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Mathematicians Solve the Mystery of Traffic Jams

Zonk posted more than 6 years ago | from the next-they'll-use-geometry-on-the-mystery-of-the-haunted-amusement-park dept.

Math 629

mlimber writes "Do you ever find yourself in a traffic jam, thinking, 'Man, there must be a bad accident up ahead,' but as you plod along you see no evidence of any crash? Some mathematicians have solved the mystery by developing a mathematical model that shows how one driver hitting the brakes a little too hard can cascade into a backup miles behind. The mathematicians' future research will investigate how automatic braking systems may alleviate the problem."

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Cover Job (1)

snl2587 (1177409) | more than 6 years ago | (#21780850)

Although apparently the mathematicians are way behind Ethan Hunt.

Old news (5, Informative)

Hatta (162192) | more than 6 years ago | (#21780860)

This has been known [] for years.

Re:Old news (1)

KDR_11k (778916) | more than 6 years ago | (#21780880)

Indeed. I've seen demonstrations of the effect back in 2000.

Re:Old news (0)

Anonymous Coward | more than 6 years ago | (#21780944)

I remember a documentary describing the flow of traffic based on peoples personalities [] [avi]

Re:Old news (1)

Hawthorne01 (575586) | more than 6 years ago | (#21781404)

"Indeed. I've seen demonstrations of the effect back in 2000."

Pshaw. I saw a demonstration of this, in person, every weekday on the I-10 from July 1983 up until today.

Re:Old news (1)

Henriok (6762) | more than 6 years ago | (#21780918)

Yeah! I was about th write the same. We saw movies on this in high school (when we learned about wave forms) and I've actually have done some calculations on these types of problems myself when I got to the University.

Re:Old news (4, Interesting)

Billosaur (927319) | more than 6 years ago | (#21780928)

I was about to write the very same... I remember several studies of traffic that showed that it only takes one driver to slow down traffic, especially on roads that are above their actual capacity. It is kind of like the Slinky effect, where you send a pulse down it and it rebounds. Car stops ahead and the cars behind begin breaking, and this begins a chain reaction... I'd love to catch this in the act at night and film the tail-lights lighting up in sequence.

Re:Old news (5, Informative)

orclevegam (940336) | more than 6 years ago | (#21781014)

It is kind of like the Slinky effect, where you send a pulse down it and it rebounds. Car stops ahead and the cars behind begin breaking, and this begins a chain reaction... I'd love to catch this in the act at night and film the tail-lights lighting up in sequence.
The term you're looking for is standing wave. The problem isn't actually the breaking, it's everyone not giving enough room between themselves and the person ahead of them to absorb small slowdowns. The time between when you slow down and accelerate back up to speed needs to be factored in. If the people coming into the jam are entering faster than people can accelerate out of the jam, it will either remain static or become worse.

Re:Old news (5, Interesting)

cyphercell (843398) | more than 6 years ago | (#21781144)

sounds good to me, the solution I've always driven for (no pun intended), is to slow down at traffic jams to the point where you can plod along without actually stopping. This does a good job of equalizing the in/out ratio. I wonder why this isn't taught in driver's ed.

Re:Old news (1)

omeomi (675045) | more than 6 years ago | (#21781394)

sounds good to me, the solution I've always driven for (no pun intended), is to slow down at traffic jams to the point where you can plod along without actually stopping.

You folks are wondrously fun for those of us with a manual transmission, where it's impossible to drive below a certain speed without constantly riding the clutch.

Re:Old news (1)

LowSNR (1138511) | more than 6 years ago | (#21781264)

Problem is though if you leave enough space to absorb slowdowns, someone will invariably change lanes to take up that space. At least that's how it goes here in the crazy-driver land of LA.

Re:Old news (0)

Anonymous Coward | more than 6 years ago | (#21781380)

that's how it happens everywhere. traffic, like nature, abhors a vacuum. if there is empty space, someone will fill it.

in light of this fact, the traditional advice to leave 1 car-length per 10 MPH is utterly ludicrous. if there are 6 car lenghts of empty space in front of you, you can count on 6 cars trying to squeeze in there. then you have to slow down enough to let 6 more car lengths build, only to be filled again.

eventually you will be driving backwards in order to make enough room for the people filling your traffic vacuum.

Re:Old news (2, Informative)

Gregb05 (754217) | more than 6 years ago | (#21780934)

I actually remember reading this from a series of books called Imponderables [] , years ago.

Re:Old news (4, Interesting)

dyefade (735994) | more than 6 years ago | (#21780994)

UK motorways are proactive with this in that they adjust the speed limit when the volume of traffic is higher. I remember seeing basically TFA printed a few years ago explaining all this.

Re:Old news (1)

onemorechip (816444) | more than 6 years ago | (#21781178)

Hmm...That might actually work, except for one thing: People routinely ignore speed limits. Maybe they don't in the UK? And they don't in Mississippi. I drove through that state once, and nobody was going faster that 65 MPH. I saw one guy get pulled over. Must have been doing 65.1, because he wasn't passing other traffic.

Re:Old news (1)

rockout (1039072) | more than 6 years ago | (#21781274)

or because he had a NJ license plate.

Re:Old news (2, Informative)

jonbryce (703250) | more than 6 years ago | (#21781318)

On the M25 and M42, two of the busiest roads in the country, the variable speed signs have revenue cameras attached to them, so anyone who disobeys them gets fined.

