Traffic WavesCOMMENT BOOK
It doesn't happen often, but leaving space in front of you would help in making room for emergency vehicles. tama USA - Wednesday, October 29, 2008 at 10:05:46 (PDT) Great work! One idea, though: I think you could sell the fuel-saving aspect harder. Cars use a lot of fuel when they accelerate but very little when they maintain a constant speed. Creating a steady flow of traffic will reduce fuel consumption and fuel emissions dramatically, and this would be the case even if there were no improvement in road capacity. More uniform car speed also reduces break pad wear. Knut Olav Homlong <khomlong att online dott no> Stavanger, Norway - Tuesday, October 28, 2008 at 06:38:41 (PDT) Greetings Bill, I like your thinking and analysis. I concur with your thoughts on the overall affects of facilitating better merging and it's positive affects on traffic behind you. However, in terms of waves from rubberneckers or an errant brake light flash - the drive slower, keep a gap, minimize use of brakes does only two things ... it gets rid of the stop and go traffic, which you define as the traffic jam, and it allows you to relax and have a "better" commute. It does not get you to your destination any faster. [I've seen traffic jams break up ahead of me. In certain situations the gap very definitely does get you there faster. Ask this question: when traffic "stop-waves" arise, does the average flow of traffic get changed? I've found several sources saying yes: the waves cause a significant drop in average traffic flow. And so various cities across the world have provided systems to wipe out traffic waves (e.g. variable speed limit signs, etc.) Second, if a "wave" gets trapped at a merge zone, the merge zone jams up. This jam creates a long upstream backup. It also creates very sparse traffic downstream, so once you get past the jammed merge region, you can drive fast. Clearly this jam is acting as a major bottleneck, and if one or a few drivers could wipe it out, the flow would increase. So... waves and jams really are bad, and if we could remove them, traffic flow really would improve. -billb] I've thought long and hard about this - the simple fact is that what you do to the wave does not affect the average speed of the traffic in front of you. The average speed of the traffic in front of you is the only thing that controls the average speed of your commute. Would the world be a better place if we all had more relaxing commutes? Absolutely yes. Would there be fewer accidents? Probably. Would fuel and brake economy go up? Yes. Now - if someone way up in front of you - say someone who was following someone who taps their brakes to change a lane would use these techniques, and some very low percentage of cars between you and them would also use them I think we might see an improvement in traffic - but the key person is really only the one right behind the idiot that only cares about them and not the rest of the traffic. So what should we do ... start by adopting your suggestions. The most beneficial thing you can do for traffic, in my opinion, is to move over to allow cars to pass you as long as by moving over you do not cause the new driver behind you to brake or slow. This effectively creates additional road capacity by moving cars from behind you to in front of you. Second, do not change lanes with your brake pedal - use your eyes, mirrors and turn signals instead. Third, drive with space to minimize your use of your brake lights (they come on before you even start to slow). The cars 2 or 3 places behind you will react to your brake lights by slowing (or braking) even when you don;t really slow much - this is a implied safety/uncertainty thing. Fourth, maintain speed and direction - an old sailing trick. If everyone knew that everyone else was going to drive predictably we could merge, change lanes, not brake, etc. with comfort and implied safety. This also means that when you go around a corner or up a hill you should (safely) maintain your speed as well. And finally, be polite - it's the culmination of all of the above. (And never, never rubberneck - not that this helps but it feels good!) Just my 2 cents - thanks! Dean Dean Suhr <trafficwaves - att - deansuhr - dott- us> West Linn, OR USA - Wednesday, October 01, 2008 at 11:01:41 (PDT) I have tried this idea and it really works. I now incorporate in my driving style both in my car and in the Big Rig. Cheers Martin Davies-Roundhill <martindr2@cheerful.com> Brisbane, QLD Australia - Saturday, September 27, 2008 at 16:27:04 (PDT) I had no idea there were so many others that think just like me. It's refreshing and kind of exciting. I need to get out more. Thomas May <knobs@roadrunner DOT com> Chesterland, OH USA - Saturday, September 13, 2008 at 08:26:55 (PDT) "KEEP RIGHT EXCEPT TO PASS" "DO NOT CROSS SOLID LINE" Ever see either of these signs? They are the law on the Interstate Highway System. [My usual policy is to ignore angry comments. But I'm making an exception. Please cool down and watch/listen to videos before criticising. Did you see the signs? That's not a passing lane, that's an EXIT ONLY lane going to the express-lanes. Note that *everyone* ahead of me is taking that exit. This is a famous Seattle traffic jam, "Northbound I-5 Expresslane Left Exit, South of Seneca St." It's a jam where all commuters are jockying for position in the left lane. Usually during rush-hour that left lane is needlessly packed solid and crawling very slow, with occasional stop/go waves. By the time I arrived at the actual backup, it was already flowing. I barely had to stop. Also, if I closed up my forward space and blocked all merges, I could be arrested for *tailgating,* because I'd be driving unsafely with less than one second between cars. And finally, the solid white line marks the HOV lane. See those diamonds painted on the lane? -billb] Next time, why not show us what your pious selfishness [ Drivers are trying to merge into the exit-only lane, and I'm the *only one* letting them in... and you think that's SELFISH? No, that's called "Trucker's Politeness" or ""Gravel-pit Etiquette." Watch how the professional truckers behave in congested conditions. They have an overhead view, and can see which selfish behaviors are triggering the congestion. If we merge like gear teeth,the jam will drain away. If we block all merges, the "gear teeth" come to a halt. -billb] is doing to the traffic BEHIND you. [ Please stop and think. Obviously the the traffic behind my car is moving as I do: flowing totally smooth with no stop/go waves (well, except for that one clot down at the actual exit.) By letting ten cars in, I pulled the entire region of slow traffic backwards by about 10-20 seconds, but then the jam was unplugged and the stop-and-go traffic was erased. That's how one driver can un-jam a merge zone: pull the jam backwards, so down at the end, fast merging can commence. What I *really* needed to show was a split-screen view, with the second screen being my camera on the overpass (that's the same view as the first five seconds of my video.) Here's what you'd observe: first some periodic "cheaters" are forcing their way into the solid-packed left lane and perpetuating a long backup. But then the supply of cheaters would mysteriously dry up. That's because I'm letting them all in early. Next, with no cheaters to halt traffic, the long backup in the left lane would rapidly drain away. Finally I would arrive, and the cars behind me would be flowing fast and smooth, with spaces between cars which allow merging. It *almost* worked, but there was still a small backup remaining when I arrived at the end, which halted everyone for a few seconds. (A single traffic-wave still remained after I'd gone past. ) But how long would my unplugging last? There's nothing downstream to re-trigger the jam, so it might remain smooth for the evening. Or perhaps two angry drivers would intentionally block each other, "get stuck in the doorway," and re-start the whole thing again. -billb] antwan <thunderclap@lightning.com> altoona, la USA - Saturday, August 30, 2008 at 09:22:45 (PDT) You know, I've actually had some of the same thoughts about "pressure waves" of traffic as you talk about here... but I've let myself become so irritable and competitive that I've never taken full advantage of the phenomena I've observed. You've given enough credence to the hypothesis that I may be able to get out of the rut. Thanks! Dave <nevthederanged@aol.com> Schaumburg, il USA - Sunday, August 24, 2008 at 15:53:09 (PDT) In Michigan, you have to drive slower on the right and pass on the left which makes sense since the driver sits on the left side of the car. Driving below the speed limit, not passing anyone, and leaving open lanes to the right will force people to pass on the right. If a traffic jam sneaks up on them because they can't see through your car to the right side to make the pass, then it could cause an accident in those lanes and tie up traffic. Why don't you do this in the right lane? You also crossed a solid white line in your video. [Look at the overhead signs: that's an exit-only lane and not a passing lane. Look at the diamonds painted on the lane with the solid white line: that's not a "cars not allowed" lane, that's an HOV lane. -billb] John B royal oak, mi USA - Monday, July 28, 2008 at 10:15:33 (PDT) Maintaining a minimum safe follow interval is the key to maximum vehicle thru-put. For example, if 18' LOA cars drive 60mph at 2 second (176')intervals, 27 will go by per minute. Vary the speed in the range of 40 to 80 mph and the thru put stays at 26-28! Why? THE SAFE FOLLOW SPACE GOES UP WITH THE SPEED. Cut the follow time to 1 second (88' or ~5 carlengths at 60mph) and thruput doubles to 46-52 cars per minute. At 3 sec. intervals only 18 to 19 cars go by. Shorter intervals don't work well if larger, higher, wider vehicles obstruct forward vision leading to unnecessary braking, passing, and increased follow distance. Not to mention driver fatigue and frustration. What can we do? Where possible, open the left/ HOV lanes to any CARS of compatible dimensions. NO TRAILERS, CAMPERS, SUVs, VANS, TRUCKS, BUSES, ROOF RACKS. Keeping the bulk of the cars out of the way should make things easier and less congested for the truckers, especially with the move to smaller personal vehicles. Ron <lrh1@earthlink.net Williamsburg, VA USA - Saturday, July 26, 2008 at 10:13:05 (PDT) i too am from seattle and have been pondering this same situation, but have yet to put it to pape. hats off to you for doing so. george <madmonkey23@yahoo.com())*(*> marysville, WA USA - Thursday, July 24, 2008 at 21:30:26 (PDT) Hi, I have been a long time advocate of this idea. I even had it published in our local newspaper (Philippine Daily Inquirer) in 2004. Had it named Greenzone Traffic Scheme. Sadly, it came on deaf ears. People can't seem to grasp the idea that keeping a large space in front as a headway decreases the chance of congestion. The fear of being cut into is more a concern than having themselves a hand in removing the congestion. You're site is heaven sent for me. You're FAQ's answered every questions asked at me everytime I tried to present it to Traffic Managers in the Philippines. It is the solution that can be used worldwide. Tailgating is such a bad habit that causes these traffic jams all over. Thank you for letting me know that I am not alone. mars de jesus <marsdejesus@yahoo.com> marikina, Philippines - Thursday, July 17, 2008 at 02:15:30 (PDT) Good read. Haven't thought through the "math" but generally agree that in most circumstances cooperative behaviour increases the size of the pie while competetive behaviour decreases it. If you believe life is a zero-sum-game it will be... Recently I was in a miles-long standing wave jam on a rural stretch of I-75 and noticed that two semi trucks ahead of me would park side-by-side for a minute or more and then slowly roll up to the tail end of the jam. This did not have the effect of busting the jam (maybe it was too large), but did allow (force) those of us behind the trucks to take our foot of the clutch and relax. Long story short... I think the trucking industry is probably a better change agent than state troopers since they are out there anyway (free to taxpayers), have 2-way communication, and are extremely interested in highway efficiency. As for urban signalized arterials, I understand that in Germany, some traffic signals have an LED display showing the progression speed of the green wave (which may differ from the posted speed limit). This provides feedback to drivers to maximize the throughput of the road. Demian Miller <dmiller@tindaleoliver.com> Tampa, FL USA - Wednesday, July 09, 2008 at 03:53:44 (PDT) Interesting article.. I unwittingly have been doing this for about 6 months now. Strictly for economic reasons I slowed down and started hypermiling a bit. Which leaves those huge gaps sometimes. I drive a diesel pickup. I often wondered why I wasn't seeing the huge jams I was used to dealing with. And my commute time had not really increased that much. Strange.. Then I read you article. And it dawned on me. I was actually eliminating those jams by driving just 5 mph slower than anyone else and employing hypermiling techniques! My stress level is lower, my mpg is increased, and I'm helping the overall traffic situation. Can one person make a difference. YES! By forcing the Lemmings behind us to conform to the traffic pattern, we ALL benefit. Lemmings line up on the left, now in one lane instead of 2, and smooth drivers are now on the right. Maintain that space and all is well. Very cool article! Thanks! very enlightening! Bruce <hipshot7@earthlink..netl> Cumming, Ga USA - Tuesday, July 08, 2008 at 08:43:16 (PDT) Looking at the traffic around my area I'm constantly amazed by the similarity between it and 1D non-steady internal compressible gas flow!! You see the compression waves and expansion waves travelling through the medium. Traffic lights are a source of unsteadiness in the flow; the further away you are away from them the more like steady-flow appears. Stop the flow and, as you show, a compression wave is created. I'm glad I'm not the only mad man that sees these things! Graham. Graham C. Williams <graham@speechrecordings.co.uk> London, UK - Tuesday, July 08, 2008 at 04:15:34 (PDT) Hey, someone else did the wave-eating experiment independently. And on I-520 too! Don't Stop Moving (on Seattle 520) bill beaty seattle, wa USA - Friday, July 04, 2008 at 09:51:25 (PDT) Hey, I just read your piece for the first time. Exactly right! I've been using these techniques for several years. At the worst jam on