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MIT mathematicians model traffic jams like detonation waves

Most drivers have been stuck in a traffic jam at one point or another. Some of the jams are caused by an accident or closed lanes. Other traffic jams crop up with seemingly no reason.

A group of mathematicians at MIT is working on the development of a new model to explain how and why these so-call phantom traffic jams form. According to the researchers, these types of phantom traffic jams form when there are a lot of cars on the road and small disturbances like a driver hitting the brakes too hard or getting too close to another car. These little disturbances can escalate into a self-sustaining traffic jam.

The model developed by the team of researchers may help road designers build roads to minimize the possibility of phantom traffic jams. The key to the study is the discovery that the mathematics of these jams called jamitons are very similar to the equations used to describe the detonation waves produced by explosions.

The discovery of the jamitons allowed the researchers to solve traffic jam equations first theorized in the 1950's. The equations are reportedly similar to those used in fluid mechanics and model traffic jams as self-sustaining waves. The equations allowed the researchers to calculate the conditions that case a jamitons to form and how fast the jamiton will spread.

According to the researchers, once this type of jamiton forms it is nearly impossible to break up and a driver’s only choice is to wait the jamiton out. The researchers say that the new model can help road designers to determine speed limits that are safer and find stretches of road where accidents are more likely.

One of the researchers, Aslan Kasimov, said, "We wanted to describe this using a mathematical model similar to that of fluid flow." Kasimov and his team say that they discovered that jamitons have a sonic point that separates traffic flow into upstream and downstream components. Communication of the cause of the jamiton to drivers it the downstream segment of traffic is impossible say the researchers.

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The source is pretty simple really
By FITCamaro on 6/10/2009 11:25:09 AM , Rating: 5
Large population centers + people going to work + roads not being large enough + stupid drivers who get in accidents or tie up lanes because they try to move from the far left lane to the far right lane for their exit at the last second = traffic jams

RE: The source is pretty simple really
By FITCamaro on 6/10/2009 11:25:47 AM , Rating: 5
Oh I forgot stupid people who feel the need to slow down to 5 mph to gawk at said accidents.

RE: The source is pretty simple really
By mdogs444 on 6/10/09, Rating: -1
RE: The source is pretty simple really
By mmcdonalataocdotgov on 6/10/2009 11:38:32 AM , Rating: 4
How does that help anything? I mean besides your alone-time fantasies?

RE: The source is pretty simple really
By mdogs444 on 6/10/2009 11:41:35 AM , Rating: 1
It may not change what happened, but it sure makes me feel a lot better...

RE: The source is pretty simple really
By Iaiken on 6/10/2009 1:12:18 PM , Rating: 5
mdogs444 said:
Look at me! I need attention from people on the Internet in order to find validation for my driving and my life!

Maybe not those words exactly, but that's how it read to me...

From what you just said, I can pretty safely state that you're a part of the problem. Safe following distances not only allow you to stop safely in the event that the driver experiences an emergency, but allow room for drivers in other lanes to maneuver in the event of an emergency and allow for merging traffic to zipper correctly.

But since your driving likely stems from a bloated ego and the mistaken notion that you are more important than the other drivers sharing the road with you, no amount of logical discussion or lecturing will cure you of your bad habits. (You certainly sound 'special' btw...) You might want to consult a therapist...

Have a nice day! :D

RE: The source is pretty simple really
By invidious on 6/10/09, Rating: 0
By Danger D on 6/10/2009 2:07:14 PM , Rating: 5
F*** You is hardly a carefree attitude.

RE: The source is pretty simple really
By Chaser on 6/11/2009 8:42:28 AM , Rating: 2
Safe following distances not only allow you to stop safely in the event that the driver experiences an emergency, but allow room for drivers in other lanes to maneuver in the event of an emergency and allow for merging traffic to zipper correctly.

When "merging traffic" is entering the highway from an entrance ramp you might want to show some basic courtesy and merge over to the next lane. Rather than your "behind the wheel only, childhood bullied revenge, courage rush."

By Spuke on 6/11/2009 11:45:44 AM , Rating: 2
When "merging traffic" is entering the highway from an entrance ramp you might want to show some basic courtesy and merge over to the next lane.
When you can safely do so without causing unnecessary braking from those behind you, yes we should be courteous to those merging. At the same time, those that are merging with traffic should understand that the drivers on the freeway do have to allow you to merge and YOU should take the necessary steps to merge properly with traffic without causing undue slowdowns of that traffic. In other words, don't be an a$$hole whether you're on the freeway or merging onto the freeway.

RE: The source is pretty simple really
By bhieb on 6/10/2009 11:49:31 AM , Rating: 5
Agreed, so mdog you'd rather I stop while entering a 70+ MPH highway via the on ramp, rather than you following the correct distance at that speed, which would have created more than enough room for a safe merge. If every ahole on the road drives that close at those speeds, where is that an oncomer is supposed to merge. Guess just screw him he can park on the on ramp that will not cause a slow down at all.

I'm not talking about the grandma doing 35 and trying to merge, but your example was that no one should merge because your following too close. And if we assume that your way is the right way then the guy behind you is too close and the guy behind him.... and there is no way to merge.

Here is an idea how about you follow at the correct distance let the people merge, and within a half mile or so spacing should be back to normal.