Re:Old news (1)

jellomizer (103300) | more than 6 years ago | (#21781234)

Or they can teach the 3 second rule (Six seconds in bad weather) Where if you drive behind an other car you stay 3 seconds aways from them. So you see the Car past a post you go 1 one thousand, 2 one thousand, 3 one thousand then you should past the same pole. I am not supprised that it is not know in UK Europe because it is rairly used in America. But it is a good rule because it gives you pleanty of time if the car does a sudden stop To evaluate the situation see if there are other cars in the other lane, and deside to stop or drive around the car, with using your blinkers.

Re:Old news (2, Insightful)

Andy_R (114137) | more than 6 years ago | (#21781340)

Very few of our motorways are actually equipped with this system, as far as I know it's only the middle of the M42 near Birminham and the Western 1/3 of the M25 London ringroad. As I have to drive on both of these occasionally, I am all too aware that while the idea might be sound, the implementation is hopeless. The M25 system is very basic, and unless you go there in the dead of night, you'll have to fight through exactly the sort of standing wave that this system is supposed to get rid of, caused by cars braking from the 70mph permitted outside the system to the 60 that the controlled section seems stuck at most of the time.

The M42 system is more complex, with limits enforced by hundreds of spy cameras, with the ability to allow cars to use the hard shoulder at busy times. This seems more of a revenue generating exercise than a congestion removal system, as the limit is nearly always 50mph even if there is barely another car in sight. Drivers have responded by speeding up between the camera traps and braking just before them, which is dangerous, causes exactly the standing wave effect it's designed to avoid, and wasted petrol increasing CO2 emissions... well done UK government!

Re:Old news (1)

GuyMannDude (574364) | more than 6 years ago | (#21781046)

Indeed. Even looking at Orosz's website [] , his most recent publication regarding traffic that appeared in Proc. Royal Soc. London was in 2006. Sounds like this work is old, even for him.


Re:Old news (1)

smtrembl (1073492) | more than 6 years ago | (#21781076)

The title sound like popular science (con)descending from the ultimate knowledge heavens.

God, everybody knows that breaking cars cause jams when cars are packed and spaced evenly and in a row long enough -- and if mathematical models were few, it's because of the obvious triviality of its concerns.


Wrong (1)

InvisblePinkUnicorn (1126837) | more than 6 years ago | (#21781094)

The article you linked is simply a hypothesis, not backed up by any actual evidence other than conjecture. The article in the story actually tests this hypothesis. Nothing was "known" until now.

Re:Wrong (1)

onemorechip (816444) | more than 6 years ago | (#21781308)

An article linked from that article suggests otherwise [] . And lest you object that that article is discussing mathematical models only, read the current article linked from the story: "The team developed a mathematical model to show the impact of unexpected events such as a lorry pulling out of its lane on a dual carriageway." Does a model count as knowledge?

Re:Old news (1)

suso (153703) | more than 6 years ago | (#21781362)

His cure [] is practiced by truckers and smart motorists it seems. Having driven around the country a lot, I think that it works sometimes, but then there are always jackasses that use that space you've created in front of you. From what I can tell, drivers have been getting more and more aggressive. When I took driver's ed 15 years ago, they told you about keeping 2-4 seconds between you and the person in front of you. That is probably based on driving in the 60s, but today that is nearly impossible. People generally drive about 1/2 second or less behind the person in front of them and better braking and tire traction have allowed this.

Small miscalculation (4, Funny)

TJ_Phazerhacki (520002) | more than 6 years ago | (#21780864)

Sure. But what they forgot to include was the variable of EVERYONE IN THE OTHER LANE STOPPING TO WATCH.

Re:Small miscalculation (0)

Anonymous Coward | more than 6 years ago | (#21781228)

But what they forgot to include was the variable of EVERYONE IN THE OTHER LANE STOPPING TO WATCH.

Actually my experience in Houston isn't that everyone is stopping to watch, they're all stopping because of the fucking psychopaths pulling out into traffic from a dead stop because they were too stupid to pull out of the lane with the flashing lights in it back when they were still moving. It's up there with idiots driving all the way up to the end of the lane and stopping before merging into traffic that could have been moving at 50+ MPH if it weren't for the guy pulling into the lane at 5.

Einstein (3, Funny)

imstanny (722685) | more than 6 years ago | (#21780866)

"Two things are infinite: the universe and human stupidity" - Einstein

...and he was only sure about the latter.

Re:Einstein (5, Insightful)

MyLongNickName (822545) | more than 6 years ago | (#21781026)

Not necessarily stupidity. if I can see past the driver in front of me, I can make a better decision. I can see that he is simply adjusting speed to allow for a more reasonable space between him and the car in front. If I am stuck behind an SUV in my car, then I am not sure if his tap on the brake is about to turn into a full fledged stomp of the brakes, and I have to adjust, and possible harder that I need to. This becomes a cascading event.

Traffic Waves (3, Informative)

Phroggy (441) | more than 6 years ago | (#21780870)

Does this mean now there's math to support this [] ?

Re:Traffic Waves (1)

Conspiracy_Of_Doves (236787) | more than 6 years ago | (#21781364)

Thanks! I found that page a long time ago, but forgot to bookmark it, and couldn't find it again.

Stop tailgating (0, Redundant)

Anonymous Coward | more than 6 years ago | (#21780876)

The effect would be mitigated if everyone would refrain from following other cars so closely. There would be less need to automatically break when the car ahead briefly does so.

Re:Stop tailgating (4, Insightful)

MyLongNickName (822545) | more than 6 years ago | (#21781096)

The effect would be mitigated if everyone would refrain from following other cars so closely.

Yeah.... I tried this for several weeks. Except everyone took the opportunity to sneak in front of me so they could play a game of changing lanes repeatedly to snake their way through traffic faster.

