes. Not breaks. (Score:5, Insightful)
That as well as maintaining a reasonable following distance, traffic permitting.
Your post gave me visions of Frank Drebin [wikipedia.org] hitting trash cans as he pulled up to a curb.
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Merging sooner increases the load in the merged-to lane and effectively lengthens its backup. And it wastes the available space in the merged-from lane. It also causes fluctuations in the merged-from lane as people speed up and slow down to accommodate the fluctuating availability of space. It's more efficient to use the "zipper" technique where *everyone* goes to the end of the
Traffic flow analagous to supersonic flow (Score:3, Interesting)
Re:Brakes. Not breaks. (Score:4, Insightful)
In response: you can't always speed up, since sometimes the guy in front is driving slow and the people in the next lane over are driving too close to move over. You being a dangerous driver is not helping anyone and I'll more likely brake to piss you off - that way we are both being dangerous
What gets me are middle lane drivers that drive at 90km/h, when the right hand lane is free, forcing everyone to over-take (ok), or under-take (not ok)
Re:Brakes. Not breaks. (Score:5, Funny)
-Activate the brake lights
-Activate a set of hydraulics to boost the read of the car up an inch or two
-Release a little smoke from a point near the rear wheelwells
-Play a loud screeching sound from a loudspeaker mounted under the trunk
Simulated emergency stop! Should give those tailgaters a reason to back off...
=Smidge=
Re:Brakes. Not breaks. (Score:5, Funny)
Re:Brakes. Not breaks. (Score:5, Funny)
(stolen from myself [tdiclub.com])
Re:Brakes. Not breaks. (Score:4, Funny)
Congratulations! (Score:2)
Amazing that they will fix this but often leave completely inaccurate articles uncorrected.
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This has been done before (Score:3)
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I remember getting this as a result from a simple discrete model written in Turbo Pascal as far back as early 90-es. No need to make volunteers drive cars. Once the traffic exceeds a certain density waves and fluctuations in it will show up straight away. There is even some math proof of the instabilities in mass service theory. It's been a while so I cannot remember.
Anyway, this is Japanese science. Anyone who has had to suffer from reading a Japanese publication knows what I am talking about. P
That's why I never use my brakes (Score:5, Funny)
Re:That's why I never use my brakes (Score:5, Insightful)
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I follow the rule of taking my foot of the accelerator at a "yellow light condition" and hitting the brakes at a "red light condition." A yellow light is obviously a yellow light condition (unless for some other reason of safety I need to start hitting the brake), but several other things are "yellow light conditions" to my brain and this actually makes my driving real smooth: if the brake lights of the car two cars in front of me come on, that's a yellow light condition. If the turn signal of the car in
Re:That's why I never use my brakes (Score:4, Interesting)
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Re:That's why I never use my brakes (Score:4, Funny)
You, sir, have never driven on any of the highways near NY city. If you had, you would know that it is impossible to drive the correct distance behind the car in front of you. It's not merely that you'd be only person on the highway doing such a thing (annoying the cars behind you); it's that those car lengths will instantly be taken up by people cutting in front of you. You would then be forced to slow down, and the process would repeat until you find yourself driving backward.
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Gotcha!
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I just wish that more Americans followed the concept of "Drive Right". The far left lane is NOT for doing the post speed limit or less. Oh, and that turn signal thingy...try using is occasionally.
Sorry, I will stop ranting now.
Re:That's why I never use my brakes (Score:4, Funny)
Here in Appalachia if a vehicle has its turn signal on then it usually indicates that the vehicle was shipped from the factory that way.
Faulty drivers (Score:5, Funny)
"caused when one driver breaks" (Score:5, Funny)
You wouldn't have this problem if you wrote your own drivers.
Comment removed (Score:5, Informative)
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GOING INTO THE FIELD AND DOING PRACTICAL EXPERIMENTS.
By the look of it, it looks like these researchers confirmed what the mathematicians predicted would happen. Someone brakes too hard, or too early, and the rest of the flow of traffic behind them is now all fucked up.
I swear, I've seen people bitch that "oh, problem could've been busted on mythbusters if they just did the math and left it at that" and not realize that the follow through is to... DO THE EXPERIMENT.
