Traffic Waves

OLDER COMMENT BOOK (back to 2003)

Honestly, I have actually thought the same thoughts as you are explaining on your web site. It is very interesting to me. I drive one hour each way to work five days a week, and I have plenty of time to analyze traffic behavoir. It really does act like one being rather than thousands of people. What really makes me wonder is why do people insist on filling the gaps I try to leave between me and the car in front of me. It is comical. We, my family, observe this all the time and it does become entertaining to us. Thanks for your scientific analysis of the behavoir of traffic. This is the coolest website ever
cflukens <cflukens@aol.com>
Fremont, NC USA - Monday, July 05, 2004 at 08:25:27 (PDT)
just a small remark on your writings about trafic jams,
You might be interested to know that the technique you call 'rolling barrier of state troopers' is used in Belgium for already a very long time (I think about 6-8 years already). We have one three lane highway that brings all the trafic to the coast, and on sunny days, we have what we call 'blokrijden' or 'driving in blocks'. Basically what happens is the following... One motorcycle cop goes on the highway and drives in front of some people, they are obliged to stay behind him. The speedlimit is 120 kph here... so the cop typically drives about 90-100 kph (slower if needed). They allow for a large 'block' of moving cars to form, but little enough not to have the wave effect. Then, when the block has a sufficient size, another motorcycle cop goes in again and forms another block... Like that over and over... so we have big blocks of cars driving on the highway... I have to say it is very effective...

Geert V
Belgium - Monday, July 05, 2004 07:21:48 (PDT)
I've modified my driving over the last year since I first read your site. I can't really say if it has helped the traffic behind me but it sure has made driving I5 less stressful. I have also noticed many other drivers leaving anti-trafic space durring drive-times.

I have though found the best solution: taking the Sounder train to work. I am so much more relaxed when I get home after taking the train.
Joe Hamelin <joe@hamelin.us>
Edmonds, WA USA - Saturday, July 03, 2004 at 23:45:40 (PDT)

Hi! That's a great site! I have made exactly the same observations myself. I guess it is a professional hazard of physicists. I'm one too (astrophysicist). I usually move at three seconds behind the previous driver, but when it comes to synchronous flows, a situation that can easily jam up, I often increase that to five seconds (just count slowly). I have too found that I can make a big difference.

Now for a comment I just posted in a Slashdot discussion:

There's a funny Traffic Wave Generator in Drammen, Norway. Unintended of course, but nonetheless. It's a longish bridge going from northeast to south in this picture[1], and at the northwestern end, there's a lot of traffic coming in, and at a relatively high pace. The speed limit is something like 90 km/h, which means the average speed is probably well in excess of 100 km/h. Then the limit on the bridge goes down to 70 km/h, and at the same time, it merges to a single lane in either direction. Bound to be trouble as it is... But to make matters worse, shortly after the 70 sign (perhaps 50 meters), there is a photo box, that, if it has film it in, will shoot pictures of anybody speeding. You'd get the fine in the mail.

But the true sign that nobody in authority has the faintest idea why this is the most hated persistent traffic jam in the country is a big, official sign saying "In case of a jam, follow along!" Right.

What they officially seem to be advocating is the fast acceleration. But not everybody can. For example with my mother's little engine, I can't... There is very little you can do to assist evaporation, as you very well argue.

So they created the worst, high amplitude traffic wave in the country by putting a traffic control camera in exactly the worst thinkable spot. There would necessarily be a traffic wave there anyway, but it is making matters so much worse.

I admit that there is a thing I do not quite understand. The jam often extends the whole bridge, and does not dissolve before a km afterwards. It would be interesting to study this from the air, but I'd love to hear your thoughts on this.

[1] http://map.finn.no/Ortofoto_FINNKART22400124811593.jpg
Kjetil Kjernsmo <kk@kjernsmo.net>
Oslo, Oslo Norway - Saturday, July 03, 2004 at 12:22:54 (PDT)

Hi i just wanted to tell you in Germany there is a system on some HighWays which is rhougly translated called 'automatic traffic leading'. Instead of normal speed limits there are electronically changeable speed signs and sensors which count the cars on the highway. if a traffic jam is reported by the sensors a computer changes the speed limits ahead of it to smaller value so the jam can dissolve. this system uses just the tecnique you described and you hardly ever see a jam on these 'computer-managed' highways. If you want more information on this, the german name is ' automatische Verkehrskontrolle' .
Lorx <achzumteufel@yahoo.de>
Germany - Friday, June 04, 2004 at 04:56:08 (PDT)
Great site, and great concept. I'm looking forward to getting my license soon to try and test this theory. However, drivers in Israel are notoriously raged, so I'm not sure slowing down will work without retaliation. one other problem I encountered while reading the site is this: what all these methods do is only make the 'traffic jam' more bearable, mentally. They won't let you get to your destination any faster, though...
[Not so. "Unplugging" a merge-lanes traffic jam is not theory, I've done it myself a number of times. It's unmistakable when it happens. The whole jam vanishes, and your speed goes from 5mph to 40mph. It's like flipping a switch. -billb] for instance, when you show two variants of the traffic jam, where in one, everyone's pushing forward and condensing, and in the other, people let spaces build and drive faster. in that case, a car that is in the 50th place behind the first would get to point 'x' (point 'x' being after the traffic jam, where traffic is normal in both variants) the same time in both variants.,
[What?!! I think you didn't look at those animations. In the unjammed version on the right, the total flow is doubled: two cars per second go past the blinking arrow, and also the speed of the cars is 5x faster. In real life it could be more than this because it takes a very long time to "take turns" at the head of the jam. The benefits of unjammed merge zones are very large. But there is a big problem: once the jam is removed, WILL it rapidly reappear again? When traffic is even more dense, then I suspect it's impossible to maintain the "unjammed" condition. -billb]

it would only seem more fluid for the car that's driving by your theory... am I mistaken?

Twinpraetor <Twinpraetor@yahoo.com>
Tel Aviv, N/A Israel - Thursday, May 20, 2004 at 01:54:45 (PDT)
I was quite impressed with what you have done here. I, myself am an antitraffic supporter, and have been utilizing the technique on the North Dallas Tollway for months now. I was excited to find your site and its in-depth approach to the subject. Here is my main comment....how can we organize? How can we easily and effectively get this information out to all of the commuters I see everyday. Most drivers are so anxious to get to their destination, they punch their cars forward, riding up on the cars in front, not letting others merge...stop and go, stop and go. If there were a way to get the message across that EVERYONE would get home quicker and less stressfully if they follow a few simple rules. I would love to be involved in a re-education effort to change our rushhour habits....any ideas?
LeeDon <leedonmoore@earthlink.net>
Dallas, TX USA - Wednesday, May 19, 2004 at 12:21:31 (PDT)
I read through this, and I must say I find it quite interesting. I never thought to look at traffic patterns like this before. I'll try to put this into practice whenever I get into a traffic jam and see how it works out :)
Ashwin Vaidyanathan <ashwin@anidlemind.com>
Chapel Hill, NC USA - Friday, May 14, 2004 at 17:44:37 (PDT)
This was a very interesting site, it defined Newtons First and Third laws of physics, as well as incorporated the law of inertia. Also clearly defined the geometric pathagorin theroem in which cars move at a steady rate. We're planning on commuting to Seattle to try this experimentation using several trials, to see for ourselves if you are truly full of shit!
Darwin Fish and Natalie Shrek <weluvphysics@aol.com>
USA - Thursday, May 06, 2004 at 09:25:19 (PDT)
Neat site, and certainly brings back memories of a lecture our applied math professor gave in grad school yeeeeeeears ago. He modeled traffic as fluid flow in a pipe, and when the density and speed were great enough, the flow goes "supercritical". Once it is supercritical, any random fluctuation (a driver gawking at a sign) will cause shock waves. Depending on the density or speed, the shock wave will either propagate forward through the traffic or back. I sure wish I remembered the math . . .
Jessie <carman_jessie@hotmail.com>
Manama, Bahrain - Tuesday, May 04, 2004 at 01:39:48 (PDT)
Here's another idea I had that might actually have some real effect on traffic patterns: The New York State Thruway Authority Tarp Company. Rubbernecking on the opposite side of a highway from where an accident is, is the cause of needless traffic. There is no physics capacity problem. This is a social engineering problem. So I propose, the Tarp Company. At the site of an accident or ANYTHING 'interesting', the tarp company shows up and puts up a huge sail (there are some wind problems, I realize) but something to make the drivers quickly lose interest in what's going on, on the other side of the roadway so they don't slow down to take a look.
Stu <spamme@deadpelican.com>
White Plains, ny USA - Tuesday, April 27, 2004 at 10:46:31 (PDT)
I don't know if somebody mentioned this, but let me explain something I figured out about traffic. Actually some are here: http://nyti.dyn.ee:81/learnedcat items 30, 31 and 32. As you are, I'm an amateur traffic dynamicist and the merging problem can be explained this way. Fill up a two liter soda bottle with water, turn it upside down and watch the water pour out. There are about 5 lanes of water in the bottle, and only one that goes out the bottle (at the cap) In order for traffic in five lanes to flow at the same speed in one lane, that one lane would have to be going 5 times as fast, but do people speed up at merges? no, they slow down making the backup worse. All that crap about "if people would just not bunch up and let people in, there wouldn't be any merge problems" is all bull. Physics doesn't allow for it. Period.
[Heh. Think first, THEN talk physics! In the real world, when two lanes merge smoothly into one, the two lanes slow down and no traffic jam forms. (The two incoming lanes might move 2x slower, but that is not a "traffic jam.") On the other hand, if a traffic jam appears, then the flow in the two lanes approaching the merge zone IS NOT 2x lower than the flow in the single lane. Instead the flow drops almost to zero, and that is the problem. If traffic behaved like water which pours through a bottle neck, then traffic jams would not exist. Instead, traffic often behaves like stones pouring into a funnel: they grind together and stop, while the tube below the funnel empties out, while still more stones pile on behind the funnel. And within the funnel, only a few stones can grind past each other per minute. If instead we poured oil on the stones, so that the gravel in the funnel could easily flow into the smaller tube... that is called "having no traffic jam!" Back to the cars: if there is no traffic jam, then the flow in the two incoming lanes must be twice as low as the flow in the single outgoing lane. But when a traffic jam develops, the flow is much much lower than 2x. A single driver can sometimes remove a traffic jam. But of course a single driver can do nothing about the 2x slowdown. -billb]

