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Chaos and Your Everyday Traffic Jam

timothy posted more than 7 years ago | from the could-often-be-my-dad's-nutty-driving dept.

Science 477

An anonymous reader writes "What causes these mysterious traffic jams that continually appear throughout the day for no reason whatsoever? Is it simply the fact that most people just don't have a clue how to drive? That's very possible, and in reality there are so many variables involved in something like a traffic jam. But is it possible that the entire traffic jam could be both the continuing and end result of a chain reaction set in motion by a single driver who was in too much of a hurry?"

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Passion of Traffic (5, Funny)

P(0)(!P(k)+P(k+1)) (1012109) | more than 7 years ago | (#17374704)

From TFA:

So the next time you find yourself stuck in bumper to bumper traffic, it's very possible that the jackass that caused it is already at home watching the latest episode of American Idol[...].

I like the idea of a single blameworthy agent to bear the brunt of my hideous imprecations: a Christ of traffic, if you will; except I'm the Romans, and it's Mel Gibson's Passion all over again.

teen (-1, Flamebait)

Anonymous Coward | more than 7 years ago | (#17374706)

Driver in a hurry isn't half as bad as teenage girl on cell phone. Add friends to the equation or have her text messaging instead of talking (i've seen it before) and she's suddenly a deadly force.

ahem.. (0, Flamebait)

Tacylm (775168) | more than 7 years ago | (#17374708)

"it possible that the entire traffic jam could be both the continuing and end result of a chain reaction set in motion by a single driver" single driver I don't know, single _woman_ driver.. no comment.....

Site jammed up (4, Funny)

johnw (3725) | more than 7 years ago | (#17374718)

Only three comments and already the site seems to have been totally jammed up by a single Slashdot article in too much of a hurry.

Re:Site jammed up (-1, Offtopic)

Anonymous Coward | more than 7 years ago | (#17374738)

anyone else noticing that groklaw is down?

I know, I know!! (5, Insightful)

quokkapox (847798) | more than 7 years ago | (#17374720)

"What causes these mysterious traffic jams that continually appear throughout the day for no reason whatsoever?

Too many cars?

It's both! (1)

raehl (609729) | more than 7 years ago | (#17374878)

Hey, look, the obvious has made it to the front page of Slashdot disguised as an article again.

If some bonehead makes a bad driving maneuver, he might cause a traffic jam. And whether or not he actually causes a traffic jam is dependent on how many cars are on the road!

This whole thing is just dumb. Yes, if all drivers drove perfectly, then we could push more cars through the same piece of road. But that's not the way it works. Roads don't have a hard capacity. As the number of cars on the road increase, the chances of a traffic-jam-causing event increase. The more cars, the greater probability of a jam. Maybe at 120 cars a minute there's a 50-50 chance of a jam, but at 140 cars a minute a traffic jam is virtually certain.

So, if cars were driven by perfect-driving robots instead of people, we'd could put more cars on the road without traffic jams. Thanks Slashdot!

Re:It's both! (1)

kasperd (592156) | more than 7 years ago | (#17374918)

I agree with everything you said except from the actual numbers. I guess they are probably random numbers picked to show the point but still...
Maybe at 120 cars a minute
If you have 120 cars per minute, they are most likely driving too close. The adviced distance between cars to avoid collisions is minimum two seconds (may even be a law in some places). Which means you will always have less than 30 cars per minute per lane. So with 120 cars per minute you will either have at least five lanes, or cars driving too close.

Two seconds? Not during rush hour (1)

wasted (94866) | more than 7 years ago | (#17375380)

During rush hour where I live, separation is more like 1/2 a second, if that. That small separation doesn't seem to cause as many problems. I've driven in Houston, TX during rush hour, where 70+mph bumper-to-bumper traffic is considered slow.

Re:It's both! (-1, Offtopic)

Anonymous Coward | more than 7 years ago | (#17374944)

When you're a complete retard like Timothy, the completely obvious is like a moment of divine inspiration. Don't worry, I'm sure his handlers will be in to change his man-diaper soon.

Re:It's both! (1)

trentblase (717954) | more than 7 years ago | (#17375240)

at 140 cars a minute a traffic jam is virtually certain.

But if there is a traffic jam, you aren't going to be pushing 140 CPM. I have a feeling that CPM will stay mostly constant and the speed will vary inversely with the total number of cars. Therefore, you would never get enough cars going fast enough to hit a CPM that makes a traffic jam certain (self-limiting). Or maybe it's late and I'm going crazy.

Re:It's both! (1)

Tony Hoyle (11698) | more than 7 years ago | (#17375306)

It's just that the capacity (bandwidth if you like) of the road is extremely variable.

If someone decides to drive slowly that reduces the capacity all the way up the road behind him. Similarly if (as seems to happen a lot around here) the authorities put an artificial speed limit on the road for 'traffic management'.

If you have 120CPM, and the road capacity is 140CPM - no jam.

As soon as someone decides they're too scared to drive at the speed limit.. road capacity drops to 100CPM.. jam.

Re:I know, I know!! (1)

SpinyManiac (542071) | more than 7 years ago | (#17375048)

Too many cars?

Exactly.

Studies have shown that a shockwave occurs when the density of the traffic reaches a critical level. Unstable traffic speeds combined with sudden braking creates a shockwave which travels back through the traffic at about 12mph.

Drivers experiencing a shockwave find that they suddenly have to slow down, then a few moments later they can speed up again. The causes of this stop-start driving are varied, some are due to incidents, some are due to the physical layout of the road, such as traffic merging at a junction, and others appear to have no cause.

From here [highways.gov.uk] .

Re:I know, I know!! (0)

Anonymous Coward | more than 7 years ago | (#17375106)

Then I'd seriously like to meet the idiot that causes all the "shockwaves" here in Germany.

If you've ever driven in Germany for a decemt length of time, you know how bad of a day you're going to have when you see the word "Stau" somewhere on the Autobahn. They're so bad here that the Germans uses automated systems to track them since they happen so fast and, for no apparent reason. (I've never seen so many sensors on a roadway anywhere else I've been) I can't tell you how many times I've been stuck in 5mph traffic for upwards of a half hour and then *poof* - the heavens open and traffic magically goes back to normal for no reason.

