road rage redux

It's fun to snicker at bad (or just mediocre) movies, especially those that take themselves a bit too seriously. But that doesn't mean those movies can't spark interesting discussions on important issues on occasion. Take the 1997 Demi Moore vehicle, G.I. Jane, as a case in point. Sure, the premise is a bit far-fetched: Demi Moore plays a female soldier determined to be become a Navy Seal by enduring a grueling all-male boot camp. (Jen-Luc Piquant doesn't find this the least bit far-fetched, but then, she's a bit of a scrapper herself, and still bitter that her plans to found an uber-tough Cybergang called the Virtual Visigoths hasn't met with more enthusiasm.) The writing is pedestrian, the tone often a bit too melodramatic. We are not offering it up as an example of High Cinematic Art. But there's nonetheless something viscerally appealing about it, and in between the overwrought cliches, there's some very nice moments, such as Demi shaving her head as a symbol of renouncing her femininity and becoming All Soldier (an entire blog post in itself). Then there's Demi getting the crap beaten out of her by the drill sergeant, going to a bar afterwards and running into another woman in the ladies room. The woman takes one look at her battered face and says, "Honey, it's none of my business, but if I were you I'd leave the bastard."

My favorite scene is when a female military counselor asks Demi's character (Jane) why she's doing this to herself. "Do you ask the men the same question?" Jane says. The counselor says she does, and notes that the guys invariably answer, "'Cause I get to blow shit up." Jane shrugs: "Well, there you go."  I like that scene because, while the stereotype is that men like to watch big explosions, the truth is, this is almost a universal human fascination. I'd argue that, under properly controlled conditions (i.e., onscreen in a movie theater), it can be strangely cathartic. (Not that we're engaging in this kind of behavior, mind you; we limit our explosive experiments to Mentos and Diet Coke.)

Perhaps that's why project officials in the DC area have just announced a contest, in which one lucky frustrated commuter will win the opportunity to detonate part of the old Woodrow Wilson Bridge that connects downtown DC with the suburb of Alexandria, Virginia. I kid you not: drivers are invited to fill out forms detailing their horrific commuter experiences using the old bridge, and the winner will get to trigger an explosive charge that will reduce a half-mile section of the structure to rubble. It's the ultimate act of road rage, and it's fully sanctioned by the bureaucratic Powers That Be in a rare show of solidarity with the long-suffering public. Per project spokesman John Undeland: "This is a thank-you and a recognition for all the folks who have had to endure a miserable time getting across the old bridge." (Say it with me: "Hoo-yah, Master Chief!") It all goes down at midnight on August 24th, and Jen-Luc Piquant and I will most certainly be on hand in the "public viewing area" on Washington Street to pay our final respects.

For non-locals, the old Wilson Bridge (constructed in 1961) has been a notorious commuter nightmare, prone to frequent traffic jams and long delays. The Washington Post article linked above features the experiences of Virginia resident Jack Hay, who has commuted back and forth from Maryland and Virginia every day since 1982. Hay estimates that he spent over an hour each day stuck in traffic near the bridge; over 24 years, that adds up to losing about a year of his life to traffic jams along the Wilson Bridge. And that's a whole year of his life he'll never get back. Ponder that next time you're in a jam, and watch your blood pressure rise to unprecedented levels. The new Wilson Bridge is a $2.4 billion project to alleviate all that backed up traffic. The first six-lane span of the new bridge opened earlier this summer, but the second span won't be done until 2008, so motorists have a bit longer to wait before true relief is at hand.

In general, traffic in Virginia has gotten so bad that it became a major issue in the most recent gubernatorial election. Nor is this merely a local problem: it's happening in most major urban centers, in part because new highway construction in the US just hasn't kept pace with increases in population and the number of cars on existing highways. In fact, from 1980 to 1999, the total number of miles of vehicle travel increased by 76%, while the total length of highway miles increased a measly 1.5%. The Washington, DC, region currently ranks third among the top 5 cities with the worst traffic flows. Los Angeles, not surprisingly, tops that list, with San Francisco placing second, and Atlanta and Chicago falling into fourth and fifth place, respectively. (We're frankly surprised New York City didn't make the Top Five, or our former hometown of Seattle: these days, the traffic on I-5 is congested even when it's not prime commuter time, and some local motorists are convinced that the notorious "S" curves along I-405 were designed by the spawn of Satan.)