That is the problem. You can do what is best for the group, but then selfish individuals abuse that for their own gain which hurts the group more. I can't wait until we have self driving cars... I could easily foresee traffic signals going away, much more efficient cars and no more worrying about getting to old to be safe on the roads. Add to this a dropped death rate, and this breakthrough would easily be the greatest advancement of the 21st century.

Re:Stop tailgating (3, Insightful)

Anonymous Brave Guy (457657) | more than 6 years ago | (#21781336)

Yeah.... I tried this for several weeks. Except everyone took the opportunity to sneak in front of me so they could play a game of changing lanes repeatedly to snake their way through traffic faster.

It's funny how often I hear this. I try to hold back a safe distance all the time, and sure, a handful of morons weave through the gaps and I have to drop back a little more. But I never see this horrendous influx of morons people keep telling me about. I manage to maintain a much better distance (and a much smoother drive in terms of both vehicle speed and mental stress) than most people other than for a few moments if someone cuts in, and since those people usually cut out again almost as quickly, I doubt it even slows me down noticeably.

FWIW, this is the UK, and the comment above apply to both high-speed motorway driving and crowded conditions around the city. I've never driven in the US, but I do hear the same sorts of complaints the parent post was making all the time.

Re:Stop tailgating (1)

Oliver Defacszio (550941) | more than 6 years ago | (#21781134)

I'm not so sure if following distance would play a meaningful role, frankly. Consider how often you'll see this scenario:

Car B is following car A at a reasonable distance on a city street. Car A begins to gradually slow down for whatever reason. The driver of car B, whether due to lack of attention or just brutal stupidity, doesn't slow down until it's necessary to apply the brakes strongly. Car B applies the brakes strongly, as do all the cars behind car B who can't see what's going on in front of him and have thus had no time to prepare.

So, in summary, even when not tailgating, drivers seem to "prefer" using the brakes at the last minute instead of just getting off the gas and allowing the engine compression and transmission drag to slow down in a less "panicky" way. I think it's similar to how you'll often see a driver accelerate toward a red light and then use the brakes at the last minute. Why? I don't know, but I could guess... (coughminivanorunnecessarilyhugetruckcough)

If you're lucky, the light may even turn green as you're coasting and you'll not need the brakes at all (this means more to those of us who drive manual transmissions).

I read about this once (2, Informative)

Neil Blender (555885) | more than 6 years ago | (#21780884)

20 fucking years ago.

Not suprised (3, Insightful)

plague3106 (71849) | more than 6 years ago | (#21780896)

I've often seen this. People slow down too much for no reason, especally near ramps. I've actually gotten pretty good and figuring which jams are accident related and those that are just people being retarded.

It doesn't help that speed limits on interstates get lowered as you approach larger cities. This is a good reason to remove enforced upper limits on these roads completely. Much of the braking is due to the few goody-goodies cramping the whole flow.

Re:Not suprised (4, Funny)

dkleinsc (563838) | more than 6 years ago | (#21780988)

I've actually gotten pretty good and figuring which jams are accident related and those that are just people being retarded.

Most accidents are also due to people being retarded.

Re:Not suprised (2, Funny)

bhima (46039) | more than 6 years ago | (#21781160)

Me too. I remember the last traffic jam I was in where it was just people being retarded.

It was 1960.

Re:Not suprised (1)

bhima (46039) | more than 6 years ago | (#21781204)

amazing how leaving out a "n't" ruins an otherwise good joke.

Re:Not suprised (1)

rockout (1039072) | more than 6 years ago | (#21781352)

Trust me, the n't wouldn't have made it a good joke.

Re:Not suprised (1)

ucblockhead (63650) | more than 6 years ago | (#21781058)

We saw this very clearly in the SF Bay Area a few years ago when they were repairing the Bay Bridge. They put these inch thick metal plates down in the roadbed. No end of exhortations from Caltrans could get people to drive normally over them. People would brake and cause just such a cascade, causing horribly traffic on the bridge. (Well...even more horrible than normal that is.)

Re:Not suprised (1)

suso (153703) | more than 6 years ago | (#21781074)

Here [] were my thoughts on it from 3 years ago. Several of the traffic backups I've gotten into on major interstates have not been the result of an accident but just people slowing down or changing lanes. I always wish that I could see a video from overhead.

Last month, we drove down to Florida and near Gainesville, there was a huge backup that would slow down for a while and nearly stop, then speed up, then a few miles later slow down. This was going on for like 10 miles. It turns out it was all because people on my side where slowing down to look at an accident that happened on the other side.

Re:Not suprised (1)

internetcommie (945194) | more than 6 years ago | (#21781168)

No speed limit has been tried. I remember it from Montana in the 90's, where it did an excellent job of eliminating both the unfit and those who happened to be near them on the road when something went wrong (or right, from a Darwinian point of view).

And believe it or not, I've never seen more traffic backups on the freeways there. Montana has hardly any population of its own, so maybe it was people coming from other states to drive fast and stupid on Montana freeways.
Or maybe it was that the lack of speed limits made people more aggressive and more set on staying five feet behind somebody else's tail lights. I don't know, but it was not a success and it did not solve any problems.
But it was great for the undertakers.

Re:Not suprised (0)

Anonymous Coward | more than 6 years ago | (#21781170)

I guess you are one of those people who cause traffic jam. The problem is with people who want to go too fast, then stop, then start moving again too fast, then stop. So instead of everyone starting slowly and picking up speed after a few seconds, it is start-stop-start-stop for the next 30 minutes. Unfortunately, this concept is obviously too difficult too understand for most people.