Or just keep honking and flipping people off that won't make them tap the brakes and slow traffic further at all will it /sarcasm.

RE: The source is pretty simple really
By mdogs444 on 6/10/09, Rating: -1
By bhieb on 6/10/2009 12:06:57 PM , Rating: 5
Actually if you paid attention in driving school, yes they have to yield, but as a courtesy driver you also have a responsibility to let them in safely provided they are doing roughly the same speed (again not the grandma here).

What is your grand solution then. Assuming the highway is at max capacity (everyone is bumper to bumper no more room) do they just sit on the on ramp until rush hour is over? Then you'd be the guy 3 cars deep honking and flipping them off because they cannot merge using your standards. The problem is too many cars simple as that. Yes dumb drivers are a problem, but your point here is not an issue. The guy trying to get in at highway speeds is not the BIG problem, the ahole honking and flipping people off is causing far more "ripples" than that guy.

RE: The source is pretty simple really
By Mitch101 on 6/10/2009 12:36:34 PM , Rating: 5
On the flip side there are idiots who have the mentality NOT IN FRONT OF ME YOU DONT! and speed up closing the hole which would have made merging with the flow smooth but now have a do I go for it or apply the brakes situation because I am running out of room. Sadly I want to say there are more people trying to close that gap by speeding up instead of working with the person trying to merge. Im not trying to pass you but there is much more room in front on you because there are 4 cars tailgating each other behind you.

In all cases I try to change lanes if possible to make for the person merging but not everyone is capable of changing lanes for courtesy.

The reality is there are many people who just cant drive and if you listen to Ron White sometimes you will learn that while you can change just about anything on a person but you cant fix stupid.

By OCedHrt on 6/10/2009 8:26:13 PM , Rating: 2
Everyone is a bit over sensitive here. I don't think mdogs intended the "NOT IN FRONT OF ME" mentality. I have frequently encountered drivers who think turning on the turn signal gives them the right to merge. It doesn't. These are the same drivers that cause accidents by merging into the car next to them.

Applying this to the on ramp: Just because you sped up to 65 or 70 doesn't mean you can merge without looking. As the person entering moving traffic, YOU have to find the space to enter. Of course, a courteous driver on the outside lane does help. In the case of bumper to bumper traffic where there is no space to merge, I'm pretty sure the flow up traffic is not 65+ mph and more like 5 mph. If the traffic can flow up 65+ mph, there WILL be more than your share of adequate spaces to merge into.

RE: The source is pretty simple really
By croc on 6/10/09, Rating: -1
RE: The source is pretty simple really
By omnicronx on 6/10/09, Rating: -1
RE: The source is pretty simple really
By bhieb on 6/10/2009 12:16:25 PM , Rating: 2
Of course traffic jams are another situation, but when speeds are approaching 60+ MPH you have absolutely no excuse.

The whole point here is in jams or heavy traffic. And even at 60+ in heavy traffic the OP was saying it was the mergers fault. Assuming that there is no available "gap" then the bad driver here is not the guy trying to merge at speed, but the guy not following far enough back. A parking space worth of space at 60+ is too close. If a guy is coming on the ramp at speed and you refuse to let give him a 1/2 second release of the gas, then you are the one forcing the cut off. If he slams into you of course legally he was supposed to yield, but every class/book/teacher out there says you should make room if possible.

RE: The source is pretty simple really
By omnicronx on 6/10/09, Rating: 0
By omnicronx on 6/10/2009 12:48:47 PM , Rating: 1
And please do not bring 'How do I merge when there is a traffic Jam then, if nobody will let me in?' as this is beyond the scope of this study. It has nothing to do with traffic jams that have already occurred but the little things that occur before that could create or make traffic worse than it has to be down the line.

RE: The source is pretty simple really
By Xerstead on 6/10/2009 2:16:22 PM , Rating: 3
The right of way is held by those on the main highway. And if they are driving sensibly with at least a 2 second gap between them and the vehicle in front it is easy to merge with the trafic so the 'right of way' isn't really an issue. This also applies to people tailgating from the sliproad 'demanding' space for a group/stream of cars to join all at once. So back off and leave space.
The 3 car lengths mentioned above is nowhere near enough at those speeds.
I always look far behind me...

So you've built up enough speed on the sliproad to merge with the traffic, getting near enough the main carrageway to see the traffic... Ahhh, no space for 5,6,7+ cars back up the road. You now have 40 meters to hit your brakes AND STOP from over 60Mph. Hope the person behind you isn't doing the same and concentrating of the traffic 1/2 mile back up the main road as he ploughs into your rear. If you do survive that then you'll need to wait for an even biggher gap to get back up to speed.
it is your responsibility to merge safely not theirs.

But everybody has the responsibility to drive safely with consideration for other road users. Failure to leave enough space for merging traffic forcing them to hit the brakes is more likely to cause an accident.