my commute in San Jose, CA, there are just two lanes plus a commuter lane. Usually nowadays someone will cruise alongside me with a huge space in front of us so we reach the jam just as it is breaking up. No stopping! I imagine it evens out the traffic flow behind but I never stopped to check it out. Certainly much safer. Regards, Mike Mike A USA - Friday, July 04, 2008 at 01:11:46 (PDT) We love your website. My husband and I traversed the 520 for about 6 years. We used to try to eleminate the jams by going very slow. It worked really well. I did want to comment that your zipper/merge theory does really work. In California it is law that you must merge every other car. Merging is fast and effortless and there is rarely a slow down. Most of the time we merged at relatively high speeds. I was suprised when I got my Washington Drivers License that it was not a law here. Then I noticed that people here feel it is doing a favor to let a vehicle merge. It then becomes a waiting game with many cars starting to merge too early, stopped with there blinkers on hoping someone will have pity and let them in. I think it would be great to get the "merge every other one " on the books and make it state law. At least the new drivers will know how to merge like a zipper! Thanks again for your site, it was an enjoyable read. Mrs. Juliet M. Juliet M. Seattle, WA USA - Thursday, July 03, 2008 at 14:58:16 (PDT) Bill, we need to talk. For the past three years I have been formulating an outline on a new driving theory. The theory is based on psychological, environmental and other driver variables. Please email me as soon as possible. everett <everettmccurdy@gmail.com> USA - Sunday, June 29, 2008 at 05:54:33 (PDT) You should check out beatthetraffic.com and add it as one of your links for live traffic information. Michelle Rodrigues <mrodrigues@beatthetraffic.com> Campbell, CA USA - Thursday, June 26, 2008 at 12:16:01 (PDT) I also naturally developed this behavior (and amusingly I'm also an electrical engineer), but I am especially pleased that you are actively spreading the technique. It's good that you reassure readers that the weird feeling ... of doing something visibly different right in the middle of the ''traffic herd'' ... will go away as a driver raalizes it's actually working better than expected. I started driving the average speed initially for my own benefit: as an engineer who prefers to optimize most things I am repeatedly faced with, it felt unpleasant & wasteful to have to keep starting and stopping (and shifting too, if driving a manual transmission). [Two site suggestions: consider adding a checkbox option to keep commenters' email addresses hidden; Firefox (3.0 at least) doesn't seem compatible with the Security Number field.] Ken Newton USA - Thursday, June 26, 2008 at 11:42:10 (PDT) Hey man, great article, musings, collection of speculations. If people could only know... But, I had written with a specific topic. I was required to go through a AAA safe driver training course for a job I used to have, and the instructor brought up a great point, and one which has haunted me for years since. He told all of us on the first day, while we were sitting around venting frustrations on the lack of everyone else's ability to drive, that if everyone were to actually maintain the 3-second window (between you and the car ahead of you), there would be no traffic jams, no accidents, nothing. Unfortunately, it would seem that our more basic instincts drive us to, well, drive like asshats (with a rare exception here and there). And it's true, a lot of people absolutely suck at driving. Obtaining a DL should be a lot more difficult, and the testing a LOT more in-depth, but that's just me ranting my own personal opinion. Just thought I'd throw that so-close-but-will-never-be-reached goal out there for the people who, apparently, care enough to post this kinda stuff. Enjoy, and don't let the thought of how easy life would be if people didn't suck so bad at controlling their own f*cking speed and direction get you down too much. JNovak. Joe Novak <landshrk@gmail.com> Sacramento, CA USA - Wednesday, June 25, 2008 at 01:37:12 (PDT) Last week I was driving across lower Manhattan during rush hour - something not for the feint of heart. I was driving from the Williamsburg bridge (at the East River) to the New Jersey-bound Holland Tunnel (at the Hudson River), a distance of only two miles. I noticed that the traffic control agents were pushing cars through the intersections as I arrived in Manhattan, and as I got closer to the West side and the Holland Tunnel, the congestion at the intersections became progressively worse until it took nearly twenty minutes to proceed across one intersection. It ould have been better if the traffic control agents had been in touch with each other and directed the agents closer to the Williamsburg Bridge to hold or slow incoming traffic so as to prevent the buildup on the New Jersey-bound west side with its resultant gridlock. The point is clear...there are only four lanes of traffic exiting that part of Manhattan, and those four lanes have a discrete capacity. Therefore, the incoming traffic rate must be limited to equal to or less than the outbound rate. If this is done, gridlock will be lessened and traffic will flow smoother even in an extremely congested urban setting. Len the Pharmacist <LenRx1@aol.com xxx> New York, NY USA - Wednesday, June 18, 2008 at 01:55:28 (PDT) I think that the backups where, for example, 3 lanes merge down to 2 lanes, are a perfect illustration of Bernoulli's Law, in two dimensions. And in order to eliminate the backup, you would have to reduce the incoming traffic speed and thus the input volume to match the output volume. This would require constantly updated speed advisory signs for the approaching traffic, perhaps half a mile ahead of the merge. Has this ever been tried? Clyde Revilee <revilee@cox.net> Santee, CA USA - Friday, June 13, 2008 at 10:51:31 (PDT) I was going through this site and reading the experiment along with some comments. What struck me is the common sense of it all and the fact that it really boils down to simple courtesy. I have often wondered why, when there is a sign that points out this lane ends, no one takes the time to merge BEFORE the lane ends. When the lane ends, they have to slow down to merge and they get "punished" for not merging sooner. I have often slowed down before such events to allow those in the lane that ends to move over but they apparently don't think that far ahead. Larry Hanson <heiferhopper1@msn.com> Houston, TX USA - Friday, June 06, 2008 at 09:24:26 (PDT) I have been watching traffic waves in Sacramento for about 8 years now. I thought I would share a few observations: 1) The sun can cause a wave to start. This is especially true in the morning comuute on I-80 eastbound. There is a location where the road changes direction, and during the right time of year, that direction directly faces the rising sun. Drivers can't see as well and naturally slow down. The wave that starts can last for quite a while. 2) The traffic waves that start can move quite fast under certain circumstances. I was driving and there was a traffic wave started by an accident on the freeway in the opposite direction of traffic. I was driving roughly 65 m.p.h. For about 2-3 minutes I was driving alongside the wave departure point of the wave (where cars were leaving the wave and finding a big open space). The wave was moving backwards at 65 m.p.h.! 3) I design computer chips that move data quickly and I have been able to apply my observations of traffic patterns to my job to make the computer chips work more efficiently. Neat Huh! Jon Sacramento, CA USA - Thursday, June 05, 2008 at 12:23:36 (PDT) Like you, I have have an interest in traffic, and like you, I have spent a lot time trying to educate people about the wave-like motion of traffic congestion... although not on the web. Compaction waves cause much of the traffic that we experience, but people are quick to blame only the rubber-neckers or slow drivers. The truth is more complicated. I wish you had addressed it, although admittedly, your web site is focused more on the "cure" and one form of prevention. I feel like you've missed a major point: if most people traveled the speed limit, most traffic congestion would cease to exist. To illustrate the point, consider your animated graphic on page 2 (Traffic "experiments") that shows a typical traffic compaction wave, where the input equals the output -- thus a pinned wave that doesn't move from its origin. You do an excellent job of addressing the properties of such a wave when the stopped cars are moving at 0 mph. Now imagine a situation where you are moving at 65 mph and observing those "stopped cars," which would therefore have to be moving at 65 mph (given relative motion). What causes such a wave? It's simple. When people travel varying speeds, faster moving traffic will ultimately run into slower moving traffic. If there are enough cars on the road, then enough fast-moving traffic will hit slow-moving traffic and create the compaction wave your graphic illustrated. Since most sane people do not drive 70+ mph while only a foot or two off someone else's bumper, you don't simple create a pinned wave moving at 65 mph down the highway (relative to your observational speed of 65 mph). Instead, the speeders at the rear start slowing down, which causes the people behind them to slow down, and so forth. Eventually, the wave moves slower and slower until (if there's enough continuous traffic) the wave stops relative to an observer at rest (or moves backwards relative to the observer traveling 65 mph). Many people like to claim that slow drivers are the cause of slow-downs. As the example above illustrates, it's actually a combination of both slow drivers and fast drivers. The fast drivers pile up behind the slow drivers, and as passing opportunities dwindle (based on the carrying capacity of the road) and inter-car distances shrink, traffic slows down. Obviously, the best solution is to homogenize speeds -- have everyone travel the same speed. Impatient drivers think that slow drivers should just speed up, but to what speed? One fast driver may wish everyone was traveling 75 mph, while the impatient driver behind him/her wished everyone else would just speed up to 90+ mph or just get the hell out of the way. This is where the magic of the speed limit comes in. You don't have to rely on undocumented convention (such as "everyone just travels 5 mph over the speed limit"), which may not be known to all drivers. If everyone traveled the speed limit, to the best of their abilities, many (but not all) traffic problems would be solved, and major roads would be able to carry capacities closer to their theoretical limit. (Not to mention the fact that a lot of fuel would be saved, since fuel economy and speed do not have a linear relationship. As you drive faster, wind resistance actually gets stronger and reduces your fuel economy. Therefore, driving the speed limit has other advantages, not just for the individual driver, but for all of society.) I sincerely wish you would re-write your website to address this issue first. Although you do an excellent job addressing anti-traffic techniques, you really need to address the other sources of the problem. Remember, an ounce of prevention is worth a pound of cure. If people would just learn to drive the speed limits and leave a safe distance between themselves and the car in front of them, we wouldn't have nearly as many traffic problems as we currently have. Furthermore, in discussion of linear vs. non-linear dynamics, when you claim that a single car can make a difference and supports the non-linear view, consider that you also admit that you have to do the job of 10 drivers by leaving much larger spaces than you should normally have. Basically, if everyone left a single space in front of them, you hypothesize that many of these congestion situations wouldn't exist. That sounds very linear to me. Personally, I don't see traffic congestion as a linear problem, though exponential or logarithmic seem more likely to me. However, traffic definitely has its dynamic components as well, since each car in a defined segment of traffic will be moving at a variable velocity. But since vehicle speeds usually vary around a mean (or two or more peaks in a distribution, such as when one segment of traffic is mostly traveling around the speed limit and another faster wave traveling 15 mph over the speed limit passes them), I suspect a more of a middle-ground between dynamic and linear dynamics. Also, without having known any professional truckers personally, I cannot speak to their knowledge. Like many of your critics, I've suspected braking distance was part of the explanation of their behavior. However, the other part of the explanation could also be fuel economy. To move a very large truck with a heavy payload, you burn a lot of energy. Common sense -- which is apparently lacking from people who travel more for convenience than for a living -- tells you that in a traffic jam, you'd be burning a lot of fuel just to quickly close a gap with the car in front of you, only to hit the brakes once you got there. It's kind of like my criticism of people who accelerate towards red lights. What's the point? So for truckers, fuel economy is critical for being able to make a living, and their large, heavy trucks greatly amplify the affects of poor driving habits on fuel economy. (If you don't think they're more sensitive to fuel economy than the average financially irresponsible American, consider all the recent trucking strikes that have been in the news lately.) Personally, I suggest stopping at a major truck stop and interviewing truckers to get a definitive answer as to the true nature of their behavior. This is one problem I noticed with your spacing idea, assuming that it is adopted by everyone, as you wrote in the following: "Do large spaces between cars cause traffic to fill highways? Only if people increase their spaces on average, but that's not what I'm discussing here. Suppose traffic is moving at 40mph. Those cars will have several car-lengths of space between them. If those drivers encounter a slowdown... what happens if they REFUSE TO PACK TOGETHER. This doesn't increase the space between drivers, since they already were widely spaced when they were moving at 40mph. Yet if they maintain their wide spaces as they slow down, then they will have little trouble in speeding back up again." The problem here is a practical one, whereas the situation outlined in a nice theoretical