Re:Not suprised (1)

Professor Oompa (258687) | more than 6 years ago | (#21781190)

Increasing the speed limit would likely have the opposite effect, as drivers are unlikely to increase the distance between them and the vehicle ahead of them.

This would just increase the effects of 'slam the brakes' reactions which are a large part of the problem.

Re:Not suprised (1)

lhorn (528432) | more than 6 years ago | (#21781324)

-- This is a good reason to remove enforced upper limits on these roads completely. Much of the braking is due to the few goody-goodies cramping the whole flow.
Ahh, I agree mostly sincerly, these pesky speed limits are quite restricting, especially for heavy trucks capable of 160 Km/t (100 miles/hour) on our narrow, often icy Norwegian roads. ALL drivers should be allowed to drive as fast as they want as long as she or he feel they are in control.

only works in certain cities? (1)

192939495969798999 (58312) | more than 6 years ago | (#21780908)

How come certain cities seem to have extra bad, slow, etc. traffic? Just go drive in Silicon Valley on the freeway, then come to Columbus Ohio and see how infuriating the difference is.

Re:only works in certain cities? (4, Insightful)

TheMeuge (645043) | more than 6 years ago | (#21780976)

The difference is the overall level of asshole-ness of the drivers. Much of the braking in dense traffic is caused by desperate maneuvers. In New York, the maneuvers are caused by the fact that I'd say less than 10% of the drivers will allow anyone to merge ahead of them for ANY reason. In dense traffic moving at 50mph, it's not uncommon to be within 3-4 meters of the car in front of you, or even less. And since nobody will allow you to merge, you're forced to perform pretty daring high-acceleration maneuvers to force yourself into the target lane... which will cause that lane to rapidly decelerate, clearly creating the traffic wave.

All it would take to stop this from happening, is for people to stop being assholes, and to let you through, when you're trying to get into an exit, 1/4 mile away.

Re:only works in certain cities? (4, Interesting)

Ohio Calvinist (895750) | more than 6 years ago | (#21781056)

I lived in Columbus for 5 years, then moved to So Cal, so I know exactly what you're saying. When I get back there, I think "why can't it be like this in Cali?" I love it, I can just sail down the 670 to the college from the airport.

I think some mid-major cities like Indianapolis and Columbus have a good surface street infrastructure so people going in-city (or from the suburbs) take the surface streets. I think you have people living closer to work too... You also don't have entire towns communiting to the city to work, trying up the freeway (the only way) to get to work at the same time in the morning. There are very few good jobs in the town I live in, but it is the only place working class folks can ever hope to buy a house, so... the commute begins." I mean, I took a $25,000 pay raise to work in San Bernardino, but inheritied 1:15 commute each way, if I'm lucky.

When I moved to Cali we started visiting my wife's parents every Sunday, like an hour away. I lived 1:30 from my parents (in Cincy) when I was in Columbus and going home was a huge weekend affair, not a afternoon trip. Strange how that all works out.

Arrgh! (1)

sm62704 (957197) | more than 6 years ago | (#21780916)

The problem would be alleviated quitre a bit if dimwits would stop tailgating, and even more annoying, braking for no reason whatever.

Here in Springfield they race to the red light, but brake going through a green light. If the dimwits would let off the gas when the light ahead turned red, and even speed up a bit if the light is green, they would save themselves a lot of gasoline, global warming, and aggrivation.

I don't like the idea of "automatic braking systems" as I try to keep my foot off the brake. Every time you touch your brake you're converting the momentum you spent gasoline obtaining into heat, and throwing it away. If it's an electric or hybrid that converts momentum into stored electricity I wouldn't mind an autometic braking system so much.

Re:Arrgh! (1)

Billosaur (927319) | more than 6 years ago | (#21781006)

Yeah, automatic breaking would really be kind of pointless unless the car was actually doing the driving itself. I remember watching a science show years ago (thinking it was Scientific American Frontiers, but could have been Nova) where they were discussing the automation of driving and showed a group of cars driving around a circular track bumper-to-bumper, maintaining speed and distance using sensors and each cars' on-board computer to hold the cars steady relative to each other. They claimed that this was far safer, as the cars would automatically react to each other far quicker than human drivers, and more importantly by taking advantage of the drafting advantage, the cars got significantly better mileage. I haven't seen much about this since, but I imagine the first thing that will come up is the cost followed by driver's being unwilling to give up control of their cars.

Re:Arrgh! (0, Troll)

Reziac (43301) | more than 6 years ago | (#21781316)

We already have those automatic driving contraptions. They're called "trains" and "busses". Trouble is, they don't go everywhere that people need to go.

The trouble with automated systems is that they assume ideal conditions. Anyone who's experienced at driving on ice and in deep snow will tell you how much fun it is to have your ABS take over and spin you around a couple times (or crawl up the side of the plowed-snow bank along the road), when left to your own devices you'd have geared down (yes, auto trannies CAN do that), likely not used the brakes at all, and slowed *safely*.

Re:Arrgh! (1)

corsec67 (627446) | more than 6 years ago | (#21781038)

I live in the mountains, and what really annoys me is people who brake going uphill, slower than the speed limit, on a 2-lane road. Yes, there are curves. Yes, there are rocks everywhere, it is the rocky mountains. That doesn't mean you are going to die if you go the speed limit, or even faster. Especially in summer when it is 90 degrees outside.