Wikipedia states that "Stau" is just the German word for "Traffic Jam" - everyone I've met begs to differ. I've personally been stuck in a 4 hour Stau where I moved less than a half mile.

Re:I know, I know!! (2, Insightful)

SpinyManiac (542071) | more than 7 years ago | (#17375318)

I'm guessing here, but I'd say it's a large amount of traffic in a small area. I've seen it happen on motorways (typically three lanes in each direction) when a truck overtakes another one very slowly and all the cars pile up in the other lane. Everything behind is forced to slow down and the congestion propagates back up the road behind them.

Re:I know, I know!! (1)

Tony Hoyle (11698) | more than 7 years ago | (#17375366)

The effect is fairly minor though unless lane 3 was congested already.

I don't agree with TFA that the 'ripples' will propogate very far - that relies on everyone tailgating, which really isn't going to happen - a percentage of drivers will be at a proper 2 second gap.. and even though that's (sadly) the minority each one of those will cushion the affect, causing it to die out fairly quickly.

Re:I know, I know!! (1)

Tony Hoyle (11698) | more than 7 years ago | (#17375336)

OMG the highways agency think their screwing around with the limit *helps*????

Their system simply doesn't work. I've so often seen the situation clear road -> 60mph limit (jam) -> clear road that I can even predict the jams from the signposts now.

You have a road that is flowing freely at somewhere approaching (say) 85-90% capacity. Then you put a 60mph limit on it. This reduces the speed limit by ~15%.. simplistic calculation - reduce the capacity by 15% on an 85% capacity road. That ain't gonna make the traffic flow more freely. WTF are they thinking?

What's worse is if they continue this for a long time (sometimes they leave these limits on for days.. heck, there's one not far from me that's been the same for 3 months!) the jam backs up all the way up the motorway beyond the limit, backing up into the roundabouts and causing further jams on the roads leading up to the motorway.

Re:I know, I know!! (2, Interesting)

iangoldby (552781) | more than 7 years ago | (#17375144)

But is it possible that the entire traffic jam could be both the continuing and end result of a chain reaction set in motion by a single driver who was in too much of a hurry?

No, it isn't possible that a single driver could be the cause. The mechanism described in the article relies also on a large number of other drivers all following too close to the car in front. If enough people kept a safe distance from the car in front, the shock wave caused by the sudden movement of one car would die away instead of being amplified.

Aside:
There's no justice in motoring. Responsible drivers just have to get used to the idea that they can help avoid jams and accidents, and they themselves will get less benefit from their own responsible actions than will the idiots who cause the trouble in the first place. The idiots won't even realise they've done anything wrong...

Re:I know, I know!! (1)

It'sYerMam (762418) | more than 7 years ago | (#17375320)

But it didn't say cause, did it? It said "set in motion," which is a much better description of what happens. The first domino sets the chain in motion, but if there are no intermediary dominoes, there will be no chain.

Re:I know, I know!! (0)

Anonymous Coward | more than 7 years ago | (#17375270)

i blame it on pedophiles

Re:I know, I know!! (0)

Anonymous Coward | more than 7 years ago | (#17375372)

Too few roads. Its that simple. Build more roads, and you won't have the traffic density you do now.

Where I live ... (1)

eric76 (679787) | more than 7 years ago | (#17374736)

Where I live, we don't have traffic jams.

In a community of about 70 people covering 50 square miles, it's not hard to imagine why traffic jams are nonexistent.

I used to live in Houston. After years of moving back here, I've nearly forgotten what traffic jams are like.

Around here, the closest thing to a traffic jam is me. Even the old people think I drive too slow.

Re:Where I live ... (5, Funny)

Patrik_AKA_RedX (624423) | more than 7 years ago | (#17374930)

I've nearly forgotten what traffic jams are like.
It's like waiting in front of a traffic light. Except there are no lights, especialy no green ones. And a lot of people can't make up their mind about which direction they'll take after the lights and switch lanes accordenly.
It's not the waiting that's so troublesome about a traffic jam, nor is the fact your boss will be very angry about you being 3 days late for work. It's the seeing other people's weird-car-habbits that's truely painful.

Luckly there are a few ways to make it less painful:
1) Bring your wife. Get her head in your lap. Remember to "read" a map or newspaper at the proper time. Nobody wants to see your face at that particular moment.
2) Bring your kids! Yelling and screaming is very good to get oxygen in your system and the kicking might actually get your lower back pain to disappear. People tend to pay a lot for such a massage.
3) Portable TV! Makes your waiting in the jam a painless affair. Might, ofcourse, make you the cause of the next traffic jam.
4) Laptops! Pass the network cable from car to car and have a mobile LAN-party!
5) Cellphone: Ask the number of other people in the jam and have conversations. Now you can ask what the h*ll he was thinking and discuss why he should stay the f*ck on his lane.
6) music intruments! They call it jammin' right?
7) Mexican wave ... with sound!
8) strip poker with car parts! A El Cheapo car with the hood of a ferrari, now wouldn't that rock?
9) Bring candy and beer! Instant party! Would suck if you're picked to be the sober driver. Thought bringing drunk friends home was bad? Think how bringing 12,000 drunk strangers home would be like.
10) Disassemble your car, climb over the fence, down to the street below with as many part as you can carry. repeat as necessary. reassemble the car. Takes some time, but you'll be home quicker anyway.

Re:Where I live ... (2, Funny)

aussie_a (778472) | more than 7 years ago | (#17375274)

Around here, the closest thing to a traffic jam is me. Even the old people think I drive too slow.
Wow, that must be pretty embarrassing considering you live in an Amish community.

Field of Study (4, Informative)

WaXHeLL (452463) | more than 7 years ago | (#17374740)

There's actually a field of study for this: Traffic Analysis. Of course, this is not to be confused with all of the material out there relating to internet/network/packet analysis.

This mainly deals with optimizing freeways and the like, based on people's behavior in traffic, and the ripple affects.