one. Assuming you could condition all drivers to drive as you suggested, there would still be a lag time as drivers reacted to the change in speed of the drivers in front of them. In the ideal situation, where you can see far in front of you, you only have to worry about people being distracted or tuned-out from their monotonous commutes or long trips. In hilly situations, curving roads, or where some people drive huge SUVs, while other drivers drive smaller cars, not everyone can see what's going on in front of them. In those cases (and others like it), the distance between cars will change in proportion to the driving speed since you will be dealing with reaction speeds and driver distractions. Faster moving traffic will result in faster changes in inter-car distances, and the reserve is true for slowing moving traffic. Either way, the distances between vehicles will not remain constant. Another issue: "If EVERY driver was to constantly maintain a HUGE space regardless of speed, then it would probably cause problems. The capacity of major highways would be reduced. On-ramps would become choked as traffic backed up into them, and there would be slowdowns extending far out into the countryside. Yet if ALL drivers were to change their habits, then only small spaces would be required, yet waves and stoppages would be seriously squelched." If the carrying capacity of every road and freeway were infinite this would be true. However, each road can only carry so many cars per minute. Despite all your points and mine (regarding homogenizing speed), the truth is that waves and stoppages will continue to occur as traffic overloads the carrying capacity of the roads intended to carry it. This is simply a growth problem that lies in the hands of urban developers, not traffic-busters like you and speed-limit-drivers like me. FYI: Your charity example in your FAQ is short-sighted... for exactly the same reasons that most conservation is short-sighted. (Sorry.) You wrote, "Giving to charity improves the whole world in the long run even though you lose money in the short run. Reciprocal altruists give to charity (they aren't true altruists, instead they are paying out money and expecting long term results!)" The second sentence is correct. (I have a degree in evolutionary biology, so I know exactly where you're coming from.) Giving to charity won't improve "the whole world in the long run" because the money will be used within a capitalistic system that is unsustainable. (This is known as Jevon's Paradox.) You're adding fuel to the very fire that's consuming the world. (A good, biological example of this is giving food to starving nations, since giving them food raises their carrying capacity and, without the social structure to encourage small family sizes, ultimately increases population, creating even more hungry mouths to feed.) Even most conservation efforts that result in monetary savings don't help because the money saved is ultimately spent on our unsustainable economic system or put into savings, which then gives banks loaning power to fan the economic flames. Therefore, charities do not improve the world, but make it worse. We need to be living sustainably for them to truly make a difference. If you're looking for an good ethics lesson, dig a little deeper. ;-) Alex Dunkel <visionholder*AT*gmail*DOT*com> Newbury Park, CA USA - Wednesday, June 04, 2008 at 00:42:28 (PDT) I think Gravel-pit etiquette has moved to http://www.skaggmo.com/gravelpitetiquette.htm Your jam solution reminds me that years ago when my parents were living in Aruba, I found that it was actually the law that one had to maintain at least one car's length behind the car in front "to allow merging in emergency". Everyone drove wickedly fast, with lots of passing, on roads with one lane in each direction. But it all went very smoothly. Smooth driving to you, Ken Ken Landaiche <Kenneth.LandaicheETl-3com.com> Santa Rosa, CA USA - Tuesday, June 03, 2008 at 17:57:09 (PDT) Yes! Yes! I thought I had come up with this idea and I even have a great business plan to boot that would make this sort of driving a money-making venture. One key idea to help you learn this technique, "Try to use your brakes as little as possible and try to make other people use their brakes as little as possible." Sounds scary, but it forces you to leave space in front of you and to plan ahead so you don't cut other people off (so they don't have to brake). One place this technique can also help is when YOU are merging, say from a metered light. Instead of speeding up just to slow down again, create a space in front of you to eat up the slow-pokes who had to stop to merge, then ride the merge lane all the way to the end, gradually picking up speed and merging! It works great! I haven't noticed anybody be angry at me because I went to the end of the merge area and I suspect it is because I was able to merge without making them hit their brakes. They were none the wiser and we were now going 20 to 30mph from a complete stop. (Okay, maybe somebody cursed my name for being a jerk and waiting until the end, but it fixed the merging for minutes behind me.) For those skeptics out there, just give it a try. You will be amazed! Also, like anything else, it takes practice to get it just right. But when you do, you can claim victory over traffic and feel great about helping those behind you. Who knows, maybe because you did this, you changed the whole mood and course of someone else's day! -- Cody Cody <codeman9@hotmail.com> Seattle, WA USA - Tuesday, June 03, 2008 at 10:26:36 (PDT) Nice job on a very interesting and thought-provoking article; I have a long commute myself over here on the East Coast, and I appreciate the usefulness of fluid dynamics when it comes to analyzing traffic patterns and the causes of traffic jams. But I often find myself wondering if anyone's given any thought to the impact on traffic flow of the ever-increasing size of the "molecules" themselves. Everybody knows tractor trailers, school buses and other big vehicles can't move nearly as fast as our zippy little Toyotas and Hondas, and many of us get extremely frustrated when we get stuck behind them. Simple physics is all you need to realize that the bigger and heavier a vehicle is, the higher its center of gravity and the longer it takes to get up to speed, slow down, turn and do all the other things you need to do in traffic. As a result, the more of them there are on the road, the slower traffic moves overall. But what are we doing in America? We're buying bigger and bigger SUVs and minivans and more and more of them every day. I can't help but thiink this has to be a major contributor to traffic problems. To keep traffic moving, we're going to have to move slower and slower ...and slower... Just something to think about. Joe J. JJ <gr8rwritr@yahoo.com> King of Prussa, PA USA - Friday, May 16, 2008 at 13:21:19 (PDT) I'm no expert in this, but I have a friend who did an extensive research project regarding general queue theory. There is a very precise mathematical model for traffic jams out there, you just have to be crazily into math to figure it out. I just thought I'd throw that out there for anyone interested enough to look into it. Joseph <rather not say> Richardson, TX USA - Monday, May 12, 2008 at 15:25:55 (PDT) Ideally, if everyone drives at 100 mph and keep a large distance between them, and all the merging cars merge in at 100 mph and fit into the slots, and the slots are slowly expanded before and after the newly-merged cars, then disruptions to the throughput of the highway will be minimized. But of course that's not possible because everyone has to be smart, deft, young, non-Mexican, imprudent, ungreedy, and not in a hurry. I believe throughput can be maximized in traffic jams, but only before the jam happens. It takes only one idiot driver to quickly cause a congestion; and resolving a jam is difficult if not impossible. Your theory is a good theory, but make it more concrete with a simulation. ken <ken_love@hotmail.com> Milpitas, CA USA - Friday, May 09, 2008 at 09:10:18 (PDT) Interesting reading, I have myself cancelled out waves travelling back down a line of traffic many times, but am a little ashamed to admit I'm not very good at allowing people to merge in front of me. Inspired to give it a try now though. Interesting to read the comments about the M25 around London, UK. Within days of the variable speed limits being introduced and enforced commuters around the south and western sections of the M25 realised their journey is often quicker, far less tiring and stressful, as the variable speed limits restrict the flow of traffic into the congested areas. This tends to be worse around Heathrow airport Europe's busiest air port, lots of entering and exiting the motorway/freeway across several junctions and junctions with other major motorways. These days people are pretty good at observing these speed limits as the benefit is now so well known. Adrian <adrian at camdaw.net> Alton, Hampshire UK - Thursday, May 08, 2008 at 08:30:15 (PDT) Wow, somebody else who gets it. I've been busting clots like this for years, but not for traffic reasons. I do it to save gas. Mine and everybody in the line behind me. Thanks for the "let them merge" tip. Kind of like "pay it forward". Thanks for all your effort. J Blob <dontblobme@mail> USA - Wednesday, May 07, 2008 at 12:43:52 (PDT) I have always thought that with a merge coming up, if everyone merged to the center so that everyone drives over the center line, things would go faster. It makes both lanes merge and eliminates the lane where people can pass ahead and merge near the front. David Sliter MI USA - Wednesday, April 30, 2008 at 13:13:24 (PDT) Fellow Road Warriors: I am so AMAZED that Bill and others have discovered/studied what I have, over the course of living in many states, including Montana(my home now) and living in Seattle for years. I just remembered what I call 'Autobahn rules' or 'hedgehopping': ALL traffic stays extreme RIGHT unless passing. This in its basic theory will have the slowest drivers in the right lane, with the next speed strata 'hedgehopping' them. Then the next speed strata will be passing the faster mid traffic, and merging back extreme right if possible. Imagine that the right-lane right wall is viscous and the left-lane left wall is teflon. Theoretically the inevitable faster traffic will 'slip' over the doofusesXXXXXX, er, I mean slower drivers. Signalling your intentions is considerably important, and courteous. I have long believed that speed laws exist for revenueing purposes alone. I remember when I-5(Interstate 5) was 55mph; Now it is 75mph..did something magically happen to make the highway safer? NOT! If they handed out tickets to incapable slower people who did not stay right, instead of capable faster people who leap-frogged, a huge amount of congestion would be relieved from the highways. Take Oregon I-5 for example: from Salem to Portland(100miles), you generally have 'freeway plugs' infesting EVERY LANE going enough the same speed, so it is very difficult to expedite your trip. Now if everyone 'stayed' right, the inevitable faster people could would clear the highway faster than the inevitable slower people, cause everyone does not drive the same speed. I could go on for hours about the wisdom gained from YEARS and hundreds of thousands of miles spent driving the western United States, But I am glad Bill and others are voicing the words of reason-Remember: they don't drive bad because they are stupid, just ignorant.. -Christian Christian von Delius <alpineglobalprivate@gmail.com> Kalispell, MT ` - Thursday, April 24, 2008 at 20:17:00 (PDT) Thank you for putting together this layman-friendly website! I had started a Care2 group, Drive Aware for A Safer Traffic Environment as a resource for information, advice and community-action encouragement. I have now delightfully mentioned your site as a place to go for good information! I have always had similar theories about traffic flow and congestion. I had even experienced the ire of another driver behind me because I was letting people merge ahead of me in a road construction area (about 2 blocks ahead of the CVS where this driver ended up going, how impatient is that?). Although it is difficult to sell someone on an attitude adjustment, the rational, pragmatic advice here can make sense to just about anybody. I wish I could leave flyers about this stuff on cars in parking lots everywhere I go... Have you ever visited John Farlam's Smart Driving website? He's another gem of driving widsom: http://www.smartdriving.co.uk/Driving/DefensiveDriving/Space/Space.htm Here is my group website: http://www.care2.com/c2c/group/drive_aware There are dozens of sites like mine, but I don't believe there is such a thing as "too many resources" with something like this. Thanks again, Mr. Beatty! Malee Holland <mholland2@cfl.rr.com> Orlando, FL USA - Sunday, April 06, 2008 at 07:04:28 (PDT) I already new this by instinct. I have been driving this way from the start (since 1976). Courtesy always pays. Lynne Calvin <leoncat_shelter@yahoo.com> Harrisonville, MO USA - Wednesday, April 02, 2008 at 08:29:56 (PDT) Fascinating stuff. I've observed similar dynamics in my travels, and have experimented a bit, though usually with the goal of improving my gas mileage. I read the FAQ about a particular spot on a hill in Seattle-- sometimes I think it's just a hill itself that can create a wave or jam-- people slow down slightly without noticing as they go up a hill, creating bunching at the bottom. (An example that some readers in Boston might be familiar with is on 128 travelling North leaving Needham, before your get to route 9). Another aspect that I don't see explored is the effect of external constraints on a highway jam. For example, a traffic light at the begining of an on ramp or end of an off ramp. Or, an off ramp that then merges with a street that has heavy uniform traffic with close spaced cars that the cars on the off ramp can't merge with. For example, on my current commute home a traffic light controls the entrance of traffic to an on ramp that then merges onto a small highway. So the on ramp releases a big clump of cars, that have insufficient gaps to merge onto the traffic already on the highway. This slows down the cars travelling up the on-ramp (which is already an uphill climb) as well as creating a jam right at the onramp (which is also uphill, which doesn't help). Anyway, just two situations I'm familiar with. We could probably develop a systematic index of all these factors, and look at the results of their combinations on flow and