Stu < spamme@deadpelican.com>
White Plains, ny USA - Tuesday, April 27, 2004 at 10:38:27 (PDT)
I thought there might have been a chance to encounter the term "correlation length of the system". It's inversely proportional to "stress in the system" brought in by stressed drivers.
Jan Storms <jan@storms.org>
Haarlem, Nederland - Saturday, April 10, 2004 at 13:49:15 (PDT)
YES, YES, YES !!! Someone GETS it...greetings and kudos Bill, for taking the time to inform others by posting all this. This is a wonderful site. Chock full of interesting and informative information on traffic and flow. Especially the 'cures'. As an airborne traffic-reporter in Los Angeles (who also drives 75 - 100 a day on those same roads), i can second your thoughts on most of these dilemas. Our roadways are - for the most part - constant, yet the number of vehicles using them is ever-expanding. Thus, creating quite a problem. It takes a bit of thinking, planning and COOPERATION from others on the road to make this all work. Will definitely create a link to your site for others to explore and learn from. Keep up the great work! ...taylor (non-expert...just an observer)
M taylor baez <EyeintheLAsky at ya-hoo dot com>
Ca USA - Saturday, April 10, 2004 at 12:03:29 (PDT)
I have just found the perfect site for car mad science students in Oman. Thank you
KathyS <kathys@squ.edu.om>
Muscat, Oman - Wednesday, March 24, 2004 at 23:30:47 (PST)
For many years I have suspected the traffic wave phenomena. Your articles make it very clear. They should be required reading in any driving education program. I have pointed out your articles to my local newspaper (Doctor Gridlock at the Washington Post).
Tim Brown <tbrown59@verizon.net>
Wash, DC USA - Monday, March 22, 2004 at 10:46:59 (PST)
Great theory! Now I will not feel so helpless when I get lost in the maze of traffic.

It seems to me after reading your theory that two things could be done to improve traffic slow downs.

1. The speed limit of traffic could be lowered during the crush hours. If it were a stanard to lower the speed limit to say 45 mph during the moring and evening hours traffic could maintain itself better. It's either that or go 2 mph all the way home.

2. There could be acutal traffic monitor cars that cover all lanes and purposely slow traffic down. They would form one line across all lanes and back down on the gas to 45 mph.
Mark Rankin <m.rankin5@verizon.net>
Hemet, Ca USA - Friday, March 05, 2004 at 03:55:29 (PST)

What a fantastic site. It really is what the Internet was intended for. I have a question which I am fairly sure ws not answered, though must admit I did not read every line of the other comments.

I believe what you say is true. However, only a few of us are sensible, mature and professional enough to understand and adopt this way of driving. I'm not even sure I'm one of us myself! The fact that your web site's been around for a long time but I don't seem to meet many people like you on the roads tends to confirm that this sort of behavior will not rise up spontaneously from the driving population in my lifetime. And I wish it would. Do you, therefore, have any suggestions as to how to coerce or enforce the population to behave in this way? I was wondering about some kind of "good driver reward", where some cameras and image recognition stuff picked out such people and rewarded them in some way?
Andrew B
USA - Tuesday, December 30, 2003 at 14:55:48 (PST)

Hey I just wanted to say your website is dead on, I realized the traffic wave idea about a year ago and Its the best thing ever. I can go a smooth 20-30MPH in solid rush hour traffic and never have to stop once not to mention its sooo much easier and stress free! I dont think you covered this but have you noticed the middle lane is usually the fastest? The left (fast) lane is filled with people who dont want to wait and think they can zip past everyone. The right lane is filled with people who slow down to exit the freeway and leave the freeway system so thats -1 car and frees up space, so it might look faster BUT its also got people who enter the freeway system, so thats +1 car PLUS most of them havent reached the same speed as everyone else which causes cars behind to slow down. Plus the middle lane has the added bonus that if something were to happen ahead of you, you have more options on what to do. you can get into the left OR the right lane.
USA - Friday, December 19, 2003 at 18:06:12 (PST)
Great site! The more you get the word out, the better the driving experience will be for more people right? Driving a manual trans., I have been doing this for a while myself. Saves wear and tear on the brakes. Keep up the great work. We sure do like to amuse ourselves while in traffic don't we? ;) You might like a site that keeps my mind ticking in traffic, it's www.AboveAverageDriver.com My handle is "gowiththeflow" Catchy eh?
Kimberly Demyanovich <kimberly@aboveaveragedriver.com>
Woodhaven, MI USA - Friday, December 12, 2003 at 18:29:38 (PST)
ANTITRAFFIC DESTROYS TRAFFIC ... I think your observations are "spot on". I thought I was the only "lunatic" who observed and practiced this on the highway. With the amount of miles (25-30k) I put on the car every year, I have plenty of time to observe. I routinely leave the gaps you describe, and often play a "game" while driving and see how many miles I can drive w/o having to apply my brakes; leaving large gaps of "anti-traffic" between. Without qualifying it, as you have, I have thought that I was contributing to "anti-traffic" by driving in this fashion. It's hard to do in densely-populated NJ, but I do it anyway. It's also less stressful -- not competing. Keep up the good work! How can we get others to follow?
Larry G <gruberz@aol.com>
NJ USA - Tuesday, December 09, 2003 at 04:26:14 (PST)
Thanks so much for your website. My students (many new drivers) and I are investigating waves in my trigonometry class, and I have put up a link to your site from the school assignments webpage. Thanks again!
J. Euchler <jeuchler@mccanntech.org>
North Adams, MA USA - Sunday, December 07, 2003 at 14:02:38 (PST)
Thanks so much for your website. My students (many new drivers) and I are investigating waves in my trigonometry class, and I have put up a link to your site from the school assignments webpage at http://www.mccanntech.org/ showPersonal.asp?ID=JE&area=MAT
J. Euchler <jeuchler@mccanntech.org>
North Adams, MA USA - Sunday, December 07, 2003 at 14:01:46 (PST)
I really love your web site. Keep it up.
asaba owerri <homeboy_owerri_asaba@aba.us>
miami, florida USA - Monday, November 24, 2003 at 03:22:03 (PST)
Since it is all about waves what you've done is create a wave 180 degrees out of since with the original wave ( a big space as large as the wave.)
Dan <ddesloovnospam@ nospam.monroe.lib.mi.us>
Monroe, MI USA - Thursday, November 06, 2003 at 09:07:04 (PST)
Nice theory, but I don't think it can work, [What theory? I'm describing what I do personally during commutes. Please go and try using a large empty space, and try it at least ten times before you declare that it can't be done. -billb] even with the rolling blockade. Too many impatient people to screw it up. And even if there weren't, there is usually just too much traffic, especially with people entering the freeway. I have found in trying to leave a 2 second gap in front of me, it constantly gets filled by cars passing from either side. If I want to maintain a gap, I have to keep slowing down more and more, as the gap keeps filling. It has been impossible for me to do what is described in the link, because the gap never develops, I just keep slowing down. I have been able to do it when coming to a closed lane, by being in the closed lane and matching speed with another vehicle (usually a long truck) in the open lane beside me. The closed lane invariably moves faster (in any city I've driven), because too many people are too courteous in the open lane, letting multiple selfish ones in the closed lane get ahead of them. I have been successful many times in making the flow fair, and kept the closed lane at the same speed as the open lane, which Im sure made the open lane go faster. I start matching speed after I have passed at least one, some times two notifications that my lane will end. I stay aware of the possibility that the closure is no longer in effect. This results in a lot of pissed off impatient people in the closing lane behind me. Some times they pass on the shoulder. Even the people in the open lane dont always appreciate the fairness, and dont want to let me in, even though I could have gone 20 car lengths ahead of them, and had a lot of other drivers pass to get in front of them. Unlike the other authors, I have usually been able to speed out of a jam, and make a point of jumping into a newly opened lane as soon as possible, to show the drivers behind me that they can speed up too, (the end is near). Alas, I always see rubberneckers or trucks going slowly in all lanes behind me as I leave them behind.
mark <comercial@ev1.net>
Houston, TX USA - Monday, November 03, 2003 at 12:06:03 (PST)
Sounds good, but is it not true that all of your ideas simply move the "wave" further behind you? [No. When I smooth out a series of traffic waves, I'm actually taking the dense parts of traffic and putting them into the sparse parts, so no waves exist after I pass. And with merging-lane jams, I'm destroying the traffic-jam effect by pulling the dense part of traffic backwards away from the merge zone. Yes, when unplugging a merge-lanes jam, you do move the dense wave backwards. But then it STOPS GROWING, since the "plug effect" is gone and free-flow merging can occur. The remaining wave then drifts backwards into the distance. If I did nothing, then that wave would remain pinned in place at the merge zone, and as more cars pile in behind, it would grow larger, and larger, and larger. And finally, while you're right about the "standing wave" in that animation, the genuine "rubbernecker waves" instead grow larger and larger because the front of the wave remains pinned in place while the back of the wave still moves backwards as more cars pile in behind. In that case, if I pull the standing wave backwards away from the accident, then the front end starts evaporating normally again, so it starts moving backwards at the same rate as the rear end, and the whole wave moves backwards but no longer grows rapidly larger. - billb] Just because you slow down into a "standing rubbernecker wave" does not mean it will erase the wave, it just means that the wave will move further behind you. In essence, it moves spots. It doesn't disappear. If you are the only driver on the road that is taking part in these "anti-traffic" methods, then you cannot control the other drivers on the road who are still speeding into rubbernecker waves.
Jonathan <weeple81@yahoo.com>
Portland, OR USA - Sunday, November 02, 2003 at 23:50:06 (PST)
Thanks for this great site. I'm confident that traffic will be the scourge of the 21st Century. I've been referring my family, friends, and co-workers here to see what they think. Of course, they are all skeptical. I've found the "large space" has done wonders in the morning commute on I-84 westbound in Portland, Oregon at the I-205 junction and again at I-5, where it is basically merge-zone jams and stop-go waves. But I'd like to say something about the role of expectations when driving in heavy traffic. Drivers behind me clearly expect me to go as far forward as I possibly can. I've seen several drivers gesturing angrily behind me because I have refused to close the gap in front of me... it is as though tailgating has become a basic requirement for highway survival. The underlying psychological principle seems to be, "We're all resigned to the same fate of being stuck in this jam, so why bother trying to make it better?" So the question I have is whether there is any hope for disspelling the common belief that once a jam has started that it cannot be changed?
Portland, OR USA - Thursday, October 30, 2003 at 01:05:54 (PST)
It is incredibly awesome that this site is still around. I found it years ago and have been following the philosophy implied here ever since. I have gone from a 35-mile commute back then to a 50-mile today and everyday I see the proof of the things talked about here. Love the site! Keep it up!
Timothy Michael <tmichael@igwebgarden.com>
Dallas, TX USA - Friday, October 17, 2003 at 21:02:06 (PDT)
An impressive site on a subject that has intrigued me for a number of years. I have a number of observations from driving the I10 to and from Lousiana where there is continual construction. 1. Traffic jams where a two lanes merge in to one are perpetuated by selfish drivers that want to get to the front of the closing lane and merge. What causes the initial jam is hard to say since I've never been there to witness it.
2. A State Trooper with flashing lights on the shoulder next to the closing lane will encourage all drivers to merge early and avoids the worst symptoms of the jam. This suggests that the selfish drivers know they're doing something wrong.
3. In lieu of a State Trooper to remind people to merge early perhaps some kind other incentive to get out of the closing lane would work. "Rumble strips" across the lane that make driving in it noisy perhaps? I have considered throwing glass bottles into the closing lane, but that's just me ;-)
4. Trucks will often sit in the closing lane and match the speed of the merge lane. This stop drivers rushing to the front and perpetuating the jam. Of course everyone behind is still screwed, but at least part of the problem is solved, and it pushes the jam further back away from the merge.
5. In Houston we have on-ramp stop lights for rush hour traffic. They control the amount and frequency of cars entering the freeway. These appear to have helped, but they aren't linked to actual traffic flow. I've seen them off when traffic is backed up, and on during a holdiay when the freeway is empty. Good science, bogus implementation.