Re:Field of Study (1)

DDLKermit007 (911046) | more than 7 years ago | (#17374870)

Which is why we get things like carpool lanes. It's the one thing I kinda like about LA. People can't impulsively jump in & out of the lane like all the rest (at most places I've seen). It keeps the quotient of people who can drive higher speeds themselves at a much better rate. To me those don't have as much to do with you having more than one person in your car. Just look at the hybrids, motorcycles, and other cars that are exempt from the two or more rules. If you are running anything but an old clunker that runs on just gas, or more than one person; your far more likely not to be doing stupid crap like others, have a car that can handle better (newer/maintained better), or quite possibly, a better driver.

If only we could get carpool lanes in Las Vegas where I live. If only they'd study traffic here right to find out how badly we need those -_-

Re:Field of Study (1)

value_added (719364) | more than 7 years ago | (#17374990)

Which is why we get things like carpool lanes. It's the one thing I kinda like about LA.

Those are the lanes at the side of the road that are a few miles long and are mostly empty throughout the day, right? Or where people drive bumper-to-bumper at a barely noticeable faster rate than the folks driving bumper-to-bumper in the regular lanes?

Personally, I think everyone in the LA area should get get over the political correctness and shitcan the idea. No one carpools (except by accident of circumstance) and no one ride shares, and if the money wasn't taken from the kicking and screaming residents, there would still be zero public transportation. In other cities, typically those without the seemingly insurmountable sprawl that defines most all of the LA basin, car pool lanes do work. Oddly, those cities have better roads, less congestion, better drivers, lower car registration fees, and lower fines. Go figure.

As for the subject of "traffic analysis," I've read about case studies where neighborhoods and/or regions have been dramatically improved by the act of "synchronising" traffic lights. I don't know enough about the subject or the practice to offer a comment, but I doubt there's anyone who hasn't noticed that driving through any area with moderate traffic, the lights seem to work OK, but come 4-5:00pm (or 6-7:00am), irrespective of traffic flow, the lights start turning read with increasing frequency, and traffic starts backing up. My guess is there's a BOFH version of a traffic controller in every city doing it on purpose.

Re:Field of Study (2, Interesting)

micheas (231635) | more than 7 years ago | (#17375058)

. . . but I doubt there's anyone who hasn't noticed that driving through any area with moderate traffic, the lights seem to work OK, but come 4-5:00pm (or 6-7:00am), irrespective of traffic flow, the lights start turning read with increasing frequency, and traffic starts backing up. My guess is there's a BOFH version of a traffic controller in every city doing it on purpose.

As I understand it, you are sort of correct. Lights are timed to slow cars down at rush hour to reduce the number of traffic accidents, resulting in a net increase in the average speed of traffic at rush hour. There is also the concept called "metering lights" which are stoplights on the freeways (bridges mostly) in the San Francisco Bay Area, The Idea is to get some space between cars so that they will move faster.

poll time (0)

Anonymous Coward | more than 7 years ago | (#17374746)

Who was the initial driver

a) old person
b) teenage girl + cell phone
c) teenage girl + friends
d) teenage girl + friends + cell phone
e) teenage boy + camaro or civic
f) mom + kids + ginormous suv + cell phone
g) executive type + cell phone

Re:poll time (1)

bl8n8r (649187) | more than 7 years ago | (#17375096)

You forgot Teenage girl + Teenage Boy + Hummer
A multitude of distractions.

Roads and CSMA/CD (5, Insightful)

rar42 (626382) | more than 7 years ago | (#17374750)

I'm inclined to compare roads to shared medium Ethernet. As the traffic builds up you get more 'collisions' and both systems have collision detection built-in.

With Ethernet, as the 'traffic' builds to about 40% of the theoretical capacity, collisions become the norm and the re-tries start to overwhealm the system and it locks. With roadways, as the traffic builds to a certain limit, then awareness of potential collisions magnifies in the drivers, so reactions to situations increases and the road stalls. This is why variable speed limits work, because the road and drivers can cope with more vehicles if there is a lower maximum speed.

Re:Roads and CSMA/CD (1, Funny)

Anonymous Coward | more than 7 years ago | (#17374904)

We need to come up with a way so that all drivers are in their own domains, and therefore there will be no chance of them colliding with eachother. I suggest the following:

Car Sensing Misguided Asshat / Collision Diversion (CSMA/CD).

Re:Roads and CSMA/CD (5, Interesting)

DynaSoar (714234) | more than 7 years ago | (#17375062)

rar42 (626382) sez:
> I'm inclined to compare roads to shared medium Ethernet. As the
> traffic builds up you get more 'collisions' and both systems
> have collision detection built-in. With Ethernet, as the 'traffic'
> builds to about 40% of the theoretical capacity, collisions
> become the norm

You're pretty much completely wrong, and the last quoted line sums up why.
Collisions are not the norm in traffic jams.

Traffic jams happen due to the ripple effect from cumulative reaction time
delays in response to changes in traffic. The effect accumulates until there
is so much loss of speed that people drive closer together. Then when they
have to react, they react more abruptly, and that causes yet a stronger ripple
effect.

Packets collide, cars don't. Cars change speed, packets don't.
Well, OK, sometimes cars do collide. But it's not the collision itself that
causes the traffic jam, it's the bottleneck in the right of way and/or the
rubberneckers.

If people could and would simply maintain the 2 second following distance
no matter what speed, when the fewer traffic jams did occur, they would resolve
themselves much more quickly. But just try telling the person 500 cars back to
just sit still for 10 minutes. They'd probably want to punch you, and they'll
still insist on driving stopgostopgostogostopgo despite the fact that doing so
means they'll be doing it for several times longer than just waiting.

90% of drivers think they're better than average.
90% of drivers are below average drivers.
So I give free driving lessons.
Like braking suddenly for tailgaters.

Re:Roads and CSMA/CD (0)

Anonymous Coward | more than 7 years ago | (#17375064)

This is why variable speed limits work, because the road and drivers can cope with more vehicles if there is a lower maximum speed.
This is a myth ! I know of two concrete experiments where the goverment lowered the speed and introduced heavy enforcement of it (read: extra traffic controls). And the effect on the traffic jams was huge: the average traffic jam length INCREASED dramatically.