When going downhill I usually try to let my engine slow me down when necessary, but I have this incredibly mysterious thing called a manual transmission, which lets me do very cool things to my speed and engine RPM. (Hint, why do you think that on Pikes Peak there are signs "hot brakes fail", and they suggest you use a lower gear instead of standing on the brakes?) Some of this is different in a hybrid with regenerative braking, true.

Re:Arrgh! (1)

db32 (862117) | more than 6 years ago | (#21781080)

Actually there has been research showing that attempting to time lights causes a huge number of accidents. You are far safer when you come to a complete stop at a red light, and then wait a moment before leaving when it turns green just so you can avoid the people trying to adjust their speed to time the lights.

You are right on the money with tailgating, I freaking hate that crap, it is dangerous and it causes all manner of traffic problems.

Re:Arrgh! - Don't you mean "Dohhh!" (1)

slas6654 (996022) | more than 6 years ago | (#21781202)

Springfield, right?

Nervous brakers? (4, Insightful)

Anonymous Psychopath (18031) | more than 6 years ago | (#21780936)

One of the most irritating driving habits I can think of are people who obsessively cover the brake every 20-30 seconds or so. Usually soccer moms in Suburbans or elderly in the largest Lincoln they could find. There's nothing ahead of them, no reason really to tap the peddle, but they do it anyway out of habit.

If an automatic braking system can solve this problem, I'm in for my tax dollars.

Re:Nervous brakers? (1)

Manchot (847225) | more than 6 years ago | (#21781260)

I think that I sometimes annoy people because I like to maintain an above-average following distance. To someone behind me, it might appear that I'm braking for no reason, but in reality, I'm braking to someone pretty far ahead of me. Sure, it has its drawbacks (for example, people frequently use the opportunity to change lanes in front of me), but I think this is one of the reasons that I've never had an accident. Not only does this (obviously) give you the ability to avoid rear-ending people, it also helps to prevent yourself from being rear-ended should the person in front of you brake quickly. That is, because you won't need to brake so hard, neither will the person behind you.

Re:Nervous brakers? (1)

Anynomous Coward (841063) | more than 6 years ago | (#21781276)

A somewhat related issue: my mother in law seems to think that an accelerator is a binary switch, so she uses a rudimentary form of PWM to control (if you can call it that) her speed (if you can call it that).

I think the nervous brakers operate brake and accelerator together as a single ternary digit.

Re:Nervous brakers? (1)

archen (447353) | more than 6 years ago | (#21781348)

If I notice this sort of person I usually avoid them or back off if following. You typically find these sorts of people have very poor reaction times and have no idea what they are reacting to. This leads them to be skittish and hit the brake all the time. The net affect is that they will either not react in time and hit something ANYWAY, or they will slam on the brakes when they didn't have to and potentially cause and accident behind them.

next (4, Funny)

kurtis25 (909650) | more than 6 years ago | (#21780938)

maybe mathematicians can solve why old news appears on slashdot.

Preach It. (1)

Ohio Calvinist (895750) | more than 6 years ago | (#21780946)

I know on the I-10 around Yucaipa, California, this is definately true. There are 2 downhill slopes (1/2 mile each, 5% grade) right before the town on the freeway where everyone going 70-80mph (I get passed at 75) slams their brakes to not loose control on this hill and never get back up to normal speed, and because the person in front of them is slow, rides their brakes and never gets up to top speed for the next mile or so, everything piles up and its gridlock. If everyone slowed to 60 or so, but KEPT MOVING knowing, there wouldn't be the daily 15-20 minute delay every single day at this point.

In other news.... (2, Insightful)

v_1_r_u_5 (462399) | more than 6 years ago | (#21780954)

Scientists discover that if people act in society's interests rather than their own, society is better off. Seriously, how hard is it to follow the two-second rule on the highway?

Drivers tend to be self-centered. (1)

Radon360 (951529) | more than 6 years ago | (#21781212)

Seriously, how hard is it to follow the two-second rule on the highway?

It's quite difficult when the majority of other drivers see the space in front of you as an opportunity to "get ahead" in the flow of traffic.

It's not hard to follow the rule, instead, it's hard to maintain it without ending up going significantly slower than the traffic around you, and you'll still get cut-off occasionally simply out of spite for your perceived slow speed.

Drivers tend to be very self-centered in their driving actions and habits...even when that's entirely not the case when they're not behind the wheel. It stems from a variety of issues, from having to share the road with people that are distracted, aren't perceptive enough to notice what traffic is doing and adjust, or simple driver incompentence. With every driver eventually having an occasional encounter with another that is causing them some form of mild aggravation (usually unknowingly), can you blame them for taking an egocentric approach to their driving habits?

Of course, the problem then becomes self-propagating.

Re:In other news.... (4, Insightful)

berashith (222128) | more than 6 years ago | (#21781226)

It is absolutely freakin impossible!

If I give 2 seconds to the car ahead, it is likely that two drivers and maybe a third idiot will wedge into that gap. Now I have to slow down to achieve the new two second gap, which will cause everyone behind me to react with breaking and more slowdowns. Eventually there will be a wave of breaking that causes a huge delay in traffic with no apparent cause. I may even be lucky enough to be run into from behind, and then 2 seconds at zero mph would be the exact lack of distance between our now entangled bumpers.

Now if we could actually give space to everyone and not have the self-righteous take advantage of these gaps as there way to shave 8 seconds off of their commutes you may have a point.

Sorry to be cynical to your point, but I live in Atlanta, and people here suck.