By omnicronx on 6/10/2009 2:57:31 PM , Rating: 1
So you've built up enough speed on the sliproad to merge with the traffic, getting near enough the main carrageway to see the traffic... Ahhh, no space for 5,6,7+ cars back up the road. You now have 40 meters to hit your brakes AND STOP from over 60Mph. Hope the person behind you isn't doing the same and concentrating of the traffic 1/2 mile back up the main road as he ploughs into your rear. If you do survive that then you'll need to wait for an even biggher gap to get back up to speed.
I'm not too sure what you are trying to say here, you preach safe driving and you give a situation in which this is not the case. If there is a car in front of you on an on ramp, you are suppose to give space, a good 4-5 car lengths at least probably more so that you can accelerate and have time to compensate in case the flow of traffic changes. At this point what you are saying is a non issue, you can still find a space to merge and the person 4-5 car lengths behind you will also have ample time to merge.
But everybody has the responsibility to drive safely with consideration for other road users. Failure to leave enough space for merging traffic forcing them to hit the brakes is more likely to cause an accident.
If you read my posts, I agree with this. That being said if I am giving 3+ car lengths in front and behind me (not that I can control the cars behind), I am not going to slow down because someone can't figure out how to fit into the huge space in front and behind me.

The point here is you should not have to adhere to cars merging in the first place. If you leave enough space in front and behind you, and merging cars watch the oncoming traffic to find a spot to merge(following the advice above of course). This is far more ideal than anything you mention. Perhaps slowing down may be safe for you, but 1 mile down the road, cars also slowing down due to a snake effect that you just caused could be far more harmful in the long run. To others of course, and I guess is half the problem, what do you care as long as you are safe..

RE: The source is pretty simple really
By omnicronx on 6/10/2009 12:08:45 PM , Rating: 2
Here is an idea how about you follow at the correct distance let the people merge, and within a half mile or so spacing should be back to normal.
Forgot to mention, this is exactly what the article is talking about! Unneeded slowing down causes these ripple effects. If you just compensated your speed until their was a space, the car behind you would not have to slow down to let you in and the snake effect would not occur.

RE: The source is pretty simple really
By bhieb on 6/10/2009 12:25:00 PM , Rating: 2
MIT or no MIT there has to be slow downs. If the highway is full there are no safe gaps to get in, thus a slow down MUST occur. It is a simple bandwidth problem, at least where I live. No amount of "good" driving will fix the lack of roads. Bad drivers add to the problem, but ultimately a road will only hold x cars per min. When more are added via merging then a slow down must happen.

Again not talking about the grandma doing 30 or the ahole cutting in just to cut in, but during rush hour in most metros everyone cannot just keep doing 60+ on good driving alone.

By knutjb on 6/10/2009 12:52:54 PM , Rating: 2
One way to do it is the way it's done on the ring road around London. They have cameras on the road any car causing problems to traffic can be identified and services or police sent. That combined with active signs over each lane that can display different speed limits for each lane and can lower the limit as traffic gets heavier, preventing stop and go and can close down lanes and slow traffic down approaching accidents.

Perfect, no, but I never stopped on the highway like I have in LA. If you can eliminate the surging, traffic moves a whole lot faster. In the UK they have way too many cars as the greenies would like to say, or for the rest of us, not enough roadway for the traffic and their system works remarkably well. It's a far more sophisticated system than how Seattle controls lanes in and out of the city at rush hour(s).

By SilentSin on 6/10/2009 1:24:11 PM , Rating: 2
Absolutely. People do not understand how to drive correctly and are usually far past the point of being "bad drivers" and have landed themselves squarely in "seriously dangerous to drive near" territory.

I live in the greater DC area right in the middle of what I would have to consider one of the top 3 worst areas to drive in the US. The two major culprits are I-66 and I-495/I-95 between DC and Richmond. Here's my list of the most aggravating things I witness on a daily basis that not only annoy the absolute crap out of me, but also add greatly to the problem this article is discussing:

1) People using acceleration lanes, exit lanes, and even EMERGENCY pulloffs as shortcuts around traffic/passing lanes. WOW...I just can't even put it into words how angry these people make me. They don't even make up that much time this way, if any.

2) Changing lanes for no reason. I see people do this a lot. There's no one immediately in front of them to pass, no exit to get over to, nobody tailgating them...I guess they just got bored of their lane so they come into mine to find a friend and invariably go 10 mph under the speed limit, forcing me to change lanes around them. Stay put, jackass.

3) Speed mimicking drivers. I'm referring to the driver who will go the exact same speed as you are no matter what you're trying to do. Ex: They are in my lane going a tad slow so I change lanes and try to pass, fair enough. Obviously this sets something off deep in their innermost psyche. None shall pass! They will try to fit in with the group and go your speed, honest, just give them a chance! When you get over to pass, they increase their own speed to match yours and sit there at your side or in your blind spot so that you cannot effectively pass them or let someone who has come up behind you through because they block you from getting back into your original lane. BE CONSISTENT.

4) Truckers trying to pass one another while going up a steep grade. This usually happens near the bottom of a valley where they've picked up speed and are about to go up the other side. This is especially heinous when the road is only two lanes and so *everyone* behind them must now go the speed of a semi going up a hill (I'll give you a hint: not very fast). Read signs. Remember that one that says "No commercial vehicles except buses in the left lane"? Or how about "Vehicles moving slower than 65mph must use right lane"? Yeah THOSE signs. That's you, buddy.

Most of these issues are all about how people change lanes and merge like idiots, which lead to people slamming on their brakes as talked about in the article. I really feel like the states need to up their standards substantially for the driving portion of the driver's license tests. Specifically concentrate on interstate driving and etiquette and I think we'd see a nice reduction in these "phantom" traffic jams. </rant>

RE: The source is pretty simple really
By UNHchabo on 6/10/2009 4:36:50 PM , Rating: 2
Here is an idea how about you follow at the correct distance let the people merge, and within a half mile or so spacing should be back to normal.