Apart from quality of life issues, why should we care? Well, it's expensive! The Texas Transportation Institute estimated that in 2000 alone, the 75 largest metropolitan areas experienced a collective 3.6 billion hours of delay. That translates into 5.7 billion gallons of wasted fuel and more than $78 billion. The average US motorist spends 36 hours every year in traffic delays. In fact, it costs an individual driver living in a large city an estimated $1000 every year, especially when you factor in wasted productivity.

So traffic is important, people. Fortunately, physicists are hot on the case. Traffic physics has been a fairly hot area of research for almost the last ten years. Conventional scientific wisdom has compared traffic jams to the process of freezing -- namely, a phase transition between a liquid to a solid.

Think of it this way: On a sparsely populated highway the cars are far apart and can move at whatever speed they choose while freely maneuvering between lanes -- much like the movement of molecules in a gas. In heavier traffic, the "car molecules" are more densely packed, with less room to maneuver, so cars move at slower average speeds and traffic behaves more like a liquid. If the the "car molecules" become too densely packed, their speed is reduced, and their range of movement is restricted, to such an extent that they can "crystallize" into a solid. So traffic jams aren't random. There's a threshold "value" to the flux of cars traveling along a highway, and if that threshold is exceeded sufficiently -- if local perturbations are large enough -- then the flowing "liquid" traffic jams into a "solid," akin to the critical temperature/pressure point threshold where water turns into ice.

It's a useful but rather crude analogy. The situation is a bit more complicated than that, and scientists would love to understand the phenomenon in far greater detail. A major breakthrough occurred in 1998, when a physicist named Boris Kerner with the Daimler Benz Research Institute in Stuttgart, Germany, published a paper in Physical Review Letters. (Kerner has since written an entire book on the subject, called The Physics of Traffic: Empirical Freeway Pattern Features, Engineering Applications and Theory.) Kerner analyzed data collected from several years of traffic monitored along German highways and found that traffic tends to follow the physics of self organization.

Based on that data, he developed a model that essentially broke traffic into three basic categories: freely flowing, jammed (solid state), and a bizarre intermediate state called synchronized flow, in which densely packed "car molecules" move in unison, like members of a marching band (or the highly disciplined troops in G.I. Jane). When this happens -- when all the cars are traveling at close to the same average speed because of the vehicle density on the roadway -- they become highly dependent on one another. A physicist might compare the relationship to the correlated motion of electrons in metals, which gives rise to weird phenomena like superconductivity.

Highly correlated traffic means that a tiny perturbation -- a butterfly flapping its wings, or a single driver braking unexpectedly to change a CD -- will send little ripples of corresponding slowdowns through the entire chain of cars behind him/her. That's one reason why slowdowns and traffic jams occur most commonly at merge points, especially exit and entrance ramps, or when lanes are closed due to road (or bridge!) construction. A state of steady synchronized flow, punctuated by these tiny ripple effects ("narrow jams") can persist indefinitely, but the balance is delicate and highly unstable. If the volume of cars continues to increase, the density continues to increase, and eventually you get a "pinch effect" -- that frustrating "stop and go" phenomenon, in which you escape one narrow jam only to encounter another a little further down toe road, until they all converge into a single wide jam. Traffic comes to a standstill. Collective road rage may ensue.

As Kerner and his fellow traffic-obsessed physicists can attest, a key component to building better traffic models is collecting better real-world data. That's another expensive undertaking: State and federal agencies spend about $750 million each year on traffic monitoring. So they're always on the lookout for new, innovative yet inexpensive solutions to the data collection problem. Things like cellular phones, which have become pretty much ubiquitous in modern society.

Several state transportation agencies (Maryland, Virginia, Missouri, and Georgia) are experimenting with new software that uses radio signals from drivers' cell phones as tracking devices, so they can better monitor traffic patterns. Officials are quick to point out that they are not monitoring actual conversations, just the radio signals transmitted by the phones; the phones don't even need to be in use, just turned on. "Listening posts" are placed throughout a region capable of detecting but not sending radio signals. It will pick up a cell phone signal and time-stamp the signal's arrival. By analyzing how long it takes the radio wave to reach the listening post from the cell phone, a computer can calculate almost precisely where that phone is located on the highway. You need three such posts to determine a 2D position of a cell phone user. Adding radio tags along the highways to time when vehicles pass between given points can determine the car's location and speed. All this information can be collected and disseminated via Web sites, electronic road signs, even sent to cell phone users who sign up for customized traffic reports.

