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Mathematicians Solve the Mystery of Traffic Jams
mlimber writes "Do you ever find yourself in a traffic jam, thinking, 'Man, there must be a bad accident up ahead,' but as you plod along you see no evidence of any crash? Some mathematicians have solved the mystery by developing a mathematical model that shows how one driver hitting the brakes a little too hard can cascade into a backup miles behind. The mathematicians' future research will investigate how automatic braking systems may alleviate the problem."
Although apparently the mathematicians are way behind Ethan Hunt.
This has been known for years.
Give me Classic Slashdot or give me death!
Sure. But what they forgot to include was the variable of EVERYONE IN THE OTHER LANE STOPPING TO WATCH.
Physics is nothing like religion. If it was, we'd have an easier time trying to raise money!
Does this mean now there's math to support this?
$x='S24;r)>63/* h@<5+oZ)32"5cz';$me='phroggy'x$];
$x=~y+ -xz+\0-Tx+;print$_^chop$me for split'',$x;
20 fucking years ago.
I've often seen this. People slow down too much for no reason, especally near ramps. I've actually gotten pretty good and figuring which jams are accident related and those that are just people being retarded.
It doesn't help that speed limits on interstates get lowered as you approach larger cities. This is a good reason to remove enforced upper limits on these roads completely. Much of the braking is due to the few goody-goodies cramping the whole flow.
How come certain cities seem to have extra bad, slow, etc. traffic? Just go drive in Silicon Valley on the freeway, then come to Columbus Ohio and see how infuriating the difference is.
stuff |
The problem would be alleviated quitre a bit if dimwits would stop tailgating, and even more annoying, braking for no reason whatever.
Here in Springfield they race to the red light, but brake going through a green light. If the dimwits would let off the gas when the light ahead turned red, and even speed up a bit if the light is green, they would save themselves a lot of gasoline, global warming, and aggrivation.
I don't like the idea of "automatic braking systems" as I try to keep my foot off the brake. Every time you touch your brake you're converting the momentum you spent gasoline obtaining into heat, and throwing it away. If it's an electric or hybrid that converts momentum into stored electricity I wouldn't mind an autometic braking system so much.
mcgrew's razor: Never attribute to stupidity that which can be explained by greedy self-interest
One of the most irritating driving habits I can think of are people who obsessively cover the brake every 20-30 seconds or so. Usually soccer moms in Suburbans or elderly in the largest Lincoln they could find. There's nothing ahead of them, no reason really to tap the peddle, but they do it anyway out of habit.
If an automatic braking system can solve this problem, I'm in for my tax dollars.
Eagles may soar, but weasels don't get sucked into jet engines.
maybe mathematicians can solve why old news appears on slashdot.
I know on the I-10 around Yucaipa, California, this is definately true. There are 2 downhill slopes (1/2 mile each, 5% grade) right before the town on the freeway where everyone going 70-80mph (I get passed at 75) slams their brakes to not loose control on this hill and never get back up to normal speed, and because the person in front of them is slow, rides their brakes and never gets up to top speed for the next mile or so, everything piles up and its gridlock. If everyone slowed to 60 or so, but KEPT MOVING knowing, there wouldn't be the daily 15-20 minute delay every single day at this point.
Forgive my spelling from time to time. I'm often posting during short breaks.
Scientists discover that if people act in society's interests rather than their own, society is better off. Seriously, how hard is it to follow the two-second rule on the highway?
I think this has been known for _years_.
I've observed it many times from the vantage point of a light aircraft - in busy traffic times, you can even see the genesis of traffic jams on busy roads - someone jabs their brakes, the car behind hits the brakes harder, and before you know it, you have a standing wave of stopped cars in the traffic maybe 20 or 30 cars deep. It's very interesting to watch from a light plane. It's very frustrating to be in on the ground.
Oolite: Elite-like game. For Mac, Linux and Windows
I'd be curious to see whether these geniuses analyzed the impact of HOV lanes? http://www.thenewspaper.com/news/02/292.asp
Not only that, but it seems clear that congestion at one time - whatever the cause - can set up a standing traffic density wave that might last for a long time after the original cause is gone. Beyond some minimum traffic level (easily achieved on the highways around DC, for example), at least.
