Slashdot Mirror
Traffic Sim Predicts Jams Before They Happen
Via_Patrino writes "The New Scientist reports that: A traffic simulation system is helping drivers by predicting jams up to an hour before they happen. Traffic flow can be divided into three categories: freely flowing, jammed, and an intermediate state called synchronised flow in which dense traffic moves in unison. Physicists at University of Duisburg-Essen have developed 'the first model to reproduce all known traffic states.' Predicted conditions are displayed on the official website, and more than 90 per cent of the time, traffic density is predicted correctly."
What if people start using it? They avoid the traffic jams, thus no traffic jams. Wrong prediction!
But the system still wouldn't be able to predict traffic jams caused by accidents and cars breaking down, so it wouldn't be perfect. And if everyone reads when there will be a jam, no-one will drive then, and the traffic jam will be at a different time.
I remember a few years ago being told by a teacher that traffic flowing under 28mph on Motorways obeys hooks laws for compression waves travelling through a spring almost perfectly...
The compression waves travelling through the traffic are the reason that everything goes stop/start once traffic slows below a certain speed...
For those people concerned that releasing the predictions will interfere with the results, please remember that not many people will actually use this tool.
I hate seeing people speeding to red lights, when if they'd just follow the flow of traffic and the lights they'd get where they're going just as fast, and without causing traffic jams. I'm a terrible driver, but I figured this simple thing out pretty early on. Why can't the rest of drivers?
Hi! I make Firefox Plug-ins. Check 'em out @ https://addons.mozilla.org/en-US/firefox/addon/youtube-mp3-podcaster/
An idea borrowed from quantum mechanics...
Measuring the system changes the system.
What if everyone takes the same alternate route to avoid the "busy" route?
As the story points out:
"But the website has already become a victim of its own success, admits Schreckenberg. Some of the 300,000 people a day who are visiting the site are replanning their journeys on the basis of its forecasts, and this is beginning to make the forecasts themselves less accurate."
There were and are several projects in Germany that develope traffic models in conjunction with models simulating the route choices of people depending on their lifestyles. The problem is that there are people that do not believe that people can be simulated by cellular automata and reject those simulation. But there are also city planers who use those models when planning new structures like stadiums, airports and others that need road connections.
There is a sourceforge project thatsimulates multimodal traffic with cellular automata. Also have a look at this link for more information about traffic simulation.
***Quis custodiet ipsos custodes***
Both are fundamentally chaotic.
Sure, you can calculate expected probability based on past performances and expected flow... but we've all seen freeways humming right along at 70MPH and no problems until just ONE driver makes an error... then all hell breaks loose.
I don't think even predicting the weather is as tricky as predicting traffic flow, as at least the weather patterns follow known laws of physics for at least near-term before losing out to the chaotic nature of weather patterns. People are just flat out unpredictable.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
So what your telling me is, the traffic jam sim is a jedi? And he can see jams before they happen.
And I guess he has an evil father right? "Luke, I can feel the road rage in you, you must let is out"
And I guess news stories about traffic jams have to use lucas/powerpoint diagonal slides instead of hard cuts?
And Han Solo is the guy in the riced up car that speeds? Chewie likes "phat bass beats" in his WQRX p27983tyXX extreme ear-bleed SUB WOOFER SYSTEM.
And I guess there will be massive traffic jam merchandising? Possibly even a prequel traffic jam series with JAR JAR BINKS who is the pedestrian who always presses the walk button even when he has no intention of crossing the street?
And all the people who were caught in the traffic jams ages ago are like "this traffic jam sucks compared to the originals".
Anyway, enough of this, may the green lights be with you.
about it is the hard part. Changing behaviors is the most difficult thing to do. If people staggered the time they leave work and if they could tolerate a little bit of inconvenience of car pooling or riding a bus or train or subway then we might see the traffic ease up. Building more freeways and adding more lanes to existing freeways doesn't provide a lasting solution. Most people would reap the benefits of walking more to get mass-transportation and getting out of their cars more often. Of course there are the lucky ones that don't even need a car and can commute soley on public transit. Or just on foot.