It all sounds just a wee bit "Big Brother"-ish to us. And in Berkeley, California, they're taking the wireless option even further with a testbed project dubbed "Smart Cars and Smart Roads, part of the Vehicle Infrastructure Integration Initiative. Participating cars would be equipped with technology to pick up signals transmitted form the road on which they are traveling, thereby relaying critical information, like whether there's an accident or icy road (in California?) up ahead. In this way, the cars themselves would serve as anonymous data collectors.

Kerner's self-organizing model would seem to indicate that while drivers think they are acting of their own accord, they are really just behaving like a tiny unthinking particle, a single grain of sand in an enormous sand pile, unconsciously following the "rules" of self-organized flow. But that's not quite the case: driver behavior really can impact traffic patterns in significant ways. The unpredictability of human behavior is one reason why many traffic models aren't as accurate in their predictions as they could be. In 2004, a team of German scientists led by Michael Schreckenberg (University of Duisberg-Essen) sought to rectify that.

They came up with new predictive models that took realistic driver behavior into account: you know, all those jerks on the highway who keep changing lanes and cutting in front of you just when your lane is starting to move, which in turn arouses your competitive instincts so that you (a) honk angrily and tailgate him for a few yards, determined not to let any other "cheaters" infringe on your valuable space, or (b) switch over to a new lane in turn, thereby causing another slowdown. Not that we're bitter or anything. As team member Robert Barlovic put it, "Real drivers tend to hinder each other when doing things like changing lanes."

The model was quickly put into use to forecast traffic along the autobahn network around Cologne, based on real-time traffic data gathered by  embedded sensors in the road. Our German readers (both of you!) can check these forecasts -- up to an hour ahead -- on this handy Website. More than 300,000 people are already doing so. The problem is that this broad access to more accurate information is actually changing traffic patterns. People modify their behavior based on the new information provided by the forecast models: they all flock to the same exits to avoid upcoming congestion, for example. This in turn eventually makes those models less accurate in their predictions. More information is not, as it turns out, the answer to all our traffic woes.

The good news is we are not helpless grains of sand in an endless flow of avalanche dynamics. A single driver resisting the competitive urge really can make a difference. William Beaty, the self-proclaimed "Science Hobbyist," maintains a fascinating Web page ("Physics for Bored Commuters") with his own informal "experiments" on the physics of traffic flow, illustrated with cute little animations. (Jen-Luc Piquant obviously doesn't drive on anything other than the Information Superhighway, but even she has been able to experiment via this nifty online traffic game.) Beaty offers these handy tips: (1) Maintain a large space ahead of your car. (2) Encourage one, two, or even three cars to merge ahead of you. Yes, we know this is hard, but try to be the bigger person. (3) If traffic slows to a complete stop, still try to keep two car-lengths of space open ahead of you. (4) Never "punish" merging drivers by closing your gap. Apparently, this really works. People cause the problems, but people can also be part of the solution.

I find that strangely comforting today, in the wake of disturbing headlines about a thwarted planned airline terrorist plot in the U.K. Needless to say, airport security lines are experiencing their own "solid state" traffic, as panicked officials confiscate such mundane items as shaving cream, shampoo, contact lens solution, hairspray, and bottles of soda or water -- in short, any liquids or gels. Look, I realize that these threats are serious, and human lives are at stake, but this is getting out of hand. I'm all for taking stringent measures to protect travelers from the threat of terrorist attack, but I doubt very much that taking away my shampoo will make the skies one whit safer, any more than collecting tons more data for predictive models will automatically solve our traffic woes.

Panic and fear over the potential for terrorist attacks has been encroaching, inch by inch, on our personal freedoms, not to mention those tiny day-to-day conveniences one takes for granted until they're gone. The result is a drastically reduced quality of life. A friend of mine once observed that the only truly safe and secure society would be a fascist society. He wasn't advocating that, mind you -- just making the observation that security comes at a cost to personal freedom and convenience. There's always a tradeoff that must be made. But what will we be asked to give up next in the name of our own "safety"? Why not just go all the way and simply ban "People" from boarding aircraft? It is people, after all, not the things they carry, that pose the deadly threats. Anything can be a weapon in adequately trained hands, even a ballpoint pen.