Re:In other news.... (1)

The-Ixian (168184) | more than 6 years ago | (#21781310)

Not hard. However, the problem is that assholes will continually take advantage of your "huge" safety cushion and cut in front of you. Which causes you to back off more, which then invites the next asshole to whip in front of you. I get to the point where I feel like I have to fight fire with fire.
The thing that really irritates me, though, is the fact that nobody uses turn signals anymore, even when making 90 degree turns. As a matter of fact, if people would just use the signalling devices included in their car I think that quite a few accidents could be averted.

Known for _years_ (1)

Alioth (221270) | more than 6 years ago | (#21780964)

I think this has been known for _years_.

I've observed it many times from the vantage point of a light aircraft - in busy traffic times, you can even see the genesis of traffic jams on busy roads - someone jabs their brakes, the car behind hits the brakes harder, and before you know it, you have a standing wave of stopped cars in the traffic maybe 20 or 30 cars deep. It's very interesting to watch from a light plane. It's very frustrating to be in on the ground.

Indeed (2, Funny)

Colin Smith (2679) | more than 6 years ago | (#21781248)

Once you understand how it works, you can create traffic jams in even relatively light traffic. If you're really good, they're still there when you go home the other direction.


Ummm... DUH? (0)

Anonymous Coward | more than 6 years ago | (#21780970)

Is this new news? I saw videos years ago that showed how cars bunching up were just like the compression waves on a slinky. Everything gets stuck together and can bunch up cars way down the line from were the event happened.

Saying you've mathematically discovered why traffic jams happen is like saying you've discovered a proof that proves that if you ask why your girlfriend's pants seem too tight, you'll end up sleeping on the couch.

No Shit, Sherlock!

What About HOV Lanes? (3, Interesting)

slas6654 (996022) | more than 6 years ago | (#21780982)

I'd be curious to see whether these geniuses analyzed the impact of HOV lanes? []

Standing Waves (1)

drooling-dog (189103) | more than 6 years ago | (#21780996)

Not only that, but it seems clear that congestion at one time - whatever the cause - can set up a standing traffic density wave that might last for a long time after the original cause is gone. Beyond some minimum traffic level (easily achieved on the highways around DC, for example), at least.

This is not new math (1)

Joe Snipe (224958) | more than 6 years ago | (#21781022)

Although their proof might be (IANAM). I remember reading this article [] on slashdot around the time it was written. Although, for what it's worth, I don't think it technically qualifies as a dupe.

Erm, it's pretty obvious really. (1)

caluml (551744) | more than 6 years ago | (#21781034)

shows how one driver hitting the brakes a little too hard can cascade into a backup miles behind.
Of course. This is obvious. People generally brake for a little longer than the car in front. I worked this out years ago, and as a result, I try never to use my brakes on a motorway, instead watching the tail lights coming on towards me down the queue, and dropping off back of the last car to try and "iron out the kinks".

Some relatively old news (0)

Anonymous Coward | more than 6 years ago | (#21781050)

And I don't think too many of us needed a mathematical model to prove any of it. The fact is, it takes longer for people to accelerate than to decelerate. And the delay in change from "gas to brake" is a LOT less than the change from "brake to gas" as a matter of urgency. Personally, I have always found this fact annoying as I have observed this as being as plain and obvious as anything can be... and I wonder why more people don't see it themselves. Why is it that when traffic starts to move in front of someone that they have to wait a full 2 or 3 seconds before they start moving themselves?! Why can't they just ease into the movement more simultaneously?! I know I always make effort to do that personally as I feel that being in other peoples' way is a terrible rudeness! (This is a rare point of view in the U.S. unfortunately, as I have observed that in general, people in the US don't care in the least if they are in anyone else's way. And I have also observed many trends along social, cultural and, indeed, ethnic/racial categories! The least likely people to be in someone else's way are asians and the most likely are negroes. And YES there are exceptions and there are shades all along the spectrum, but in general, as a white male, U.S.American, these are my observations and I stand by them firmly whether it's politically incorrect to point out the obvious or not!)

XKCD (3, Funny)

RobBebop (947356) | more than 6 years ago | (#21781060)

Re:XKCD (1)

dkleinsc (563838) | more than 6 years ago | (#21781272)

They'd have a better time causing traffic jams with creative road designs [] .

Do not discount this (1)

bogaboga (793279) | more than 6 years ago | (#21781066)

Some mathematicians have solved the mystery by developing a mathematical model that shows how one driver hitting the brakes a little too hard can cascade into a backup miles behind.

Some drivers are always under some kind of external or internal influences. Internal influences would include the influence of drugs.

At a place I normally frequent, I always see "smart/well-dressed respectable men and women" dying to get a fix before getting behind the wheel. By the way, I do not do drugs of any kind.

Bad drivers = traffic jams (5, Insightful)

stewbacca (1033764) | more than 6 years ago | (#21781072)

I'm with the rest of you. This is hardly a revelation. At Texas Motor Speedway, during a NASCAR weekend with 225,000 fans trying to leave, a person stopping for three seconds causes a 20-minute delay to the last car in line. Until they fixed the number of exits flowing back out to I-35, it usually took 3-4 hours to get out of the parking lot.

Another cause for bad traffic is the ridiculously easy driving test we have in the States. Couple that with law-enforcement only ticketing speeders instead of bad drivers in general, and you get the traffic we have in most of our cities. I also hate how all accidents are chalked up to "failure to control speed", which makes it sound as if speeding were the main cause of all accidents. In reality, failure-to-yield is overwhelmingly the #1 cause of collision accidents, not speed. But the revenue hungry cops would rather sit on their motorcycles with radar guns than actually pull people over for changing 5 lanes at once, or cutting off other drivers by pulling out in front of them and then NOT accelating.

