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Supercomputers Used to Study Urban Traffic
itachi writes "This is a great article in the [Washington] Post about using supercomputers at Los Alamos and physics modeling to study traffic jams. The basic notion is that light traffic is a fluid state, with cars instead of particles, and traffic jams are sort of equivalent to a change of state to a solid. There is even talk of trying to simulate traffic along the east coast from DC to Boston, using a computer along the lines of Blue Mountain. "
To give you an idea of the scale of the modelling problem itself, there are commercial companies selling software in the $500-1500 range (and up, no doubt) for analyzing these problems. Here's an example: http://www.trafficware.com. In addition to demos (sadly, only for Windoze) it also contains many links and information on the mathematics behind traffic modelling.
All I can say is that I modified my driving habits after reading these sites, not out of any altruistic desire to improve traffic flow, but because it was fascinating to experiment with the theory that even a single car in a large traffic jam can act as an "antiparticle" and singlehandedly improve flow in two or three lanes. The improvement in traffic flow behind me (and my reduced blood pressure as a driver) was just a happy side effect.
I know I've read articles on why random traffic jamc occur on clear highways. It's surprising that this is the first time they've attempted such a simulation. The concept is very straightforward.
I agree that the bad driver factor is an important consideration. Take I-280 between San Francisco and San Jose. Running primarly though the 'green belt', it is usually lightly travelled.
The average speed in the left lane is usually 75-80 MPH, that is except for the people who just feel like driving 60-65 MPH. Nobody really wants to slow down for these people, so they swerve right a couple lanes to get around the back up.
To make matters worse, there seems to be a large portion of the population that can't turn on their turn signal without hitting their brakes, leading tailgating drivers to slam on their brakes harder. People start cutting other people off and acting generally stupid just to try to get past the one or two retards blocking traffic.
Pretty soon, traffic speed is down to about 45 MPH - same amount of traffic, just one or two blockages thrown in.
(Note, most Americans might think it wierd to bitch that you can't drive 75 MPH all the time, but that's California.)
--
Business. Numbers. Money. People. Computer World.
Another big problem, especially here in Portland, Oregon, has to do both with driver skill/courtesy and street/highway design. There are a lot of places where a right lane begins for no apparent reason, and then ends abruptly, usually on the far side of a signaled intersection. A certain percentage of rather discourteous people will attempt to drive in this lane as far as they physically can, and then swerve into traffic at the last second, causing everyone else to hit their brakes.
Most cases of this could be eliminated by only terminating right lanes into right turn only lanes, preferably with a cement barrier to prevent people from illegally going straight through the intersection.
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(Note, most Americans might think it wierd to bitch that you can't drive 75 MPH all the time, but that's California.) Not really, from what I drove in chicago people go 85 or so until they hit traffic and then sit still for 30 minutes and repeat. It sucks, and there is no reason for it. I hope these guys get around to doing chi town soon, we sure as hell could use it.
One question about the supposed EZPass - FastLane compatibility: I am a NYC resident who travels to Boston frequently. I use an EZPass transponder in the NYC area. Here, we are warned to go no faster than 5MPH through EZPass toll lanes. I have never used a FASTLANE system but it seems that Boston driers can blow through the tolls a lot faster, the posted signs are 15MPH. Is it using the same technology or a different technology? And I agree with you about the bank agnosticism being a Good Thing. I would never sign up for FASTPASS if I had to use Bank of Boston.
I occassionally drive north on US101 to San Francisco during afternoon rush hour. Traffic is usually very heavy between the San Mateo bridge and I380 a few miles north. At that point, enough people get off the 101 that traffic opens up until you to San Francisco.
The traffic bufferers are fine in the heavy traffic. Less stop and go, and as has been noted, they 'plug' up the lanes so people stay put.
However, when traffic opens up and people should be driving the speed limit, the "bufferer" guy is always the one who sits in the left lane and forgets to get up to 65. By the time his buffering algorythm has informed his brain that he can speed up, several people have already made dangerous lane changes to get around him.
So, while a theoretical approach might make sense, without practical observations on traffic condition in particular locations, it just makes you look like a bad driver and gets others frustrated enough to do stupid things which could endanger you.
--
Business. Numbers. Money. People. Computer World.
Sound argument, except for the car costs. Bus pass is X numbers of dollars.
Cars cost more then Gas. They cost insurance and maintanence. Which does add up to a LOT more then $50 a month in the long run, especially if you do something dumb like lease a car.
Sadly, the dollar value isn't enough to get ppl off the roads and on the busses. Because there's more to life then just commuting.
Anyone know of any good books on this subject?
I've culled all the URLs I can from the posts above, but I'm looking for some good texts, too.
Please, suggest a few!
Tweet, tweet.
It's SO cathartic!
Yeah! Fsck you you slowpoke! SLOWER TRAFFIC KEEP RIGHT! The PASSING lane is for PASSING you moron!
Then there's tolls.
It tends to be in states (like Florida) where there's no state income tax - DAMN, $1.50, for one lousy toll? (of course this road is like a ghost town, because nobody can afford to drive on it - it's the hwy just east of Orlando).