what kinds of behavior changes might affect them... Reed Hedges <reed@interreality.org> NH USA - Wednesday, March 26, 2008 at 13:28:52 (PDT) What's best to do in this situation? On a two lane divided highway, my lane is ending ahead. However, the cars in the continuing lane are bumper to bumper moving very slowly, crawling. Should I slow down (almost stop) and merge immediately or should I continue forward as far as I can go then merge. I usually do the latter; however I find that people in the continuing lane get upset, I'm sure they feel that I am cheating to get to the front of the line. Comments please. nooper <noop99@rogers.com> Ottawa, ON Canada - Monday, March 24, 2008 at 08:52:00 (PDT) How about adding a webpage to this site, organized by city, with suggested places to try the anti-traffic technique? You've mentioned a couple of spots in Seattle... I'd like to say that, in Austin, Northbound IH-35 at the 183 North exit is a great place to observe the effects of Big Empty Spaces. There's traffic merging left onto IH-35 from the ramp just north of 290/Koenig, and traffic trying to get right so they can exit to 183N. The result is usually a horrible jam in the morning. I'm pleased to say that by decreasing my speed a tiny fraction (foot off gas, nothing as drastic as braking) and letting people merge in front of me from both sides, I have singlehandedly broken up jams half-a-mile in length. Any other Austinites practicing BES? Seems like MoPac near downtown and Loop 360 would be good candidates. Oh, and southbound MoPac around 45th/35th, which is prone to those Mystery Jams, where you think there's an accident ahead but when you get there... there's absolutely nothing and people zoom off! To email, add my first name to the addy given. Cheers, --Kathy Kathy <grace at austin dot rr dot com> Austin, TX USA - Monday, March 24, 2008 at 08:06:48 (PDT) Great explanation and it matches my experiences also. I like your idea about merging and will adopt your suggestions and see how it goes. Chas Albuq, NM USA - Wednesday, March 05, 2008 at 08:02:36 (PST) In Oklahoma they have passed a law that says that you have to merge as soon as you first see the signs that a narrowing will occur ahead of you. This is to prevent jerks from intentionally zooming along in a lane that they know will close then bulling their way into the open lane. I'm curious if this will help create more zipper merges or if it will just move the standing wave further up the highway. [I think the empty lane is the only thing that lets people cheat. With a law that creates empty lanes, you'd need a cop at every merge zone if you wanted to stop cheaters. Since that won't happen, I think the law is creating traffic jams. If instead it became illegal to block merging cars, and the law recommended wide spaces and "let one in ahead" merges, then Zippers would be created on purpose. -billb] Aaron Stillwater, OK USA - Friday, February 29, 2008 at 20:40:00 (PST) This is not a question ;) I'm glad I found your article! I'm a wave-smoother myself, but i couldn't convince any of my friends/relatives of it's benefits. Everytime I miss a greenlight, the passanger says that it was because i was not rushing after the empty space ahead of me. I became a wave-smoother after a fluid dynamics class. Considering some ideal conditions, you can easily show that the flux rate of a fluid is constant at all times - everything that enters must come out. This helped me in the following aspect: if i'm driving in a 60km/h*2-lanes road, and one road gets blocked, the only way the flux stays the same is by driving at 120km/h in the available lane (which's not likely). What´s usually happens is that the flux is now half (60km/h*1-lane flux) so there´s no way but slowing down to 30km/h, before the block, (30km/h*2-lanes = 60km/h*1-lane). Simple, but people find it hard to apply! My 2 cents. Samuel Samuel <mukaobr@uol.com.br> Brazil - Thursday, February 28, 2008 at 07:28:58 (PST) Just want to tell how interesting are your articles-of-life:) It's 4:07AM, had to go sleep but found your article... and now reading them non-stop... Thanks for such work. Vahan A. <vahan@avgnint.com> Los Angeles, CA USA - Thursday, February 14, 2008 at 04:08:20 (PST) I agree with (and practice) almost everything you suggest, with one exception -- the "cheaters" in merge situations DO need to be punished. Otherwise, you create an environment that will simply breed more cheaters. [ True, but if we don't block cheaters, then soon everyone will start "cheating," and the empty lane will fill up. Does that mean *all* of them cheaters? Of course not, since both lanes are now going the same speed. Nobody can race ahead when the lane is filled! I conclude that "cheating" only arises: 1. when everyone merges early, 2. then they start driving bumper-to-bumper and refusing to let anyone merge early or late (or merge at all, ever.) At jammed exits or lanes which are ending, the traffic jams appear when people in the "through lanes" try to block merging cars. If instead I open up a huge space and let all the cheaters merge ahead of me, then no cheaters are racing to the far end and bulling their way in. And then there is no reason for anyone to drive slow. And that's what busts the traffic jam. Yes, that's right: you can shatter a merging-lanes traffic jam by letting lots of cheaters jump in ahead of you. I've done it many times, and it's stunning to watch the entire backup suddenly evaporate. There are two places in Seattle where this works amazingly well. -billb] I always allow people to merge into my lane for exiting, until it gets to be "too close" (which is admittedly a matter of judgment) at which point I'll absolutely refuse to allow people to merge. I'm not thinking "just merge behind me" but rather "you waited too long, you have to skip this exit and loop back." Having grown up in NJ (where this type of practice is quite common -- we HATE "cheaters" there) I know that this type of behavior eventually discourages cheating to the point that it diminishes. When I moved to the Bay Area I was astonished at how people would let others merge -- even across multiple lanes of traffic -- and was constantly irritated by the backups this would cause near every single exit, even when I was in the through lanes. There is NEVER a backup in the through lanes in NJ, no matter how much traffic there is at the exit, because everybody knows better than to try to cheat and cut across at the last minute. I think this is probably why people driving through NJ consider drivers there to be complete jerks, but it's really just adaptive behavior for a region of the country that's had to deal with high levels of congestion for much longer than anywhere else. Bill Clark <wclark@xoom.org> Oakland, CA USA - Tuesday, January 08, 2008 at 08:57:40 (PST) I take a weekly trip north on I-93 and for a while got stuck in traffic every week. Like you, it gave me plenty of time to watch the patterns of traffic around me. Where pinch points happen and where the waves of traffic seem to emanate. Picturing it in my head and creating "rules" allowed me to observe how my own actions can affect other drivers behind me. (And sometime around me too) Eventually I began to practice the same scenarios that you describe. Slowing down gradually to create a gap in between my car and the car ahead of me that would be caught in the jamb first. I certainly noticed a difference after practicing a few weeks in a row. I began to notice that drivers behind me would start to emulate my behavior. They would stop changing lanes often and remain in their spot. The biggest kick i got out of the whole experiment was watching aggressive drivers fly up to the jam weave through a few people and then get stuck as I coast by. (This was not always the case but in most instances I found that I would maintain a semi-permanent position in relation to aggressive drivers.) It was also a thrill to look to my right (I am usually in the far left lane) and see that people around me were doing the same thing. Within a 20-yard radius the cars were behaving in a similar manner, eating up the waves that we came up against. I just want to add a few notes from my own experience. 1. I believe it is easier to "eat" traffic waves in a car with a standard transmission. a)Breaking automatically alerts the person behind you that you are slowing down. In a standard you can slow down without breaking by down-shifting so that the person behind you must become conscious of their own speed and position within the group. b) Shifting gears and attributing certain speeds to what gear you are in helps you identify the severity of the traffic jam and the period of each traffic wave 2. You mentioned that at first you thought it was a philosophical solution, ie maintaining a "cool-head" and driving with patience, but later abandoning that reasoning and adopting a more scientific view of upholding certain driving habits. I would counter, and say that it is both. a) I don't think one is capable of doing one without the other. If I had not let go of my own ego and released myself from the recurring negative thoughts that I must be first, and that I must continue to pass people to make headway in traffic, i would not have been able to observe the laws that were governing the traffic jam. Thus, I would not have been able to improve my driving and (since conscious driving alleviates the traffic for those behind me) the drive for those other people with whom i share the road. b) if you "project" your good driving behavior you cause other drivers to become aware of their own driving and, perhaps, improve themselves. Which would cascade into better drivers all around. (we all know Massachusetts needs more of those) Lastly, I just wanted to say thanks for taking the time to put together your essays and post them publicly. This is a great resource for others. Peace. ~ML Morgan Lawless <mmmorgan.lawless@gmmmail.commm> Boston, MA USA - Wednesday, December 26, 2007 at 09:15:09 (PST) Hi Bill You might want to check out these two links: http://www.exeter.ac.uk/news/newstraffic.shtml http://www.sciencedaily.com/releases/2007/12/071219103102.htm Someone should have spent a little time on Google searching for "traffic waves"... I blogged about it here: Synthstuff Dave Halliday <dh@synthstuff.com> Maple Falls, WA USA - Saturday, December 22, 2007 at 19:07:24 (PST) I've personally seen this work. When I lived in Hurricane, WV and they were doing major construction on the interstate (it has major traffic flow between Charleston and Huntington, and I know this is no big city traffic) but when people fought to merge traffic slowed to a crawl. Since a lot of trucks move through the area they started forming roving barriers that increased traffic flow. Other drivers noticed the improvement and formed barrier partnerships with cars beside them. Worked wonders, cleared up hours of traffic hassle at least for the people doing it and those around them. Since I've moved up to Morgantown I've noticed the people don't do this and are very competitive (due to the high student to town population ratio). For a "smaller" town traffic is hell here mostly because of this competitive behavior. Tom Morgantown, wv USA - Friday, December 21, 2007 at 16:46:53 (PST) I don't have a question. But I read your "theory" a couple of years ago and follow it on a regular basis on the 10 or 405 with much success. It takes some of the stress out of traffic jams when you can single-handedly improve traffic flow. It really does work and I've never had a road rage incident.. Thanks! james <stoptimela <@> gmail.com> los angeles, ca USA - Saturday, December 15, 2007 at 01:35:10 (PST) This is why I believe now that traffic lights are far inferior to roundabouts. If you think about it, traffic lights promote a hurry up and wait system. Roundabouts promote average speed driving. What you’re describing is driving the average speed. When I see a red light way ahead, I begin to slow down. Ahhh… look at all those fools continue racing toward the light, some even come into the lane in front of me (I’ll get to that in a bit). I rarely ever actually stop at red lights, unless the light turns red right in my face, which is the worst! Because if I had known that it would be red, I would have slowed down a long time ago. This is why I mention that traffic lights promote a hurry up and wait system. Also, since traffic lights work in letting everyone through in this half of the time and the other half people build up the queue, if you are driving the average speed to the light and someone is behind you and unable to make it to the left hand turn lane because you didn’t feel like stopping, there is obvious peer pressure for you to go faster to a light that is red. This is why roundabouts are much better. No left turns at a roundabout. With a roundabout, I can actually drive the average speed, slow down early to a long line of cars, and I’ll only piss off totally ignorant fools who have no idea about anything, but they won’t actually have any point to be mad. Where as, in the traffic light with a left turn lane example, the guy behind me kind of has a point, after all, it’s not his fault that the traffic light is designed for me to move up as fast as possible allowing him to go left. But getting back to the point I said I would get back to, if I’m going the average speed and some guy goes around me, (ESPECIALLY if he does this when no one else is in front of me and he just wants to get to the front spot) when the light is green and I’m prepared to move past everyone at 20mph since I didn’t stop and he’s the only one holding me up, I usually honk my horn, flash my high beams and pressure this person to get on their horse. After all, they were in such a rush to get to the light, I assume they’re in a mad rush like all hell to get to wherever they’re going. And if he wasn’t there, when the light turns green, I’m zooming past everyone because I wasn’t stupid enough to stop. I “used my space” to keep my speed and my lane didn’t stop behind me. I do this ALLLL the time, drive the average speed that is. One night, it was CLASSIC when a cop (late at night, no one else on the road) did this to me on a 2-lane (each direction) road. The light turned green, I started to accelerate but not that fast, on a 45 mph road I slowly accelerated to about 30 mph and then started to cruise. The cop behind me was clearly pissed off because he raced around me at 50mph and then… yes that’s right, his brake lights turned on and then came to a complete stop. I was still going 30 mph and approaching a red light where he was stopped at. Light turns green, and before