I'd be interested in studying what driving habits cause the initial jam at merging lanes. The 59/I610 intersection in Houston is notoriously bad. Perhaps I could ask one of the high rise buildings there to let me set up a video camera before rush hour and record what goes on.
Bob E <bentwhistle.AT.hotmail.DOT.com>
Houston, TX USA - Tuesday, October 07, 2003 at 13:23:31 (PDT)

This isn't a question, rather a comment. I just wanted to say I enjoyed reading your page. I never thought about this principle as technically as you have but discovered it in 1993 while stationed in Norfolk VA. In Norfolk construction was always going on somewhere and I started slowing down slightly ahead of the construction zone and end up moving steadily through the construction zone. I heay trafic I have noticed when I come to a place where traffic has stopped when it starts to move I can move steadily even if it is only at 10 mph and then steadily increase back up to the speed limit. Even on a four lane highway (two lanes in each direction) this process has shown sucessful for the idiots who wait until the last minute to merge, because unlike the majority I am not trying to punish them for their stupidity. I large metropolitan areas through traffic can help by staying away from the outside lanes. These lanes should be reserved for commuters to and from that area. If you will notice when you enter a large metropolitan area there are usually two lanes designated for through traffic. This principle also seems to work on controlled highways (highways with traffic lights) because in many larger cities the light cyles are synchronized. If I don't treat each stop light as a drag racing start I can usually negate a light cycle delay. I saw a comment about truck drivers knowing this principle. Though truck drivers may be courteous to other trucks they seem to be rude to cars. I know and have ridden with friends who are truck drivers and they will talk junk about the cars on the road. I have learned for every impatient idiot in a car there is and impatient idiot in a truck somewhere. For example I'll hear truckers talk about cars tailgating them, but there have been sveral times I have had a truck tail gate me. Later, Erik Fruits
Erik Fruits <stiurf@yahoo.com>
Wilson , NC USA - Monday, October 06, 2003 at 23:32:08 (PDT)
3 more points. The first one can also be handled by leaving space as you've already covered: I've noticed most car drivers stop when they should slow down. This has to do with lack of foresight and delayed human reaction time. Looking at least 2-3 cars ahead for slow-downs ahead can help eliminate this problem because you'll know to slow down earlier. Also, when stopped (in stop-and-go traffic) looking ahead and starting slowly and obviously when the car that is 2-3 spaces in front of you starts to move can help you. Your movement (attentive inching) can sometimes give the stopped motorist in front the "hint", and they start moving earlier. This works for traffic lights too. I heard that in France some traffic lights blink yellow (or green) before changing to green. This gets most drivers' attention and they start moving almost synchronously. I'd like to see this done in the U.S.A.
John C
Rockville, MD USA - Thursday, September 11, 2003 at 20:56:59 (PDT)
Thank you so much for these insights. I have wondered about the same concepts in passing, but this site's full discussion adds a new understanding. I will be taking Driver's Ed in October, and getting my learner's permit in April 2004. I now plan to use these techniques in my everyday life eventually. Thanks again!
NC USA - Monday, September 08, 2003 at 21:45:20 (PDT)
I blundered onto your site from Slashdot. Very good analysis of the traffic problem. I have a daily commute of about 30 miles to Manchester some of which is on road, some on motorway. I observe the behaviour you describe daily and have found that similar behaviour to what you describe really works. I started doing this as I hate stop start lines and think the chances of accidents are much higher in these events. I find that to make a difference, If I can slow down very gradually the cars behind me go into a pacified mood and evenly space taking my example. If I forget and speed up, closing a gap, then the traffic behind does likewise and all three lanes get more busy as people hunt for the faster lane. I find that in general about 3-5 cars will carry on following me in the morning even if the next lane is 10 mph faster. Possibly a confidence thing going on in their mind and would rather follow than weave between Lanes. Will be interested to hear if any police forces in the US start applying any of the methods you have tried. I did some mind experiments a while ago and figured that rolling regulation of dense traffic should be possible. It would be interesting to do an estimated financial analysis in terms of cost vs savings if police did employ this technique.
Richard Price <richardprice@lineone.net>
Halifax, UK - Wednesday, August 27, 2003 at 02:34:23 (PDT)
Okay...but how do you create a space in front of you, when as soon as you leave enough space for one car, someone in a hurry cuts you off and fills it? Then you back off and leave space and someone else cuts you off and fills it? It seems that all you would really accomplish is allowing many people to cut you off, thereby impeding your own progress... How's this. One day while returning to New London, CT from Hartford, I turned the cruise control on at 65mph as soons I I left Glastonbury on Route 2 (where the traffic finally opens up.) Two vehicles immediately zinged past me to rush forward-a white hyundai and a red toyota pick-up truck. Half an hour later, in Waterford, CT (nearing home), I was stopped at a traffic light just after exiting the highway. One of the vehicles, the Hyundai that had sped past me 30 miles away in Hartford, was in the lane to my left, and only one car ahead. I looked behind. There was the other vehicle, the Toyota truck that had sped past me upon exiting heavy traffic in Hartford. So, their excessive speed had gotten them nowhere, fast...
tony <baldwinets@lycos.com>
New London, CT USA - Tuesday, August 26, 2003 at 17:53:14 (PDT)
Your ideas about traffic are very similar to my own, but I came to the same conclusions through a different route. Mine are based on manufacturing simulation, in which a statistical model is built of some process. A good model includes the variation of the process, not just average numbers. What you've observed about traffic, stated in terms of a statistical model, is that variation in speed (velocity, really) is the cause of traffic jams. This is particularly clear when driving along a stretch of freeway that has a number of small hills. Traffic builds up going up the hill but completely clears coming down. After the first hill it seems like the traffic should be clear the rest of the way, but it's not - it just collects at the next hill. The problem is not that *everybody* goes slower up the hills; it's that *some* people go slower, which causes others to step on their brakes, change lanes, and so on. All of this compounds the variation in speed and makes the problem worse. Traffic is a system which includes the behavior of the people involved in it. As you've noted, if we change people's behavior, we'll change the traffic patterns. You may be interested to know that your idea of slowing traffic by using a highway patrol car is being used in southern California near Knott's Berry Farm (probably other places as well). I've been through that stretch of freeway several times; a patrol car drives back and forth across the lanes, slowing traffic down. I've never been stuck in a jam there (always with normal traffic conditions), I've just gone slower. I read through some of the other comments and have to say that increasing capacity will not always solve traffic problems; it's certainly not the cheapest way to do it. In particular, adding one lane to a jammed freeway at a hill may not help. It would be cheaper and perhaps more effective to slow the traffic down or maybe to hand out tickets for driving outside a certain rather tight speed range. Of course, you'd have to hand out the tickets well after the point of the problem :=) For anybody interested in a rather common sense discussion of problems introduced by variation, try reading "The Goal" by Eliyahu Goldratt (a physicist turned manufacturing engineer). It's more of a novel than a text book.
Bob <bob.kannon@excite.com>
Encinitas, CA USA - Monday, August 25, 2003 at 18:30:03 (PDT)
Let me first start off by commending your site. Your site is one of the most insightful sites that I have read. Keep up the good work. I am originally from New York and just moved to the Seattle area recently. In the two weeks that I've been here however, I have noticed two things about Seattle roads that seem to cause the traffic plugs more often than when I was in New York: (1) The numerous number of left lane exits and merges, especially on I-5. Cars are continually jockeying from one side of the road to the other in order to make their exits, as a result slowing down the cars behind them. (2) The excessive use of braking on the expressways (or freeways as you call them here). I don't mean to complain about Seattle drivers in general, though I've seen many occurrences where cars will brake to slow down even when there are 10 car lengths in front of them to the next car. This is especially true during slight bends in the road where just releasing the accelerator is sufficient. I've noticed that cars that brake will cause cars behind them to brake even more since they see the brake lights, with the result being the traffic plugs you describe. The suggestions on your site are especially helpful in relieving this particular situation. Thanks for the great site!
Clyde Law
Redmond, WA USA - Wednesday, August 20, 2003 at 13:32:14 (PDT)
Very interesting to come across your web page on traffic dynamics. Up until Aug 2002 I lived some 15 miles North of London, UK. For 3.5 years I had to commute to my office South of London, a 150 mile daily round trip. My daily drive usually took between 3 and 4 hours total (incl to and from). I observed many of the wave effects mentioned. The M25 motorway encircles London, and my journey took me on almost exactly half of it. I used the East half despite having to spend ?1 each way at the Thames toll crossing, because the traffic is much worse on the West side (around Heathrow airport etc). Along much of the busy Heathrow section they have variable speed limits displayed prominently on overheard bridges every few hundred yards. The idea is precisely to smooth flow, preventing waves and congestion and junctions. Not sure if anyone pays any attention though. I am ashamed to make an admission, in fact should not be saying this here... there's another benefit to driving at the average speed and leaving nice gaps in front of you, other than the social benefit of deleting waves. If you take a book or magasine with you, and drive slowly and smoothly with a nice big gap, you can read while you drive in the traffic jam! NOT RECOMMENDED... One eye on the road and one on the magasine works Ok at low speeds. Many drivers seem to think the fast lane is still faster than the slow truck lane even when the whole thing is barely crawling along. The fast lane is usually more congested because of all the desparate drivers blind to the reality and because of this it's usually quicker to fit comfortably in between two huge trucks than stress with the rest in the fast lane. The accelleration and braking of your typical freight vehicle are also so slow that they automatically create a wave deleting effect of their own. Plus there's the added advantage that if you're reading a magasine, the looming truck in front of you is a lot easier to spot out of the corner of your eye. In 120,000 miles I never had an accident while crawling along with my magasine/book - I read almost the whole of the Lord of the rings like this... but I know it's wrong and I shouldn't have done it. Fortunately now I live a mere 2 miles from my office and if my journey takes more than 7 or 8 minutes it's a bad day.
Hans Summers <Hans.Summers@Tudor.Com>
London, UK - Tuesday, August 19, 2003 at 05:44:39 (PDT)
a comment to your state trooper idea: They do that sometimes here in California, A highway patrol will swerve back and forth between all lanes with his lights on keeping traffic slow. I had no idea why the hell he was making me go less than the speed limit so I called my step dad who was a cop and he told me it was to fix traffic conditions. They do not do this too often, and I am not sure why they do it sometimes while most times they dont, or what the criteria to do it is, or if maybe its only in a certain location. What I do know is they figured it out too. Figured you might like to know that. -Jeff
krzee <krzee@ircpimps.org>
Petaluma, CA USA - Wednesday, August 06, 2003 at 02:35:44 (PDT)
Great site and a lot of food for thought, especially for a daily commuter who hits 2 of the worst 18 bottlenecks in the US (I-95/495 and I-95/Rte 1). I definitely agree with your observations and conclusions, especially having practiced some of the 'traffic-eating' solutions myself!