Although their proof might be (IANAM). I remember reading this article on slashdot around the time it was written. Although, for what it's worth, I don't think it technically qualifies as a dupe.
Sometimes, life itself is sarcasm...
From last year: http://science.slashdot.org/article.pl?sid=06/12/27/0350218
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Disgruntled traffic engineers cause traffic jams!
:)
Support the 30 Hour Work Week!!!
Some drivers are always under some kind of external or internal influences. Internal influences would include the influence of drugs.
At a place I normally frequent, I always see "smart/well-dressed respectable men and women" dying to get a fix before getting behind the wheel. By the way, I do not do drugs of any kind.
Another cause for bad traffic is the ridiculously easy driving test we have in the States. Couple that with law-enforcement only ticketing speeders instead of bad drivers in general, and you get the traffic we have in most of our cities. I also hate how all accidents are chalked up to "failure to control speed", which makes it sound as if speeding were the main cause of all accidents. In reality, failure-to-yield is overwhelmingly the #1 cause of collision accidents, not speed. But the revenue hungry cops would rather sit on their motorcycles with radar guns than actually pull people over for changing 5 lanes at once, or cutting off other drivers by pulling out in front of them and then NOT accelating.
Not to mention, hell will freeze over before they ever ticket a slow driver in the left lane.
I already cringe when I hear car ads mentioning Microsoft software. Not to be a luddite, but I'm not so sure I'd feel comfortable letting software partly control my brakes.
Developers: We can use your help.
The article you linked is simply a hypothesis, not backed up by any actual evidence other than conjecture. The article in the story actually tests this hypothesis. Nothing was "known" until now.
The effect would be mitigated if everyone would refrain from following other cars so closely.
Yeah.... I tried this for several weeks. Except everyone took the opportunity to sneak in front of me so they could play a game of changing lanes repeatedly to snake their way through traffic faster.
That is the problem. You can do what is best for the group, but then selfish individuals abuse that for their own gain which hurts the group more. I can't wait until we have self driving cars... I could easily foresee traffic signals going away, much more efficient cars and no more worrying about getting to old to be safe on the roads. Add to this a dropped death rate, and this breakthrough would easily be the greatest advancement of the 21st century.
See my journal for slashdot ID's by year. Mine created in 2005. http://slashdot.org/journal/289875/slashdot-ids-by-year
What really amazes me is how smoothly the traffic on German roads flows. I've been in traffic jams that lasted for miles, yet everyone managed to stay at around 45 mph the whole time. In fact the only time I ever really see stopped traffic is when an accident has blocked the entire road system, there is construction, or a roadway merges 3 lanes into two or something.
Of course the other funny thing is that it was the Americans that removed the speed limits on the autobahn oh so many years ago, yet they enforce such strict speed limits on the stateside highways.
I always thought traffic congestion was like those experiments you did as a kid with cornstarch and water where it can feel like a solid and liquid. the starch dough moves if it's relaxed, but solid when there's pressure. I'm not sure how accurate my analogy is...
I'm not so sure if following distance would play a meaningful role, frankly. Consider how often you'll see this scenario:
Car B is following car A at a reasonable distance on a city street. Car A begins to gradually slow down for whatever reason. The driver of car B, whether due to lack of attention or just brutal stupidity, doesn't slow down until it's necessary to apply the brakes strongly. Car B applies the brakes strongly, as do all the cars behind car B who can't see what's going on in front of him and have thus had no time to prepare.
So, in summary, even when not tailgating, drivers seem to "prefer" using the brakes at the last minute instead of just getting off the gas and allowing the engine compression and transmission drag to slow down in a less "panicky" way. I think it's similar to how you'll often see a driver accelerate toward a red light and then use the brakes at the last minute. Why? I don't know, but I could guess... (coughminivanorunnecessarilyhugetruckcough)
If you're lucky, the light may even turn green as you're coasting and you'll not need the brakes at all (this means more to those of us who drive manual transmissions).
-
Inventor of the term 'pardon my French'.
I first read about this in my Astronomy textbook in high school. The idea is that the spiral arms of galaxies happen the same way, except that instead of braking, we have gravitational attraction between stars. Stars in the arms are stuck in traffic jams; stars between arms are the lucky few who aren't.