I predict that traffic will get so bad and car ownership will become so expensive that people will figure out ways to get around without a car and possibly even change their lifestyle in the process. But it will happen gradually, I think it is already.
http://tinyurl.com/3t236
I believe the algorithm was leaked a few days ago:
// double jam sandwich
if ((time == 8am-ish) || (time == 5pm-ish))
double jam =1;
if (city == LA)
long long jam = 2^64;
Yeah, it's pretty common practice nowadays to use computer models to assist in urban planning, not just for designing new roads, but also to see where best to widen lanes, where to add additional lanes, and even how to time traffic lights. One problem with prediction, over the long term, is that it turns out no matter how much road you build, it isn't enough. So building in 5% additional capacity staves off traffic problems in the short term, but within a decade or two you've got 10% more drivers, the additional traffic coming from the fact that your original (planned) increase in capacity made it that much easier to drive. Of course, this is why governments are more and more turning to congestion tolls as a way to thwart this cycle. More here.
"in which dense traffic moves in unison, like marchers moving in step"
Some important facts, which the system designers seem to have forgotten: Real systems veer towards chaos and orderly behavior is anathema to all nationals except Germans. That apart, any traffic simulation design could be considered a success if it can be put to use in all conditions. I am quite sure that this system will come a cropper on Indian roads where cars have to jostle for space with cattle, cycles, pedestrians, three wheelers, two wheelers and so on. (Digression: I always find the sight of a stray dog crossing the busy road a lesson in traffic manners. The dog looks either side, ensures that there are no vehicles in vicinity and then crosses: A case of animal adapting his behavior to real time situations.) Human beings are not so adaptable and would do the best they could to defeat even the most beautifully designed systems.
If there is just a small change in velocity of one driver, the next guy is going to respond to it by hitting the breaks. The next guy is going to panic and hit it harder, and so it goes. I've seen this happen in real life many times: Just a small riple can make a jam, three or four cars involved is sufficient.
I fact, I think I saw an article about this too, it could have been long ago in Europhysics News or something. They like publishing stuff like that.
I'm trying to keep a lot of distance when I'm driving: Three seconds in normal situations (just count), and up to five seconds if I'm in synchronized flow. That way, I can absorb many ripples if the three or fours cars in front of me is slowing down. I think it helps, but surely it doesn't help a lot if it happens further ahead.
It is of course important not to lag too much when the cars starts moving again, so I generally speed up to follow in the start, but then try to build up some good distance, when the flow gets going.
But then, I'm just speculating...
Employee of Inrupt, Project Release Manager and Community Manager for Solid
Use the "effects" of the prediction to get the desired results. For example, if you want clear sailing on Route 9 going north at 4:00pm, predict bad traffic ahead of time.
If you want more predictable traffic patterns, fudge prediction differences downwards so that less people will take action based on the predictions.
It's all one big feedback loop, dampen accordingly.
...the slashdot effect on their site
oops, different flavour of jam
The ring road around Eindhoven has recommended speed indicators that show what speed you should be travelling at to hit the next light on green. It seems to work quite well.
The Hanshin Expressway network around Osaka has video processing equipment that can automatically recognise traffic congestion, including the characteristics of traffic accidents. It then alters roadside information boards to route drivers around the congestion. Other areas do the same thing.
adio bReacons update vehicle navigation systems in real time to show time to destination, congested roads, and if you're following a planned route, will re-route you as traffic conditions change.
Unfortunately most signals in Japan aren't load-sensitive, but set to 1 minute green in each direction irrespective of time of day, day of the week or class of road. So circular routes around Tokyo, for example, become major barriers to traffic entering in the morning and leaving in the evening.
On Japanese freeways, the major cause of congestion is the humble tollbooth.
Here is the source code:
#!/usr/bin/perl -w
$now = `date +%H`;
if($now == 7 || $now == 8 || $now == 16 || $now = 17){
## Genius part!!
die "Rush hour, take another route!\n";
}else{
die "Roads are clear!\n";
}
## Please note, code is not optimized yet, but it's 90% accurate!
Probable impossibilities are to be preferred to improbable possibilities.
Aristotele
Just some ideas.
1. Reduce the number of redlights needed and make the ones left more intelligent
2. Use more public transportation, especially for commuting
3. Get the idiots off the road
4. All exits should be to the right, because exits to the left mix fast and slow traffic
5. Restrict 18-wheelers to the right lane only and make them use by-passes when available
6. Get the idiots off the road.
7. Move wrecked vehicles off the highway as soon as possible, even if it means coming back to tow them later. Why shut down a whole interstate because of a vehicle in the median waiting for a tow truck?
8. Make not using turn indicators a MAJOR fine, at least $500.
9. Extend onramp and acceleration lanes
10. Get the freaking idiots off the road!
Idiots include - people talking on the phone, reading the paper, putting on makeup, sight-seeing, watching DVDs or TV, . . . you get the idea.
Why has nobody made a "Rubbernecker screen"? After an accident or incident, clear the roadway and put a screen up. Nobody can see the accident, and therefore they start moving again once the road is clear.