Then there are states like California, where there is an obnoxious state income tax, and NO toll roads (yea! I'm for that - on some of these roads the booth slows you down so much that you don't really save any time over the sidestreets).
Then there are states like Illinois, which just SUCK, because the state income tax is high, and they still bend you over at toll booths.
"The number of suckers born each minute doubles every 18 months."
-jafac's law
These are my friends, See how they glisten. See this one shine, how he smiles in the light.
What they *should* be trying to do is use the traffic as a computer. Manipulate the lights in such a way as to have the traffic break RSA...
Good point. The least crowded way out of Chicago is the Skyway--a toll road. The free roads are always clogged.
Part of the problem is that if you reduce the congestion, by building a new road or whatever, you make it less painful to drive--therefore more people will, bringing you back to the same problem.
We've got two lives, one we're given, and the other one we make. --Mary Chapin Carpenter
Atlanta's got a worse problem.
Everybody's LOST, because every frickin street is named Peachtree.
"The number of suckers born each minute doubles every 18 months."
-jafac's law
These are my friends, See how they glisten. See this one shine, how he smiles in the light.
"Finally, there are many modeling software systems used by the transportation planning community.
Here are the names of some: TranPlan, TransCAD, EMME/2, TModel/2, TranNetSim, and QRS/2.
Their prices range from (US) $70 - $25,000 per computer license."
Obviously, these aren't doing any good.
"The number of suckers born each minute doubles every 18 months."
-jafac's law
These are my friends, See how they glisten. See this one shine, how he smiles in the light.
Sounds like you should get what the motorists got: a $140/month raise.
---- "If we have to go on with these damned quantum jumps, then I'm sorry that I ever got involved" - Erwin Schrodinger
Sounds like a study done by a company that sells traffic lights.
"The number of suckers born each minute doubles every 18 months."
-jafac's law
These are my friends, See how they glisten. See this one shine, how he smiles in the light.
option 1:
30-50 minute commute in car. Can't do anything but drive and flip off assholes.
option 2:
60-90 minute commute by bus. Hmm... I can read paper. I can read book. I can snooze. I can be amused by people. I can think to myself, "I'm glad I'm not driving in this f'd up traffic!"
I can use my laptop and cell phone to do work.
option 3:
90-120 minute bike ride. both ways. That's 55 cheezy miles per day of training (for me). that's time I don't have to feel like I'm depriving my wife and new child of to get training time in, since it's blocked out anyways.
Lessee... for my cars, doing this 2-3 times a week is 2-3 days more time between fillups for the car. At $22/tank (regular is ~$1.45-$1.70 here in SD land), that could add up to one less fillup per month. Hmm...
YMMV. Of course, I'm in San Diego, where weather is rarely a detriment to riding. Even in Seattle, the weather can be a bummer, but it is survivable and doable. Makes you appreciate hot lattes more, that's for sure...
Traffic flow is more analogous to flow of something like bb's through a pipe. If the pipe is big enough and/or the density of bb's is low enough, you have optimal flow. But there is a point where increasing the density of bb's which the flow actually stops, and restarts randomly. It has been modeled well. Sorry I have the URLs for a couple of interesting pages at work. When they talked about this in Discover magazine, several people from Chicago wrote in about anectodes about chicago highways, where the flow occaisionally got into a steady state, although lower than optimal, flow. There is another of a guy in Seattle who practiced on SR-520 floating bridge just going a fixed speed, trying to keep his speed constant between all the stop-and-gos. Sure enough, traffic behind him appeared to be moving steadily along as well. He had/has some interesting ideas on how to keep traffic moving smoothly, such as have cops driving in traffic to regulate packet spacing and speed. Ever notice that people are loathe to pass cops on the highway, even non-highway patrol cops? Going 20mph the whole time is better than averaging 20mph in stop-and-go traffic (i.e., 30, stop. wait. 30, stop. wait, ad nauseum).
stop-and-go sucks in a manual transmission car, too, especially if it has a strong clutch...
I wonder if the plethora of auto transmission cars contributes also to stop-and-go? People don't have to think about shifting, so they never get to the point of getting tired of shifting and driving accordingly (like never shifting out of 2nd).
Yeah, San Diego's worst commutes: I-5 and I-15.
I-8 into town is pretty bad between I-15 and El Cajon. I-805 is pretty gnarly, too. For a real-world example of how a cross highway doesn't necessarily improve traffic flow, there is SR-76 between I-15 and I-5. Funny how it is that people are buying "cheap" houses up in North SD county. Funny how it is that I-5/15 are now totally f'd up for commutes to/from SD. Funny how people don't think about this when they buy their houses.
And you should see down here what happens when it rains. 10x worse than what happens to Seattle traffic when it snows...
SD traffic reports also blow big-time. They're almost all done by AirWatch (of course, 90% of the SD radio stations are owned by Jayco). So half of the report time is and ad. But all they're doing is reporting stuff that is on the Maxwell Tech. web page and CHP incident reports.
--LazyCoward
water in pipe is bad analogy. BBs in a pipe is better. Flow the water through the pipe at high enough velocity (pressure), and you can get waves flowing back through where pressure builds up due to turbulence. But the more macroscopic model works better. You don't have to use Napier flow equations, etc., to model BB "turbulence" in a pipe...