I used to carry a bottle of whiskey for snake bite. And two snakes. -Nefarious Wheel
As if I really needed mathematicians to tell me that there are idiots on the road that cause traffic problems.
Knowledge is how to play a game, intelligence is how to win, wisdom is knowing what game to play.
And these solve the problem permanently.
http://news.bbc.co.uk/1/hi/uk/7148731.stm
Deleted
Springfield, right?
It's quite difficult when the majority of other drivers see the space in front of you as an opportunity to "get ahead" in the flow of traffic.
It's not hard to follow the rule, instead, it's hard to maintain it without ending up going significantly slower than the traffic around you, and you'll still get cut-off occasionally simply out of spite for your perceived slow speed.
Drivers tend to be very self-centered in their driving actions and habits...even when that's entirely not the case when they're not behind the wheel. It stems from a variety of issues, from having to share the road with people that are distracted, aren't perceptive enough to notice what traffic is doing and adjust, or simple driver incompentence. With every driver eventually having an occasional encounter with another that is causing them some form of mild aggravation (usually unknowingly), can you blame them for taking an egocentric approach to their driving habits?
Of course, the problem then becomes self-propagating.
As a motorcyclist, the idea of "automated braking systems" scare me almost as much as women who are applying makeup while driving SUVs so large they should have "USS" on the license plate.
Regarding traffic jams, the main cause of traffic jams is very simple, and doesn't require a mathematician to figure out: There are too many people on the fracking road! Whether people are braking perfectly efficiently or not, if enough cars are crammed on the road, there's going to be a traffic jam.
Gifts for Geeks - Stuff that really matters!
Once you understand how it works, you can create traffic jams in even relatively light traffic. If you're really good, they're still there when you go home the other direction.
Deleted
Unfortunately, the mathematicians weren't smart enough to follow through to understand the cause of heavy braking: following too closely, less than 2 seconds behind the car in front of you so that when you brake lightly the next guy has to brake hard.
Nor did they follow that back to its root cause: too many cars on a section of road so that they pack too tightly. Nor did they notice that in light traffic flows fine regardless of braking because the large gaps consume the time lost so that more than a couple cars behind you no braking is needed.
If you want to understand road traffic, you need only understand data traffic on CSMA/CD half-duplex Ethernet. It works poorly after about 60% of theoretical capacity and has a cascade failure approaching 100%. Actually, that's badly phrased because half-duplex ethernet never approaches 100% throughput. The wire can be consumed 100% of the time, but when it is, total throughput is close to zero. Most transmission attempts are retried due to collisions and most packets that do get through end up in a higher-level retransmission because a timeout has been hit or the packet is out of sequence with another packet that was dropped from the overflowing transmission buffer.
Ethernet collisions are analogous to someone tapping the brakes lightly while a packet lost due to a buffer overrun is analogous to someone hitting the brakes hard. As the probability of each event increases, the throughput on the approaches zero.
Moderating "-1, Disagree" is simple censorship. Have the guts to post your opinion.
In his song "Asshole" the lyric is, "I drive really slow...in the ultra fast lane...while people...behind me...are going INSANE! I'm an asshole! he's an asshole I'M AN ASSHOLE OOOOOHEEEEEEEOOOOO! He's the worlds biggest asshooooooooooole.
I live in Arizona and the drivers here are just dreadful. I see them on the freeways day after day, they have no confidence in their driving skills. They tap their brakes constantly whether something is in front of them or not, and it makes me crazy.
I can't help but wonder if the onslaught of snowbirds that migrate here year after year during the winter.
It's true no man is an island, but if you take a bunch of dead guys and tie 'em together, they make a good raft.
Now what? Seriously, as obvious as this is, what good will it ever do? People aren't going to change their traffic accidents now that's there scientific data to back up what everybody already knew.
I'm pretty sure we all know that automating driving would get everybody there faster, as long as it works.
They need to study why IDIOTS slow down when they get to tunnels and redesign the fronts of tunnels to avoid it.
Or why a guy on the side of the road changing a tire is so damn interesting.
Yeah.... I tried this for several weeks. Except everyone took the opportunity to sneak in front of me so they could play a game of changing lanes repeatedly to snake their way through traffic faster.