When I lived in New Hampshire, this is what I believed.

In California, if you leave more than 6 feet of following distance, you will be cut off, causing you to slam on your brakes. The only way for traffic to flow at a consistent speed on California highways is for everyone to tailgate everyone else. I don't like it, but that's how it is.

By Spuke on 6/10/2009 6:34:24 PM , Rating: 2
I agree here. In CA traffic, any gaps are just filled in by other cars. I don't tailgate but it seems that any space larger than a car length is filled in. Mind you, this usually occurs at slow speeds but you need to be ready to brake. Because traffic brakes pretty heavy out here.

By Mojo the Monkey on 6/10/2009 6:46:38 PM , Rating: 2
Absolutely true. The rules are different in Southern California, as I am sure is true for various other localities. When I drive in Northern CA, I look around in bewilderment about how calmly everyone is driving.

By PAPutzback on 6/10/2009 4:15:06 PM , Rating: 2
No it is the people riding the left lane not letting people merge. If I am not the fastest on the highway then I am in the middle or right lanes. But I always move left before coming up on a merge lane. Those people doing 70 are trying to get to the speed of traffic. It is the person merging into 70MPH traffic at 40 MPH is the problem. Instead of leaving a small hole get the he11 over.

RE: The source is pretty simple really
By mindless1 on 6/11/2009 2:08:38 AM , Rating: 1
Then you should have your license taken away as this is not safe driving and may incite retributional road-rage too. Thanks for making excuses to justify even worse driving conditions for the rest of us.

Oh BTW, thse people do not cause rear end accidents, rear end accidents are caused by those who follow too closely for the speed they are going or inattention, taking their eyes off the road for a moment. It is not the fault of someone driving too1 slow if they get rear-ended by someone else.

RE: The source is pretty simple really
By Spuke on 6/11/2009 12:13:29 PM , Rating: 2
It is not the fault of someone driving too1 slow if they get rear-ended by someone else.
I rear ended someone once when the traffic in my lane (right lane) suddenly stopped (panic braking). I swerved into the open left lane to avoid hitting the person AND to avoid the person behind me (too close) in front of me only to smack into a person stopped in the left lane who was trying to make a RIGHT turn!!!. This person caused the panic braking in the right lane. Who's fault was it? Mine AND the person I hit.

By mindless1 on 6/12/2009 1:45:09 AM , Rating: 2

If traffic in your lane slowed down and you could not slow down enough to STAY IN YOUR OWN LANE because of the speed and distance you chose, you are 100% AT FAULT.

This is FACT. It is taught in driver's school, is on driving exams, and is a point of law.

By afkrotch on 6/11/2009 4:36:14 AM , Rating: 1
FYI, I'd suggest not doing that. Ppl do get shot over stupid stuff like that.

RE: The source is pretty simple really
By keegssj on 6/10/2009 11:36:49 AM , Rating: 4
I was behind someone once who actually came to a complete stop on highway, and I watched as all four heads in the car turned to gawk at an accident.

I usually ignore it, but that driver got a full blast of the horn.

By nixoofta on 6/10/2009 12:32:03 PM , Rating: 2
Yeah,..those are looki-loo-itons. Previously known as rubberneckitons. MIT is working on a better name for them but as yet has come up emptyiton.

By Teancum on 6/10/2009 12:06:45 PM , Rating: 3
People forget that the "Acceleration Lane" is for ACCELERATING!!

By mikefarinha on 6/10/2009 12:26:59 PM , Rating: 2
Or more to the point...

Car's + Stupid People = Traffic

RE: The source is pretty simple really
By drycrust on 6/10/2009 1:31:18 PM , Rating: 2
True. One of the basic laws of physics is the speed of a car is less than or equal to that of the car in front.
As the density of cars on any given road goes up, the cushion between cars gets smaller. Since a car cannot travel faster than the car in front, when the car in front brakes or misses a gear change, the car behind must brake equal to or greater than the car in front.
As the average gap between cars gets smaller, so the need to brake harder than the car in front goes up. These two factors (speed car behind <= car in front, braking car behind >= braking car front) causes speed oscillations, which is really just classical wave theory. As with a normal amplifier, where the amplifying device cannot exceed its power supply's capability, so the traffic problems really start to happen when the physical bounds of the environment (speed limit or grinding to a halt) are approached.
This is why you get congestion around areas with merging traffic, because cars merging into a dense traffic stream with no extra lanes is just like an impedance mismatch. If the merging stream is also dense then really the only way to fix it without causing congestion is to have the merging traffic have their own lane.
However, it is important to note that if a line of cars is long enough, as happened when they were evacuating New Orleans, then you will get vehicle speeds that oscillate, which will cause vehicles to grind to a halt for no apparent reason.

By Xerstead on 6/10/2009 3:01:45 PM , Rating: 2
I was sure I'd seen a video of this effect before so i had a look and found one on YouTube:
This is like a mini version of the M25 motorway around London. This is one of the busiest roads in the UK and frequently has major traffic jams for miles. There is a variable speed limit around much of it indicated by overhead signs and speed camera enforcement. Traffic is slowed down at peak times to 40/50/60/70mph to help prevent and controll the problem.
The example is a circular road but it will have the same effect on a straight one.