Nah, people still "pack" on their own. Drive on a highway late at night. Drive above the speed limit. You will come across packs of cars moving slower than you. Hopefully the pack is not not spread completely across the highway, so it's easy to just go around them, or that the pack is loosely packed, so you can weave through it. Usually, though, there is enough of a spread across the front, and the pack is tight enough, that it can be almost impossible to get past the pack. And then there are the nimrods who drive -5 or -10 in the lefthand lanes. Speeding doesn't cause nearly the problems on highways as speed differential. As far as "brake as late as possible"... some of teh people who do that are trying to psyche the asshole in the 5000-7000 lb truck/suv tailgating your ass like a tatoo. It is a risky game of chicken, but so many of those fucks think they can stop in the same distance as the 2800lb sports car (MR2 to be more specific) that they're tailgating... Sure, it may be my car and body that gets fucked, but it's your insurance that rapes you for the next 3 or so years...
I remember it being more relaxing to drive this way, but this works in the "fluid" state, not in the "jello" state, 'cause that's when people jumping in front of you causes a problem.
Well, It isn't an exact science. If you have to brake, do so, and try again, going a mile or two per hour slower. No calculus is required :)
As to your second point, check out the web sites that other people have posted. One of them has the observation that even though some people will cut into your buffer, they cars that don't cut in front of you form a "plug" of patient drivers who don't change lanes, and that "plug" holds the lane-changers behind you.
- John
I'm in the transportation buisness, albiet a bridge designer. Traffic modeling, signal timing, etc is common place and there are many mathematical models that are in use today requring no more power than a P2 and some time. The accuracy is fairly good compared empiracle studys. The article is proposing a highly complex/accuate method, if properly calibarated. A lot of engineering goes into transit planning and design. The fundamental probelm is lack of funding for needed improvements. Though research into traffic models never hurt anuyone.
Sounds to me like an extremly detailed version of SimCity 3000. But on a 6200 processor machine. (And probably no 3d accelerator)
Fellowship 9/11
Yes. This is when angry motorists at the edge of traffic flows turn around onto the empty other direction.
This is exactly what I have experienced. I used to drive to school, and there was one place where the traffic slowed down *just* before I had to exit. By doing the buffer thing (leaving space before me), and helping the merging traffic, I at least always thought I got through faster.
Fellowship 9/11
Would be nice if such a simulation could determine the optimal human behaviour for maintaining a high flow of traffic. For example, do speeders endanger lives or reduce the risk of accidents by doing there best to increase the rate of flow, thus decreasing the trafic density and preventing solidification? Do cops, trying to catch speeders, make the road safe, or increase the risk of accidents, by causing everyone to slow below the speed limit (cars speedometer might be off), increasing the traffic density and hense the chance of solidification/accidents... I would love to play with different scenarios, such as a 100MPH speed limit and very severe penalties for drivers driving BELOW the speed limit. On my way to do battle with the DC Beltway. Sigh
- People waiting too long to move when traffic in front moves (with slow-moving trucks failing to keep right greatly exacerbating the problem);
- People not merging before lanes close, forcing traffic to stop to let them in;
- Opaque vehicles, such as semis, panel trucks and SUV's, not allowing any visibility past them and increasing the necessary following distance (this reduces the carrying capacity of the road). And every time one of them moves between two cars, the usable pavement decreases again.
I have never understood the people who drive that way. I watch the traffic several vehicles ahead, and I can often manage just fine by "driving" the cruise control while the driver right in front of me has to hit the brakes. It's not hard to guess how I have 82,000 miles on the original brake pads. It only takes one. A single driver who reacts to a near-miss by stopping to recover from the scare will do it.We could get rid of a lot of these problems by having tighter qualifications for drivers, and eliminating things like cell-phone use while in motion (vehicle-integrated cellphones could easily be made to refuse to dial or answer if the driver was alone and the car was moving). The problem is, we lack the will.
Time is Nature's way of keeping everything from happening at once... the bitch.
Was told of this perplexing oddity:
A traffic light can speed up traffic throughput (!).
Reasoning:
Drivers don't monitor the distance between themselves and the car infront. They monitor speed. Front car slows down, they slow down, etc. This leads to: if one car brakes, the next will brake, etc. etc., leading to braking "waves". This most often happens near narrowing entrances (eg bridges, tunnels).
An arbitary stoplight placed a distance back from this narrowing can be used to stop the multiple brake waves into one larger brake-and-go (more fuel efficient, too, I guess) that gets stopped at other already present traffic lights before.
Oddly enough, throughput increased from 8000 cars/hr to 12,000 cars/hr.
This was a few years back when i heard it, so I can be completely off, too
It's easy to say, "people would ride public transit if it worked". But the simple fact is that "modern" urban developments, like what is now San Jose, are incredibly hostile towards working transit systems. Consider:
- Residents don't want busses going down residential streets, but major streets are far enough apart that it can be at least a 15-20 minute walk to the nearest bus stop.
- San Jose can be reasonably neatly divided into two pieces along route 280. South of the freeway, the city is primarily residential, but all of the jobs are north of it. This means that, in a north-south transit system, everybody will get on at the south end and get off at the north end, meaning you need higher capacity than if people were continuously getting on and getting off.