It's funny how often I hear this. I try to hold back a safe distance all the time, and sure, a handful of morons weave through the gaps and I have to drop back a little more. But I never see this horrendous influx of morons people keep telling me about. I manage to maintain a much better distance (and a much smoother drive in terms of both vehicle speed and mental stress) than most people other than for a few moments if someone cuts in, and since those people usually cut out again almost as quickly, I doubt it even slows me down noticeably.
FWIW, this is the UK, and the comment above apply to both high-speed motorway driving and crowded conditions around the city. I've never driven in the US, but I do hear the same sorts of complaints the parent post was making all the time.
If you disagree, post your argument. (-1, Overrated) isn't your personal censorship tool for views you don't like.
Don't worry! You can fix this problem by driving 1 inch off the bumper of the SUV in front of you!!
-- "It's not stalking if you're married!" My Wife.
I've been following the "traffic waves" procedure for years now, but I guess when that chunk of concrete aims for your head, that's all she wrote!
Stressed? Me? Of course not. Stress is what a rubber band feels before it breaks, silly.
I really want automakers to announce simple autodrive systems for cars.
I see the first place this will work is in the 0-10 MPH creeping behind another car system. No steering, just holding a constant speed (not stopping if possible) and not crashing into the car in front of you. Go > 10MPH, turns off. Turn the steering wheel, turns off. Hit the brake, it turns off. But, sit there for 40 minutes in traffic, creeping along and it works like cruise control. Why don't we have this yet???
My intuition tells me that if everyone drove this way: working hard not to stop, but going slow enough not to crash to the next guy in front -- then the traffic jams would undo much more quickly. In fact, if even a low percent of drivers drove this way it would clear up the jams more quickly. The rolling stop waves that roll back through the chain of cars keeps the jam togteher. If even 20-30% of the cars never stop (creep slowly betweeen the waves) then the whole jam would start to move fast enough to disperse. I have no modelling or math proof of this, just a gut understanding of how could work.
- Flow Equals Density Times Velocity
- Conservation of the Number of Cars
- Experimental Observations
- Traffic Density Waves
- After a Traffic Light Turns Green
- Wave Propagation of Auto Brake Lights
- Stationary Shock Waves
- Effect of Red LIght or an Accident
and so on. It made for an interesting class (and the only math class where I ever assigned a paper!). I recommend the book. If only we could train people to behave in traffic as if they were an incompressible fluid, we would never have traffic jams; but to do that, you'd need to be trained to speed up when traffic got heavy.FWIW, this is the UK, and the comment above apply to both high-speed motorway driving and crowded conditions around the city. I've never driven in the US, but I do hear the same sorts of complaints the parent post was making all the time. It's not just the UK, I've noticed the same sort of thing in the US. This style of driving is also a lot more conducive to not getting bent out of shape.
It helps to realize that some people are assholes, and a lot of those assholes are not just bad drivers, they're dangerous to themselves and others. Keeping a safe distance instead of trying to block people probably isn't slowing you down and is definitely increasing your safety margins.
You have hundreds of "flying cars" in this stream bumper to bumper traveling at fast speeds. Of course the Jetsons is anything "realistic", but its still a good analogy.
The episode where the town charter declares the smartest people to be in charge in the absensce of Mayor Quimby.
Lenny comes up with the best idea. Traffic lights only have red and yellow, no green. Traffic is speeded up immensely.
Automated cars could also save gas on the highway. We all know that driving right on the bumper of an 18-wheeler will increase your gas mileage. The main danger is unexpected braking. If we had automated vehicles, they could all ride up against each other and make great use of slip-streams.
There would be savings at stoplights as well. When the light turned green, all cars would start moving, instead of this inch-worm movement. More cars get through the light, less idle time, more gas/electricity saved.
OK, so people are driving too closely and over-respond when the car in front of them slows down. Sure, it seems like things must be slower when you come to an almost stop, but does this result in an overall reduction in flow, or just an temporary reduction (as following distance is increased) that is compensated for by an increase afterwards (as the previous too-close following distance is resumed)?
So a little chaos theory for traffic eh?...interesting.
The trick when driving to try and iron out these hold-ups is to keep the traffic moving, by slowing down well in advance and leaving a large gap. As soon as the impatient and selfish start driving inches behind the car in front the whole system grinds to a halt.