A parallel occurence you might find interesting that exists in military marches, aka the accordion effect. My credentials are I am currently in the military and have hiked hundreds of miles in large formations. The military 'solution' to hiking traffic (usually occuring with an injury or when approaching steep terrain, bottlenecking bridges, etc.) is to have each man (or woman) 'keep it tight'. Anyone who has humped (military term for hiking with a pack) knows the worst place to be in the formation is at the end, because keeping up with the tail end of the accordion means going from a complete standstill to an all out sprint to catch up with the traffic 'wave' that is travelling all the way back from the front. Why is this a problem? Drivers coming out of a traffic wave just push on the gas a little harder to resume normal speed, but when you're on foot, it means you must do an all out sprint to catch up with the rest of the formation. Recruits are ordered by their drill instructors in basic training (at least in the Marine Corps) to always keep an arm's length of distance between yourself and the person in front of you (simulating the tight spacing of vehicles in traffic). Any large gaps would instantly arouse the ire of a drill instructor, who would order the recruit to 'tighten it up' in a full out sprint. That would cause the recruit behind THEM to sprint as well, and so on, and by the time the gap 'wave' passed to the end, some recruits were running several dozen yards to 'keep it tight'. When an injury/bottleneck/slowdown occurs in the front, it makes nearly the ENTIRE formation come to a stop in a huge accordion-like fashion. When I was in basic training and was paired up with an experienced infantry marine, when gaps occured we would hasten the pace a bit but not break out into a run. By doing so we slowly closed the gap and sometimes 'ate' the traffic waves coming backwards as a result of recruits in front of us crashing into each other as they went from an all out sprint to slowing suddenly to a walk (again, simulating stop and go traffic in a tight flow). The slow closing of the gap allowed the formation behind us to stay together but it didn't screw over the guys at the end who would have had to 'eat' the biggest part of the gap 'wave'. Some units have caught on to this and normally will leave large gaps (several hundred feet or even meters) between units on the move to accommodate for this if the hump involves large numbers of people.

It took some courage to maintain a hump gap (especially with DIs yelling in your ear ordering you to do otherwise) just like it does when you leave large gaps in front of you in highway traffic, but through trial and observation I know it WORKS. Keep up the good work!
washington, dc USA - Monday, August 04, 2003 at 00:58:51 (PDT)

Peace be unto you
maga <mugu@maga.com>
NY, USA - Saturday, August 02, 2003 at 12:04:35 (PDT)
The techniques seem to mainly pertain to highway congestion. Is there anything that individual congestion busters can safely do in city traffic with all manner of stoplights, cross streets, driveways, and parked cars?

[ I've seen articles pointing out that in inner-city driving, cultures with extremely aggressive drivers have fewer traffic jams! So apparently the best philosophy for city-grid driving is opposite of the best philosophy for driving during rush hour on highways. - billb]

You mention that stoplights are better than 4-way stop signs. An idea that is catching on now in the US is the modern roundabout. The relevant feature of roundabouts is that cars spend less time stopped. (They have yield signs, not stop signs and no stoplights.)

You mention signs with light displays, where the speed limit can be changed at any time. Ramp meters and variable speed limits controlled in response to traffic conditions are among the techniques advocated by physicists to prevent or disperse congestion. As you point out in a couple of places, it is hard for an individual to know whether their efforts to improve traffic are optimal or even whether they are doing more good than harm. What helps in one place may make things worse elsewhwere. Theoretically, with sufficient information about area-wide traffic conditions, these decisions could be automated. (I'm not sure how a few speed limit signs could maintain the desired space between cars though.)

Your discussion comparing people in traffic and molecules in a fluid, says that molecules are all alike and that maybe people tend to act alike in heavy traffic. Well, molecules aren't really alike: They vary in energy level. Then again, there are astronomically more molecules in a fluid than people on a highway. And I would suppose that the percentage of a fluid that is molecule (versus empty space) is tiny. (The molecules are all congestion busters). In short, I think the fluid analogy could use some work. (Don't look at me!- I'm no physicist.)

Thanks for such a good site. This is what makes the internet so great!
Jerry Bridgman <jerrydenise@juno.com>
Madison, WI USA - Wednesday, July 30, 2003 at 00:19:36 (PDT)

Leaving space and letting people merge is good advice. It surely would help if people here in LA would take this stuff to heart. Unfortunately the first thing you learn here is to NOT use your indicator before changing lanes, as this will cause the gap you have been aiming for to close immediately. I'm originally from Germany and German drivers are famous for being aggressive but here many people are more than rude they are psycho. Took me months to get used to it (as far as one ever can).

Another factor you should point out is that stop-and-go traffic is a major source of air pollution (another thing that LA in abundance besides traffic jams). Smooth traffic wastes far less gas and greately reduces vehicle emissisions compared to repeated acceleration and deceleration, especially if everybody is driving ridiculously heavy trucks and SUVs. Additionally, leaving plenty of room and not shoving your air intake into somebody else's exhaust pipe will make breathing in your own car so much easier.

So, regardless of wether it actually does improve traffic flow (of which I'm quite convinced), leaving space will save you nerves and gas (<=> money), reduce your risk of accident, help the environment, keep you out of other peoples ehaust cloud and generally make the road a less nasty place to spend time on for everybody. I guess that's good enough to give it a try.

Thank's Matt, have a good drive.
Franz <trax_s@hotmail.com >
Los Angeles, CA USA - Saturday, July 19, 2003 at 03:21:46 (PDT)

The only way to alleviate traffic through a change in driving philosophy is for all drivers to go FASTER. [But everyone in the jam already wants to go faster. Why don't they? Simple: there's someone ahead of them who also wants to go faster but cannot. All of us are in the same situation. OK, so go look at the very the start of the jam. What's the big hold-up? Often it's caused by turns-taking at congested merge zones. Or perhaps it's caused by a "traffic standing wave" which has become pinned in place at a hill or at a turn. Drivers can't go faster, there's various sorts of "traffic plugs" blocking them. This website is about these plugs, and about ways that individual drivers can unplug them. Driving faster (or just trying to drive faster) seems to trigger the Three-Stooges doorway effect; it seems to be the cause of traffic jams. It makes drivers close up spaces, which triggers traffic waves and prevents merges. Ease off, give space, and see if you can unplug a major stoppage singlehandedly. (It's certainly possible, I've done it myself.) - billb] If each car travelled twice as fast there would be half as many cars on the road at any given time. It's a matter of velocity and pressure, greater speeds and greater distances between cars. Your proposed solution would make it imposible to get to your destination any faster, the rate determining step is the driver infront of you, who has not changed behavior. Plus you are being kind enough to let a mile of merging cars infront of you, so you can only expect to get to your destination slower. The drivers behind likewise can only expect to arrive later unless they pass you. The simulation you cite is flawed since it is only simulates a half mile highway, what about the endless miles of congestion that exist in real life? [But what if the simulated road was much longer than you're visualizing? In that case something amazing happens: it still acts the same! Doubling the length of the road does not make the traffic waves behave differently. And unplugging the stoppages always causes traffic to speed up, regardless of how long the road might be. - billb] The only relief is getting the clog off the road, in other words, getting the cars to their destination faster. The simulation only needs to get a half mile of clog off the road, which is not difficult. The only solution is to lower the pressure of the system, which means drive as fast as you can. The faster you get your car in the garage, the faster there will be one less particle in the pipes.
Keith <kclemens@hotmail.com>
LA, CA USA - Friday, July 18, 2003 at 18:19:07 (PDT)
hey there...loved the spot on traffic jams. can you preach the gospel to LA drivers? pretty please.

i've actually been practicing the "lubricant particle" driving for years, and it works like a charm...plus i won't get tendinitis in my wrist from having to shift gears so often. cheers.
jonnie5 <jonatmudd@yahoo.com>
pasadena, CA USA - Thursday, July 17, 2003 at 13:30:24 (PDT)

A colleague of mine who used to commute some 30 miles each way to work along the oft-clogged 128 highway in Metro Boston used to refer to this as the "water hammer" effect, which is pretty much the same analogy you are using, only in a different vernacular.