By bpurkapi on 6/11/2009 1:33:25 AM , Rating: 2
People driving fast, slow, lots of people all leaving for work and leaving work at the same time. Solved! I'm in Taiwan right now(live in Portland,OR) and must say that USA traffic jams are shocking. Taiwan has smaller roads, and a whole lot more people on them, the difference is that they have a crap ton of motorcycles and scooters. The scooters travel in something similar to bike lanes in the states, and are allowed to split lanes. So what I'm trying to say is that here traffic jams are less severe even though the roads are much smaller, plus the cities are super dense so work is usually somewhat close to home, and commuter rail comes every 10-15 minutes. Its all about options, more modes of transport means its less likely to have horrendous traffic jams.

By Sunner on 6/12/2009 4:24:23 AM , Rating: 1
The source of many problems is that people see traffic as "A bunch of independent cars" instead of looking at it as one "organic" form.
Like cells and organs in a human body, every car affects the whole organic body of traffic, and if these cells or organs start shitting all over each other, the whole body will suffer as a result.
If the heart suddenly decided that "Fuck you brain, I'm not going to pump blood up to your lazy ass anymore!", things will soon be going south for the heart as well, same with assholes in traffic, they're just too stupid to realize it.

By xsilver on 6/10/2009 11:30:15 AM , Rating: 2
Im not sure how it is in the US, but here in australia on the freeways there are LED signs that light up during peak hours in order to take advantage of this fluid dynamics.
eg. speed is reduced to reduce stop start.

Only problem is, humans are greedy/inconsiderate and many ignore the speed sign anyways only to stop 3 cars in front and ruin the fluid dynamics model.

I always love hearing how people complain WHY speed limits are reduced when its peak hour rather than sped up. lol.

RE: humans
By mdogs444 on 6/10/2009 11:31:43 AM , Rating: 2
Studies have shown that accidents are more likely to happen at lower speeds than at higher speeds. That is also why we have minimum speed limits on freeways.

No matter which way you look at it, its better to stay with traffic, even if that means speeding. When I lived in Chicago, the speed limit was 60, but if you were not doing 80 then you had people 6" from your rear bumper blasting the horn. In that case, the slow driver is the danger because 90% of the cars are going over the limit. Staying with traffic is safer, causes less congestion, and gets you where you need to go faster.

RE: humans
By mmcdonalataocdotgov on 6/10/2009 11:40:18 AM , Rating: 2
True to that. It is not speed, but variations in speed that cause density waves. The people who go slow force other people to go around them, which forces people in the other lanes to slow and try to go around further, which forces etc. Density wave.

RE: humans
By radializer on 6/10/2009 8:03:46 PM , Rating: 2
On those lines, when I was living in the Phoenix metro area, I was once pleasantly surprised when the speed limits of a certain stretch of the Loop 202 freeway increased (yes increased! ) from 55pmh to 65pmh.

As for the reasons behind this ... everyone used to drive that stretch of freeway at speeds of 70mph, and rumor has it that those who actually stuck to the 55pmh speed limit were causing a traffic hazard - so I guess ADOT (or whoever sets these limits) figured they'd up the limit to 65mph to improve traffic flow.

By the way, if you drive out on I-10 headed east from Tucson towards El Paso ... the posted Minimum Speed Limit is 65mph almost through all of New Mexico.

RE: humans
By GaryJohnson on 6/10/2009 11:41:09 AM , Rating: 2
That doesn't compute. The higher the speed the more cars per second a roadway can hanlde. Lower speed = fewer cars per second = more traffic.

RE: humans
By mmcdonalataocdotgov on 6/10/2009 11:45:13 AM , Rating: 2
The more cars on the road, the more cautious and overcorrecting the drivers become, and the slower the traffic. The net affect is that the roadway can handle lower car counts at higher speeds, and higher car counts at lower speeds. Its called Rush Hour.

RE: humans
By Chernobyl68 on 6/10/2009 11:50:35 AM , Rating: 2
not really true. At high speeds, the headway increases, and you while your vehicles are travelling faster, there is more space needed between them.

2400 vehicles per hour per lane is about the maximum theoretical capacity of a freeway lane. This volume gets reduced by a host of factors, including:

Truck percentage
driver familiarity
Interchange spacing
lateral clearance
lane width

just to name a few.

RE: humans
By Seemonkeyscanfly on 6/10/2009 3:47:05 PM , Rating: 2
that's only if you want to be safe and live.... :)

RE: humans
By Ratwar on 6/10/2009 7:01:39 PM , Rating: 1
Look, if you want a real world example of why your explanation is... well... bullshit, come drive around Atlanta, GA for awhile. Going ~70 mph with maybe a car length behind you and a car length in front of you is kinda standard.

Going slower may ease traffic on roads that aren't going to be over capacity anyways, but on roads that are already well beyond capacity, they only make the situation worse.

RE: humans
By Xerstead on 6/10/2009 3:33:19 PM , Rating: 2
In theory, yes. You may be able to get more vehicles along a road all travelling at high speed but can the road/drivers handle it safely? Faster traffic requires increased spaces between vehicles and at higher speeds with heavy traffic these 'phantom' traffic jams become more likely. Also there is an increased risk of a collision. The aim is to create the highest (within reason) average speed which is done by keeping everybody moving even if this means starting at a slower speed.