My solution is to just go the speed limit. Everyone else is going speed limit +5 or +10 or more. The net result is a very smooth drive where everyone goes around me and there is always plenty of room in between me and the car in front of me. Unless the bastard in front is going speed limit minus x, which people tend to do when they are talking on their mobile. I hate those annoying bastards.
A beneficial side effect is I never have to break or worry about pulling over if I see a police car. I believe another effect is slightly better gas mileage, but I have no proof of that.
Also, I've done the math, even going 20 over the speed limit only gets me to most destinations something like 6 minutes quicker, so I figure I might as well use that 6 minutes to remove a significant source of stress from my life.
So here is the problem, there are two classes of people on just about any road, anyplace:
Drivers. These are the people you see driving, not overly fast, but driving with intent. They pay attention, they are generally never talking on a cell phone, their eyes are always scanning the road ahead, their mirrors and their instruments. They use blinkers AND turn them off, they can be pretty much any age and any gender. You will notice that they drive consciously.
Motor Vehicle Operators - These are the people you see driving a car that scare the crap out of you. They are NOT paying attention, they are shaving, eating, reading the paper, putting on makeup, doing their hair. Their cell is glued to their ear, are fiddling with the radio very three seconds. Their left turn blinker is invariably on.
Some things I would like to see tickets given for:
I think that should prime the pump, as I am sure my fellow /.'rs will add many many more.
Hey KID! Yeah you, get the fuck off my lawn!
I live in Los Angeles and commute 30 miles to work one way. It takes me an hour or more on most days, less at very early hours (pre 5AM). I've made a little mental hobby of traffic pattern prediction and on my route I can accurately predict where the slowdowns will be, and know which lanes to be in on the freeway in order to keep moving. I also know that the pattern changes from time to time and for various reasons and account for that as well.
By far the biggest problem with traffic here, other than the staggering number of people on the roads, is a false sense of entitlement and/or lack of courtesy for other drivers. I start my drive from a decent neighborhood and go through a pretty big slice of the city hitting East LA, Korea Town, West LA and downtown (including skid row and not in that order). It's not just soccer moms, it's not just the elderly, it's not just the Asians or the Latinos or the Blacks or the Whites or anything. It's ALL of them. For every decent driver out there, there's literally a thousand or more assholes. I moved here from Boston 10 years ago and I remember thinking "what's all this road rage shit I hear about?". How could you possibly get so worked up in your car that you'd want to KILL other drivers. Well I've seen it myself first hand out here.
About a month or so ago a Mom was killed and possibly her 2 kids as well (not sure) because 2 guys were fighting with each other on a busy surface street. One would hit the gas and then the brakes trying to get the other to rear end him or cutting the other off from getting in a lane or passing. Oh and by the way, yes one guy was about 19... but the other guy? He was in his 40s. You'd think after a certain *I'm invincible* phase people would grow up and mellow out. Most do, but some don't and some just want to go about their business, but when they're pushed, they push back. This is where I fit in. I mind my business and I try to drive quickly and efficiently without being too much of a jerk about cutting people off and I try to let people in when they need to. In other words, I *try* to be a courteous driver. If I'm in the fast lane out here with no one ahead of me, I'll be doing 90 easily, but if someone comes up behind me in a faster car, or just generally wants to drive faster than me, I'll move the fuck out of the way. I pay attention to my surroundings and I realize I'm not driving the fastest car on the road. Same applies no matter what lane I'm in on the freeway. I get the fuck out of the way, safely, efficiently and without waiting an hour. So few people do that here it's sad.
You say "drive the speed limit" its the law, it's there for a reason. I say, fuck off, I'll drive as fast as I think I can go safely. If I feel safe at 90, then I'm going to go 90. If I think it's safe at 40, I'm going to go 40. But I'm damned sure not going to BLOCK traffic or try to be the amateur police force by sitting in a lane, driving much slower than necessary and making it hard or next to impossible for anyone to get around me. I'm simply going to move OUT OF THE WAY. As for distances between cars, I try to leave plenty of room to stop, meaning at least 2 or 3 car lengths depending... BUT, here's the thing out here. You just CANNOT leave the 3 seconds or more of room that you'd like and still get anywhere. We're all not on a plane. We all don't *get there* at the same time. And yes, I think it's reasonable to assume that most people just want to get to where they're going in the least amount of time safely. Not necessarily in a mad rush. Not race day at the Daytona 500, but relatively quickly. And yet, if you try to observe the simple 3 second rule and leave a nice gap between you and the car in front of you, you get stepped on. Not cut off, but you'll get bumped back, again and again and again.