it even turns green I accelerate to 35mph and on my way to 40mph as he’s only just starting to move. Without speeding (I don’t ever speed past the speed limit), I had gotten about 15 cars lengths ahead of him, it was sooo funny. And the best was, once I got through, I started to slow down again because I noticed the light was red again ahead, stupid cop raced past me trying to show me he’s faster and I have a slow car, and I did it to him AGAIN! He then passed me again going about 55 mph on a 45 mph road, he passed me at 10 mph faster. Good for him… Simon Hartigan <simonhartigan@cox.net> Mission Viejo, CA USA - Thursday, December 06, 2007 at 20:50:47 (PST) It's always nice to see someone thinking about traffic dynamics. The discussion here has addressed mainly highway traffic, but I'd like to point out that the application of some intelligence can make city driving easier, particularly with respect to stop-light behavior. Chris from Sierra Madre (Nov. 26, 2006) asks us to imagine how much better it would be, when a red light turns green, if all the stopped vehicles could begin at the same time, like the linked cars of a train. He suggests that everyone start moving together and "accelerate quickly" as soon as space is available. It should be obvious that this is a risky strategy in dense traffic, where the failure of even one driver ahead of you to behave as you wish can create a chain of rear-endings. Ed from San Diego (June 21, 2007) describes the "red light shuffle," by which drivers who have already stopped at a light compress the open space between their vehicles, moving up one at a time as if being slightly closer to the light itself will enable them to get a head start when the signal changes. He mentions brake wear, but doesn't really address the shuffle's effect on traffic dynamics. The answer, of course, is that compressing distance at stop lights has exactly the opposite effect of what the drivers are presumably seeking. It slows down everyone (except the very first car), because each driver, practically sitting on the bumper of the next car forward, must wait for that driver to move before he can. The next car, in turn, must wait for EACH preceding driver to get going, one at a time, and so it builds. With enough vehicles on the road, you eventually get the frustrating situation in which the light turns red again before everyone in front of you has gotten through. The simple solution is this: NEVER CREEP UP at a red light. Stop a modest distance behind the stopped vehicle in front of you, and STAY THERE. Let the vehicles in front of you creep up. Let the vehicles in adjacent lanes creep up. Let people give you funny looks because you are not seizing absolutely every last inch of "available" asphalt. Watch the signal light. The instant it turns green, begin rolling forward slowly, past those people who gave you funny looks as they crept up and passed you while the light was red. They will be waiting for those in front of them to get going. When this move works to its fullest, the vehicles in your lane will be under way before you catch up to them, and you will be able to put some gas on while adjacent vehicles are still barely moving, if at all. Accelerating at this stage is much safer, because everyone in front of you will have had several additional seconds to pick up speed and disperse themselves back to cruising distances. Everyone behind you in your own lane will benefit too. Their benefit will be have been reduced by some creeping of their own, although your action will have reduced the harm they could do to themselves. Maybe one of them will notice what just happened, and stop creeping at red lights themselves. Erik <spark240@excite.com> Floyd, VA USA - Saturday, December 01, 2007 at 12:19:40 (PST) I am an undergraduate physics and math student at the University of Cincinnati, and this past quarter we have been pounding away at everything that is periodic--from the simple harmonic motion of a mass on a spring, to the behavior of RLC circuits, and ultimately, the physics of waves. To my surprise and immense delight, as I sat down tonight to work on this week's problem set, I opened my book, Vibrations and Waves, turned to the end of chapter seven, which is titled "Progressive Waves," and read the first problem that was assigned, 7-22, which goes as follows: "You are given the problem of analyzing the dynamics of a line of cars moving on a one-lane highway. One approach to this problem is to assume that the line of cars behaves like a group of coupled oscillators. How would you set this problem up in a tractable way? Make lots of assumptions." Thanks to this website, my response has just become much more interesting--I am even going to suggest to my professor that he include it in the syllabus! Also, for the curious, this book written by A.P. French, and was first published in 1966 by the Massachusetts Institute of Technology. Aaron Eiben <hawk22@gmail.com> Cincinnati, OH USA - Monday, November 26, 2007 at 19:48:55 (PST) One factor I believe you have ignored is that of grain-size. Traffic can indeed be modelled by fluid dynamics, however in order to accurately model actual traffic flow you must also account for the varying sizes of the individual vehicles. The understand the significance of this, just imagine this: You are pumping ready-mixed cement into the basement of a new house. If there are any over-large stones in the mix, then the flow is constricted and a "cement jam" ensues. Applied to a real-world traffic problem, if there is a large bus broken down in the middle of a lane, only smaller vehicles will be able to get past it. Having driven cars and motorcycles thru many cities around the world, it always surprises me how little this principle is understood. In the city I live, the urban planners seem to think that buses are a better idea than cars. They think that getting ten people out of their cars and into a bus is a good idea. They don't seem to realize that a bus has to stop very frequently. This results in a reverse wave travelling backward through a crowded city, causing traffic jams miles away from the actual location of the bus. This is why I prefer to ride a motorcycle thru congested traffic - so why don't planners ever consider this???? Patrick Magee <patrick_magee@hotmail.com> San Francisco, CA USA - Wednesday, November 07, 2007 at 00:20:45 (PST) "Merge now, or get out of my way!" I could almost hear the driver shout. The situation was this: we were heading into Bristol, England along the M32 when we started to see signs saying "lanes merging, keep left". So we dutifully merged, as did most drivers, into the left lane. This meant the left lane started moving slower and slower, and the right lane became virtually free of traffic, except for a few ignorant drivers who didn't see the signs, or worse, the "cheats" who chose to ignore them. The left lane got slower and slower, and almost came to a standstill, while drivers on the right whizzed past to the front of the merge. Frustrated by this, the driver in front of us waited for his moment, signalled right and cut into the right hand lane. We thought he would simply speed up and head to the front of the merge so we got ready to occupy his space, but instead he simply drove at the same speed as us, stopping when we stopped. Seeing his intention, we left the space he had previously occupied empty so he could move back into it when we reached the merge. "Why not?" we thought, he is clearly acting for the common good, and it might actually work. A few moments later of course, a few drivers started to jam up behind him, parping horns, waving hands from side to side, asif to say "what on earth are you thinking of?" Then a few moments later, to our amazement and glee, the traffic in our lane started moving much faster. Clearly we had unlocked the merge for an instant, freeing up the traffic ahead. Before long, we were through the merge, we gave eachother a visual "hi-five" and went on our way. What came after us was anyone's guess, certainly we had helped to free up the traffic ahead, but whether that would carry on was anyone's guess. My guess is that the right hand lane filled up a little more, the cheat drivers saw there was little to be gained from being in the right lane any more and merged, the ignorant ones slowed down enough to notice the signs. Once again the right hand lane would have become emptier and the cycle may have started all over again. But the point is, being in the correct lane IS important, and often there is nothing to be gained from queue jumping, collectively and perhaps even individually, as the lane you are jumping into may be the cause of the delay in the first place, and certainly can't guarantee a quicker route through the merge ahead. Henry Bainbridge <henry@dubstudio.co.uk> Bristol, UK - Wednesday, September 19, 2007 at 05:37:50 (PDT) I'm an old math and science teacher. I figured this stuff out over a few months when I was about 26. Now 16 years later, I find that I've persuaded about 15 people to drive this way--a frequency of about 1/yr. The method of building lead space and trying to adopt a very uniform speed works well in cities and (normally) on the autobahn. It works in Korea and Japan as well. It does not work in countries in which drivers are seemingly suicidal such as France, Italy, Greece and Mexico. Where it works, it solves all sorts of problems, but it cannot, ultimately, resolve the issue of super-aggressive drivers. Germany has perhaps 20-30% super-aggressive drivers (normally these folks are found in high-performance gas guzzling cars). This results in their wonderful highway system being plagued by "Der Stau". As in a Wagner opera, Der Stau is a traffic jam of truly epic proportions. Imagine a 20km line of closely packed traffic with 20km until the next exit. In one stau near Aschaffenburg I becamse so overheated, dehydrated and helpless that I was on the verge of a medical emergency. Four hours after the authobahn stopped there it began to move again. I've suggested solutions to the Germans, but they will not listen. I'll try here as well. 1) Emergency exits, 2) Gated stau relief exits, 3) gated autobahn entrances, 4) electronic signs to reroute traffic prior to entering the autobahn, 5) strictly enforced speed control and exit advisories ahead of staus, and 6) teach your population to increase their following distances to that needed at their target speed. Just two days ago I broke a traffic jam on the B13 in Ansbach by letting an about 100m gap build ahead of me and then trying to keep my speed constant. I was moving at 20km/h for about 2 minutes and up to 50 km/h in another 2 minutes. I observed MANY cars turn left across my path, lots of traffic was also able to merge into my road. In short I had created usable anti-traffic. For this service I was flashed perhaps 100 times by the gentleman in the BMW behind me. Fortunately blowing the horn within city limits is tantamount to calling Der Polizei--so German city traffic is quietly seething :-) Scott <4dr3sp0ns3@googlemail.com@whatit.com@deletethisandwhatit.com> Nürnberg, Bayern Deutschland - Tuesday, September 18, 2007 at 16:08:14 (PDT) You are obviously a very thoughtful person and want to make things better for everyone, so I hope this post helps. First, we have to mention a make clear a few properties of roadways. Roadways are like a high-density fluid. For example, imagine a funnel. If the hole at the bottom of a funnel is 1 cm, and one pours water into the funnel from an opening that is 2cm, then a "traffic jam" will form in the funnel due to the capacity restriction. Second, it helps to keep in mind that roadways are inherently unstable for two reasons. 1) They have low throughput of only about 2250 cars per hour per lane of travel. This is because people almost follow the "two second rule" when driving at speed. Actually, each person maintains a "comfort zone" that consist of roughly 1.5 seconds plus about two car lengths. 2) Because of this minimum distance between cars, as the rate of travel slows, the throughput of the system drops, too, as described here: http://en.wikipedia.org/wiki/Fundamental_diagram_of_traffic_flow Think about that for a moment. Even with a freeway with 4 lanes of peak direction traffic, only 9,000 people can get to work during the peak hour of travel. So, what happens when person number 9001 comes down the on-ramp? Everyone is already traveling down the freeway, maintaining a comfortable 1.5 second comfort zone, and there are no extra gaps for a new car to fit. The inevitable result is that someone will slow down to accommodate the merge and regain that 1.5 second comfort zone. But since the highway is already at capacity, everyone behind the merge also experiences a 1.5 second delay. But it doesn't stop there. Since the throughput of the highway decreases as speed decreases, there is also a corresponding loss of throughput for the lane, as well. In fact, assuming travel of 60 miles per hour prior to the merge, and assuming a speed decrease of just 1.5 miles per hour for just one second, the throughput for that lane of traffic would have dropped by 34 cars/hour during the merge, thus creating a rippling effect all the way down the lane to some point where the bandwidth of the roadway is no longer saturated. Of course, the effect of this one merge is not much. But multiple that by 20 cars per minute coming from 10 on-ramps? Well, we can start with a 300 second (5 minute) delay just to accommodate the space taken by these cars (at 1.5 seconds separation per car) and the throughput for the lane after the merge drops right to 0. So there's really not much one can do to ultimately unwind the traffic jam except to avoid driving during peak periods. And even though people want to blame others for the traffic jam, it's a simple matter of physics -- too much water poured into the funnel all at about the same time. With all that said, your suggestion to create an "anti-wave" is helpful. In addition to reducing stress and saving energy caused by unnecessary brake/acceleration cycles, you may increase the throughput of the roadway by spending less time driving at the speeds with the least throughput. I do have a suggestion for to consider regarding merging for lane reductions. Allowing extra space for all the aggressive drivers to merge in front of you at the merge point creates a moral hazard by rewarding the anti-social behavior. The net result is a net increase in travel time for yourself and all the rule-abiding people in your lane of traffic, while the anti-social behavior is rewarded with a net decrease in travel time. An alternate approach is to drive