On a related note, I am curious your opinion on a (perhaps?) related phenomenon. I commute home on a different highway, Rte. 3, which at one stretch is heading pretty much due west. There is often a "solar slowdown" in this stretch, as people slowdown presumably becuase they are momentarily blinded by the sun directly in front of them. The thing is, this slowdown occurs even on overcast days. Is this just a force of habit among the regular commuters?
Mark Timmins
- Thursday, July 17, 2003 at 13:05:04 (PDT)

The equivalent of a rolling barrier of state troopers is the system that is applied in the Netherlands on major highways with lots of traffic. There are overhead panels that can show varying information, including actual speed limits. When it is crowded, the panels will show a lower speed limit, which decreases even more when a traffic jam is near. Since these limits are stricly enforced (radar), people stick to these limits. Complete jams are avoided, there are just long lines of slow-moving traffic.
Renate <renatew@xs4all.be>
Belgium - Thursday, July 17, 2003 at 01:37:18 (PDT)
I was delighted when my husband sent me the link to your page about traffic waves. I grew up in a rural area in Virginia and never had to deal with traffic problems simply because everyone was relaxed in their driving habits. Having recently moved to the Washington DC Metro area, I am astounded at the idiocy displayed on a daily basis by the drivers in this area. The first time I drove on the Capital Beltway, it took years off my life- people rushing to fill the gaps in front of them and then slamming on their brakes and causing traffic to squeal to a halt. I drive a manual transmission car, so needless to say I can't drive like that and expect my transmission to last. I have observed the same types of behavior when I let large gaps open up in front of me. Yes, there are the people that immediately rush to fill in the gap, but they usually don't stay very long, seeing another gap in a different lane that they can rush into. I just back off and let more space accumulate. It saves wear and tear on my car as well as my mental wellbeing!

Thanks for your site- it was refreshing to know that there are people out there who are aware of the problem and know how to solve it. I wonder if there is any way to educate the public of the DC metro area... hmm.
Jessica C
Purcellville, VA USA - Wednesday, July 16, 2003 at 11:04:40 (PDT)

These are very interesting observations and I'm anxious to try them in my own commutes. Atlanta's traffic is awful to what is becoming legendary degrees and I'm intrigued by the possibility that a very small percentage of cars on a busy interstate might be able to "lubricate" the whole road with this technique.

I'm also thinking of how nice it would be to leave my gearbox more or less in one gear (2nd?) in order to maintain a constant speed.
Atlanta, GA USA - Wednesday, July 16, 2003 at 10:38:24 (PDT)

Great site.
Here in the Netherlands they have done experiments with state troopers that slow down traffic. They just start to ride on the middle of the road, keeping all other traffic behind them. This effectively enforces a lower speed limit on that road. This increased the throughput of the roads in question by a noticable margin by reducing the traffic jams greatly. It works.
Martijn Lievaart

Martijn Lievaart <m@rtij.nl.removefromhere.invalid>
De Bilt, Netherlands - Wednesday, July 02, 2003 at 08:05:37 (PDT)
It's nice to see such a comprehensive treatment of this, but it really is nothing new. The "fluid dynamics" of traffic flow has been around at least as long as the National Traffic Laboratory, and anyone who drives on motorways with any frequency knows how to keep things moving.
[Actually, this stuff is cutting-edge research, only discovered in the late 1990s: chaotic dynamics of particle flows applied to auto traffic. In fact, many traffic engineers apparently hate the new ideas because they're brought in by outsiders (by physicists rather than by traffic experts.) Much older research treated traffic like plumbing. It's not. Many nonlinear phenomena were noticed, but not explained until very recently. See the article on the links page, especially in 1999 Science News for more about the new science, and especially the part about the politics and the resistance to the new traffic concepts. And as for drivers already knowing how to keep things moving... I don't believe you. I've been driving for decades, and I never heard ANYTHING about any of this. A few truckers know about it, but drivers in general do not. If drivers knew how to keep things going on congested highways, then we wouldn't all participate in creating traffic jams! If you think it's well known, then just point out some older articles about traffic smoothing and un-triggering of traffic jams. (I suspect they don't exist, but I'm happy to change my mind, and I'll add any articles you find to the ones already listed on my links page.) -billb ]

I noticed your suggestion of a barrier of State Troopers to maintain an average speed rather than stop-go. While I doubt many places have the police resources to do this every day, the principle is used on much of the M25 (Britain's most famously overcrowded motorway). They have cameras to monitor the traffic, and variable speed-limit signs (large dot-matrix displays) that are set at the right speed for the conditions. Exceeding the limits on motorways is the norm here, so I didn't expect this scheme to work when I heard about it, but they put up large boards explaining how the variable limits would speed up everybody's journey, and asking people not to change lanes unnecessarily, and by and large the regular drivers seem to have got the message.

As someone who only drives there from time to time, it's tempting to zoom ahead into the space that's empty as far as we can see, but when most people are obeying the variable limits (in a way they'd never obey the ordinary ones) and we know that it's preventing a huge jam just round the corner, it all seems to work.
UK - Wednesday, June 25, 2003 at 17:12:55 (PDT)

inspired. i've had similar thoughts as to teh wave nature of traffic, but have never been able to put it in these terms. is there any way to connect with traffic choopers to get video of this perhaps? as well as an experiment with a car creating a gap? maybe set it up with a local tv station?
alex <the_leaking_pen@yahoo.com>
mesa, az USA - Wednesday, June 25, 2003 at 09:17:19 (PDT)
Some information I've come across over the years. The "wave" effect you are talking about has been known about, by the military, for a long time; probably as long as there have been marching armies. It is called the "accordion effect." It occurs in columns or convoys. the military's only solution was to tell every soldier/driver to pay attention to the gap between himself and the next soldier/vehicle. Didn't work. If you were at teh end of a column of 125 marching soldiers or 15 vehicles, you would sometimes have enough time to take a smoke break, then you would have to run/put the pedal to the metal to catch up.

The "accordion effect" is caused by slight differences in slowing down/speeding up, multiplied by each person/vehicle in the column/convoy.

The was recently an article by some German traffic engineers who studied the psychological phenomenon that causes traffic jams even when there is plenty of room and no distrctions.

There is also another phenomenon that was described by California Highway Patrol officers, called "wolf packs." Drivers seemed to speed up when the freeway was clear until they encountered another car. They then slow down slightly and follow the traffic ahead until a "wolf pack" forms with long stretches of clear freeway in between.

None of these articles had any good solutions except to suggest that drivers try to maintain a steady pace and the standard one car length gap for each 10MPH, which, we know nobody ever does.

since the "accordion effect" hasn't been solved by the military in thousands of years, I don't see much hope for a solution short of automated vehicle control which is probably a good many years off.
Irvine, CA USA - Wednesday, June 25, 2003 at 08:06:02 (PDT)

Great Site! - I have been practicing your techniques on London's Orbital M25 for some time (but from next week I may never have to again). Yes it has Variable Speed Limit signs and Yes they are enforced with Speed Cameras but what tends to happen is rather than imitating the 'rolling roadblock' effect they imitate the 'frequently spaced car wreck' effect. What I mean is people drive faster than the current limit until the moment they drive under the sign and associated speed camera whereupon they slow down and then (once they are out of the trap zone) they speed up again. This exaggerates the stop start. If only people would realise that the speed limit applies to all the road and not just the bit under the sign!
P. Smith <karnuvap@netscape.net>
London, UK - Wednesday, June 25, 2003 at 05:43:28 (PDT)
Hey, I discovered another one! In my neighborhood there's a common situation where a single driver can double the traffic flow by flipping an "invisible switch."
During morning rush hour there's a 4-way stop sign which becomes severely clogged. Frequently the people each take turns in clockwise or counterclockwise order. While sitting in line I realized that TWO cars should always go at once, yet politeness demands that nobody steal a turn and proceed early. Ah, but we can always go backwards: slow down and give away one turn. So... when people at the 4-way stop are each going one at a time in CCW or CW order, when it's my turn I refuse to budge, and I wave the person through in the cross street. Then I take my turn, and so does the person facing me. Then both people in the cross street take their turns at the same time, etc. By becoming a "big loser" and giving away my turn, I've just converted the 1,2,3,4, pattern into a 1,2 pattern and doubled the traffic flow! (But will the pattern persist? Yes, I think it will last for awhile until those turning right/left mess it up, or until a large gap arrives in one of the lanes and politeness forces everyone to start up the 1,2,3,4 pattern again.)

Bill Beaty <>
Seattle, WA USA - Wednesday, June 18, 2003 at 16:34:59 (PDT)
I've been playing with some of these methods for the last 3 years or so in Minneapolis, and it's nice to find that I'm not the only person (or the first) to think like this. The sad part is, whenever I talk to anyone here about leaving space in front of you, they just say "But then someone will just change lanes into that space and you'll have to slow down." So far I haven't been able to get the fluid idea across to people (maybe now I'll just point them to your site). Best of luck!
Steve Gigl <traffic@gigl0002.mailshell.com>
Minneapolis, MN USA - Thursday, May 29, 2003 at 13:27:52 (PDT)
The zipper method works! For many years I commuted 62 miles (one way) from the Baltimore area to downtown Washington D.C. My route took me thru Rock Creek Park, a two lane (no shoulder) winding road with only two intersections (limited additional cars). This is the perfect lab for your experiment and I say it works. The trick is a single line of cars entering the park at the north end and exiting at the south end. Also, the southbound line of cars has a good line of sight to the upcoming merge. It is accepted practice by the locals to zipper merge and this behavior is transferred to the unknowing by example. The long line of sight approching the merge area demonstrates the zipper method to those approaching. Traffic moves at a steady slow pace. This works because access to the park is limited.
Roy Eisenstadt <royezz@aol.com>
Owings Mills, MD USA - Tuesday, May 27, 2003 at 06:20:42 (PDT)
I am 55 and have been driving for fourty years. In the early days many vehicles with dodgy or no brakes. In those days of course Australia had not developed a large system of freeways or motorways so I suppose our driving developed in parrallel with the quality of roads. Not that bad roads did not teach skills but it was necessary to develop skills to match conditions. At an early age I joined the Navy and had experience of driving all over Australia. It is true to say that the conditions and styles of driving in our States varies greatly and it takes some time to gain experience and confidence when travelling from one State or City to another. It is always a good idea to see that the people around you who may be driving differently have a foreign plate so you can make allowances for them and give them room to think.
As a new driver we often allow a large gap behind the car we are following until we find everybody pulling in front you seem to go backwards and the gap always stays too small. Worse still these drivers that pull in have a tendency to brake hard. The problem with this is if you have maintained a large gap and these cars keep pulling in front you must look as far ahead as possible in your land and react to the cars way up ahead. If you wait for the car in front of you to see the car in front of him stopping in a hurry, it will be too late as he will jam on his brakes and you will be at fault. Also the damage can be quit substantial. On the other hand if your bumper is touching the car in front and you brake on his lights there is less chance of contact being made and is so it will only be minor.