Traffic out here is like a line at the bank. Would you, in person, stand in line at the bank and let anyone cut in front of you simply because you didn't take a step or two forward when the person in front
One thing I've noticed in my state is that if the light is a left turning lane arrow, it might not give you the opportunity to go first if you coast up to it while its red, and instead lets the opposing traffic go first. But if you were stationary in front of it while red it would have let you go before the opposing traffic.
That is not to say its smart to speed up to it and brake suddenly if its red. But it is annoying when there is a guy in front of me and we both are approaching a turning lane where I know if we were sitting there during the red it would give us the arrow to go first, but he just coasts up to it and screws us all.
Not road rage annoyed mind you, just mildly annoyed.
Mod parent up...
I've found it's often cell phones, not that they have too big of a vehicle. I'd guess that probably 10% of the people I pass on my daily commute are holding phones up to their ears, and not paying attention because of it. I can't count the number of times I've been cut off without someone signaling or had some moron creating a "Polish road block" (as my Polish fiancee calls it) in the passing lane because they're chatting with someone. No cars in front of them for a mile, but they just have to match speed with someone beside them, forcing people who want to go faster queue up behind them... ignorant twits.
My blog. Good stuff (when I remember to update it). Read it.
Yep, when I drove the M25 regularly I got to know where it'd slow down - right on the crest of a hill, as every muppet going over it picks up an extra couple of knots and touches the brake.
Part of the problem, I think, is that brake lights are binary and braking isn't - the light shows that you're braking, but gives no indication of how hard. When you're daydreaming along too close to the vehicle in front, you have to assume the worst and brake harder than you need to. I've often wondered why tail lights couldn't give some indication of braking intensity.
The article referenced was actually published in the September 2006 edition of the Proceedings of the Royal Society A: http://journals.royalsociety.org/content/h107x295723j3734/fulltext.pdf
It's a longitudinal wave.
Engineering is the art of compromise.
I think I did this as a homework assignment in an undergrad class.
You all can quit your damn tailgating! Three second rule, not only a good idea, it should be the law.
What?
From the article: "Our model shows that overreaction of a single driver can have enormous impact on the rest of the traffic, leading to massive delays."
This is a manifestation of Lehman's Corollary to the Second Law of Thermodynamics: "All it takes is a couple of idiots to ruin things for everyone else."
This post hits all the points. I also have a problem with selective enforcement of the driving laws. Speed is not the cause of most accidents. When will people wake up to this fact? Speeding tickets should be abolished. In return the fines for speeding if you are involved in an accident should skyrocket. That way safe drivers are rewarded.
People tailgate and then apply their brakes. This is the proximate cause of the whole thing.
Math has little to do with it.
Install a program into the onboard computer chip that detects tailgating and then punishes
the driver for following too closely, by warning the driver and then shutting the auto down
for 15 minutes. "Pull over to the side of the road, this car will power down in 1 minute".
Yeah, we have to drive safer and if we are not smart enough to plan our day, then we deserve to be late.
Rushing-to-get-to-work because they overslept or partied too much bastards need not be rewarded.
They would have gotten the answer a long, long time ago if only more mathematicians would race bicycles.
There is nothing worse than flying along at 40+ KMh and having some inexperienced joker using her brakes to back off the wheel in front of her. It sends the riders behind her into convulsions.
FYI: that's why bicycle track racing (fixed gears) is much safer despite fantastic speeds and tight(!) groups.
Got Trader Joe's? friendwich.com RSS feeds work now!
. . . fly over Interstate 15 between Las Vegas and San Bernadino on a Friday night.
I think you can see the brake lights from space. . .
What?
My solution is to just go the speed limit. Everyone else is going speed limit +5 or +10 or more.