- People are already quite attached to their cars, and I'd suspect the automotive and petroleum industries have quite a bit more political clout than the nonexistent mass transit industry. So funding is more likely to go to big road projects than to big transit projects.
- And without funding, public transit is stuck at the same level it is now: busses that run on extremely sparse routes every half hour at most, and sometimes just don't show up.
All of this means that public transit systems have to fight a hard uphill battle to keep the minimal level of service they have now. And this level of service isn't encouraging; when it takes six times as long to take the bus as it is to drive, anybody with a car will prefer to use it at almost any cost.Edinburgh Parallel Computing Centre had a group several years ago working on this problem using big iron hardware - they have now downsized their software from MPP's to workstations and PC's, and it's being flogged by a commercial company called Quadstone Last time I saw a demo of Paramics (c. 1996) it was doing the whole of central and suburban Edinburgh (inside the A720) in close to realtime on a then state of the art SGI workstation, and they had just put in modelling for different nationalities' driver tempraments.
I'm sure the Russians thought about using supercomputers to model bread lines before they gave up and decided to let market forces take over. Here's my prediction, based on empirical observation, which can be a remarkable tool for predicting the output of computer models: if you tax people to build something, and then give it away free, there will always be shortages.
---- "If we have to go on with these damned quantum jumps, then I'm sorry that I ever got involved" - Erwin Schrodinger
Hopefully my employers will never find out about this, but I think the only real solution is to put fewer cars on the roads. Mass transit will help do that, but here in the US you're considered some sort of second class citizen if you ride the bus to work
Everybody on motorcycles! They use less space.
You answered your own question, Alan.
-------
Warning: Slashdot may contain traces of nuts.
In order to keep traffic moving on the M25 (London orbital motorway) they have introduced variable speed limits. As the traffic get heavier, the speed limit gets lower. Supposedly this stops the traffic flow from becoming "turbulent", and so everything keep moving.
Unfortunately, the way it is enforced is rather scary. They have electronic cameras placed at intervals along the road. The cameras do OCR on each car's numberplate as it passes, and if your average speed exceeds the limit, you get a fine+points through the post a few days later. Being digital, the cameras never run out of film, and as they track your average speed, the normal trick of slowing down when you see a camera and speeding up inbetween does not work.
Apparantly the caught 4300 speeders on the first day the system went live. And of course, tracking cars all over London via their numberplate isn't an infringment of civil liberties. Honest.
It already is possible to use ezpass on it - goto www.ettm.com - it's somewhere in there. SPUI
Old news. PARAMICS simulator at the Edinburgh Parallel Computer Centre (EPCC) has a simulator which models the behaviour of each verhicle (microscopic simulation). Last time I saw it you could click on a car and get a driver's eye view. IIRC they had different classes of vehicles/driver behaviours / they could simulate _Scotland_ in better than real time. http://www.epcc.ed.ac.uk/industry/PARAMICS/index.h tml
SPUI
This is a real (no pun intended) problem. When a major arterial runs through many jurisdictions, there is no coordination between them, even if there is coordination within the jurisdiction. There are lots of reasons for this and the industry is attempting to address some of them. One is that two adjacent cities may not be using the same vendor's equipment so therefore they can't communicate with one another. I am involved in an effort to standardize the comm. protocols used by all manufacturers. This new protocol suite is called NTCIP and is based on HDLC, TCP|UDP/IP, and SNMP. If you're interested, there's a website at http://www.ntcip.org
btw, some terminology - the diamonds you refer to are called 'loops'. They are literally loops of wire in the road surface that senses when a large piece of metal passes over them. When a traffic controller is using detectors (loops or otherwise) it is said to be actuated.
aj
Admit nothing, deny everything and make counter-accusations.
Just the important ones. ;)
Seriously, I wonder if these folks have taken into account the possibilities of sporadically placed street signs.
That is called a "pressure wave" or "shock wave". One slowdown ripples backwards in the flow. There can be positive feedback to make things wors, such as 3 lanes to 2 lanes; the funnel effect causes one wave slowing traffic in the 2 lanes but the lane which ends is empty because everyone merged...a car hops out of line, runs up to the front of the line, jumps back in where the lane ends, causes another wave...
If cars moving freely along the freeway equals a fluid, and cars stuck in a jam on 42nd street equals a solid - just heat the cars up to get them to change state to a fluid? Any idea how much energy we would have to put in to get this to work?
The difference between reality and fantasy is a nice soundtrack.
...especially the processing power available at Blue Mountain. Did I read that right? 6200 processors?
That they can put this kind of effort in is really interesting, and the practical applications like variably-timed onramp traffic signals and wireless traffic co-ordinaters sound useful, is it really worth all the effort? Why not just telecommute or encourage people to use mass-transit?
Who am I?
Why am here?
Where is the chocolate?
What is your Slash Rating?
If you think about efficiency in the roads
around where you live, it's pretty clear that
most of them arn't particularly designed well.
An ideal road system would minimize the number
of stops neeeded to go somewhere, as this would
both reduce waste of fuel (F=MA), wear on
the brakes, and reduce time spent behind
stoplights (or otherwise waiting for other cars
to act). IMO, tossing a supercomputer at the
problem is a bit silly when the problems are
obvious.