A few years ago I was in England travelling through Birmingham on the "spagetti" junction where a large amount of traffic merged in a major set of intersections.I was amazed that both at a.m peak and p.m. peak the traffick did not stop but rolled along at a steady 10 to 20 MPH. This may be in part to the drivers courtesy, and you must always give praise in the area when due as it creates a pride and need to improve. But also that the off and on ramps were all in the outside lane and that the law states that it is an offence to overtake on the inside. The law is the same in Australia with the rider that all vehicles must travell in the left lane. Which is stupid when three lanes are provided so this lane is ignored by law enforcers as well as the undertaking law. If however you get into the "inside" lane and plant your foot you are unlikely to be held up by those squabbling in the inner lanes. The other thing to do is get in your off lane as soon as you can and stay there.

I used tyo live twenty miles from work and start time was 8 am. Ususlly because of traffic I was an hour late so after a number of years I left home an hour later and got ot work at the same time. I left an hour gap in front and working the extra hour after work had tyhe same result. Anyway twenty years ago Idecided that I did not want to send my life like this so found an alternative, with less money but I was just as well off. Anyway you made the anology with water I would like to make a comparison with a column of marching troops. The romans did it and untill recently modern armis have done it. Squads of about 50 to 100 troops marching at about 50 or more paces were kept on the move by using this space in between as a buffer. The reason being that exhausted troops on the march upon reaching a jam would stop and lay down or generally become totally disorganised, but when allowed to put one foot in front of the other they would march forever. I had a experience in the Navy at a march past when strangely enough the right hand marker of one group was hypnotised to stop when ordered eyes right. There was a huge pile up and at least one serious injury. It would have been much worse if there had not been a reasonable gap between groups. My query if not comment is have you considered the case or marching soldiers. And if it was possible that in theory no car on the freeway could overtake another and remained parallel and that at stoppages or lane blockages alternative access should be provided with the right side car having first priority.

Apart from this Iagree with you in every respect and anyone who disagrees lacks true road sense. I know it works or at least it used to for me as in the end I gave up the contant struggle of fighting everybody on the road. I now gesture for people to pull in front and leave a huge gap in front whilst maintaining a reasonable speed. Which is deliberately below the speed limit. One problem with this is the tendency to day dream which is just as dangerous as speeding. When deliberately speeding you are living on the edge and tend to be more aware of external circumstances but if you speed all the time you tend to become far too casual. The biggest bogey in the pack is road ragers and as they are becoming more and more persistant I would suggest let them pass or turn off out of their way as soon as possible. No doubt with your analytical mind you could arange for them to self destruct without taking us with them. Best wishes with your work I wish governments were able to undertake such research.......Guy
guy jennings <randall6662000@yahoo.com.au>
PERTH, WA Australia - Thursday, May 22, 2003 at 08:18:40 (PDT)

I noticed something simliar to this, although less rigously and for different reasons. While sitting on 520-West on a Friday night I noticed that it was quite mentally tasking (from a reptition/boredom point of view) to keep accelerating / stopping. Very frustrating. So instead, when the car in front of me accelerated I just let the car idle forward, maybe lightly touching the brake to keep the movement slow. In doing so I was able to let a few car-length space develop, and I was able to idle my way all the way to the bridge. The cars behind me were able to crawl as well. This is a great theory!
Jason Martin <jhmartin@toger.us>
Bellevue, WA USA - Friday, May 16, 2003 at 16:10:02 (PDT)
Interestingly, I noticed this phenomenon before I heard you on KIRO radio several months ago. Your article explains exactly what I was seeing. When traffice begins to build,I simply begin driving with lots of space on the freeway and trying never to step on the brakes. All of a sudden, it was like I was driving in my own traffic "bubble" and I was able to go faster then the lanes around me. The hard part is to keep the space in front and let other cars merge and change lanes as they wish. Often, it seems that a car or two behind me will take the que and we end up with a couple of cars doing the same thing. One time I was with my nine year old son and explained to him what seemed to be happening and he grasped the concept immediately commenting that it would make the "backup" longer and slower but keep moving without stopping. Great stuff, thanks for your observations and articles. By the way, we're about to do one of your electricity science experiments, building a simple generator. I'm not sure I'm ready to take on the "elementary school scientific establishment" with your thoughts on all of the misconceptions taught to the youngest kids.
Dave Russell <davidar1@attbi.com>
Seattle, WA USA - Tuesday, April 01, 2003 at 19:09:37 (PST)
Here is a case where the theory is flawed: A multilane freeway connects to another similar freeway, but only with one connecting lane. Depending on time of day, up to 3 lanes of traffic try to exit though one lane (which includes a 35mph curve). The backup can be 4-5miles long. People who play fair enter the back of the line and spend 30+ minutes to go through it. I can run up to the last half mile and only spend 3-4 minutes in line (thanks to people opening spots as you suggest). Some fpeople merge in the last 100 feet.

It turns out to be a "priority queue" where your degree of selfishness is directly related to a wait ranging from seconds to fractions of an hour. It's unfortunately skewed to reward the selfish behavior that causes traffic jams.
MN USA - Saturday, February 01, 2003 at 03:01:12 (PST)

[Not flawed. In fact this is exactly the situation where a single driver can bust up the entire jam, at least temporarily. We have one of these in Seattle, on northbound I-5 just south of the city at the exit into the northbound express lanes. The jam is only at the exit, and the exit ramp itself doesn't limit the flow. I personally have caused this jam to evaporate about once for every four attempts. Many hundreds of cars in the jam, lined up for miles! Ask yourself why the huge lineup exists. It's because people in the two jammed lanes at the very head of the line are slowly taking turns going out the exit.

Also, ask yourself how can you tell who is a cheater? If that jam has already formed, then any driver who cannot change lanes fast enough to get in the line will be blocked out of the exit lane. It's not like a bank-teller queue, since drivers cannot go backwards to get to the back of the line once they realize that the lineup exists. The people IN THE LINE are selfish, they're packing together and refusing to let anyone in adjacent lanes use that exit. Incoming drivers who need to exit have no choice but to drive to the FRONT of the line, that's the only place that empty spaces exist. (Did you ever try to merge early; merging into the SIDE of such a wall of cars? People behind you will get violent! It takes many minutes for a space to open, so most drivers won't chance it.) In fact, incoming drivers are often punishing the selfish idiots in the solid wall of cars. "If they won't let me in, screw them and their 'I'VE GOT MINE' attitude, I'll just go to the front of the line!" See how the psychology works? Both parties think the OTHER one is selfish, yet they never examine their own selfish behavior. It's called HSelf-serving Attributions." It's a hypocricy standoff.

But by letting twenty or fifty cars go in ahead of me, those cars no longer have to block traffic at the very front of the jam. The so-called "cheaters" are now merging early because I've given them a hole in the solid wall. Hence the entire line drains out at high speed. Once the speeds are high, the entire "cheaters" issue is gone, and everyone can merge easily. This is the way that one car can often "flip the switch" to produce high speed zipper-merge dynamics. This really works, I've succeeded many times. And it shows that the whole situation is unnecessary. When people give up the right to punish others, the jam vanishes like magic! Sometimes it only takes a single non-punisher to burst the jam.

Of course this only works if the jam is causing itself, and the road is clear after the exit-jam. If something far downstream is making the exit itself go very slow, then the jam isn't caused by turns-taking at the exit. In that case it does no good to let extra drivers merge early. I've seen this happen too, but more often it is the turns-taking itself which is responsible for the jam. -billb]

I've had this exact discussion with colleagues at work. My contention has been that traffic must follow simple rules of fluid dynamics. if people were to consciously try to facilitate a laminar flow pattern we would all move more efficiently. Of course i still break for tailgaters. ;-)-
roy <th_royd@yahoo.com>
fresno, ca USA - Tuesday, March 18, 2003 at 20:20:58 (PST)
Thanks for the excellent explaination of traffic phenomena that we've all witnessed. I used to live in Toronto, and made the same "experiments" during my daily 1 hour commute. I came to the same conclusions as you. It's amazing the effect (both plus and minus) that a single car can have, even on a 8 lane highway.

A couple of other thoughts.... I agree completely that the truckers have long had this figured out. I don't know about Seattle, but in Toronto the truckers will often use their size to intimidate "jerk drivers" into not trying to jump to the front of the line by screwing everyone else. I always smile when I see this because I know exactly what they're doing. Have you wondered why truckers universally behave this way? As you discovered, it's not really to help themselves. They can have a large impact, but it really benefits those behind them the most. So why do they do it? It's easy to say that they're helping other truckers who they know are stuck behind them, but I think that's the easy answer. Human nature doesn't seem to support that conclusion. (unfortunately).