RE: humans
By micksh on 6/10/2009 4:57:29 PM , Rating: 2
There is a way to measure distance in time units and this can be found in some safety guidances.
Theoretically if all cars keep distance considered safe (3 seconds to the next car) the distance will be proportional to speed and highway throughput will stay the same at any non-zero speed.
But, that is only if we don't count car length. Safe distance between cars increases with the speed but cars don't elongate. So the throughput should increase with the speed unless drivers increase safe distance measured in time units (which is probably the case).

On the side note, people just don't seem to use gas pedal here, in North California. I see a lot when people enter highways at 45-50 mph where limit is 65 mph, and these are not grandmas, these are otherwise normal-looking young and middle-aged men. Maybe they are trying to save on gas that way?
And then "inverse race" starts with some car in right lane. The car on highway which is already well below speed limit slows down trying to yield to entering car. And the entering car slows down trying to yield to the car on highway. At around 40 mph they finally settle this desperately slowing down all right lane. And all that when highway is not crowded, there is a lot of room to merge into it.
Many people just can't estimate at what point they need to merge and they think the slower the safer.

Why do they happen?
By mdogs444 on 6/10/2009 11:23:08 AM , Rating: 2
I've often wondered how traffic can come to a full stop when there are no stop signs or streetlights and no cross roads to turn off onto.

The biggest reason is too many cars getting on and off the exits close to the same time. The exit ramps are notoriously too short, and the entrance ramps usually merge onto traffic way too soon.

I wish they'd create a wall for a half mile before the exit so people cannot merge at the last second, and a wall at the entrance for at least half mile that splits into two lanes before it can merge with traffic. This won't solve all the problems, but i'm sure it would help.

Some might say its a danger putting a wall there because someone might hit it...but if they hit the wall at the merge/split...then its one less driver we have causing traffic jams! :)

RE: Why do they happen?
By FITCamaro on 6/10/09, Rating: 0
RE: Why do they happen?
By mdogs444 on 6/10/2009 11:28:38 AM , Rating: 2
Yup - we all win in that case. Less cars on the road, population reduction by survival of the fittest, less emissions, less gasoline consumption...and I can get where I'm going faster.

RE: Why do they happen?
By inighthawki on 6/10/2009 11:33:43 AM , Rating: 5
What happens is that a car will step on a brake, and any good driver behind them, especially on the freeway, wants to make sure they also slow down to a point less than or equal to the speed of the car in front. More often than not it will be less then, in which case the cars behind that car also brake, and we have something of a chaos effect going here. A small step on the brake can eventually lad to a huge traffic jam.

RE: Why do they happen?
By arazok on 6/10/2009 1:52:16 PM , Rating: 2
I read a study a while ago regarding the impact of adaptive cruise control on traffic congestion, and the authors determined that if only 20% of cars utilized it, then traffic congestions would be cut in half.

These are cruise control systems that will slowdown automatically if another car is in the way, then accelerate again when if moves.

It’s funny how governments focus on MPG, biofuels, and expensive hybrid technology as a solution for our environmental problems – but if they simply mandated an existing and (somewhat) cheap technology be installed in every car we could reap benefits far in excess of these solutions.

RE: Why do they happen?
By mmcdonalataocdotgov on 6/10/2009 11:33:47 AM , Rating: 2
These traffic jamitons, long called "brake checks" to truckers, are more like the density waves that form when there is a slower particle in the fluid.

The real culprits are LONG on ramps since people stuck back in the jam jump the white line to the right and get on the on ramp and perpetuate the problem. A long on ramp with foils to prevent on ramp jumpers would be more beneficial.

Another cause I notice is that traffic will move along pretty well when the road twists and turns, or has been straight for awhile, but as soon as the twists stop, the lane that is on the inside of the last turn stops. It is because people look up the lane they can now see for a long distance, count all the cars (regardless of speed) and think there are too many people in the lane and they brake. I call this the telephoto effect. They think since there are a lot of people ahead (that they can now see but couldn't when they were in the twisties) they stop. Watch this yourself. Whenever a twist in the road goes on to a straight, if the last twist is to the left, the left lane stops. If the last twist is to the right, the right lane stops. I'll bet lunch on it. But it is a visual effect, not a density effect.

RE: Why do they happen?
By bhieb on 6/10/2009 11:40:03 AM , Rating: 2
That would only push the jam further up stream. They will still wait until the last minute to get over inside the wall, thus creating a slow down further back. Problem is just too many cars not enough road. By the time a construction project finishes that was meant to "fix" the problem the number of cars have outgrown the fix, and construction has to start over. The fixes are 10 year ordeals.

RE: Why do they happen?
By nixoofta on 6/10/2009 2:33:14 PM , Rating: 4
The fixes are 10 year ordeals.

Often referred to as "Godd4mmitons"

Okay, okay, I'll stopiton already...:P
(In my own defense, I laughiton-ed so hard at "jamitons". I don't know how someone could say that with a straight face....iton.)

By Amiga500 on 6/10/2009 11:31:25 AM , Rating: 2
3D is needed.

It won't come before proper electrogravimetrics techniques arrive.