For every problem, there is at least one solution that is simple, neat, and wrong.
The folks at Maxis (creators of the SimCity family of "games") could very likely be of some help here. From the reading that I've done, their simulations of traffic flows and city modeling behavior is actually pretty sophisticated, though, obviously on a much smaller scale than these people are talking about. Regardless...their experiences with the SimCity "games" might be useful.
Jeff
Heating isn't exactly what makes a solid into a liquid. More precisely, it is the _exciting_ of the molecules. So instead of heating the cars in a jam, we just need to get them excited! I don't know about cars, but what works for me is a little fender bumping, some hood rubbing, flashing headlights, etc.
The Scientific American Frontiers program on PBS here in the US did a show awhile about answering some of life's little questions and one of the segments was about this topic. They talked to some guys in Atlanta (I think) where they modeled a huge traffic tunnel to find out the best ways to get traffic jams under control and how to take care of accidents. They also did a talk with the guys from LANL who modeled their entire city. They even gave the city people with tasks to perform and places to go in certain time frames. It was really neat and if the show reruns in your area, try to catch it. As a semi-side note, the Scientific American Frontiers program is usually really good, it's one of my favorites.
Tucson is the opposide, Winter time is the worst (all the vacationers come home.)
*Carlos: Exit Stage Right*
"Geeks, Where would you be without them?"
*Carlos: Exit Stage Right*
"Geeks, Where would you be without them?"
"Got Linux?"
Is it possible for Quantum Tunnelling in this model? Or is this strictly a classical model with no Quantum bias?
Is there a method for sublimation? (Transition from Solid to Gas (ie. Carbon Dioxide.))
If traffic gets too "pressurized" (like in the center of a star) will the result of Gridlock be a black hole?
*Carlos: Exit Stage Right*
"Geeks, Where would you be without them?"
*Carlos: Exit Stage Right*
"Geeks, Where would you be without them?"
"Got Linux?"
They're modelling my home town (Portland, OR). I wonder if they'll have a pseudo-me particle, waiting in the rain for a bus every day. :-)
I hope they take weather into their equasions: I know a lot of people who look out the window before they decide to take public transit or jump in their car (or skate to work, or whatever).
perhaps this will fix the backups on my street, which occur only because the side-street lights are always green and the main street is where all of the traffic is so about half of the cycles are idle in one direction while there are bottlenecks in the other. Obviously, not designed by network engineers :)
I think one of the areas where city planners can improve things out there is with stoplight design.
For example, the "diamond" stoplights (stoplights that detect cars at the light, and change accordingly) are an excellent design when traffic is extremely light, such as the middle of the night. It is a terrible design when traffic is moderate to heavy.
What happens when traffic is moderate with diamond stoplights is this: they slow down traffic. Since the lights are controlled by traffic, which is essentially random, the chance of a given stoplight being green is simply a flip of the coin. This makes "liquid" traffic "solid" traffic.
The ideal design once traffic hits the "liquid" state is to have the stoplights be timed lights. In other words, If one is going down the road at 40mph, all of the lights are timed to be green at the time one drives throught them.
Once traffic gets really heavy and enters a "solid" state, all bets are off. The only options traffic lights have are to either be timed at a slower driving pace (10mph or whatever the traffic can handle). One also needs to keep the main artery intersections green for as long as possible.
- Sam
The secret to enjoying Slashdot is to realize that it should not be taken too seriously.
I've been following this topic of research for some time now and the article didn't mention and interesting effect of on ramps.
The team in Germany has determined that the best way to keep a traffic flow fluid is to stagger the traffic merging onto the highway in a random manner. They initially tried a regular pacing of cars onto the freeway, but this turned out to be worse that just letting people come on whenever they got there.
Their work seems to be focused on maintaining what they call "synchronized flow" in the article, or the intermitent state of driving at a fair speed in dense traffic, and usually signals the onset of a jam somewhere around the next on ramp.
If anyone is interested further, send me some mail and I'll give you some other related articles, if I can find them.
Hey, we've been having a ton on traffic jams lately, and most of them don't make sense. Often, they are not during rush hour. It's caused by the domino effect, I believe. One old guy who can't see is driving along, taps his break lights for a second, and the red lights travel back a mile. Multiply this by a few old people cars, over a short period of time, and you have a traffic jam given enough normal throughput on the road.
Most interesting of all, is that I live in Florida. I know we get lots of tourists here for the beach, but it's summer! I didn't know anyone came to Florida in the summer. However, for some strange reason, it's actually cooler down here (90-95 F) than up north (95-100 F).
thanks for posting those!!!
I drive to and from work in the Seattle area, and I know what you mean about the ripple effect and the buffering. I have tried to accomplish the same thing myself. However the biggest problem I can tell (in Seattle anyway) is that there are so many times that there are 1 or 2 lanes that are exit only, exits on either side of the highway, and short, combined, heavy used on-off ramps (I am thinking of the SE 8th street exit on I-405 South if anyone here knows about it). What happens is, the stop and go can have really long periods of "stop." No matter how slowly you go it will not be slow enough when the stop comes. If you leave any space between you and the car in front of you it will get filled in, even if there isn't any space (people wedging in). This is due to the great number of lane changes required to go anywhere in pugetopolis.