Not to mention, hell will freeze over before they ever ticket a slow driver in the left lane.

Re:Bad drivers = traffic jams (1, Funny)

Anonymous Coward | more than 6 years ago | (#21781224)

Probably because the exit ramp required a right turn, and all of the NASCAR fans were befuddled.

Car software (1)

truthsearch (249536) | more than 6 years ago | (#21781090)

I already cringe when I hear car ads mentioning Microsoft software. Not to be a luddite, but I'm not so sure I'd feel comfortable letting software partly control my brakes.

Re:Car software (1)

Anonymous Psychopath (18031) | more than 6 years ago | (#21781286)

Some cars already offer this. Acura has a system called PAX where it has a forward-looking radar that figures out if you're approaching something too fast to stop in time, tightens the belt restraints, gets ready to pop the bags, and hits the brakes for you. It's an available option on the Acura RL, not sure about other makes/models.

Re:Car software (1)

shofutex (986330) | more than 6 years ago | (#21781322)

If you have anti-lock brakes or electronic stability control, software already partially controls your brakes. Why fear added complexity and make it do more!! We want more features on our brakes, don't we?

autobahn (1)

n3tcat (664243) | more than 6 years ago | (#21781114)

What really amazes me is how smoothly the traffic on German roads flows. I've been in traffic jams that lasted for miles, yet everyone managed to stay at around 45 mph the whole time. In fact the only time I ever really see stopped traffic is when an accident has blocked the entire road system, there is construction, or a roadway merges 3 lanes into two or something.

Of course the other funny thing is that it was the Americans that removed the speed limits on the autobahn oh so many years ago, yet they enforce such strict speed limits on the stateside highways.

Like Cornstarch? (1)

aphxtwn (702841) | more than 6 years ago | (#21781128)

I always thought traffic congestion was like those experiments you did as a kid with cornstarch and water where it can feel like a solid and liquid. the starch dough moves if it's relaxed, but solid when there's pressure. I'm not sure how accurate my analogy is...

Astronomy (1)

PresidentEnder (849024) | more than 6 years ago | (#21781140)

I first read about this in my Astronomy textbook in high school. The idea is that the spiral arms of galaxies happen the same way, except that instead of braking, we have gravitational attraction between stars. Stars in the arms are stuck in traffic jams; stars between arms are the lucky few who aren't.

Re: Mathematicians Solve the Mystery (1)

CheekyBastard (1142171) | more than 6 years ago | (#21781180)

As if I really needed mathematicians to tell me that there are idiots on the road that cause traffic problems.

Unintended traffic-calming devices (1)

davidwr (791652) | more than 6 years ago | (#21781184)

The 4 biggest causes of traffic jams I've seen, in no particular order:

  • loss of a lane/wreck/construction
  • things which cause individual cars to slow down, such as narrow lanes, curves, accidents on the side of the road, potholes, etc.
  • poorly timed stop lights
  • too much traffic for the road even under ideal circumstances

Oh, HELL no (1)

Cleon (471197) | more than 6 years ago | (#21781242)

As a motorcyclist, the idea of "automated braking systems" scare me almost as much as women who are applying makeup while driving SUVs so large they should have "USS" on the license plate.

Regarding traffic jams, the main cause of traffic jams is very simple, and doesn't require a mathematician to figure out: There are too many people on the fracking road! Whether people are braking perfectly efficiently or not, if enough cars are crammed on the road, there's going to be a traffic jam.

Re:Oh, HELL no (1)

stewbacca (1033764) | more than 6 years ago | (#21781422)

There are too many people on the fracking road! Whether people are braking perfectly efficiently or not, if enough cars are crammed on the road, there's going to be a traffic jam.
Unfortunately, this incorrect premise is what leads to yet even MORE stupid traffic regulations that don't address the root of the problem (bad drivers). In the US, outside of Manhattan and parts of the Bay Area, I've never seen a city that doesn't have enough usable road space to handle 2-10x more traffic than it already has trouble holding. Sadly, cities like mine (Austin, TX) take a hostile attitude towards improving road infrastructure and intersection designs because frankly, they want everyone to ride bikes and take non-existent mass transportation (which I'd be for, if they'd build it).

Although there aren't too many cars on the road like you suggest, I give your premise a bit of credibility because of the SIZE of the cars on the road; too big and completely unnecessary. We need to tax SUVs into oblivion.

Not smart enough (1)

Spazmania (174582) | more than 6 years ago | (#21781252)

Unfortunately, the mathematicians weren't smart enough to follow through to understand the cause of heavy braking: following too closely, less than 2 seconds behind the car in front of you so that when you brake lightly the next guy has to brake hard.

Nor did they follow that back to its root cause: too many cars on a section of road so that they pack too tightly. Nor did they notice that in light traffic flows fine regardless of braking because the large gaps consume the time lost so that more than a couple cars behind you no braking is needed.

If you want to understand road traffic, you need only understand data traffic on CSMA/CD half-duplex Ethernet. It works poorly after about 60% of theoretical capacity and has a cascade failure approaching 100%. Actually, that's badly phrased because half-duplex ethernet never approaches 100% throughput. The wire can be consumed 100% of the time, but when it is, total throughput is close to zero. Most transmission attempts are retried due to collisions and most packets that do get through end up in a higher-level retransmission because a timeout has been hit or the packet is out of sequence with another packet that was dropped from the overflowing transmission buffer.

Ethernet collisions are analogous to someone tapping the brakes lightly while a packet lost due to a buffer overrun is analogous to someone hitting the brakes hard. As the probability of each event increases, the throughput on the approaches zero.