Sure, you can alleviate some problems with bridges and underpasses (2-D routes) and perhaps solve this with variable speed limits that traffic controllers impose, but with traffic forever growing, its pissing into the wind.

By mmcdonalataocdotgov on 6/10/2009 11:43:42 AM , Rating: 2
When we go to 3-D, I will go back to practicing law. Think of the exponential growth in accident cases as people collide in two planes (I mean, two dimensional planes, not airplanes - although it will be the same thing.) Plus the people on the ground will always win. Let me get those ambulance chasing shoes on... btw, where will we get the fuel to keep all these vehicles in the air?

By Amiga500 on 6/10/2009 3:39:29 PM , Rating: 2
You honestly think strict autopilots will not exist to over-ride collisions?

Heck, its why the personal car/plane thingy won't take off... ever... until there are sufficient safeguards against user (read: Driver) stupidity.

By acase on 6/10/2009 11:46:14 AM , Rating: 4
I seem to recall George Jetson still having quite a bit of trouble in the mornings.

Can't fix stupid
By cecilbaron on 6/10/2009 11:37:15 AM , Rating: 2
Rubber-necking at accidents on the opposite side of the road seem to cause most of the senseless traffic jams. If you can change human nature or allow computer-driven vehicles on the road, that'll take care of the problem.

Otherwise, we're just going to spend an enormous amount of tax-payer dollars to find out the hard way, that you just can't fix stupid.

RE: Can't fix stupid
By mmcdonalataocdotgov on 6/10/2009 11:49:45 AM , Rating: 2
Overhead signs that change messages to warn of traffic are the worst. Traffic slows to the speed of the slowest reader as a new message comes up telling of traffic 30 miles ahead. And when it takes up two alternating panels, just park.

What we need are screens that rescue workers can put up that people learn they are never going to be able to gawk around so they forget it. Alternatively, a mobile jumbo tron parked 1/4 mile upstream of the accident so everyone gets a good look while at speed and passes it by. Dolts.

RE: Can't fix stupid
By mdogs444 on 6/10/2009 11:49:39 AM , Rating: 1
Otherwise, we're just going to spend an enormous amount of tax-payer dollars to find out the hard way, that you just can't fix stupid.

We've been doing that for decades....but look at this year alone! Bailouts, stimu...i mean "pork-ulus" bills, and a wealth of social programs like the recent "studying how gays react in South American bars" and "how to help hookers in China".

They don't fix anything, they just show how stupid our elected officials really are - and they think the masses are stupid.

RE: Can't fix stupid
By ClownPuncher on 6/10/2009 12:46:29 PM , Rating: 4
Yay, overpoliticized comments on every article!

By Danger D on 6/10/2009 12:07:02 PM , Rating: 5
Most jamitons are sparked by the funkilicious grooves of Kool and the Gang or Chaka Khan.

Despite the best efforts of science, and as noted in this story, "once this type of jamiton forms it is nearly impossible to break up."

I do my part.
By mikefarinha on 6/10/2009 12:30:14 PM , Rating: 3
I do my part to reduce traffic jams.

I use my blinker when changing lanes!

If more people did this I believe there would be less traffic jams.

RE: I do my part.
By True Strike on 6/10/2009 4:14:59 PM , Rating: 2
Yeah, but also on the other side of the spectrum there are those people who use their blinker, and then leave it on...on...on...

Biggest problems I encounter
By callmeroy on 6/10/2009 2:38:04 PM , Rating: 2
I work in a different state than where I live so I see plenty of bad driving.

Here are some of the most frustrating and most common issues (in fact I'm sure I'll see them today!):

1) Frequent lane changes in heavy traffic. A lane change for a reason , like coming up to your exit or because the lane ahead is blocked by an accident is fine....but when ALL lanes are moving 5 mph why on earth do some folks insist on changing lanes every 5 minutes?

2) The can't make up his mind type. You've been behind this person before I sure --- he's driving 10 mph under the speed limit when you are behind him then when you go to make your move to pass he suddenly speeds up to match your speed, so you think ok I'll stay here then -- you stay there and now the guy's back down to just at the speed limit or below it again. It might be an amusing game to you -- if you do this, but I just was trapped in an office for 10 hours, I'm tired and I'm hungry and I'd like to get home you selfish prick....

3) What lane is my lane again? I see this more and more frequently -- folks that look like they are drunk, tires skirting along the lines in the road that divide up the lanes, some times dipping into one lane a few inches and then going back into another. This is annoying as hell --- first don't drink and drive and second if you are too stupid to figure out what lane you should be in, you really need to burn your now.

4) The cheaters. Folks stacking up on the shoulder because they are too good to wait for their exit like the rest of us, meanwhile I'm thinking "that would really suck if an emergency happened right now with no shoulder available".
Also in this group are the line butters.....often on my final exit before my house the line to the exit is about a mile or two long -- sometimes someone will drive by on and squeeze into the front of the line. These people should be drug from their cars and beat to death. Apparently they think they are better than the rest of us and only their time is important not ours.

5) People who don't know how merge/exit a highway properly. I've seen folks come to dead stops as if a red light was at the ramp and then they try merging, I've seen people ride the full length of the "merge lane" even when they have plenty of time to get over before the merge....and i've seen jack asses speed out like a bat out of hell to merge at the same time I'm driving by and I nearly have to lock up my brakes to make sure I don't hit him because there was no sign of him coming when I passed the point of the exit.