Don in Seattle.
Roughly considered you only need to vaporize a small porttion of the traffic Jam to unleash the remaining partticles ... I mean cars . ...
Let us consider this :
a mirror roughly 6000 meters squared ( cross section to the sun and not hte actual surface area of the mirror without accounting for angle of incidence , of course ) would bring enough energy in one second to vaporize approximately 28 tons of iron . ballpark estimate ; 1 ton per vehicle ( for simplicities sake we will assume that the majority of the mass is an iron derivative and discount aluminum engines --- not to mention fieros ) that would remove a traffic jam in Chicago's loop every hour .
I will be fine as I have several layers of mylar lying around here somewhere and can get up to a 95% reflectance . It should , at the worst cook the Mylar and let me scramble out of the new oven that I was driving
your Squire
suqireson
I have picked up a theory on driving on the urban freeways. The speed limit is 60MPH. Alan Anal wants to drive 59MPH. Let's assume we are not in Seattle, therefor he will drive in the right lane. Busy Bob wants to drive 65MPH. There are enough A's in the right lane to make it impractical to stay in the right lane, so all the B's drive in the second lane. Then there's Crazy Commuter (that's me) who wants to drive 70MPH. When the traffic is high enough, there are enough A's and B's that I will drive in the third lane. Now add in Dangerous Dickheads, the fact that all the semis drive in the second lane, and the right lane often becomes an exit only lane... well you get the picture. Oh yeah, I forgot the mention, the carpool only lane is completely empty.
signed,
drivers
I'd prefer a PRT system like Taxi2000. Walk less than 4 blocks, push the button to call a vehicle, while waiting tap the touchscreen with my destination, get in the car. The vehicle goes automatically to the stop nearest my destination. The vehicles are for 3-4 riders and do not stop to pick up/drop off more riders.
The traffic sensors can fail so the traffic light designers may make the light change every few minutes to prevent trapping vehicles.
Or the traffic sensors are overly sensitive.
Or the traffic designers put in some light changes to keep that light synchronized with the rest of the traffic flow.
Or you simply did not see the car which hit the sensor, turned right on red, and vanished from sight before you came along and got the red light.
Feel free to improve LinCity traffic...
The advantage of computer-controlled cars is they could chat and agree to do things such as alter spacing and balance between lanes, and cars would not jump ahead in the line to the detriment of everyone behind them.
but if it's stop and go, and the car in front of you goes (as soon as possible, instead of picking their butt for a half-hour), then if you DON'T apply your brakes until the last possible second, chances are that the car in front of you will move, and you won't have to stop at all, which would have the enormously beneficial effect of eliminating the stop for all the people behind you.
Unfortunately, the guy in front of you apparently has hemmorhoids.
"The number of suckers born each minute doubles every 18 months."
-jafac's law
These are my friends, See how they glisten. See this one shine, how he smiles in the light.
Jafac's first law of freeway driving:
Your punishment for leaving at least one car length of space in front of you, is that that space will be filled by another car changing lanes.
Leave the car length of a Hot Wheels car, because they can't drive on the freeway, so you won't get cut off by some geezer in a Ford Fiesta doing 20mph.
Here, try a Java Traffic Light Simulator.
I don't think that the "three-phase" model is a good model. Stop & go traffic, at least the freeway variety, appears to be more a combination of people not leaving intervals between cars, and people waiting too long to reduce speed.
...
:)
A hypothetical driver comes up on stopped traffic on a freeway, and is forced to stop. A few seconds or so later, traffic restarts.
"Ah", he says, "Moving again.", and start to drive at the speed of the car in front of him, leaving a car length or two maybe. A few seconds later, the car in front of him puts on his brakes, lighting his brake lights.
Now they teach you in driver's ed that you're supposed to leave one car length for every 10 miles per hour, and you're supposed to start braking the instant you see the car in front of you put on his brakelights, both to reduce speed, and to warn the car behind you to start braking also, but hardly anyone seems to do that. Instead, the typical action seems to be to coast as long as possible, then brake to avoid collision.
The result is that our hypothetical driver has to break harder and faster then the car in front of him because of his delay.
If a dozen or so people do this in a row, it will naturally cause the traffic to stop and go in a ripple pattern.
Just watch the brakelight patterns next time you're in heavy traffic on a curve. The lights move backward in waves; the speed of the wave is a combination of the drivers' individual reaction times, and the drivers' wishful thinking time.
If you can figure out the average speed, and move at that exact speed, and force yourself to leave an appropriate interval between yourself and the car in front of you, you can break the stop & go pattern for yourself and the cars behind you. In other words, when the car in front of you zooms ahead, go at a constant speed, and let a gap open up in front of you. Then, continue at that constant speed, so that you catch up to the car in front of you in the same amount of time he has braked, stopped, and started again.
The result is that you move at maybe 15 mph, as opposed to 0, 25, 0, 25
Of course, you lose a little because people cut into your buffer space, but the sort of people who will change lanes to take your buffer space will change right back when the other lane moves again, so it appears to average out over time.