Clue (1)

Savage-Rabbit (308260) | more than 7 years ago | (#17374752)

...most people just don't have a clue how to drive?

YES! But that's not news, we have known this for over a century now...

On a very busy road... (5, Interesting)

Alioth (221270) | more than 7 years ago | (#17374762)

I fly light planes. Major roads, when VFR, are very good landmarks.

Quite often when it is very busy, you can see a standing wave in the traffic - there's an area where all the cars are stopped - but there is NO obstruction at all. The cars are filling the 'standing wave' from the back as quickly as cars at the front are leaving it - so it becomes self-sustaining.

When the road is full to capacity, moving at 70 mph, all it takes is one person to jab their brakes ... then the drivers behind (probably following far too close) brake a bit harder, and the drivers behind them brake a bit harder still. The adjacent lanes, in seeing one lane suddenly slow go 'whoa', and someone also brakes in that lane. Pretty soon, just from one person braking a little bit - the braking has propagated down the road with greater and greater severity until one of two things happens: usually, the traffic comes to a standstill, and you get a self-sustaining standing wave of stopped traffic until the amount of traffic on the road reduces to the extent there are fewer cars joining the wave than are leaving. This can take HOURS, especially on the M6 in England. The second thing that may happen in this cascading braking severity is that someone runs into the back of the other. Then chaos ensues for most of the day.

The other problem is lorries (large trucks) overtaking lorries with a speed differential of 0.5 mph. It takes them several minutes to get past because they are both speed limited within 0.5 mph of each other, meaning the inside two lanes are 56mph, and the outside lane is 70mph+. When a frustrated driver pulls out into the outside lane after being stuck behind a lorry for "too long", they cause one of the outside lane drivers to brake down to 56 mph quite suddenly. This can easily get the 'braking cascade' started, and before you know it - you have a standing wave traffic jam with no actual obstruction (other than the standing wave itself).

Usually then what happens, is the opposite direction traffic, seeing the stoppage rubber necks for the possible accident. An inattentive driver looking at the other side of the road finally looks back in front and realises he's about to ram a truck in the rear and slams on the brakes. The driver behind him following far to closely has to brake even harder - and there's either a shunt or if they are lucky, ANOTHER standing wave traffic jam starts on this side of the road too.

It's fascinating to watch from the air. Frustrating to be in when driving.

Re:On a very busy road... (5, Interesting)

RotateLeftByte (797477) | more than 7 years ago | (#17374814)

Some of the points are very well made.
Just ask anyone who has been a driver at the tail end of an Army Convoy. They are either flat out of at a dead stop. The concertina effect magnifies as the number of vehicles increases. This is why smaller convoys are better.

I was once in a lecture where this was explained. It all went down to the following
  Chaos Theory
  Queuing Theory
and most impostantly,
  A single thing which cause on vehicle to slow down without due cause. The nthe vehicle behind has to slow and Bingo! it all starts.
Once to get beyond a certain number of vehicles the elasticity in the queue gets to a critical size and you get the unexplained traffic jams.

Some places try to minimise these jams by artificially reducing speed limits to reduce the elasticity but IMHO, these have limited effect.
IMHO, the ONLY way to stop these elastic jams is to connect the vehicles together. I once saw a demo of such a thing. Oh, sorry, it is called a train...:)
Seriously, BMW demoed a device many years ago that would allow you to get much closer to the vehicle in front but in a safe manner. I think that it is only a metter of time before there is a viable system to connect vehicles together electronically in such a way that they can be physically very close to each other in a safe manner. The driver would join such a convoy and then switch on an autopilot system and sit back and relax.

Re:On a very busy road... (1)

kungtotte (867910) | more than 7 years ago | (#17375124)

Army convoys have strict regulations about speed and distances to avoid exactly this behaviour, so either you're pulling things out of your bum or you've encountered really undisciplined army convoys.

Re:On a very busy road... (0)

Anonymous Coward | more than 7 years ago | (#17375182)

either you're pulling things out of your bum or you've encountered really undisciplined army convoys.
Or you haven't been in a large enough convoy for a long enough time.
Discipline does not matter, it can postpone the effect somewhat, but at some point it happens regardless.
Then you "start over" by making everybody slow down and create space. Or use some other tricks.

Re:On a very busy road... (1, Insightful)

Anonymous Coward | more than 7 years ago | (#17375400)

Another problem is that brake lights don't provide enough information, and what they do provide is provided at the speed of light.

BRAKE!!!!!!!

As opposed to

Take your foot of the gas and relax for a bit.

Re:On a very busy road... (3, Interesting)

steevc (54110) | more than 7 years ago | (#17374858)

It would help to cut down on the standing waves if people applied the 'join slowly, leave quickly' rule. If you see a queue ahead then slow down to give it time to move before you get there, then as soon as the road is clear accelerate away (to a safe speed). I see waves like this every day and see many people rush to join it so they have to slam on the brakes. When I get out the other side people are leaving huge gaps that slow down the escape of others.

There's an old article on this, with animations, here [amasci.com] .

Try and be part of the solution.

Re:On a very busy road... (4, Insightful)

Alioth (221270) | more than 7 years ago | (#17374884)

Oh, I do that. The thing that annoys me is when I see trouble ahead and start to slow, as soon as the tiniest gap opens, someone in an adjacent lane leaps in. It's so frustrating. Many of the problems are caused by poor 'me first' road discipline, for example, when approaching a constriction, so many drivers go right to the end and try and force their way in - and it's not helped by people not letting adjacent lanes merge in good time before the obstruction.

The art of proper merging should be something taught to drivers and tested on the driving test.

Re:On a very busy road... (3, Interesting)

mrchaotica (681592) | more than 7 years ago | (#17375080)

for example, when approaching a constriction, so many drivers go right to the end and try and force their way in - and it's not helped by people not letting adjacent lanes merge in good time before the obstruction.