in the lane that is about to merge until it ends, while driving at the same speed as the cars in the other lane. Once your lane ends, you can merge in a saw-tooth pattern when a space becomes available. You'll find that people will be happy to let you in, since they didn't have to sit and wait for a dozen or more sociopaths to merge in front of them. This reduction of tension also contributes to people allowing a comfort zone of space to develop between their car and the one in front, which contributes to the average speed (and throughput) by eliminating some unnecessary stop-and-go driving. Further, this method makes the most efficient use of the roadway. I want to end by amplifying the suggestion to minimize the amount of driving done during peak periods. If people can give a lift to a friend, coworker, or neighbor, that would double the throughput of the roadway. Better still is to sit back and relax on a bus or train while someone else takes you to work. Not only does that the environment, the economy, and national security by reducing dependency on foreign oil, it gives you a chance to read a book or magazine during time that would otherwise be wasted driving. Finally, the best suggestion is to work from home if you can. This reduces energy consumption the most, reduces stress from commuting, lowers costs all around. Thanks again for so thoughtfully considering this issue. Almost Got It <almost@gotit.com> Chicago, IL USA - Friday, September 07, 2007 at 01:13:11 (PDT) Great article, I was gripped all the way through! I've practised your -ve traffic jamming for several years now, although never really thought about it. Alas I can't do it all the time as I get a bit worried about the guy behind me getting out at the next lights to ask 'what's up?' Needless to say I think it's a good idea if more people do this, saving tyres, brakes, engines, road-wear, emmisions and (hopefully) stress levels. Actually I've never had anyone get (visibly) mad with me, I hope that's because they can see I'm approaching the car in front as it's starting to move off, or the lights (sometimes :-P) as they're changing to green. During my commute to/from work I combine this with letting in a driver or two from side roads and bikers overtake (because they always do) safely. Have you tried getting your car and a car coming from the opposite direction through a tiny gap as quickly as possible? I will slow if they're nearer the obstruction (say a parked car on a narrow street) than me and flash my lights several times to get them through, or speed up noticeably and agressively if I'm definitely closer to the obstruction - they'll always see me speeding up and will only have to slow a little before I'm through and waving 'thanks' like a lunatic! Justin <justinclark61@hotmail.com*&^%$> London, UK - Wednesday, August 22, 2007 at 12:09:56 (PDT) Great article on traffic! I came up with most of those hypotheses on my own from my experiences driving up and down California and experiencing many of those mysterious phantom traffic jams (no accident - no apparent cause). You did a great job explaining how this can happen based on driving behavior. In my opinion, drivers in heavy traffic areas are far too jaded by constant traffic jams and accidents for the looky-loo's to be the problem. And yet, the putative notion is that rubber-necking causes ALL traffic jams to persist. I think most people never really think about it. I don't deny that rubber-necking is a factor, but I think its blown way out of proportion. Another phenomenon I find strange is something you could call the "red light shuffle". Here's how it works: 1. When cars stop at a red light they leave a certain amount of space in front of them and behind the car in front of them. For some reason the guy in front is almost always about 8 feet from the line. 2. After 20 seconds or so, the people in front start creeping forward and making the spaces they've left in front of them smaller and smaller as if they've suddenly become unhappy with the amount of space the left originaly. 3. This makes the spaces for the cars behind them bigger and bigger and then all the cars behind them start shuffling forward as the space in front of them gets larger and larger. 4. If you are near the back of the line of cars and you don't move, you end up with a car-length or two of empty space in front of you. You may feel uncomfortable about this and creep up closer, thus perpetuating the shuffle. 5. Everyone puts more wear and tear on their brakes from all the shuffling. I also think it may be possible for highway traffic jams to creep forward, but I don't know how this would work. It just seems to me that I've been through a bunch of jams that only cleared up a significant distance after the site of the accident that caused it. Ed San Diego, Ca USA - Thursday, June 21, 2007 at 13:58:49 (PDT) Excellent information. Instead of a wall of state troopers, how about "Pace Cars"... :) Ed TN USA - Wednesday, June 20, 2007 at 10:21:13 (PDT) As reassurance in the correctsness of your basic "Truckers Figured It Out" trope: I drove big trucks for several years, and the tenants of Big Spaces, Let Others Merge, and Go Slower To Go Faster aer all nearly instinctive in that World. Most of us would call it "being polite" and leave it at that, since, lumped up, that is essentially what it is. The Left Laners are jerks with a justification and probably all own Corvettes and Hair Plugs. Fronk USA - Monday, May 28, 2007 at 22:49:09 (PDT) Read some of your ingenious ideas. You might want to throw this into the mix and pass the word along to help reduce the "pressure waves". Thanks... News Release Dateline: April 23, 2007... Portland, OR Web Address: http://www.leftlanedrivers.org Enough with slow drivers in the left lane! “As traffic gets increasingly congested, it’s time for citizens to reclaim the left lane,” says J.A. Tosti, spokesman for Left Lane Drivers of America, a grassroots effort to get slower traffic to move right. “More and more these days, you find slow drivers in the left lane, causing no end of headache and frustration to those of us who have places to go and people to see. Some of these offenders are timid and tentative, some are completely oblivious to what’s going on around them, and some are self-appointed ‘hall monitors’ regulating what they alone have determined to be proper driving speeds. Whatever be the case, it’s time for us to trumpet the message, ‘If you’re not a Left Lane Driver, get out of the left lane!’” In order to actually help slower drivers move right, Left Lane Drivers of America offers copyrighted windshield decals which boldy and prominently display their unified sentiment in the offending driver’s rearview mirror. The decal, which reads “MOVE OVER” also has a large arrow showing them where to go. The words and arrow display backwards on the windshield so that they read properly when seen in the mirror (go to www.leftlanedrivers.org to see picture). According to Tosti, “Although the message minces no words, the idea here is not to be rude or pushy but to offer slow drivers a gentle prod, reminding them of the need to either pick up the pace or make room for those who choose to drive a bit faster.” In fact, slow drivers do need to move over. In many states, the left lane is supposed to be the passing lane and slower drivers can be cited for obstructing traffic. Those who stake out permanent positions for themselves in the left lane tend to provoke those wanting to drive faster, often giving them no other choice but the dangerous strategy of passing on the right in order to get ahead. Slow drivers can easily become slow moving safety hazards. Bottom Line: Moving over is a matter of courtesy. It is a matter of safety. It is a matter of doing one's part to help traffic flow smoothly. And it is the law in many states: “Stay to the right except to pass”. Left Lane Drivers of America is doing something positive to help improve traffic flow on today’s overcrowded, pressure-packed freeways. Their “Move Over” message has the potential of helping reduce instances of road rage, hazardous driving and untimely, often deadly accidents. J A Tosti <jat@teleport.com> Camas, WA USA - Monday, April 23, 2007 at 20:46:57 (PDT) Awesome site! Really interesting to read about. (: Tanya Honolulu, HI - Sunday, April 08, 2007 at 14:45:21 (PDT) Hello. I have some very naive questions: 1) wouldn't the rolling barrier idea have the supposed effect of everyone braking and creating another jam? 2) If all of this is just science, then why don't we have scientists figure out how to help traffic instead of building more infrastructure. If it requires certain behaviors on the part of drivers at large, why don't they just tell people that on the news and on commercials, etc. I've never seen any information anywhere about how I should drive on the highway to prevent jams. According to you, there is a solution, but people just need to do it. But nobody knows what the solution is, because most people don't go researching all this stuff on the internet. So why don't big cities go on a campaign to just get the information out to everyone? 3) I'm sure the answer to this is very obvious, but I'm curious: why wouldn't raising the speed limit help traffic? If everyone got on and off the highway faster, wouldn't that do something to clear it up? 4) Since you're from Seattle, I have another question -- the backup on I-5 Northbound at the Mercer exit --- isn't this all because of the traffic lights once you get off the exit? I know that if I turn right at the first light, then there's another light. And I've noticed that there's often much less traffic going crossways at that second light. This seems to just back everything up on the highway. Why don't they just put traffic lights with sensors at places like this? So that the light is only green when it needs to be? Wouldn't solutions like that be cheaper than exansions? richard pellegrin <pellegrin42@yahoo.com> seattle, wa USA - Sunday, April 01, 2007 at 21:47:34 (PDT) Hey Mr. Bill Beaty, Your site is so cool. thanks very much for your insights into this traffic thing. Experiments, analysis, animations and a good spirit of finding solutions for ALL OF US ! Whoa, behaviour on the roads is so bad, largely through ignorance I hope (and not malicious intent ..) and so the light you are throwing on the subject is potentially very useful. Only "potential", since it is up to us drivers to adopt some higher principles of action on the road, beyond ME FIRST. I wish you fun and success in your explorations. Carlos Carlos Bagnales Toronto, CANADA - Saturday, March 24, 2007 at 20:54:44 (PDT) It was very noticeable to me while driving in the Seattle area last year that people there tended to drive at a steadier pace than drivers here in South Florida. For years I'd tried slowing down traffic to ease the wave problem. It only seems to work to a small extent when there is only one person doing it. Perhaps many more people in the Seattle area know about this idea and try to implement it themselves. I've never come across any such conversations here but will begin mentioning it from now on to see if it helps on I-95. lifeisgoode USA - Wednesday, February 28, 2007 at 11:01:41 (PST) There doesn't seem to be much talk about the "safe space" factor in your explanations. Maybe I missed it, and sorry if I did. Here's what I'm talking about. For a given speed, drivers have a "safe space" that they will try to maintain between them and the next car. At high speeds, this space is relatively large. At low speeds, this space can be as small as a few feet. Anyway, the point is, by leaving space for people to merge into, you aren't necessarily gaining anything, because you'll have to slow down to maintain your safe space when they merge in front of you. If it's 100', when someone merges in front of you, you'll have to slow down 50' (relatively speaking). When you slow down, then the person behind you has to slow down, and on and on--and we have the beginnings of a jam. To me, the key to efficient traffic flow is attaining highest speed with the littlest amount of space between cars. However, if you make the space too small (or the speed too high), then the slightest disruption (as you have mentioned) will cause a jam. Raise speed limits and drive safer cars. That's my advice. Maybe those gigantic SUV's going 95 MPH aren't so bad after all... In my opinion, part of the reason why traffic is so hard to figure out is that every driver has a different "safety zone" vs. speed program in their head. When going 65 MPH, granny requires 300' of space, while you may only require 100'. If someone merges in front of granny, she's going to slow down to what she considers a safe space vs. speed ratio, and so will you. As for weaving in and out of traffic--I've often wondered if I could sneak through the holes in traffic without affecting the system at all. There's all this space--even in congested traffic. Is it possible to use that open space without adversely affecting the flow? Is it possible that I'm helping out the situation by using space that no one else will use? On a 4 lane highway, is there a hidden "5th lane"? A 5th dimension--the empty space between all the cars? Just remember, wherever you go, there you are. cheers, andy Andy <andrewRneumann a t sign gmail com> Dem. Rep. of Congo - Monday, February 26, 2007 at 10:58:08 (PST) I love this page. Generating anti-traffic can make the experience of being in a traffic jam almost bearable. Your car is acting as a low-pass filter for traffic change (slow down) and because there's inevitably some lag in a driver's moving from stop to start, by driving at the average speed (a bit below) you are removing an amount of delay equivalent to that lag times the number of cars' space you're introducing to the bottleneck (I think.) Another way to look at it: by slowing down before a jam, you are propagating information as to the u coming jam more quickly to following drivers, allowing them to adjust their speed more efficiently than stop/start, and hence allowing them to avoid the jam. On the subject of information propagating upstream: in Qingdao city Shandong province in China I noticed they have large LED signs on each traffic light visible for 100s of meters, giving the remaining time to the next light change. I'm not certain *why* they do this, but I think it could contribute to anti-traffic. Finally, thanks for giving meaning to traffic jams! Colin <colinZAP a t sign POWchinixDELETE com> Sydney, Oz - Thursday, February 01, 2007 at 06:05:57 (PST) I'm fortunate that I don't have a long commute, but I do take long trips several times