The key word here is "panic."  Terrorists traffic in the psychology of fear, and if we allow ourselves to give into fear -- well, then the terrorists win, even if they don't succeed in their nefarious plotting. The complexity of the physics of traffic flow demonstrates that we are not helpless grains of sand, doomed to unconsciously follow preset behavior patterns. Let's choose to be part of the solution, not the problem, and keep our collective cool.

Comments

[bc]

Something you didn't mention here is the wisdom of a drawbridge on the Washington Beltway/I 95.

That's what the Wilson Bridge is. And the new one, too. Somehow, I don't think that the new bridge is going to solve the problem of shutting down six lanes of DC rush hour traffic for several minutes to let a ship pass.

I'll stop here before I describe my 80 miles of commuting per day from home into DC and back.

bc

[Blake Stacey]

How opportune: just last weekend I drove from North Carolina to NYC and back. That's over the I-95 drawbridge, through the NJ turnpike toll plazas and over Staten Island, Brooklyn and Queens on I-278. And then again in reverse. Don't bother asking why. . . .

At least I didn't have to cross the George Washington Bridge. Oh sweet Moloch was **that** something I never desire to repeat.

Concluding thought: even a Fascist society is only secure as long as conditions do not change. How well do you think that Nazi planet in Star Trek could adapt to melting ice caps?

[Quasar9]

The cartoon about "if everyone else took the bus..." is so so where it's at. It represents the consequences in this modern society. Fortunately now less people get caught in traffic jams on the Internet superhighway - but they can be just as frustrating(?) but at least one is not sending up more exhaust fumes, just steam (water vapour is ok)

Panic?, gosh Jen, not wanting to be pedantic, but only certain types of people live in fear, fear of being in the wrong place at the wrong time, fear of dying. I was rather thinking you were one of those that cruise thru life with no hate or fear. After all what good are martial arts or a blackbelt if you are still going to worry that your next trip might be your last ... hmmm dunno dunno do I wanna dwell on that one?
Here's wishing you a panic free evening

[JenLucPiquant]

I think your reading comprehension slipped there a bit, Quasar. The whole point of the concluding paragraph was precisely that it is pointless to live in fear and allow panic to overtake our lives. At no point did I say I was fearful or panicked. I fly a lot, and will continnue to do so, and I won't lose any sleep over whether a given flight will be my last. Mostly, I'm just annoyed at not being able to take my water bottle on an airplane anymore...

None of which has _anything_ to do with practicing martial arts, or having a black belt, BTW. I do not define myself by that. The person makes the black belt, not the other way around.

Blake, I hear ya on the George Washington Bridge! I don't actually own a car -- not for idealistic reasons, it's just not practical, since parking around here is a bitch -- but I occasionally rent one, and I've made many a drive to NYC. That bridge is the devil's handiwork. Somehow I always seemed to hit it at rush hour, too...

[Fred Ross]

I think a case could be made that if you have traffic troubles, your public transit is inadequate. Especially for these enormous metropolitan areas, the train system needs to spread at pretty high density deep into the surrounding areas. I have friends in DC who drive twenty minutes to the nearest metro stop and then take that in. So forget repairing the roads! Build more train lines! And don't run them the way NYC does! If you have to drive (and you don't intentionally live in the middle of nowhere), then the transportation system is broken.

I have to fly this Saturday. At least I'm not flying to the UK, where you are allowed to carry on a small plastic bag containing your wallet, keys, ID card, and passport. The most annoying part is that it's entirely an illusion of security.

[Quasar9]

Hi Jen, I said some people, and I said I didn't think to include you among them. Glad you are crystal clear on that one.
Indeed it is not the cloth makes the person, and I wasn't having a dig at martial arts, since having watched the original 'grasshopper' king fu serious with David Carradine, I know matial arts are about self-control rather than chaotic action.
[the guys invariably answer, "'Cause I get to blow shit up." Jane shrugs: "Well, there you go."]
Of course, if one can casually lob a shell some 8o miles with pinpoint accuracy, one has to fully understand one can be hit with equal accuracy. It is a law of physics, a cosmic law, a law of Nature.

So let me lob best wishes your way hoping the same return onto me ... see I really I'm just a self-interested ego, self-preservation kicks in. lol!

[Runolfr]

Beaty offers these handy tips: (1) Maintain a large space ahead of your car. (2) Encourage one, two, or even three cars to merge ahead of you. Yes, we know this is hard, but try to be the bigger person. (3) If traffic slows to a complete stop, still try to keep two car-lengths of space open ahead of you. (4) Never "punish" merging drivers by closing your gap. Apparently, this really works.