Even more, it's not helped by people letting in the drivers who go to the end. Personally, I'll let people in when they try to merge soon after noticing the obstruction. But if they try to cut in at the end, I'll ride the previous car's bumper to prevent them from getting in, and give them the finger to boot! And if that makes me a bastard, that's fine with me.

Re:On a very busy road... (1)

aussie_a (778472) | more than 7 years ago | (#17375352)

They may have had to wait until the end because everyone was too much of a bastard to let them in beforehand.

Re:On a very busy road... (1)

simm1701 (835424) | more than 7 years ago | (#17375396)

I always drive rental cares, and I have a zero excess on them :)

I do the exact same as you - and frankly I really could not care less if they dent the body work trying to force their way in I dont plan to move out of their way - the car isn't mine, I can't lose any no claims and it wont cost me a penny to fix.

Its a variation of "the car with the worst body work has right of way" rule ;)

Re:On a very busy road... (4, Interesting)

MaelstromX (739241) | more than 7 years ago | (#17374934)

That article is a must-read. Also interesting is this Java traffic simulator [tu-dresden.de] which demonstrates all the ways that traffic jams can form.

Re:On a very busy road... (1)

Dachannien (617929) | more than 7 years ago | (#17375120)

Hehe, that applet is a lot of fun to play with.

Professor Helbing (as mentioned on that page) gave a talk at ALife X this past year. Normally, we're all about artificial biology and dynamical systems and stuff like that, so Helbing considered himself something of an outsider. But the emergent properties of traffic flow and the dynamical systems involved were actually a quite natural fit with our normal areas of research in the artificial life community.

He talked some about vehicle traffic, but focused more on people traffic. For example, he spoke about problems with people traffic at Mecca, where millions of people arrive at the same time to perform a ritual which essentially involves walking to the center of a large arena and throwing pebbles at some pillars [wikipedia.org] that represent the Devil. The way the arena is set up was conducive to massive traffic jams of people as well as deadly stampedes. At the time, as I recall, Helbing and his team recommended replacing the traditional pillars with wall segments which would afford pilgrims a wider opportunity to perform the ritual. Officials there also built a second layer of walkway near the wall segments to afford more traffic flow.

Of course, this didn't solve the problem of the fairly narrow entrance and exit to the facility, and stampedes in those areas still occur, though with less frequency.

Re:On a very busy road... (1)

joshetc (955226) | more than 7 years ago | (#17375142)

It would help to cut down on the standing waves if people applied the 'join slowly, leave quickly' rule. If you see a queue ahead then slow down to give it time to move before you get there, then as soon as the road is clear accelerate away (to a safe speed). I see waves like this every day and see many people rush to join it so they have to slam on the brakes. When I get out the other side people are leaving huge gaps that slow down the escape of others.

This is why I am a tailgater. If I'm coming out of a pile and nobody is on front of me I fix it real quick. I just punch it until 120MPH (about the safest my vehicle can handle in its current state) or there is a car 5 feet in front of my front bumper.

Humm... (1)

Tei (520358) | more than 7 years ago | (#17374892)

Your sign:
    "Oolite: Elite-like game. For Mac, Linux and Windows [aegidian.org]"
Makes me think.. .humm... "Dream the pilots with electronic space simulators?"
Why you like Oolite?
Why people like Elite more than Captain blood?
What the Olimphants are?

Re:Humm... (1)

Gnavpot (708731) | more than 7 years ago | (#17375052)

Your sign:
        "Oolite: Elite-like game. For Mac, Linux and Windows [aegidian.org]"
Makes me think.. .humm... "Dream the pilots with electronic space simulators?"

Sounds like a very good book. Perhaps we can persuade Ridley Scott to base a movie on it.

Re:On a very busy road... (1)

mrchaotica (681592) | more than 7 years ago | (#17375068)

Heh, I've noticed the same thing from the ground: the controlled-access part of GA 78 has exactly ONE curve, and that's exactly where the standing wave forms every rush hour. And you know what the worst part is? The curve is banked, so there's no legitimate reason to slow down for it!

Re:On a very busy road... (1)

aussie_a (778472) | more than 7 years ago | (#17375368)

Simply slowing down will not cause a traffic jam (where everyone is forced to a standstill) if everyone is driving safely. Feeling you're unable to turn at the current rate and so slowing down is safe driving. Following the person so closely you need to slow to an even larger degree is unsafe driving.

Re:On a very busy road... (1)

Pinkfud (781828) | more than 7 years ago | (#17375118)

I have no doubt this happens, I've seen it many times. Years ago, I was employed as a truck driver. You can see farther ahead from the higher vantage point of a truck, and I often saw the non-event that caused the braking. Usually just some dip either lane-hopping or slowing for no reason. Good thing sound doesn't transmit between cars, because I turned my air blue many times over that.

Re:On a very busy road... (1)

CraigV (126819) | more than 7 years ago | (#17375234)

You didn't explicitly say it, but the reaction time of the drivers is key here. The following drivers must brake harder because they have become closer during the reaction time.

WOW --- Just What we Need (2, Insightful)

meBigGuy (308215) | more than 7 years ago | (#17374768)


A pointless story with no data, no analysis, no facts, but lots of conclusions. Don't we usually leave those for Digg?

Timed lights (0)

Anonymous Coward | more than 7 years ago | (#17374786)

Around here, traffic jams appear to be caused by very poorly timed lights. When the current light turns green, the next one three blocks down the road is 10 seconds from turning red. It's insane.
A friend of mine once said that the guy who programmed the lights should be set on fire and made to run to the nearest hospital while stopping for every damn red light.

Those damn butterflies are attacking America again (3, Funny)

giafly (926567) | more than 7 years ago | (#17374790)

From the article: "The 'butterfly effect' leads to a conclusion that if a butterfly flaps its wings ... that small disturbance in the chaotic motion of the atmosphere could create a chain reaction"
America doesn't need a war on terror [slashdot.org] , it needs a war on butterflies.

Re:Those damn butterflies are attacking America ag (0)

Anonymous Coward | more than 7 years ago | (#17374890)

A lone butterfly flaps its wings and, thousands of miles away, a lonely slashdotter masturbates furiously at the thought of a new Linux release.
 

