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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 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.)
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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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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.
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Business. Numbers. Money. People. Computer World.
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...
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
Oo!oo!I know this one! There has to be a $6/gallon tax (putting gas at about $6.75, I suppose) for drivers to take into account all the consequences of driving: pollution, increased death rates, The Gulf War, etc. This according to some study I read for work in July. Can't remember the source, though.
Oo!oo!I know this one! There has to be a $6/gallon tax (putting gas at about $6.75, I suppose) for drivers to take into account all the consequences of driving: pollution, increased death rates, The Gulf War, etc. This according to some study I read for work in July. Can't remember the source, though.
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.
Here, try a Java Traffic Light Simulator.
More exciting car options to increase traffic speed:
6. Lower center of gravity or lift kit (pick one.)
7. Electronic defensive and offensive counter measures (radar guns are more useful than detectors!)
8. Full bottle of N2O (gas masks not included.)
9. Air horns.
10.Dual 3" exhaust.
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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