Denis Leary already covered this... (1)

quickpick (1021471) | more than 6 years ago | (#21781254)

In his song "Asshole" the lyric is, "I drive really the ultra fast lane...while people...behind me...are going INSANE! I'm an asshole! he's an asshole I'M AN ASSHOLE OOOOOHEEEEEEEOOOOO! He's the worlds biggest asshooooooooooole.

I call them "brake-happy assholes" (1)

merc (115854) | more than 6 years ago | (#21781256)

I live in Arizona and the drivers here are just dreadful. I see them on the freeways day after day, they have no confidence in their driving skills. They tap their brakes constantly whether something is in front of them or not, and it makes me crazy.

I can't help but wonder if the onslaught of snowbirds [] that migrate here year after year during the winter.

That's great. (1)

kevmatic (1133523) | more than 6 years ago | (#21781262)

Now what? Seriously, as obvious as this is, what good will it ever do? People aren't going to change their traffic accidents now that's there scientific data to back up what everybody already knew.

I'm pretty sure we all know that automating driving would get everybody there faster, as long as it works.

They need to study why IDIOTS slow down when they get to tunnels and redesign the fronts of tunnels to avoid it.

Or why a guy on the side of the road changing a tire is so damn interesting.

HCo8o (-1, Troll)

Anonymous Coward | more than 6 years ago | (#21781306)


Avoiding Traffic Delays (1)

kabz (770151) | more than 6 years ago | (#21781358)

Don't worry! You can fix this problem by driving 1 inch off the bumper of the SUV in front of you!!

Sometimes it's more serious... (1)

RobertB-DC (622190) | more than 6 years ago | (#21781360)

You never know, though, when something might have actually happened ahead. Yesterday, I found one of my alternate routes through Dallas traffic blocked. Nothing unusual there, but the cause was as bizarre as it gets:

Accident on tollway kills man, backs up traffic []

Irving activist Anthony Bond was driving his brother home from a day of cancer treatment Thursday afternoon when a pickup on the other side of the Dallas North Tollway slammed into the median, he said.

The collision sent a large chunk of concrete through the passenger side of the windshield of Mr. Bond's northbound PT Cruiser shortly before 4 p.m. The concrete struck William Mathew Bond, 57, in the face, killing him instantly, authorities said.

I've been following the "traffic waves" procedure for years now, but I guess when that chunk of concrete aims for your head, that's all she wrote!

slow autodrive solution (1)

drDugan (219551) | more than 6 years ago | (#21781368)

I really want automakers to announce simple autodrive systems for cars.

I see the first place this will work is in the 0-10 MPH creeping behind another car system. No steering, just holding a constant speed (not stopping if possible) and not crashing into the car in front of you. Go > 10MPH, turns off. Turn the steering wheel, turns off. Hit the brake, it turns off. But, sit there for 40 minutes in traffic, creeping along and it works like cruise control. Why don't we have this yet???

My intuition tells me that if everyone drove this way: working hard not to stop, but going slow enough not to crash to the next guy in front -- then the traffic jams would undo much more quickly. In fact, if even a low percent of drivers drove this way it would clear up the jams more quickly. The rolling stop waves that roll back through the chain of cars keeps the jam togteher. If even 20-30% of the cars never stop (creep slowly betweeen the waves) then the whole jam would start to move fast enough to disperse. I have no modelling or math proof of this, just a gut understanding of how could work.

Compressible Fluids and Shock Waves (2, Insightful)

Sigfried (779148) | more than 6 years ago | (#21781396)

This result is not only well known, it is classical. I'm sure there must be some new twist to the analysis to make it publishable, but I can't find it. The article made me search my bookshelves for an old textbook [] I used for teaching a class in Applied Mathematics back in the 80's (in my starving professor phase of life):

Mathematical Models: Mechanical Vibrations, Population Dynamics and Traffic Flow
Richard Haberman, Author
Prentice Hall, published 1977.
It has a very nice development of the math behind traffic flow, which also turn out to be the 2D equations for a compressible fluid. And in a compressible fluid the speed of flow decreases with density, causing the characteristic lines (the direction of wave propagation) to cross, causing a classic shock wave to form. The shock wave in traffic flow is the traffic jam. The section on Traffic Flow is about 140 pages of the book. Select chapters names include:
  • Flow Equals Density Times Velocity
  • Conservation of the Number of Cars
  • Experimental Observations
  • Traffic Density Waves
  • After a Traffic Light Turns Green
  • Wave Propagation of Auto Brake Lights
  • Stationary Shock Waves
  • Effect of Red LIght or an Accident
and so on. It made for an interesting class (and the only math class where I ever assigned a paper!). I recommend the book. If only we could train people to behave in traffic as if they were an incompressible fluid, we would never have traffic jams; but to do that, you'd need to be trained to speed up when traffic got heavy.

Solution from a NY Driver... (0)

Kranfer (620510) | more than 6 years ago | (#21781418)

I have the solution. As a New York Driver, most of you around the country dread me getting on your highway. I drive as fast as I won, change lanes without turn signals, and weave in and out of traffic. My solution: All your roads r belong to me. If its just me on the road, No more traffic jams. However, the idea of driving on the shoulder to bypass the jams is always a valid option here in NY. Or creating your own road. Or, theres always the horn, the middle finger, and random profanity to be yelled out the window. So, as a conclusion... stay off the road when I am around and you will not be stuck in any traffic jam I may cause. Mawahaha. Or... Give me my flying car god damn it. I want it NOW!!!
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