Chain reaction (1, Insightful)

venicebeach (702856) | more than 7 years ago | (#17374816)

One problem with tracing something complex like this back to a single event that was supposedly the cause of the "chain reaction" is that the event you choose was itself caused by something. For example, from the scenario used in the article, the event that triggers everything:
It is a clear, sunny day and the roads contain no obvious hazards that would cause problems with traffic. Traffic on this particular highway is pretty thick, but it is flowing smoothly and steadily. One of the drivers, let's say a man in a red car, decides that people in his lane are moving much too slowly for his taste. He quickly changes lanes in an attempt to get to a quicker moving lane. He fails to properly check his mirrors and cuts off another driver in the lane beside him. This forces that driver to apply his brakes to avoid getting clipped by the red car.
The story is that this man's decision caused an entire traffic jam. But his decision was a result of his interaction with the traffic conditions. One might find that given that traffic is moving at a certain slowness, there is some probability that any individual will find it too slow and make such a decision. Perhaps as traffic gets slower, that probability goes up. So what caused the traffic jam, this person's decision or the conditions that led to it?

Re:Chain reaction (1)

RiskyChris (999242) | more than 7 years ago | (#17374988)

So what caused the traffic jam, this person's decision or the conditions that led to it?
Easy. It was caused by a butterfly farting in India.

Re:Chain reaction (1)

aussie_a (778472) | more than 7 years ago | (#17375390)

IMO someone merging unsafely is the only cause you need to go. Wait until you see someone driving unsafely, then label them the cause of the traffic jam. While it might not be scientifically accurate, it sure is just ;)

slow ass drivers (3, Interesting)

mrshowtime (562809) | more than 7 years ago | (#17374824)

I have lived in the cities with the worst drivers and the worst traffic and I have seen it time and time again; it's the slow dumbasses that are the real cause of majority of wrecks. It's that asshole who is going 50 in the passing lane and won't move. Or the driver is just going so slow that normal traffic rams into him, or is slowed town greatly.

The people with really fast cars generally drive very well. After all, they don't want to smash up their fancy car.

It's the assholes who don't care that they clogging up the passing lane who really are the cause of most accidents and traffic slowdown.

Oh, I have noticed that traffic patterns and behaviors do vary by location. For instance in New Orleans (pre-katrina) the drivers were extremely agressive and would not let you in no matter what and pretty much there could be aliens landing on the side of the road and nobody would care or slow down. In L.A. the 405 would be backed up forever only to find out that it was slowed down because of ONE car broke down in the emergency lane, with no accident; everyone was slowing down in response to this one car on the side of the road. In San Antonio, TX, everyone is on crack and drives a Ford F450 Dually 100mph, everywhere. Not usually a problem, but the entire city of San Antonio is being redone road wise and it creates choke points almost instantly that can't be foreseen.

Re:slow ass drivers (2, Insightful)

dbIII (701233) | more than 7 years ago | (#17374972)

it's the slow dumbasses that are the real cause of majority of wrecks. It's that asshole who is going 50 in the passing lane and won't move.

That's just what the idiot who drives too fast without paying attention and runs into them would have you believe. To make it easier to identify them they have often purchased personalised number plates identifying themeselves by name - at least in my country. If you ram into someone under ordinary conditions you are just not paying attention or do not know how to drive within the capability of your vehicle - if you can't even stop in time for a moving target what chance do you have against a stationary road hazard?

People who drive slowly in the wrong place may be annoying idiots - but they do not cause the accident.

Re:slow ass drivers (1)

TapeCutter (624760) | more than 7 years ago | (#17375204)

"People who drive slowly in the wrong place may be annoying idiots - but they do not cause the accident."

That's how the law works in Australia. If you ram a sober, licensened driver from behind your insurance company will automatically admit liability on your behalf, even if you have independent witnesses who saw the arsehole cut you off and slam on the brakes.

Re:slow ass drivers (0)

Anonymous Coward | more than 7 years ago | (#17375264)

Oh, but they might, they might. I've once too often been in a situation where the collision seems to be imminent and its cause has been the slowpoke. Sometimes two at the same time. One that decided to block the passing lane by just cruising at 90 km/h, the other that decided it was all right to stampede towards the main road, regardless of all the cars currently on that road and obviously too close.

Or the time when I was close to hitting a truck, because its driver had suddenly almost stopped it without pulling over and the passing lane was packed with a van full of jovial transport workers with baseball hats who probably thought, "Hey, let's box this dude with his piece of shit car." When I had finally solved the situation and passed them later on, they threatened to throw a bottle in my front window. Granted, somebody with a smaller arsehole factor would probably have not boxed me like that and taking later actions into account, it was very probably intentional on their part but it's still the unexpected and uncalled for slowness of other vehicles that almost did us in. After all, it is reasonable to believe that driving at the speed limit and keeping a safe distance would be beneficial, and it was. But it almost wasn't.

Re:slow ass drivers (4, Insightful)

beelsebob (529313) | more than 7 years ago | (#17375164)

I'd agree with you partially, slow drivers getting in the way is a major cause here. But I'd suggest that it's usually actually the person in the expensive powerful car being impatient that causes the major tail backs.

Here in Britain, I drive a small Skoda, it doesn't go too fast, but it's certainly no snail (it can do well over 100 if I really wanted to). I tend to drive down motorways at 75 or 80 mph (very naughty, I know, the speed limit is 70). The thing that I observe most often is that if I pull out to overtake some slower moving traffic (a lorry, or someone doing 70), there's usually some ass hole in a beemer, a merc or an audi comes roaring up behind me at 100mph, slams on the breaks because he realises a bit too late that there's someone driving at a sane speed, and then proceeds to tail you 5m from your bumper until you deign to move over and let the selfish twat past.

Re:slow ass drivers (1)

refitman (958341) | more than 7 years ago | (#17375350)

I have the same experiences, although I find the BMW drivers tend to be OK, it's the Mercedes drivers that don't seem to have a clue.