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Anyone that has paid attention and driven in heavy city traffic has seen this. The hill coming into detroit on I96 you can watch in the early morning a wave of breaklights coming to you from a mile away. the undulation continues for the next 30 miles and probab
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A couple of early posters are making jokes about faulty drivers and writing your own. But honestly, eliminating the human component from driving would significantly improve traffic flow across the board and would allow it to be optimizable. It's
Even older than that (Score:3, Interesting)
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dark helmet (Score:4, Funny)
I knew it... I'm surrounded by *ssholes.
Keep braking, *ssholes!
stability (Score:4, Interesting)
Is that true? If the robots had been fixed to a set driving speed (open loop), maybe. But if the robots had some sort of collision avoidance, it could still happen. It's instability in the control algorithm, no?
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Absolutely. Last semester in my graduate robotics class, I had robots follow each other through loops (eventually meant to simulate an intersection control technique). I used collision avoidance on each robot.
I first tested each loop in simulation. The robots would all start at the same acceleration. At a certain saturation of robots, the whole system would break down due to the "waves" of traffic congestion caused by collision avoidance.
Mind you, this was with simulation that was nearly perfect (th
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Doesn't work that way. Response delays are a given, you don't have to configure them in explicitly. Signal comes in
prehistoric (Score:2, Funny)
there are a lot of complex things going on, but two simple principles stand out
when someone ahead of you brakes, you need some time (distance) to react
if you are far enough away, you will slow the same amount as the person ahead of you
if you are to close to the vehicle ahead of you, then your reaction time is such that you will over compensate and over brake; the same to the person behind you and
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I do as well, and I recall there was even software (e.g. GPSS) to simulate the phenomenon. But nice to see how an experiment validates historic findings (which have probably not made it to Google yet and thus practically do not exist).
CC.
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I love discussing traffic jams... (Score:3, Informative)
See when you put cars in the article, that immediately takes away the ability to use a car analogy. No car analogies = no lively discussion, or something like that. It's an approximation. Adding Natalie Portman or something involving Ron Paul changes the equation slightly, but car analogies are where it's at.
Wow, big news. (Score:3, Interesting)
Then again, I remember seeing stuff like that back at the university, where they were trying to combine traffic models with a Kalman filter to achieve better traffic jam prediction. That was, uh, over five years ago.
It's all the aggressive drivers... (Score:3, Insightful)
Its all the SLOW drivers. (Score:2, Insightful)
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Making them slow down even more, and consequentially making everyone behind them slow down even more, shockwaving to a total standstill some miles down the road.
Yeah.. So actually cutting someone off makes sure you won't have anyone behind you for a while. Hmm... There might be merit to that idea
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robots (Score:3, Interesting)
I, for one, welcome our new japanese robot driver overlords.
but seriously, I take this as a hint as to what is to come in the future for japan.
Easily explained phenomenon: (Score:2)
2. Due to reaction time, the second car has to decelerate at a higher rate in order to maintain a safe distance from first car.
3. Due to most drivers only looking at the car in front of them (instead of also checking whether the cars farther ahead are braking), repeat #2 for the following cars - each of them has to decelerate at a higher rate than the car in front of them (-> positive feedback, which is usually a bad thing in systems theory. At least if you want a stable system
it's mindboggling (Score:2)
Everything you need to know:
http://www.eskimo.com/~billb/amateur/traffic/traffic1.html [eskimo.com]
More:
http://jalopnik.com/335832/traffic-jam-mystery-solved-++-blame-the-wave [jalopnik.com]
People need to do a simple google search before starting research.
Ren Potts research in early 1970s showed the same (Score:2)
Research I wish someone would do... (Score:2)
It cause jams in BOTH directions.
Open source drivers! (Score:2)
Speed of light trumps wave speed (Score:5, Interesting)
But I could see a half a mile of cars all with little green lights, I could see (at the speed of light) the wave of yellow lights approaching and ease off the gas. The wave would be absorbed by this 'viscosity'. Traffic would flow near the speed limit or average flow rate, whichever the LED's were keyed to.
And don't even get me started on those GPS nav screens. Don't show me were I am. Show me where everyone else is. Let me see the compression 2 miles ahead and I'll chill (heh heh kinetic gas pun).