I generally curse up a storm to myself every night I'm caught in traffic. So yeah MIT or whoever -- please improve this traffic situation. :)

By Mojo the Monkey on 6/10/2009 6:51:09 PM , Rating: 2
Too bad their "discovery" that overzealous braking causes slow-downs is nothing new. Wake me up when you find out something we all didnt figure out on our own after 6 months of driving in our teen years.

want to solve traffic problems ?
By chick0n on 6/11/2009 2:03:35 AM , Rating: 1
Up the Driving test requirements by 500%, Im SURE there will be A LOT less traffic problems.

There are zillions are moron driving on the roads everyday ... I freaking hate those morons who just wanna drive 45 mph when everyone else doing at least 60+ ... jesus christ. If they cant take the speed, fuck off the roads and take subway for god's sake.

RE: want to solve traffic problems ?
By Finnkc on 6/11/2009 10:34:06 AM , Rating: 2
thank you.

I often wonder how some of these people passed a driving test when they obviously fail basic safety and good driving practices.

If you can't park your behemoth SUV at the local coffee shop, then I am guessing in an defensive driving maneuver chances are little Timmy standing on the corner with his ice cream is going home to his mother in a box, when your 4 ton poodle mover careens over the curb and bumper checks him through a Starbucks.

They need more classes ie.

-small car
-medium car
-large car / crossover SUV
-sports car
-UV / Truck

etc ... a license class for each or something like that. because a Suburban does not work in the same manner as a Civic.

never going to happen tho. Too many people with more bank roll then driving brains to fight that sort of legislation.

By acase on 6/10/2009 11:39:48 AM , Rating: 2
No doubt Charlie Eppes had something to do with this...

By Ranari on 6/10/2009 11:59:37 AM , Rating: 2
I think a lot of traffic jams COULD be avoided with education as well. While solid, well thought out road design is always the best way to go to keep traffic moving, some people just need to be taught how to properly drive in a city.

I'll be the first one to say it.
By clovell on 6/10/2009 12:18:22 PM , Rating: 2
Cool article. For all you Einsteins out there who think they know all of life's answers - if it were that easy, it would have already been done. This is interesting stuff, and is really cool to think about.

That's pretty cool
By Yaos on 6/10/2009 12:29:00 PM , Rating: 2
You can stop a traffic jam by going much slower than the car in front of you, if the car in front of you stops you may not need to stop which prevents the cars behind you from needing to stop. Stopping increases total travel time.

phantom traffic jams?
By invidious on 6/10/2009 1:35:35 PM , Rating: 2
There is no mystery as to why traffic jams occur in places where there are no contruction/accidents. The road designs are bad, the people driving the cars aren't always paying attention, and the speed limits are way too low. I didn't even need a research grant for that, though I guess I would like one.

It's idiots like this at MIT who make me glad I paid half as much for my engineering degree at a state school. I got a job doing real work instead of staying in grad school for 10 years wasting my life.

Easy problem to solve
By Seemonkeyscanfly on 6/10/2009 2:54:11 PM , Rating: 2
Just do not let any cars or trucks on the road during normal day hours.... Just like that no more problems. :P

I already know the Main Causes
By Kurz on 6/10/2009 4:31:09 PM , Rating: 2
Everyone will see this too if you stay in the right lane and do the speed limit. What I see constantly is the unconscious act of speeding up to catch up to the person in front of you. No one looks to maintain a constant speed.
Also what kills me if you are going to go over the limit at least have the gap to eat up slow downs of any kind.

The speed limit is there for a reason for safety, traffic flow, MPG, and its the law.
35MPG Tank AVERAGE!) in a car rated for 27MPG highway)

I observe the speed limit leave at least 3 car lengths in front of me if the person speeds up I maintain the speed limit no more.

I don't run to a Back up I actually slow down. So many people RUN into a back up when what they should be doing is slowing down in order to break up the Pile up.

Need visual aid do this on any major highway and Observe.
Need neat gives go to this website.

I am a Hypermiler at

By akosixiv on 6/10/2009 6:16:25 PM , Rating: 2
One highly populated city, plus one centralized business/commercial district.. and everyone heading there at the same time.

that's bound to make any driver's nightmare.

It's been done.
By Etern205 on 6/10/2009 10:52:09 PM , Rating: 2
The model has been done a quite a while ago..

Privatize the damn roads!
By androticus on 6/11/2009 10:42:34 PM , Rating: 2
The product that private road owners would be selling is drive quality -- if you are sitting on a road for an hour whose trip time at road speed is actually 10 minutes then you are basically selling nothing. It is the fact that there is a government monopoly on roads that leads to the chronic shortage of road capacity -- how come things in the private sector never suffer permanent chronic shortages like this?

And smarmy sneering cynical economics professors tell us that the government has to create government owned or controlled monopolies on "natural monopoly" resources like roads in order to... wait for it... protect us from what they claim would be the "natural monopolies" that would arise in the private sector.

Echoes of the EU saying they have to remove the web browser from Windows so consumers are protected and given choice.


Peter's problem
By WinstonSmith on 6/10/09, Rating: 0
"Nowadays, security guys break the Mac every single day. Every single day, they come out with a total exploit, your machine can be taken over totally. I dare anybody to do that once a month on the Windows machine." -- Bill Gates

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