Re:slow ass drivers (1)

Quiet_Desperation (858215) | more than 7 years ago | (#17375174)

The people with really fast cars generally drive very well.

Ha ha ha ha ha ha ha! Seriously, which universe did you just slide in from?

And this is from someone who has a fast car and drives it as such.

Every model of every car brand has bad drivers.

Anyone else noticing the Mini Coopers have more than their share, though?

"Spring Effect" (1)

Mister Transistor (259842) | more than 7 years ago | (#17374840)

The phenomenon has also been called the "Spring Effect" because from the aerial view of "Choppper 4", the waves of idiocy propagating back down the line look like the expansion and compression of a spring.

Isn't it fairly obvious? (2, Insightful)

eebra82 (907996) | more than 7 years ago | (#17374842)

Isn't it fairly obvious why we get traffic jam?

The only way to get consistent traffic throughput is to have cars that maintain the same speed at all times, do not switch lanes and do not turn left or right at all.

Since all drivers have different destinations, driving techniques, cars and intentions, it is impossible to achieve this. Someone's gonna change to the other lane, delaying the people behind him who have intentions to delay the traffic in some other way, which eventually triggers traffic jam. It's a gigantic chain reaction, really.

Re:Isn't it fairly obvious? (1)

joshetc (955226) | more than 7 years ago | (#17375156)

yah! We could call it a train [wikipedia.org] .

How to help unjam and jam (3, Insightful)

weave (48069) | more than 7 years ago | (#17374894)

This is why when in a jam the best thing for people to do is calm down and change their speed slowly to even out the speed. This means trying to predict the average speed ahead of you and do your best to maintain an even speed, even if slow. Yes, impatient drivers will move in in front of you, but they are also most likely to jump back out of in front of you in a bit too. Getting next to a truck doing the same thing helps. Pressing out the waves is what will get traffic moving again for those behind you.

Re:How to help unjam and jam (2, Insightful)

Keeper (56691) | more than 7 years ago | (#17375034)

You can even turn it into a bit of a game ... see how far you can travel without touching the brake.

A few other beneficial side effects:
* better gas mileage
* less stress
* less wear and tear on your brakes

Re:How to help unjam and jam (1)

joshetc (955226) | more than 7 years ago | (#17375168)

I used to play that game. Then I would get pissed off when I had gone multiple miles without using the brake and some random idiot was going 15 under so I would just ride his ass the rest of the way. Then when he turned off the one lane road I would do a massive burnout and speed the rest of the way home.

Re:How to help unjam and jam (1)

asuffield (111848) | more than 7 years ago | (#17375094)

Furthermore, since your prediction of average speeds will be poorly informed and therefore wrong, the very best thing to do is to drive slower than that. Taking as a given that you're currently in a traffic jam, all the cars around you are almost certainly going too fast for the jam to clear (if there's no obstruction ahead of you, and all the cars in the jam are going slowly enough, it will clear up in the time it takes one car to drive from the back of the jam to the front at that speed - typically a minute or two).

But we can do better than this. Have you ever noticed those electronic signs on busy roads, where they can display a variable speed limit? If they're being controlled by an intelligent person/system (which is, sadly, not always the case) then they'll have computed a speed at which this will occur, based on actual measurements of where all the cars are, and the signs are showing a limit of that speed.

Ever notice how everybody ignores those signs and drives as fast as they can?

That's why traffic jams happen. Obey the damn signs, you arseholes.

Re:How to help unjam and jam (1)

Tony Hoyle (11698) | more than 7 years ago | (#17375410)

Ever notice how everybody ignores those signs and drives as fast as they can?

No, because:

(a) it's illegal
(b) the police *love* picking up people for breaking these limits and are usually staked out along the stretch
(c) half of the signs have speed cameras on them that activate along with the camera anyway.

Did you ever think that, with those resources (1)

unity100 (970058) | more than 7 years ago | (#17374912)

that were spent to produce, sell and maintain those cars, we would be able to make endless lines of light rail-based mass transportation system that would have luxury that would put a 5 star hotel in shame ? and then we would be able to go anywhere we wanted by just leaning back, and faster ?

Density waves? (3, Interesting)

niktemadur (793971) | more than 7 years ago | (#17374924)

The previous theory I heard about in a documentary about traffic in major cities, said that density waves, the same phenomenon that causes many galaxies to have perfectly defined spiral arms, also cause traffic jams, which is to say, the mathematics are the same.

As a sidenote, I once read an anecdotal story about a guy who always got stuck in the road while driving home from work, and one day he thought about how everybody's trying to get home fast yet everybody gets stuck in traffic, so he decided to experiment by driving a bit slower. After a few minutes he was amazed to find how the traffic behind him was neat and orderly, instead of the usual jumble, which implies (I emphasize: anecdotally) that the behaviour of a single car can not only create, but also avoid the creation of density waves.

Re:Density waves? (1)

SharkByte (206338) | more than 7 years ago | (#17375084)

Anecdotal... but here (Netherlands) actually sometimes used by the traffic police. In those cases, they drive at a steady pace of 70 km/h in the middle of the highway on unusually busy days. This works beautifully, as no body dares to overtake the police car and has smoothing effect on the traffic behind. This works much better than matrix signs above the road indicating a 70 km/h speed limit, which everybody ignores. IMHO, the major factor contributing to traffic jams is the severe lack of discipline on the road, probably caused by the (perceived) anonymity in a car...

Traffic Simulation (1)

PatKa (1043990) | more than 7 years ago | (#17374926)

I'm not sure if someone hasn't posted it yet but there is an interesting java applet on the web simulation exactly the problem mentioned here. You can find it on http://www.traffic-simulation.de/ [traffic-simulation.de] My personal favorite is the ring road :)

I can see one solution (1)

Toutatis (652446) | more than 7 years ago | (#17374938)

Can someone catch that dammed butterfly that is causing all those traffic jams?

It's too obvious (5, Funny)

arikb (106153) | more than 7 years ago | (#17374956)

For the longest time a friend and I have theorized about the reasons for those traffic jams. We've reached the inescapable conclusion that they are the results of a conspiracy.