I have no idea whether this helps anyone but myself, or whether I'm just being annoying as hell, as my wife claims
I'd love to see a sim-traffic game.
But, I'm wondering about the variables that the programs will have to take into account re. driving "habits":
putting makeup on while driving == erractic
talking on cell-phone while driving == faster/slower than normal
screaming at the kid(s) in the waaaay back of the friggin min-van to "shut the hell up!" or "Do not touch him/her/them AGAIN!"
eating sloppy junk food while driving == crashes
smoking and dropping cigarette in lap == 20 car pile-up
etc.......
BTW, LANL must be the coolest place to work.
"shop smart:shop s-mart" ash
I'm not to sure about the Cars and Particles anology...unless they discovered that some particles have the IQ of a broken toaster and spend most of their time on thier cell phones pulling in front of me and then slowing down. Road rage...a way of life
They need to expand the model to take into account that different drivers have different driving styles, and that these make traffic behave more like a solution of different particles than a uniform substance.
Some years back I noticed that different regions have distinct driving styles, and that someone (like me) from a different region with a different style could be in, or cause, trouble - like a foreign particle acting as a seed crystal or a cavitation site.
Then there are places - like California - where waves of immigration from different regions have produced a wild mix of different driving styles.
And lots of unforseen consequences of government intervention. For instance: The 55 MPH speed limit changed freeway behavior nationally - from mutual repulsion (for safety) to clumping (forming a herd to make it harder for the blue-coated peredator to pick out a victim).
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
A friend and I were waiting in line to get into a Dead Milkmen concert, and, being the good engineering students that we were, started talking about the ebb and flow/accordion-like nature of the queue and how you could probably model the behavior as an oscillating system....
Of course then we moved onto traffic jams and how the same behavior applied....and the list of variables we deduced was quite impressive. I wish I could remember more, but I was, um, slightly in a non-remembering physical state if you take my meaning.
then we got inside, he got punched in the throat whilst in the pit, and I had to help break up a chick fight.
*sniff* memories.....
Blech. Signatures.
I commute from Boston to Framingham each day. I used to be averse to passing on the right, but it makes me feel so good. I like to drive between 75 and 80 mph and stay in the left lane. I can't stand people who drive the speed limit in the left lane. If someone is coming up behind me who is moving faster than me, I pull into the middle lane and let them by. I wish that more people did this.
The only purpose that tolls serve is to give people something to do. Most toll plazas are poorly laid out. With FASTLANE open for the length of the masspike (why does their site need Java?), things have not gotten better. FASTLANE has removed one lane (typically) from each toll station that was previously used by people paying with Real Money (TM). At Exit 13, the FASTLANE replaced one of the two 'double server/single queue' lanes (two toll booths in the same lane). Either pike officials realized that the ds/sq system was inefficient, or they aren't really concerned with efficiency. I would like to get a FASTLANE transponder, but I refuse to. I'm waiting until the fall, when, supposedly, the system will be compatible with the EZPass system. EZPass is better (IMHO) for two main reasons:
- To get a FASTLANE transponder costs $27.50, including a refundable deposit. An EZPass transponder requires a $10 deposit, unless you start your account with a credit card, in which case the deposit is waived.
- EZPass is bank agnostic. A FASTLANE account requires a $50 deposit. Unless you are a BankBoston customer and you pay tolls through your checking account. EZPass requires a minimum deposit of $25 for everyone. Both systems require a minimum balance (FASTLANE requires $20). Why do both systems need to have some of my money all the time?
Is anyone else bothered by the fact that FASTLANE needs a corporate sponsor? I have to pay a toll, and the Commonwealth is either taking money from BankBoston, or BankBoston is getting free ads in exchange for some service they are providing the Commonwealth (administration of accounts?) About a year ago, I noticed a FleetBank ad on the reverse side of a toll schedule. I do not need spam in my car.
And what about the areas not frequented by commuters? There are typically fewer toll booths, one of which is now replaced with a FASTLANE. What incentive is there for the people in those areas who don't use the highway that often to get a transponder. Is the goal here to get a "transponder in every car"? For what purpose? Will we start getting speeding tickets in the mail based on the data collected from the transponders (distance between tolls divided by elapsed time equals average speed)?
I could take the commuter rail to get to work but I don't. I would either have to get up earlier than I want to, or I would not be to work at an acceptable time. I also have meetings outside of work that I have to go to and the commuter rail schedule does not give me the flexibility (or reliability) that I need for my schedule. Just today, my roommate was 20 minutes late coming home becuase a lightning strike disabled switching on a four mile section of track, stopping traffic in both directions.
I wouldn't mind being a particle. Travelling at relativistic speeds my commute would take one millionth of a second. I could get eight hours of sleep a night and still go to bed at 1am!
BLOCK STRUCTURE breathing apparatus required for special maneuvers!!
Since Atlanta's got about the worst traffic on the planet (outside of the Beltway :), I think this stuff can apply not just to infrastructure, but also to driving skills. Since I've located myself to drive against traffic, I don't get to play with the ideas very often. But, I've noticed a few things: :)
(A) When traffic is stopped, people like to wait for the car ahead of them to move up a few lengths before they go. I think this is a function of braking distance and experience with driving the particular car.