a year. This explains something I've noticed in the past few years: I haven't encountered any significant construction merge-lane stop-and-go congestion, and I think it's because I got into the habit of getting into the thru-lane as soon as I saw the lane-closure signs, and then slowing down to the work-zone speed limit when those signs appeared. Since most other drivers were still going faster, this had the effect of creating the traffic hole you describe, the cars in the merge lane could merge, and by the time I got to the lane closure any prior congestion must have evaporated. My philosphy is, you don't fight the traffic, you learn to flow with it. If you're in the interchange lane and someone's approaching on the on-ramp, you act like a gear tooth and let them in ahead of you if they're ahead of you. (I do get pissed when some jerk passes me and immediately exits, though.) Peter Kappesser Syracuse, NY USA - Sunday, December 03, 2006 at 19:54:24 (PST) One very strong argument that would encourage folks to use your suggested techniques is fuel economy. Travelling at 20mph for 20 minutes is far more efficient than travelling at 40mph for 10 minutes and then idling at 0mph for 10 minutes. Every time you use the brakes, k netic energy is being converted into heat. So the less you use the brakes, the better fuel economy. Also, coasting in gear is always more efficent than coasting out of gear with the engine idling. When the car coasts in gear, no fuel needs to be added to the combustion chamber. Once you take the car out of gear, fuel has to be added to prevent the motor from stalling. Note this only applies to manual transmissions. Slow and steady saves you money and potentially gets every to their destination quicker. Dan Charlton Seattle, WA USA - Thursday, November 30, 2006 at 14:01:28 (PST) I have a pretty crappy commute to and from work everyday. Although I have not thought as much about this problem as you have, I know that the "gap" that you crated to erase waves actually works. Infact, if you drive in traffic where there are a lot of truck traffic, you are much better off following them because truckers naturally follow the "gap" rule so that the dont run over other cars if they do need to brake hard. When following trucks, I hit my brake a LOT less often and am generally end up being much faster than the idiots who keep merging in and out just to claim any small gaps. Dub Specialist <mc68302 (at) yahoo (dot) com> Dirty Jersey, NJ USA - Monday, November 27, 2006 at 06:21:20 (PST) I agree with most things written here. Though there's one major correction: When merging two lanes into one, if traffic maintains the same distance between cars, then it's straightforward to see that traffic must go half as fast than it was going before the merge. [No, that only applies if two lanes running at half capacity must merge into one at full capacity. And in that case, the entire single lane which is downstream from the merge will contain close-packed cars. Yet in nearly all the merge-jams I've seen, the single downstream lane is totally empty. It's not overloaded. Once I've gone past the jam and entered the single lane, I can take off at the maximum speed. This happens because congested traffic moving at a crawl is a very low flow. Within the jam, the incoming lanes are flowing at *far* below 1/2 of full capacity. When combined at the merge zone, the two flows don't instantly cause a traffic jam to fill the single downstream lane. Their combined flow is just too low (and that's why the single downstream lane remains unjammed and empty.) But whenever the jam already exists, the congested cars will keep it alive because the merging of two solid-packed lanes is such a slow process. On the other hand, high congestion can create permanent jams which nobody can fix. If the two lanes feeding the merge zone are really running at greater than 1/2 capacity (like close-packed cars moving at 35MPH,) then this is a genuine overload which will trigger a massive backup, and individual drivers cannot "un-trigger" that kind of jam. -billb ] We should do what we can to educe artificial waves that exist for no reason other than psychological reasons. However, when a road suddenly has half its capacity, that's a basic physics problem that you can't solve with psychology. If you take a water hose or an air tube, and constrict it in the middle, the stream through it is going to slow down simply because it has educed capacity. That's all there is to it. Interiot <amasci com [at) paperlined [dot) org> Chicago, IL USA - Monday, November 27, 2006 at 00:03:08 (PST) Like many people have pointed out, I've been doing this also for many years. Another thing I thought of, and which you may have mentioned in your too-long-for-me-to-read-the-whole-thing article, is that of accelarating quickly when the car in front accelarates. The best way to illustrate this is like a train. Even if there are 100 cars all attached to one engine, when the engine moves, so does the last car. This principle can equally be applied to traffic. Especially at red lights. Imagine how many more cars could get through the green light if everyone that is behind a car would not wait several seconds before they increase their speed. They should immediately begin moving and then, once through the intersection, slowly allow the car in front to create a larger gap. Happy thinking. Chris <barophobia a t sign gmail com> Sierra Madre, CA USA - Sunday, November 26, 2006 at 18:55:07 (PST) One of the CAUSES of traffic, is by people NOT driving with the flow of traffic, or driving too slow for their lane. For instance, you have a car going 50mph in the far left lane, and a car going 60 in the middle lane, the car going 50mph will automatically cause a jam because people in the far left lane are going at or above the 65 speed limit. this causes the standing wave effect. EVERYONE should YEILD to faster drivers, and if someone passes you on the RIGHT, you should CHANGE LANES. This will certainly limit traffic flow problems. joshj <joshjx a t sign gmail com> San Francisco, CA USA - Sunday, November 26, 2006 at 10:03:54 (PST) I thought of this same theory just this last year since i started commuting an hour to work each way. I works best when cars next to you begin to mimic this because then cars are unable to pass and mess up your space causing it to not work. Glad someone write this out so that hopefully this idea spreads to more people on the road, specifically the people i commute in with. Chris Germantown, MD USA - Sunday, November 26, 2006 at 09:18:06 (PST) During the Carter administration, when the 55 mph (double nickle) highway speeds were implemented, some troopers did the coordinated cross-the-highway driving. People were passing on the sides of the road, the backup was miles long. I think I prefer the single driver independently operating in one lane. This way there is less of a sense of hazard, and desperation. If they want to go faster they can, but they can also be orderly. I'm just concerned now that I'll over-think my driving. I instinctively leave the space in front of me, but now I'll pause to think about it. I'm not sure that's a good good thing. From a traffic calming perspective perhaps we need smart 'flow speed' signs every mile or so, showing the r commended speed to maintain to smooth out traffic flow. This would replace the fixed 55/60/65/70 mph signs we have now, and they could be updated by the minute. Nick <nradonic at comcast net> Derwood, MD USA - Sunday, November 26, 2006 at 08:56:18 (PST) I am an Industrial Engineer and have worked on several Queuing Theory models in my time. This experiment seems to favor Queuing Theory dynamics. In fact I have even thought of this in the past. I just never thought, like you, to perform experiments on it. I really enjoy your thorough analysis and reporting on your experiments. I believe you could mathematically describe the "traffic jam" as a Queuing Theory problem. The "traffic jam" could be seen as a queuing line with stoichastic interactions. The jam itself could be a server and the i coming traffic could be arriving at different interarrival times. I would love to explore this more. You can look up more about Queueing Theory from Wikipedia. http://en.wikipedia.org/wiki/Queueing_theory larry <larrydag a t sign sbcglobal.et> TX USA - Sunday, November 26, 2006 at 07:57:37 (PST) That is just an awesome idea! You are encouraging other people to do this, get this theory out to the world! chipdip <chipdip a t sign verizon.net> Ronkonkoma, NY USA - Sunday, November 26, 2006 at 07:27:04 (PST) LOL! I line in Winnipeg Canada, and your theories fall apart here. For some insane reason, drivers here do things different than where you live. They: - do not close the space ahead to prevent cars changing lanes - let signalling drivers change lanes ahead, or already beside you, then they speed up so they can get in behind Honestly, I can change 3 lanes in 500 feet in rush hour traffice doing 50 km/hr just by signalling and waiting for the cars to move. Its a small city, in a cold place, but the rest of Canada is the same mostly. Interesting stuff. I'm an IE. :-) Dave C. <davec//at//shaw//remove//.ca//remove//> Winnipeg, MB Canada - Sunday, November 26, 2006 at 07:23:49 (PST) Very interesting analysis! I have often applied this logic during my commute to work. I try my best to go at an even speed, minimizing the taps on my brakes. Often a long open stretch of road opens up in front of me, but I resist the urge to close it up. If more people did this, wouldn't traffic improve? David Rubenstein <dave.rubenstein a t sign verizon net> Reston, VA USA - Saturday, November 25, 2006 at 18:12:20 (PST) Many years ago I was skimming through my grandfather's stacks of Popular Mechanics and similar magazines from the 1940's and 50's. I vividly recall an article from 1950 or so, about "The New 'Freeway' Systems" in the US. An engineer was asked about the traffic jams that were already b coming a part of the freeway experience, and he answered something like, "These systems were designed with the assumption of rational, consistent behaviour by drivers. But that's not what we're seeing. If people would just drive at steady speeds, and especially, leave enough room for other drivers to merge on and off, these systems would be much more efficient." (It's always dangerous for engineers to assume rational -- engineer-like, in other words -- behaviour on the part of the, um, masses.) I've been commuting for 20 years, and have observed all the same phenomena identified here in Traffic Waves. In the mornings I come down a long shallow hill on the freeway that gives me a view ahead of about two miles -- and it's very easy to see the tail-light wave patterns created by sudden braking, or by agressive drivers filling the spaces other drivers are trying to leave open ahead of them, and so on. Too bad I couldn't convince the 100,000 or so people sharing the freeway with me each morning to read Traffic Waves. We'd all be much happier, calmer people if even just a fraction of us started driving as advocated here. Brent Eades <beades a t sign ~almonte.~com> Almonte, ON Canada - Saturday, November 25, 2006 at 03:19:48 (PST) On the production of traffic jams from merges (or nowhere). On average, drivers assume a minimum comfortable headway of about 2 seconds in a traffic stream. However, at a merge, many drivers will accept a gap between two vehicles of about 3 seconds, creating two headways of about 1.5 seconds. This will not be tolerated as the cars move along and adjust to 2 second headways. Given enough of these merges in a medium short time, traffic can end at a standstill to cope. In a way drivers "shoot themselves in the foot". Alf <arhoward34 a t sign yahoo com84/.,=111> Boston, MA USA - Wednesday, November 15, 2006 at 06:37:10 (PST) Its fun to read an article that I have been thinking about for a long time. Living in Washington DC, I see this time and time again. I have been doing the "space-buffer" in front of me for awhile now, and I can see the differences it makes. The only problem around here is that, the space in front of me will get eaten up by aggressive drivers who merge at the last minute. It is extremly difficult to keep that buffer when it occurs. Anyways, Great article. Bart Washington, DC USA - Monday, November 13, 2006 at 08:05:31 (PST) What a great site! congratulations on all the effort, specially in hours and hours of experimentation (even if you were 'forced' to do it :P ). Just for the record, I'm not sure if there's a fully developed theory about traffic waves specifically, but there is some theory about traffic dynamics anyway, and according to theory, perhaps (just perhaps) things should behave just as the way you have discovered (that's one of the greates things about science, anybody should be in possibilities of trying it) I'm a master's student from my country, and I'm specializing in studying traffic phenomena, using cellular automata (CA). My theses was about the analysis of the probability of occurrence of vehicular accidents in some CA models for traffic flow. Anyway, I'm currently developing some software for the simulation of traffic flow, using the basis of a model called the Nagel and Schreckenberg model, and a generic derivative that I've done for it. When I make my degree exam, I'll try to make a webpage for it and let you know, ok? congratulations again! Javier Javier Novoa C. <jstitch a t sign gmail com> Mexico, Mx Mexico - Tuesday, November 07, 2006 at 15:45:04 (PST) The main problem is people don't know how to drive. START BLOWING THE HORN at the onset of a traffic jam, everyone must do it, everyone should be deafened with the noise, then whomever is causing the jam will get moving. Put up buildboards at choke points, saying, "You are not supposed to be stuck in traffic at theis point. Get moving or start blowing the horn". herb stone <stoneh200 a t sign yahoo com> reading, pa USA - Tuesday, November 07, 2006 at 08:34:17 (PST) I found this site about five years ago and i have been systematicly using its suggestions on motorways, and local roads and i have found that as i have started maintinaing slow approaches to traffic congestion and obsticals i have found that other drivers have learned the behaviour by example (i am not taking credit for teaching everybody how its done) but if you do it in heavey traffic every day then the guy behind you starts to realize its a good idea and quits hasseling your bumper, relaxes and backs off and boom you have a mirror full of slow moving traffic and a windscreen full of stop start stressed out bumbleheads, it relaxes me and i can take in the scenery and relax, while my car gets a better milage on fule and my brakes and tyres last longer. It works! A final point is that if you are in multiple lane's if traffic then buddy up with a car in an another lane, they will begin to see the wisdom and you can facilitate a rolling road block at a sensible and constent speed smoothing out the traffic flow and negating pressure waves. I love it and do it all the time - thinking about the car's behind and not the cars in front. As a final point if this was taught in driving schools then there would be no problems with heavy traffic - why rely on ACC when the human brain when taught correctly is far more responsive and powerful? good job for making sense of heavy traffic - maybe you could come and teach the local government that traffic lights cause more problems than they solve! Douglas <stickygoblin a t sign hotmail com> Hereford, UK - Sunday, October 29, 2006 at 03:09:58 (PST) When a vehicle is "merging" onto a freeway off of a ramp. Who has the right of way?? PLease respond, I say, already flowing traffic in their own lane should not merge to somebody coming off of a ramp?? CindieLee <tubbie a t sign telus net> Edmonton, ab canada - Monday, October 23, 2006 at 14:30:46 (PDT) I cycle to work and frequently pass clumps of held up traffic. I am frequently amazed at the triviality of the event which has caused the clumping. Thanks for a very lucid explanation of the dynamics