Don't go your heads a-shaking now. It's really obvious. The oil companies make a bundle of those traffic jams. Every day just before rush hour a small fleet of inconspicuous unmarked vehicles, driven by selected elderly, are leashed upon the major freeways. They are trained to drive in such a pattern that makes it impossible for other cars to bypass them. Soon enough the traffic jam forms. Millions of cars are burning precious fuel while standing still, and the oil barons go cha-ching.

Denying it doesn't make it go away.

-- Arik

Throughput, not Position (1)

amitofu (705703) | more than 7 years ago | (#17374968)

When it comes to traffic I've always said that it's throughput that matters, not position. If a car pulls in front of you and sets you back 10 meters, then all you lose is 10 meters. And only you lose it. If someone DOESN'T let you in and you have to slow down 10 m/s for 10 second and then accelerate up to speed again, you and many people behind you lose 100+ meters.

I've always found it ironic that the people who seem in the biggest hurry--the ones who don't let others in--are actually the ones that slow everybody down. So when someone has their signal on, JUST LET THEM IN! Your order in traffic is insignificant (grannies and talkies excepted).

Re:Throughput, not Position (1)

ZERO1ZERO (948669) | more than 7 years ago | (#17375166)

Hear Hear, this man speaketh the truth

Learn more about traffic (1)

mocm (141920) | more than 7 years ago | (#17374984)

and traffic jams at the SUMO [sourceforge.net] site. You can also use their open source simulation software to create your on
traffic scenarios. I have always seen the creation of a traffic jam as a transition from a high density high flow state meta stable state to a high density low flow state. This can be expressed with a lambda shape curve in a density-flow diagram. The cause for exiting the meta stable state can be a
small disturbance, sometimes simulated by a random factor in CA traffic models, e.g. some guy braking without reason. In reality I don't think you can avoid the transition without maybe the help of computer guided cars.

lol (1)

george_e (961179) | more than 7 years ago | (#17374992)

so what this article is trying to explain is that its not the slow, old, asian, female or tired people to blame it on?

yeawn remember reading about this in the late 80s (1)

Petkov (1011081) | more than 7 years ago | (#17374996)

/. must be running out of stories to post. but they have rejected all MY submited stories. mod me -1. I dont give a flyin' %@(*$&%

Maintain a decent following distance!! (1)

OneDeeTenTee (780300) | more than 7 years ago | (#17375010)

All the tailgating idiots who falsely believe that they can drive safely less then two seconds behind the car in front of them are the real cause of this sort of delay.

The fool who taps his brakes is merely the trigger.

Old, old, incredibly old news (5, Interesting)

deblau (68023) | more than 7 years ago | (#17375024)

See this Science Hobbyist article [amasci.com] from January 1998. It's long and detailed, and suggests practical steps individual drivers can take for breaking up (or causing!) traffic jams. Yes, dear readers, this is a nine-year-old dupe.

Re:Old, old, incredibly old news (1)

Cctoide (923843) | more than 7 years ago | (#17375194)

This was exactly what I was going to post a link to... seems like you beat me to it ;).

Fris7 ps0t (-1, Offtopic)

Anonymous Coward | more than 7 years ago | (#17375076)

bi6 picture. What an ar3uous

The correct city driving speed (1)

Hesperus (16733) | more than 7 years ago | (#17375130)

Works out to be between 15 and 20 mph, which oddly enough is exactly the speed a cyclist can go.

Next time you're driving in a big city notice how the same guy on the same bicycle passes you over and over again.

This is why. If you slow to the same speed as the bicycle not only will everybody be a bit safer, but you'll be preventing traffic jams too!

-mark

Demonic Influences (1)

Burning Plastic (153446) | more than 7 years ago | (#17375140)

As anyone who has read Good Omens should know, a major cause of the worst traffic jams is demonic influence in the planning and contruction of roads.

The prime example is the M25 motorway around London, which, due to the work of a certain demon, actually forms the shape of the dreaded sigil Odegra of the ancient black priesthood of Mu (The meaning of the sigil is 'Hail the great beast, devourer of worlds'). The movement of the traffic around the motorway works in much the same way as a prayer wheel, with the added bonus of feeding back its negative energy onto itself in the creation of traffic jams.

Speed cameras (1)

Hanners1979 (959741) | more than 7 years ago | (#17375150)

And this, ladies and gentleman, is why the plethora of speed cameras present on UK roads cause so much traffic chaos. One driver brakes sharply to avoid getting caught in the speed trap, and the domino effect swings into action. You can see this on pretty much any motorway over here with cameras installed all the time.

Re:Speed cameras (1)

Markus Landgren (50350) | more than 7 years ago | (#17375226)

And in related news, laws are the cause of all crime.

How to resorb a traffic jam (1)

thbb (200684) | more than 7 years ago | (#17375208)

This informal study [amasci.com] has a nice description of how a single good driver can actual reverse the trend by single-handedly "breaking the soliton".

In other words, if you're caught in a traffic jam, let a wide space build in front of you, and try to adopt a constant (slow) speed. While you may not directly benefit from it, the jam will resorb itself for those who follow you.

This page includes simulations in a variety of contexts. While the study is informal, it is still quite convincing from a fluid-dynamics perspective.

Standard Office Space quote... (1)

Capt James McCarthy (860294) | more than 7 years ago | (#17375232)

Samir: Mother... shitter... Son of an... ass. I just...
[punches steering wheel]

government interference (1)

yada21 (1042762) | more than 7 years ago | (#17375268)

Government interference is the cause of traffic jams. In a libertarian society, there would be no traffic jams. People would be free to ram or push vehicles out of the way. Each individual's right to own a tank would not be constrained.

I am the cause of traffic jams (0)

Anonymous Coward | more than 7 years ago | (#17375316)

what I do is, when traffic is moving along too good, I slow right down to about ten miles an hour, this causes a chain reaction where everyone behind me has to slow down and eventually some of them have to stop, and there you go. that spot is the traffic jam for the next tree hours.
I fdo this on the way and from work, why? Its fun. hehe
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