You could even pay for it by selling ad space!! (I can't beleive I suggested that!!)
..and other 300,000 users in the "prediction" system at the same time: "hmm I-95 is gonna be jammed in one hour from now.I better go home a little bit earlier today." tada!! =D we have succesfully jammed the road with one hour in advance!! What an improvement! Thanks again modern physics!
What is best in life? To crush your enemies, to see them driven before you and to hear the lamentations of their women.
Well, yeah, call me captain obvious. I saw this show on the history channel a little while ago that did a computer simulation of traffic on a highway. It actually showed that up to a certain point, a lot of cars on the road is fine. However, once it hits a certain point, the flow dramatically drops.
Living in New Jersey, traffic is a part of my daily life. I've noticed that even when there are a lot of cars on the road, the traffic can still move along above the speed limit in rush hour. But there is still that point when all the traffic just seems to stop and you're crawling along at 10 miles an hour.
The show also mentioned a study the government funded. They spend several million dollars to try and figure this problem out. Their conclusions: "there are too many cars on the road." Now, for the low low price of $20,000, I could have told them that.
In 1998 William Beasley posted a paper on Traffic Waves in Seattle, subtitled "SOMETIMES ONE DRIVER CAN VASTLY IMPROVE TRAFFIC".
The site has great animations and excellent explanations of the impact of different drivers actions on the overall flow.
Worth a look: Traffic Waves
SimCity did this ages ago!
The view can be seen here in the most recent version.
Beware: In C++, your friends can see your privates!
On the M25, the road that circles London, grid lock is avoided with variable speed limits and discouraging drivers from excessive changing of lanes. The road is constantly monitored by CCT and the speed limit set accordingly. The speed limit is enforced by speed cameras. In the rush hour the speed limit is reduced to 50 mph as apposed to the usual speed limit of 70mph and this, some how, reduces the risk of grid lock. Also if there's congestion at say junction 15 the speed limit will be reduced prier to the congestion, say at J13-J14. This help to reduce more trafic build up at J15 and gives it time to clear.
In a former job many years ago, I did a lot of highway driving (deliveries and field service) and spent a good deal of that time thinking about traffic patterns, both as a mathematical system as well as a design process. My final conclusion after 2 years was that there are too many cases of poor road/intersection design and WAY too many cases of pathetic traffic light design, and even more cases where traffic lights hinder traffic flow in a very severe way, while not providing any of the originally-intended safety of said traffic light. The prevailing "wisdom" seems to be: if there's a traffic problem, put up a stoplight to control it. Not.
Traffic dynamics is fascinating, and certainly deserving of some studious focus, but none of this means a single, blessed thing to me unless people will:
I'd make the common observation that older folks tend to drive slower and tend to do so, totally oblivious, in the left lane. But then there is at least an equivalent problem in the soccer moms and high-strung business suits on cell phones driving SUVs and mega-SUVs who pay even less attention to what they're doing. Heck, I've seen people driving down the interstates here (I-40, I-95, I-85 -- pick one) during morning traffic, travelling at over 80MPH and reading the morning paper!
That said, I think traffic problems tend to be less a mathematical/system problem than a brainless person problem, in many cases. Not all, but very many. Sadly, you can't "in-idiot" a driver, or a person for that matter.
I've always wished for a traffic law that gave every driver a dart gun. When someone does something obscenely stupid or hazardous (e.g. driving in reverse on a 65MPH intersate because they missed their exit), you shoot them with the dart. Three darts means your vehicle is incapacitated for 30 days. (Hmmm... I think RFID tags would be perfect for this!! :) If your vehicle is tagged more than 6 times in 2 years, you lose your license for 1 year.
Harsh? Definitely. But consider the *costs* of traffic in lost time, productivity loss, frustration/rage, increased fuel consumption, vehicle wear and tear, air pollution, etc. Pulling one person or one thousand people out of the traffic system to improve the flow for the masses sounds like good planning to me.
Oh, and please direct any comments about my tendency to drive well above the speed limit to /dev/get_out_of_my_way...
See also this site.
Have you ever been driving on an interstate highway when traffic suddenly slows to a crawl? You inch along for many minutes while waiting to see the accident which must have caused the jam. At the same time you also curse the "rubberneckers" who are causing the whole problem. But then all the cars ahead of you take off at high speed. The jam is over, but no accident, no police cars, nothing. WHAT THE HECK WAS THAT! A traffic jam with no cause? In the rear-view mirror you see all the poor saps behind you still stuck in the jam. But why? If all those people could just speed up at the same time, the whole traffic jam would evaporate. Why don't they ever do that? What caused the mysterious slowdown in the first place?