of these situations; I'll be r commending it to anyone interested. Hills, overpasses and turns can also trigger traffic waves. Cars (drivers) have a tendency to slow down going up hill (or up an overpass)l, and speed up going downhill. The result is compression of cars on the up hill and a rarefaction downhill. Cruise control can cancel most of an individual's variation. Turns can also trigger traffic waves. Inside turns tend to be more compressed than outside turns (differences in radius). Drivers on "autopilot" - those who drive reactively relative to toher cars - will try to match speed with the adjacent lane. BTW: In Seattle the east end of 520 past the bridge provides an example of curve compression and expansion. Carlos Salinas <andreeasalinas a t sign mac com> Santa Clara, CA USA - Sunday, September 17, 2006 at 00:50:59 (PDT) I would like to say this is such a brilliant technique. The main problem is simply the arrogance, haste and ignorance of these drivers who think of themselves before others. A lot of the cause is "No-one let's me out, I'm not letting anyone else out" and that is the only thing which is stopping this solution. Brilliant advice. More people should know this site. Do whatever you can to advertise. :] Carl Papworth (13) <JoeP021 a t sign aol com> Watford, n/a England - Thursday, September 14, 2006 at 08:30:47 (PDT) I've been doing exactly as you describe - pacing into an u coming jam - for years on my drive up RTE3 from Burlington to Nashua. It works at least in the sense of establishing 'laminar flow' and decreasing or eliminating jams. I learned it from watching truckers. Second point: when traffic is moderately heavy and beginning to 'wave' but still allowing cars behind to easily pass I try to drive about 1 mph slower than the 'average' speed. This makes virtually everyone either follow me or pass me without causing jams. I can do my commute end-to-end on cruise control and never touch the brakes while the average commuter is speeding and braking the whole way. The fastest guy is at the mercy of everyone, the slowest rules the road. net commute time difference end-to-end is about a minute - see ya at the light at the ramp. Third point: your zipper theory is spot on. Here in Mass the genius professional traffic engineers use the 'crossover' merge cloverleaf, that is the traffic getting on has to merge through the traffic getting off (and vice versa). Talk about jams. The tendency is for drivers to follow too close and to attempt to force the merge too early (probably out of anxiety that they will miss the crossover). This ALWAYS jams up traffic in both directions. If you watch carefully though there are periods when drivers who do not follow closely meeting drivers who do not cut in too soon and the speed up is dramatic. It really happens, too bad it's basically random. education needed .... GregC <gregon77_S_P_A_M a t sign hotmail com> Burlington, MA USA - Tuesday, September 12, 2006 at 14:12:24 (PDT) Great site! What a grand idea! And for the record, for those people who don't think it will work, etc., they obviously don't understand the idea fully (proven practice, not theory!), and are probably impatient drivers, and therefore jam causers themselves. Anna Moscow, ID USA - Wednesday, May 03, 2006 at 16:33:28 (PDT) This is an incredibly interesting theory. I can hardly wait for my next commute, to give it a try. I don't think it will work, but it sounds worth a shot. A fairly frequent objection I noticed is that: "You're just pushing the wave farther back." An expirement comes to mind, where you do your well practiced anti-jamming, and someone else monitors traffic behind you - way behind you -to see whether the overall situation is actually improving or ... doing the other thing. [This article is really about experiments, not theory. I commute every day and often can unmistakably see the effects of my changes. Pushing the wave away from a merge zone is the whole point. Pushing the wave back will usually make the merge zone flow faster ...sometimes stunningly much faster. On my commutes there are a couple of places where my large empty space causes a mile-long backup to totally unplug and start flowing. When it occurs, it always strikes me as unbelievable. But the effect is unmistakable so I have no choice but to accept what my eyes are telling me. Yet as you say, what I still don't know is how long this "unplugging" will last. And I haven't kept records to see how often my efforts just redistribute the clots without increasing the flow. Fortunately the unplugging happens IN FRONT OF ME, so I get immediate direct benefit. Even if the jam gets triggered again later, this won't happen until I've zoomed ahead through the fast-flowing merge zone. -billb] One thing you failed to mention, or at least mention strenuously enough, is the mechanical aspects of driving in a more sensible manner. Gun 'n' slam is hard on cars, while sensible driving is easy. Have you noticed any detectable difference in your fuel or mechanical bills since you implemented your new driving style? Jim <jb17703kresge@wavehjsldahcable.com> USA - Monday, April 17, 2006 at 14:49:31 (PDT) I have been driving like this for years, and use the same technique with stop lights. I am completely off the gas if there is a red light blocks ahead of me. Actually, I find it actually a FASTER way to get from point A to point B, at night, when traffic is light. Routinely, a frustrated driver will pass me, then speed ahead to stop at the red light. As I approach the light turns green and I pass him as he is at a dead stop. In stop-and-go driving in LA freeway traffic, I rarely touch the brakes. At 180,000 mi, the brake pads on my mini truck have never been replaced and still look fine. I am now convinced that brake pads can easily last the life of a vehicle. Phil Phil Hobie <hobiephil@excite.com> Los Angeles, CA USA - Saturday, April 15, 2006 at 22:45:59 (PDT) Excellent observations and speculations. I do not claim to be an expert in this field, but your ideas seem to make sense, and in my experience, ideas that make sense after you fully understand them usually are correct. I am impressed with your experiments and I hope to conduct some of my own. Your "theory" is "right"! ;) Alan Hensley <misternethead Houston, TX USA - Saturday, April 15, 2006 at 19:18:11 (PDT) For almost two years I commuted from Edmond, OK to Norman, OK on a daily basis. I can tell you that these techniques have almost always worked for me during rush hour traffic. I learned about "advanced driving" from my father who was a truck driver for many years. One of the things he taught me you do not mention. Did you know you can influence the speed of the driver in the lane next to you? Many times if a driver is distracted or is "in the zone" they will stay just in front of you without realizing it. It works best if you are on their right side. This is also known as "Why the hell can't I get out of their blindspot?" By using this idea you can succesfully create a two car rolling barrier. Also you can just get next to a semi and pace him. Even better is to pace a semi on your left with the 'zoned' driver on you right creating a three car barrier. I've only done that once, but it was really cool. David H <avid.dp@gmail.com> Edmond, ok USA - Monday, April 10, 2006 at 14:05:48 (PDT) I noticed this fluid-like behaviour in the 1970s as Motorway traffic started to become (occasionally!) congested. I also noticed a "Venturi effect" where traffic speeds up as the 'pressure' drops after a blockage. The result is a much lower traffic density for a reasonable distance, and higher speeds - sometimes higher than 'normal'. Whilst it could be explained as a psychological thing (people are impatient to catch up, relieved at the unblocking, etc)it looks for all the world like a venturi regards ppl Dr. peter lennox <p.lennox[at]derby.ac.uk> USA - Tuesday, March 28, 2006 at 03:28:26 (PST) Wow! In the UK, these obeservations are basic advanced driving skills. Nothing new really. Then again in America you don't wear seatbelts, you hardly have any roundabouts and you use mobile phones while you drive. Finally, hardly any of you know how to drive a manual transmission (stick shift you call it). Basically, you Americans don't drive, you just cruise in your extra-large vehicles along your extra-large "highways". Most of you do not have the skills to negotiate hazards effectively because you "have it too easy". Although there are some terrible drivers in the UK as in any country, most of them are forced into driving better than you lot in the USA. Just my opinions. Sorry if you don't like it! ;) Youdon'twannaknow London, England - Wednesday, March 08, 2006 at 10:04:26 (PST) thats just a good example of INERTIA, the same thing happens when the red light turns green, being back in line will you make it through before the next red? chris <@@Bert-chris@worldnet.att.net> Mt Vernon, IN USA - Friday, February 10, 2006 at 18:26:44 (PST) What a great site, a scientific explanation for what i've been trying out for years. I drive the A428 from Cambridge to Bedford most days at rush hour, and yes leaving a large gap to the car in front does mean me and everyone behind goes at the average speed, we don't stop/start and so are less stressed and SAVE FUEL! I've tried it on three lane
motorways as well, it would work really well if most other drivers would
behave and not keep jumping into the gap in front. I watched a
BMW on the M42 the other week, he was choping and changing at every
opertunity. Me, I just stayed in the inside lane (or Lane 1 as the poilce
refer to it) and NOT THE SLOW LANE as most idiot drivers in the UK call
it. Anyway, he and I made exactly the same progress, we entered at the
same time, and got to the M6 at the same time, a journey of about 20miles
or so, but I bet he used more fuel than me, taking into account relative
mpg of our cars. Hi, I agree with everything on this site. I've noticed an increasing trend lately in the UK of outside-lane-blocking by vigilante lorry-drivers to prevent "queue jumping". This depresses me as this results in wastage of road space. Some brief thoughts on the optimum point at which to start "merge-in-turn": If we assume it takes say, 10 seconds to merge into the inside lane and the inside lane is travelling at approx 20mph (9 metres / second), the optimum point to start merging is therefore only about 90m from the lane cut-off. However people tend to queue single-file a mile or more from the roadworks, which is obviously excessive. Robert Tuck <robt_a_majormajor_O_me_O_uk> Wokingham, UK - Tuesday, January 17, 2006 at 13:56:18 (PST) Thank you for finaly proving that this works. I have been doing the slow steady driving after school when all my classmates are racing to eachothers bumpers and i continue to slowly move and use as little brake as possible. I have often wondered if this is the most efficient way to drive or if the other way was better and you proved to me that I am doing the best thing. Thanks...now if other drivers would realize this! Dave Huntingdon, PA USA - Wednesday, December 21, 2005 at 15:23:41 (PST) For the record, my own experiments with driving substantiate the intuitions captured on this web site. I think an appreciation of William Beaty’s observation rests on the ability to be able to discern the difference between simple, mechanical, closed systems, and complex, organic, open systems. Simple systems can be known purely from a knowledge of their parts, additively, while complex systems manifest synergistic properties, in which “the whole is seen to be greater than the mere sum of its parts”. Simple systems change at the margin, gradually and incrementally. Complex system may well change discontinuously. Traffic flows can be usefully thought of in both ways, depending on one’s purpose. Many of the skeptical comments on this web site by traffic engineers are driven by a world view that is restricted to a mechanical understanding of systems. Specifically, the idea that “capacity” is some numeric fixity that can be computed for any particular highway configuration, and that remains unchanged irrespective of individual driving behavior, is a mechanistic view that is not borne out by empirical evidence. In the years that I have been driving in Southern California, I have conducted some experiments into the effects of alternative driving behavior on traffic flow, average speeds and fuel economy. In 1992, when I moved to Los Angeles and became interested in understanding systems behavior from within an environmentalist perspective, I began to maintain a log of fuel consumption, so that I could attempt to establish, for my own satisfaction, whether and how driving behavior might affect fuel economy. My purpose, in initiating these experiments, was three-fold—one, to maximize my fuel economy, two, to make sure that I was maintaining my car as close to a state that would give me the highest fuel economy, and three, to make sure that system behavior was captured in my driving habits. (In actual fact, and in retrospect, a fourth benefit accrued to me as well, in that I was able to minimize the psychological stress of driving in frequently congested traffic by c |