I have observed this in action on the "South Loop" of Nashville, TN. I habitually leave several car lengths open ahead of me on the I-40 overpass that runs between the I-65 interchange and the I-24 interchange. A lot of vehicles have to cross all the way from the left side of the 4-lane overpass to the right in just a few hundred yards, and a similar number need to move from right-to-left. The opening I leave ahead of me in the center lane facilitates their lane changes, and very few actually stay in my lane ahead of me. It is my (potentially self-important) experience that the overall speed of traffic moving across the overpass increases significantly during my trip through.

Hey, I'm an anecdote!

[Kristin]

The Onion got it right when they wrote about how 98% of U.S. commuters favor public transportation for others: http://www.theonion.com/content/node/38644

As one who does not own a car, I am available to accept effusively expressed gratitude from all car-owning denizens of the city of San Francisco whose roads would be even more congested if it weren't for my sacrifice. Believe me, even in this compact city, riding Muni is no pleasure (see http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2006/08/11/BAGRGKGGOD1.DTL). I sure enjoy getting a break from the late trains and slow, crowded buses by using City Carshare (http://www.citycarshare.org)from time to time, because I get kind of tired of propping up Muni on my long-suffering, exceedingly patient back. Public transit is only going to be profitable enough to work the way it should (frequently, smoothly, cleanly) when most of us don't opt out of the system.

[Jessica]

The new Wilson Bridge is indeed a drawbridge, but I notice that it is a much higher drawbridge. I think the powers that be decided that they couldn't get away without a drawbridge at all for various engineering reasons, but at least this way it doesn't have to open nearly as often. In fact, back in June when the new span was open for "outer loop" drivers and the "inner loop" folks still had to use the old bridge, I heard local traffic guru-ess Lisa Baden announce a drawbridge opening for the old span but not the new one. So, there's some hope at least...

[JenLucPiquant]

Kristin, let me know if the car-owning denizens in the Bay Area ever get around to expressing their gratitude. It would be positively inspiring if it happened. I'm still waiting for my neighbors in the building to express graitude that _I_ don't own a car, given the shortage of parking spaces.

As for public transportation, I rely on it myself, and while DC's Metro system isn't bad, it sure ain't perfect. I'm reminded of a scene in the movie SINGLES, set and filmed in Seattle, in which one character pitches a "Supertrain" project for commuters to the mayor, to combat growing gridlock (even back then, it was a huge problem). The mayor gives him literally one minute of his time before saying no, and explains it thusly: "People love their cars."

[Coffee]

The last Friday of every month is Critical Mass in San Francisco. If you're not familiar with it, it's basically a party on bicycles riding randomly through the city. While I believe most people are in their cars extremely agitated about being delayed by bicyclists goofing off, there are a lot of people that genuinely applaud the exposure it gives to the zero-emissions, zero-oil consumption, and zero-energy vehicles a very large group of people ride to their works everyday. We can hear it in their voices when they yell out their support while we're riding by them.

[myspace]

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[KS Garvin]

I’ve experienced the synchronized flow of traffic. Driving to work in downtown Washington, one day all three lanes of cars were moving at a nice, steady, speed-limit-obeying pace. No one jammed on their brakes, jumped lanes, or did anything unpredictable. As a result, traffic flowed. Really, really flowed. I got to work 10 minutes earlier than usual.

[Absolute Zer0]

I've always contemplated the cause effect relationship of traffic jams, and even tried to relate any or all of the observable factors to the actual phenomena.

Bringing up the unpredictability of human behavior is why I didn't fully figure it out. Even though the shared goal of forward velocity does give way to unconcious uniform behavior, 300,000 individuals a day gives way to about 298,000 that are self centered enough to break a possible synchronized flow.

People are Douch bags, and with all the freedom we have, people can remain ignorant to things that could drastically improve the human condition. You should send a chain letter with the threat of increased traffic jams for 7 years if you don't abide by the laws of physics, and forward the laws on to your retarded friends.

A/B ZER0

[Tom]

I like the cartoon and feel myself a little appealed. In the last 20 years the number of cars exploded. But maybe this problem will be solved when the price of fuel will continue rise.

[Ben]

Great article! But just a heads up: The german town is called "Duisburg", not Duisberg. The name of the university is different accordingly. But nice to see the science of my university going around. :-D

Ben