[In fact, human nature does support this. It's called "cooperation" or "reciprocal altruism" where I rub your back and later you rub mine. I get no benefit from rubbing your back, but if a network of "reciprocation" develops, then everyone benefits, therefore evolution reinforces the development of such networks. Truckers essentially take turns smoothing traffic for fellow truckers. This sort of thing tends to develop within small tight communities where members trust other members to take turns contributing some effort which gains no immediate reward (but is rewarded eventually.) Truckers are one group. People who read this website are another! -billb ]

My conclusion is that they are helping themselves. How? Because if you were driving a rig that was severly underpowered (compared to our cars) and had to manually shift more than 10 gears to get up to highway speed, you (like I) would be much more inclined to just stick it in 3rd and roll along at the average speed (or a bit less) of traffic. So, this result is selfishly helping the truck driver be a bit lazier, but it has the great side effect of helping to smooth traffic out. What does all this mean? That more than anything else (except that human nature part...), I think the automatic transmission is to blame for the bunching up of cars that occurs.

Our cars are, relatively speaking, so overpowered, and the brakes are so effective, that we can just "stand on the gas, then stand on the brakes". This requires very little effort from us, and makes us feel like we're going to get there sooner by doing it. Try driving a stick in traffic (I do) and watch how your driving behaviour just naturally changes as a result (it's in your own interest, since otherwise you'll blow out your clutch knee). Plus, in a standard, we get the benefit of more "engine braking" which allows us to slow down somewhat without using the brakes. This has a secondary "psychological" benefit as well. If the driver behind you sees brakes lights, what's the most likely response going to be? He's going to brake as well, but with just a bit more vigor that you did. And the driver behind him will do the same thing. Ten cars back, we're at a dead stop again. Anyway, thanks again for putting this writeup together. We can only hope that enough people will read it that we will start to have a mutually beneficial effect.

Greg Holloway Vancouver, BC
Greg Holloway
Vancouver, BC Canada - Thursday, March 13, 2003 at 21:30:48 (PST)

Mr. Beaty, you are a god. What a wonderful site. Please take care of yourself and get out for some exercise. If you're in SB sometime, I'll buy you lunch.
goedon <suntaog@yahoo.com>
santa barbara, ca USA - Wednesday, March 05, 2003 at 22:08:14 (PST)
In traffic up to moderate levels, it seems that the most throughput will occur if drivers allow faster cars to pass on their left. As traffic increases, there's probably a point where the theories described in this site apply to all lanes. I encourage you to expand your study to address the "passing lane effect".
Private Krankenversicherung Vergleich
Houston, USA - Tuesday, March 04, 2003 at 08:56:54 (PST)
nice site!
Like other folks have said- been doing this on my own innitiative for years. Despite your affirmations, I do not believe it saves me time. In one case, it loses time. [Mostly it only saves time for the people behind you. If people won't help each other, then traffic jams get worse for all. - billb]

Coming into Boston on I90 new traffic merges in from the right, as on most highways. I90 ends in a three-way split with right and left bottlenecked getting onto 93N and 93S. The left lane is slowed worst. Downtown traffic is center lane, and should move freely but instead acts as a "cheater lane". Mean traffic velocity of less than 20 MPH.

Staying right or left yields no personal gain except fuel economy. Acting as a speed regulator in the ceter equalizes flow behind, but is too inviting for bordeline cheeters on right and left.

Gains for the innies and outies behind convert to losses for myself and my traffic tail.

I do it anyway because I enjoy being contrarian.
Kevin MacKay <kevin_mackay_12345@yahoo.com>
Boston, MA USA - Thursday, February 27, 2003 at 11:30:39 (PST)

Fascinating stuff! I haven't had chance to read in detail but does all this deliberate modification of traffic flows actually get you to your destination sooner? I suspect it may but I think that this is where the benefits of flow ideas (which I think are actually well known in some statistical and maybe other circles) will show their real value! I notice here in the UK where three lane motorways are the norm, the the nearside (slow) lane frequently has becomes an "eddy" i.e. the traffice moves faster in that lane when you would think it oughtn't to! I also believe that people cruising in the middle lane are the triggers for many of the "volume congestion" caused slowdowns. INteresting stuff!
Max Blinkhorn <maxblinkhorn@hotmail.com>
Edinburgh, Scotland - Thursday, February 27, 2003 at 06:09:08 (PST)
I'm very impressed, your theory is well thought out and makes a lot of sence. Doing the same thing on major sydney highways has some very impressive results, thankyou.
Frogbert <frogbert@N0SPAM.host.sk>
Frogbert Land, FL Australia - Saturday, February 15, 2003 at 02:51:06 (PST)
I have independently come to the same conclusions regarding traffic waves and always try to drive without using brakes. Most drivers stay too close to the car in front of them and as a result have to slam on their brakes when they see brake lights in front of them. Also, I think the wave theory applies to interstates between cities. I have noticed on highway driving that I am more often passed by "waves" of vehicles rather than random single vehicles. ]
Mike <mkillian@swbwell.net>
St. Louis, USA - Friday, February 14, 2003 at 19:37:44 (PST)
How do these techniques affect actual travel time? i.e. if I travel 1hr at a constant 40 mph (polite/no waves) vs. 45min at 50 mph and then 15min at 10mph (with waves) I still travel 40 miles.

Sure, less wear and tear on the car and better fuel consumption and less headaches (so therefore worth it regardless), but is there also a time savings, and what parameters affect that? Cool site!
A <mojoandy@yahoo.com>
CANADA - Friday, February 14, 2003 at 08:51:33 (PST)

[ 20% to 30% speed gain in the simulations. It's answered in the FAQ Section. - billb ]

I can't begin to count the number of times I've had to "go around" over the years in my mission to help stranded motorists because the vehicle behind me was following too close for me to be able to stop safely w-out ramming the vehicle I'm stopping to help!

When this happens, I abort the attempt and "go around" to reapproch, and THEN, knowing in advance where the disabled vehicle is, I activate my strobes and beacons on approching the spot.

You wouldn't BELIEVE the number of inattentive or just plain STUPID drivers who don't back off even THEN!!

Anyway that's my two cents worth. I LOVE what I do and won't stop doing it until I don't feel confident in my ability to do it intelligently. [ means NOT getting KILLED doing it! ]
The Highwayman <SNOWtraction@aol.com>
San Diego, Ca USA - Wednesday, February 12, 2003 at 11:59:11 (PST)

Great site. I've been noticing the same thing for years as well. And driving that way, much to the chagrin of the people behind me who look to be thinking "I can't believe this a##hole isn't rushing to fill up that 10 carlengths in front of him. He's making me late!!"

Most drivers are too self-absorbed.

I look at traffic as a flow, akin to a river. Others seem to see it as some kind of race. Ironically, its a race that can't be won. This coming from an owner of fast cars that loves to race. On the track that is.

I find that keeping my speed to the average is far less stressful on me and my car. It is funny to watch the 'jockey-ers' jump into my space thinking they're gaining something. The jump onto the the bumper in front of them. Why is it usually SUV's doing that?

Good site man.-
Roy S. <badcam@hotmail.com>
Baton Rouge, LA USA - Monday, February 10, 2003 at 11:56:29 (PST)

I saw a TV program about 'ghost jams' a few years ago. They interviewed the traffic cops responsible for policing the M25 (big freeway that orbits London). They said that these ghost jams could develop for a number of reasons. They could be the after-effects of an accident or a real traffic jam from hours before. The ghost jams do move like waves. At any time they could see several of these on their instruments at the control center. Their advice was pretty much as you stated - to stay cool. When you hit heavy traffic & it seems to clear up, accelerate gradually. Most of these jams could be cleared up if everyone just drove at a steadier pace. Its the stop-start response of people that causes repurcussions for miles behind. They showed an example of someone changing lanes to gain a few feet causing dozens of cars to brake. It was an interesting show that seemed to correspond with my experiences.
Dave <west.d@attbi.com>
Portland, OR USA - Saturday, February 01, 2003 at 13:50:18 (PST)
Your cause is futile. Most people are too stupid to live, let alone drive.
LA <landea@qwest.net>
Chandler, AZ USA - Friday, January 31, 2003 at 21:42:04 (PST)

[Read the article. In certain situations ONE SINGLE DRIVER can fix the problems caused by hundreds of others. If you don't want to make the world a better place, well, there are a few others out there who'll take on the task. -billb]

"Q: Traffic is not like air in a tube, because drivers have widely varying behavior, and air molecules do not." This is not true. Air molecules DO have widely varying behavior. Study Boyle's Law and fluid dynamics. It's similar in many ways to the physics of traffic. Solitons can be created in air and water just as easily as in traffic. These are all examples of chaotic systems. Traffic has less degrees of freedom than air, actually, so it would be more correct to say "air molecules have widely varying behavior, and drivers do not". That pretty much refutes the entire point of whoever originally asked that.
Chicago, IL USA - Friday, January 31, 2003 at 19:46:35 (PST)
I havent noticed any comments on the financial benefits of traffic- wave erasing. My (limited) knowledge of acceleration is that cars use mush more gas to move from 0 MPH to 10 MPH, than equal accelerations at higher speeds, due to the need to create inertia. Is this assumption correct? If not, what is the relative distance needed to drive at a lower but constant average-flow-of-traffic speed, than to drive at a higher speed and sit for five to ten minutes at 0 MPH? If an average sample car is used as a baseline, can this even be measured accurately? With gas running at .74/Liter (Canadian) I think the math may be worth the trouble.
Felix Wilcox
Calgary, AB Canada - Friday, January 31, 2003 at 12:22:09 (PST)
It's funny, I've noticed this too about traffic waves, but for a different reason. I ride a motorcycle pretty much everywhere I go, and I sometimes like to play a game to improve my traffic judgement skills. It's a simple game:

Never put your feet down (except at stops signs where required by law).

The trick is to look ahead at traffic (stop lights, traffic jams, merges, rubberneckers, etc...) and choose a road speed which will prevent me from ever having to come to a complete stop. So if I know a light ahead will take 10 seconds, I'll slow down so it will take 10 more seconds to get there. The same with an evaporating traffic wave.