City planners don't need access to this sort of technology in places with traffic jams. I am one... in a city with really bad traffic. Like a few astute individuals have pointed out below - the traffic jams happen at the same times everyday, on the same routes! I saw a nationally-recognized traffic engineer speak once - he was a real renaissance engineer, for his age. In his presentation he showed us data that suggested that regardless of the capacity of a road, the dynamics of vehicles and drivers in the US results in a average maximum throughput of about 35 mles per hour of any typical arterial or highway. Basically, we get to choose how many cars we want stuck in traffic by choosing the number of lanes (and the capacity at the ending points) in our arterials and freeways. Adding lanes is only a very temporarily successful measure. Another interesting point he made (I've GOT to remember this guy's name... senior moment) is that at 30 mph or less, it is much more effficient to distribute traffic over a grid system, even at lower speeds, than it is to try to puch them all through a big pipe (freeway). Sounds familiar, eh?
Bill Beaty investigated how to avoid traffic jams by recognizing the intermediate state of synchronized flow and undoing the damage six years ago. Apparently, a traffic jam can be stopped, even once started, by a single car.
Traffic Waves
When building software like this, you do a great service to take us R/G colorblind people into account. We're not as rare as you think! BWHAHAHA! ;)
As I read your comment, it struck me that the flow of cars past a given point resembles the flow of water from a drippy faucet, and that both can be modeled as a 2D strange attractor. Just as you can map the time differences between Drips [ D1, D2, D3, etc. are absolute time of drips; T1=D2-D1; T2=D3-D2; etc.], you can map the space differences between cars. Then map it on cartesian coordinates thusly:
Point1: T1, T2
Point2: T2, T3
Point3: T3, T2; etc.
When traffic is flowing smoothly, the difference in time between cars is essentially random, so the map will just be a bunch of randomly scattered dots. But when jams began to occur, the average length between cars shortens, and the dots began to describe a spiral inward. At total jam, the length between cars is, essentially, zero, leading to a dot centered at 0,0.
It's the point when the average length between cars begans to shorten that is when the graph becomes most interesting. Also, this is where intervention might occur "on the ground" so to speak.
One drawback of this graph is that it describes only a single location along the roadway. You'd need many of these graphs to simulate a large traffic situation.
And, as to the poster's note that People are just flat out unpredictable., that's only true in the *individual* sense. In the aggregate sense, people are *remarkably* predictable. This traffic problem happens to be an interesting problem because it involves *both* aggregate (so it's fairly predictable) AND individual (ONE driver makes an error...) behavior.
DNA is a Turing machine. You, however, being dynamic and emergent, are not.
Look at the clock. I predict that every weekday at 7:00am-8:00am and 5:00pm-6:00pm traffic will be at its heaviest. Avoid driving at these times and you will be set. Also, I predict that road construction will cause traffic congestion as well. In the foreseeable future, I also predict unknown random traffic accidents to cause congestion. Use your radio tuner device in your car to listen for reports of these strange incidents and avoid those routes!
They are oblivious to the fact that for the one vehicle they let in, they are causing at least one other car behind them to have to slow down and potentially miss the next traffic signal. Or worse, the person they let in does something to aggrivate the situation further:
In each one of these cases, if the good samaritan had simply followed the rules of the road and maintained their right of way it would have been better for all. The few seconds of time saved by the benefactor is a fraction of the compounded delays of the people behind the samaritan.
What aggrivates me even further, is that driving schools preach that this kind of behavior is good and will help reduce the number of accidents. BULLSHIT. The rules of the road were designed to prevent accidents by increasing the predictability of events that occur on the road.
Don't get me wrong, there are times when you are compelled to give up your right of way or even blatantly break the rules in order to maintain your safety and that of others. Unfortunately, people have been taught by authority figures (driving schools, often as a condition of getting a ticket dismissed) that this should be a matter of practice. This is reinforced by the fact that if you sound your horn (as a safty warning of course :) at someone who suddenly decides to follow this advice, you are considered an asshole.
Unless it is to mitigate an unsafe situation, follow the rules of the road people!
Wrong answer: when something like an accident happens you need to slow down. In fact anytime you see flashing lights (cop car, tow truck whatever) you better slow down until you know what is going on and have figured out how/if it affects you.
Granted most people look at the wrong thing, but at least they are slowing down. You shouldn't be watching the emergency itself. You need to have a broader focus of how the operations might affect you!