(B) If I wait for a shorter time period, leaving a smaller gap, the person behind me waits longer, so the total gap reduction (and speed increase) is reduced, if not negated. This indicates the driver behind me is also watching the car in front of me. From the point of view(frame of reference?) of the driver behind me, he's "pacing the traffic". From the PoV of the driver behind _him_, he's stalling.
Kinda wierd, makes me wish I could get a big electromagnet to tow the slacker along.
(C) For every car '1' moving at speed x, a "terminal point" is created. This "point" is the spot where a car '2', behind '1' and moving toward '1' at speed (y), will touch '1' after time t. t is the measure of time needed for '2' to reach '1's position at '2's current speed. The point slides forward, backwards, and sideways, depending on the relative position, speed, and acceleration of '1' and '2'. I.E., if '2' changes lanes, terminal point '1-2' no longer exists, but a terminal point '2-3' may be created, and terminal points '1-4', '1-5', and so on, may still be in effect. If I look at cars in terms of energy, then I could probably apply this item to a global scale.
I figure that if the above items are near-correct, certain "driving in traffic" subjects can be added or modified to fit a drivers-ed curriculum.
Which won't matter in Georgia, because the drivers-ed program was ditched, and stays ditched, for "cost-reasons".
The URL for the software mentioned is http://www-transims.tsasa.lanl.gov/
Having worked both professionally and as a researcher in this business, and having attended many of the Travel Model Improvement Program [URL: http://tmip.tamu.edu/ ] meetings... let me plant the idea in your heads that this is a public works program for out-of-work Atomic Bomb builders. It gutted five years of research money for projects that really could have made a difference. (No sour grapes here, I never lost a dime of contract money to this sillyness.)
This project's applicability is nearly zilch since they've blown all their (relatively VAST) money and they have yet to really, successfully, verifyably, model real streets to such a level that one could make plans based on a TRANSIMS model. That is what it is all about.
Finally, there are many modeling software systems used by the transportation planning community. Here are the names of some: TranPlan, TransCAD, EMME/2, TModel/2, TranNetSim, and QRS/2. Their prices range from (US) $70 - $25,000 per computer license.
Questions about this? Post and I'll try to answer in as unpleasant a detail as you would like.
Anti-Particles...
:>
Just treat every object on the road as a 'friction' point. The closer one object get to an object, the more it slows down. If there is an object with a few feet of traffic at the edge of the road (Any object large enough to be seen at several car lenghts), traffic will slow. The PERCEPTION of the size of the object and it's proximenty to the road seems to dictate the loss in speed.
So, when you see cars ahead of you stomping on thier brakes for no apperent reason, you can bet the PERCEPTION of the size of the objects ahead of that car has been viewd as being large!
This has been obvious to me for at least 10 years... If you are able to reduce the 'friction' around you, your level of stress goes way down.
If you look at water molecules flowing thru a pipe, you'll see that they speed up when the pipe narrows. This is exactly contrary to what happens when people driving encounter a narrow place in the road. They have to merge, so someone will brake, you can count on it.
If cars were under central control, a computer could merge them and speed them up simultaneously on encountering a narrow place. I don't think there is any way to teach individuals to safely speed up and merge.
Jim
There are some traffic lights in my area
(Columbus, Ohio) where there are crosswalks,
buttons for the crosswalks, and 4-way
intersections. At these intersections, the
light will periodically change even when there
are no cars waiting to use the intersection the
other way and no pedestrians have pushed the
button to request walk across traffic. This is
quite irritating...
For every problem, there is at least one solution that is simple, neat, and wrong.
Russians Develop New Tires to Combat US Threat
CNN today reported that a massive increase in tire production by the Russians has strained diplomatic relations. The situation has been made worse by the prospect that China may be retooling to produce even smaller and more efficient cars. The Whitehouse had no official comment today, but rumor has it that a new SUV will be released to combat the communist threat. "Citizens need to be aware that driving is no laughing matter! The future of democracy may well be at stake!" However, a random American was quoted as saying "I don't care, as long as I get my super-sized cup holders on time!"
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Here's one reason mass transit doesn't get the ridership it should.
I have a choice. 30-40 minutes to drive to work, or a 90+ minute commute via train/bus or train/taxi.
So, to get to work at 9am, I have to leave at 8:30 or 7:30. This means I have to get up at 7:30 or 6:30.
If I get off work at 5pm, I will get home at 5:30 or 6:30.
So here are the choices:
Option 1 (Car):
Leave at 8:30
Get Home at 5:30.
Total commute time 60 minutes.
This gives me more time with my family, and more time on my own projects.
Parking where I work is currently free.
Cost of gas is still up in the air, as I haven't tracked it.
Option 2 (Train/Bus)
Leave at 7:30
Get Home at 6:30
Total commute time 180 minutes (3 hours).
This gives me less time with my family and or other projects.
A plus here is I have more time to read, assuming I can get a book out of my backpack while packed into a standing room only train.
A transit pass is $49.00/month. I believe this is less expensive than the cost of gas for one month of commuting by car.
I'll take the additional time not spent commuting.