Tolls can do the same thing as well as other choke (Score:2)
"Those who forget the past", etc, etc, etc (Score:4, Interesting)
Guys, there really is a benefit to hitting the library and thumbing through back issues of ld technical journals.
Modern Marvels (Score:4, Interesting)
Ok, now ask yourself... (Score:2)
*scoff* (Score:2)
a good driver doesn't need brakes.
Duh (Score:2)
1998 called! (Score:5, Informative)
Very cool traffic sim (Score:5, Interesting)
http://vwisb7.vkw.tu-dresden.de/~treiber/MicroApplet/ [tu-dresden.de]
shame this post is buried down deep
Traffic dampening. (Score:3, Insightful)
I've read, and have observed for myself, that big trucks act as dampers. Because they brake and accelerate more slowly they need to maintain greater distance from vehicles in front of them. They can nullify a traffic wave because by the time they've reached cars which had been stopped they've begun moving again which essentially ensures that the truck continues rolling.
I've applied this technique to rush hour traffic myself and unless traffic is particularly bad its extremely effective. Basically accelerate more slowly than the car ahead of me giving myself a considerable gap. And by considerably I mean a good 5 to 10 car gap. Then I let myself roll in first, maybe second gear. If I see cars braking ahead I regulate my speed more carefully. Most of the time, when I reach those cars ahead of me they're already accelerating again and I keep right on moving, maintaining a consistent speed.
What disrupts this is when idiots feel the need to get into any opening they see, worse, when they can't stand the fact that I've left an opening in front of me larger than they find acceptable. To them, they're not making progress if they aren't riding someone else's bumper.
I usually find that in rush hour this doesn't happen as frequently because people seem to be worn down an resigned to slow-moving traffic. They jockey for position a lot less frequently than they would on the weekend when heavy traffic is less common.
Then there's the New York area where drivers are overly aggressive and downright idiotic. There's nothing to be done then. But I also think their driving habits have arisen as a result of horrendously designed and constructed highways. I think better highway design could go a long way to alleviating traffic problems.
Standing Wave Theory of Traffic (Score:3, Interesting)
This article is finding many of the same conclusions I had back then. Is there a fix? I don't know but traffic on a large scale is fluid.
God help us when we have flying cars and we have to deal with idiot drivers above us and below us!
Re:no such thing as perfection (Score:5, Insightful)
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http://en.wikipedia.org/wiki/Control_theory [wikipedia.org]
In the human case the basic problem is with reaction time, a little worse than a tenth of a second.
Say a driver slows down for 5 seconds then returns to normal speed. The one right behind him has to slow down, but takes a tenth of a second to respond. The one behind him also has to slow down,
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There is such thing as logic, which doesnt need it (Score:2)
If people realize that the reason the world goes 80 instead because that is the natural point that people feel safe to drive given current conditions and someone wasn't driving in the fast lane (going excessively slow and causing the feedback)
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Re:Interesting, but not a solution (Score:5, Interesting)
Breaking or other external factors (an accident or flashing lights by the side of the road) can certainly precipitate a change from a swiftly moving flow to a slow moving flow. However, they only cause a transition when the density is high enough. If there's an accident during a low traffic time, you whiz by it. If they close two lanes out of four, and it's low traffic, you get a little backup, but it reaches a modest steady state size in low traffic. In high traffic you get a "wave" - the backup moves steadily backwards from the scene of an accident, and remains after the accident clears.
I often tell my wife that I can tell if a slowdown is just due to high volume or an accident by the abruptness of the slow down. An abrupt slowdown, I think, means heavy traffic "precipitated" into a jam by an external event.
So braking as described may be a precipitating event, but it's the sensitivity of the traffic flow to it that is the fundamental issue. I'd guess that even if people didn't brake so much, in those sensitive conditions a fender bender by the side of the road could cause a major backup.
(Clearly, I've thought about this WAY too much.)
Re: (Score:2)
While I too would like to see improvement in the streets and roads infrastructure, the problem here is NOT with the infrastructure, it societal and anthropomorphic. The issue is not overall capacity; most roads are nearly deserted during certain parts of every day.
Society requires that the populace generally start and finish work at roughly the same times daily. Human nature and our anthropomorphic instinctive reactio