I have been doing this for years, essentially for the hell of it, and until I read this site, I'd never bothered to notice that I was also keeping those traffic waves from propigating back behing me =:-) -lars
Lars Friend <larsfrnd@light/*nospam*/link.com>
Ithaca, NY USA - Thursday, January 30, 2003 at 11:57:46 (PST)

Very interesting and entertaining web site. Every time I have to drive south through all that Everett/Seattle/Tacoma I-5 mess, I'm reminded agian why I live out here in the sticks instead of in the middle of that urban sprawl. Hey, an easy way to avoid most of that nasty traffic mess is to only drive the Everett/Seattle/Tacoma I-5 corridor between 2:30 am and 3:30 am. At that hour, with the drunks coming home, gang-bangers, drive-by shootings, street racers, and car jackers, snarled traffic is the least of your problems. Happy motoring, Seattle!
Bill W. <Firemarshal.Bill@verizon.net>
Oak Harbor, WA USA - Tuesday, January 28, 2003 at 16:39:51 (PST)
Very interesting insights but the goal should be to get rid of the imbalanced volumes that occur during rush hours. Volumes at or near the capacity of the highway will usually result in severely slowed or stopped traffic. If you avoid commuting during the average peak times of 7:00 to 9:00 and 16:00 to 18:00 then you can avoid the slowed traffic. More companies need to adopt staggered start times as volumes progressively increase. Either that or DOT's will have to start embracing more mass-transit solutions.
JJ <jimmyjay86@hotmail.com>
Detroit, MI USA - Tuesday, January 28, 2003 at 13:10:32 (PST)
I agree with the theory you have putting state troopers moving at 55mph to give the jam time to clear. However I have a similar theory. Here in Long Island one thing you experience is the huge fear people have of getting speeding tickets. Of course there are police speed traps sitting on the side of the road everywhere here. Even when there is really heavy traffic they are sitting there putting their time in. Meanwhile everyone is doing 25mph. I say put these police cars on the road all the time. Make them drive up and down the highways doing the speed limit. This will force everyone to do the speed limit and regulate the traffic density. This would prevent speeders grinding to a halt when their radar detector goes off and causing a build up behind them. Of course the counties would rather collect the ticket revenue (despite the court costs). But I'm totally convinced it would be beneficial (unless I'm running late) to everyone and reduce the number of accidents on the highways.
dermot <dermotfixgerald@yahoo.com>
hicksvile, ny USA - Tuesday, January 28, 2003 at 07:42:05 (PST)
The best kind of traffic theory, personal observation. It'll beat math and formulas any day. My anecdote is about in-town traffic and merging. The engineers who designed a major intersection here in town were coming under fire for designing a two to one lane merge immediately following a stop light. One of the letters printed in the paper was, "Who was the idiot that designed a merge after a dead stop?" My only reply to that was, "the same idiot who knows that you have to be moving to merge." I go through that light every morning and I see self-centered idiots race their way up into the front instead of taking the gap that I provide and subsequently we all end up stopping. My new answer to the question is, "a person who obviously didn't learn to drive here." And even when I give a person the gap, the person behind him tries to force his way up. Sheesh, no curteosy whatsoever. Thanks for the good read.
Rob <robo451@gci.net>
Anchorage, AK USA - Monday, January 27, 2003 at 18:43:58 (PST)
Great piece of work! I have an adjunct theory that supports your notion of that traffic is better modeled by nonlinear dynamics.

The thing I find fascinating is "turbelence"- especially in the early morning. The early morning think 4-6 AM is filled with cocaine addicts up from the previous night, and people that are slowly waking up after 4 cups of coffee. What I find is that there are several cars looking to break speed records, going for 90 to 100 mph, and others dispersed throughout the lanes (keep right doesn't really exist in the US, does it?) going closer to the speed limit. The fast cars careen throughout the "obstacle course", forcing the net speed to be lower than an hour later, when the lanes are full, and just flowing- the behavior is non linear, and the effect is an increased sense of risk.
George <georoad@yahoo.com>
san francisco, ca USA - Monday, January 27, 2003 at 17:47:04 (PST)

the politeness factor differs city to city. I've heard more than one commentator vote Miami as the "rudest" traffic in the nation. (and i know everyone thinks thier city is especially rude) When 95% of the people in traffic are not just punishers of insane lane changers, but guilty themselves of the same act, the formula seems to break down. The crowd behind me constantly shuffles to make a break for the gap ahead. the "polite" people you talk about never seem to build up behind me. ALSO: when I'm in traffic, i think about traffic waves we'll have in the future with "flying cars" in three dimensions.
todd <nospamlight_speed@hotmail.com>
miaimi, fl USA - Monday, January 27, 2003 at 15:11:19 (PST)
Think about this. What is the best way to alleviate a traffic jam? How about by diverting traffic to non-clogged roads? A national traffic sensor system installed on all freeways and linked to a display in your car or to a billboard display system like the one used to track flights at airports could give real-time updates as to traffic conditions so the jams could be avoided altogether. The traffic jam is alleviated because less traffic is feeding into it as the clog itself dissipates. The only issue with this is in creating a clog somewhere else in a mad dash to avoid the clog in the first place.
James D. Marchant <marchantj505@hotmail.com>
Pearl Harbor, HI USA - Monday, January 20, 2003 at 03:59:58 (PST)
I found your site very interesting. Have you thought about how your ideas grok with Nash's game theory? This seems like a perfect example of it.

You need to go around to DOTs and do seminars. I'd like to see patrol cars used to mitigate traffic jams as you describe.
John <john@mciann.com>
Birmingham, AL USA - Thursday, January 16, 2003 at 12:58:08 (PST)

Your page provides a number of good arguments for something I've been practicing for a long time. I completely agree from practical experience that it's easy to maintain a large gap without driving slowly!

I'm surprised you didn't mention the following two things:

A large space in front of you is really good for safety!

Avoiding constant breaking and acceleration is really good for your car!

Also, this is another possible explanation of the drive-slower question:

Q. How can I drove slower, yet somehow cause traffic to move faster?
A. Imagine you are driving by yourself on a street with traffic lights. Let's look at the two extremes of behavior. With one, you slam on the gas as hard as you can when the light turns green, then race to the next red light, and screech to a halt right before it (and then wait). With the other, you move at such a speed that you reach the next light right as it is turning green. While your car certainly goes faster in the first stragety (at least some of the time), the second strategy will probably get you to your destination faster because you don't need to spend the time accelerating from 0mph at the last light. (It's also much easier and safer to drive this way.)

Tom 7 <no@spam.com>
Pittsburgh, PA USA - Thursday, January 16, 2003 at 11:36:42 (PST)

Very interesting. When I drove a truck I left big gaps in front of me as I approached slow traffic because my truck was glacial in its accelleration. If I had to stop it would take a looooong time to get back to 50mph and all the traffic behind me would be held up. Boy, was I annoyed when a car in front slowed me down instead of speeding off at the same rate as the guy in front of him.
zack mollusc
USA - Thursday, January 16, 2003 at 03:32:18 (PST)
I think this article should be mandatory reading for every driver's education course.
Andrew Berg <andyberg@u.washington.edu>
Seattle, WA USA - Wednesday, January 15, 2003 at 15:04:38 (PST)
Driving in Seattle I also have noticed traffic waves and I have also tried (before reading this article) to alleviate them by driving the average speed. I think, however, that you are leaving out a major benefit to this responsible driving. Not only is driving at the average speed more relaxing than stop and go, but it is much more fuel efficient. There is nothing worse than stomping on the gas to speed up between waves only to waste all that energy by slamming on the brakes a few seconds later.
Andrew Berg <andyberg@u.washington.edu>
Seattle, WA USA - Wednesday, January 15, 2003 at 15:01:27 (PST)
I agree with most of your points but not once do you ever mention keeping right except to pass. I regualrly see drivers creating bottlenecks by riding alongside other drivers when they could ease the burden by keeping right and let other drivers past.
Don Lawrence
Denver, Co USA - Wednesday, January 15, 2003 at 12:54:16 (PST)

[Are you sure? Read the article again. Maybe those drivers are preventing TRUE bottlenecks from forming. I don't mention anything about "keep right" because I do the very opposite! To wipe out traffic waves in my own lane, I drive at the average speed. To wipe out waves in two lanes, I team up with another driver doing the same. This keeps anyone from rushing madly forward only to come to a complete stop up ahead. During congested conditions, trying to drive fast is what causes stop-and-go traffic! But I do agree with you that during UN-congested conditions drivers shouldn't create rolling barriers. People should remain free to drive fast unless the conditions are such that this would trigger waves or trigger a full-blown traffic jam. The thing that we all miss is that our fast-driving behavior during low traffic is OK, but if we try to use the same behavior during heavy traffic then we end up going SLOWER, not faster. Hey everyone, when traffic becomes thick, start driving differently! -billb]

I agree with most of your points but not once do you ever mention keeping right except to pass. I regualrly see drivers creating bottlewnecks by riding aloingside other drivers when they could ease the burden and let other drivers past.
Don Lawrence
Denver, Co USA - Wednesday, January 15, 2003 at 12:53:28 (PST)
Great site. Nice to have words put to the concepts I've also seen. One point to note is about handling bottlenecks. You suggest that if everyone maintained a decent gap so that traffic can merge at high speed then waves should not occur. I wonder if this will work cause surely when a person merges into the gap the drivers who maintained that gap will slow down so as not to be very close to the person infront. This could create the wave. I also like the comments by Jeff Martin and the idea that leaving at different times to everyone else could also come under the concept of maintaining a gap.
Dean <dean@nospam.com>
Reading, UK - Wednesday, January 15, 2003 at 07:21:18 (PST)
The M25 motorway (freeway) around Heathrow Airport in London has been suffering this for years, until variable speed limits were introduced. Intelligent speed cameras were also introduced which kept drivers observant. As traffic builds the limits are dropped either side of the airport exits until the flow stabilises, and can then be gently raised or lowered as requested at a central control point. This creates the standing waves required to clear jams when they start. If you ever come to the UK, hire a car and take a trip around the M25. It's surprising how well the phased limits area works, and how badly the sections just before and after flow!
UK - Wednesday, January 15, 2003 at 01:26:01 (PST)
Nice theory and I use it all the time. Not that it helps traffic as a whole, it takes more than 1 person to do that. But it's just a whole lot EASIER than driving gas-brakes-gas-brakes-gas-brakes for an hour! Haven't these people ever heard of COASTING? No, they don't have a clue and use the "horse parade" method - keep your nose in the arse in front of you. Most people are so far away from comprehending your ideas it's unbelievable. Witness them tailgating each other at 80 mph in the driving rain and fog. And they're allowed to reproduce.
Al Bergo <yes_I_would_ like_more_spam@ getlost.com>
Vallejo, CA USA - Thursday, January 09, 2003 at 23:26:42 (PST)

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