Most speedometers display a speed 5-10% lower than the actual. Check yours - you'll probably be surprised.
it's in my head
"When you tap your brake, the traffic may come to a full stand-still several miles behind you. It really matters how hard you brake - a slight braking from a driver who has identified a problem early will allow the traffic flow to remain smooth. Heavier braking, usually caused by a driver reacting late to a problem, can affect traffic flow for many miles."
A lot of studies have shown that reaction times are slower when the driver is distracted by phones, music, makeup, etc. I'd be interested to know if traffic problems have become worse due to the increased dispersion of cell phones.
Under capitalism man exploits man. Under communism it's the other way around.
I feel like the only place this would be applicable would be the interstate highway system. It would obviously have to be one of the most robust, reliable and secure system in the world; the only place I could see that happening due to complexity and cost is on something like the interstate highway system. I suppose that they would develop certain problem highways at first. The driver would be required to have a car up to spec with the highway system, and possibly pay a small toll. The highway would be a bypass to a heavily congested area and demand would be spurred by peoples' need to get to work in an efficient way. This would also open the doors for pay-and-go public transportation systems; people would get to the station attached to the highway and then rent a vehicle that would take them to another station along the highway with no user interaction. The system would be first adopted by people who can afford the expensive cars that can utilize the highway system, as well as those that can't afford a car or the gas. The technology would then trickle down (and up) to mainstream, middle-class consumers as demand grows, highway support increases, and manufacturing costs fall. The possibilities for the economic viability of an automated system are certainly there, but I would be shocked if it ever trickled down to streets that currently have stoplights on them, the need is just not great enough to warrant remaking in-place urban infrastructures.
Scratching their asses doing nothing while several lanes are closed that messed up traffic.
We are already have self driving cars. I drove myself to work today.
In other news, today scientists proved that Hurricane Katrina was caused by that butterfly in China flapping its wing a little too hard.
Hey, Windows users, there is no such thing as "forward" slash, there is only slash and backslash.
And what exactly does your car look like? License plate number? I need to know which one to pop all the tires on, as well as smash any glass components. Thanks!
My blog. Good stuff (when I remember to update it). Read it.
is not self-driving cars, but public transportation. And if you need something heavy moved, have it delivered or rent a pickup for a day. Owning and operating cars make sense where the population density falls below a certain threshhold, say in the country, but in sub/urban spaces, which is what we're talking about here, there's no good reason to use the car as the solution to personal transportation.
And that's just for logistical reasons. When you consider the cost to the environment, the justification weakens more. When you consider the cost to our foreign policy and national security in being dependent upon other countries for oil, the justification weakens still more. When you consider the sheer hassle and productivity lost to accidents, finding parking, breakdowns, time lost sitting in traffic, and aggravation of driving (people cutting you off, getting stuck behind a slow poke, etc), the justification almost evaporates. And when you think about what the $15K you drop on a car and the $5K/yr. worth of insurance, gas, parking, and repairs you have to put into it to keep it running, and the reality that the value of the thing itself loses half its value every year, versus what that money could do for you if you even put it into an index fund, then financially it's the last nail in the coffin for the justification of owning a car.
Do what you can, with what you have, where you are.
[Sir Garlon] is the marvellest knight that is now living, for he destroyeth many good knights, for he goeth invisible.
There's an amazing phenomenon where I live in California caused by "Amber Alert" signs and retarded (or possibly illiterate) drivers.
A boatload of tax money was used to erect these signs on major freeways throughout the state, supposedly so that we can quickly disseminate vehicle descriptions to the public in the event of a kidnapping. (Space constraints usually cause the info to be abbreviated beyond all recognition, though, like "BLK CHVY SUV LIC 5TRG345 CALL CHP." Try parsing that while driving by a 65 mph...)
Anyway, these signs rarely have kidnapping info on them. But I guess someone thought it was a waste to have all these signs if they are always going to be dark. So they now cycle through "helpful" tips from the California Highway Patrol. "Don't Drink and Drive." "Speed Kills." "Click it or Ticket" (oh, that one's cute, isn't it?). And sometimes weather or wind advisories that never seem to actually be correlated with current conditions (I'll be battling wind gusts one day with the signs off, then the next day when it is clear the signs have a warning on them. Gee, thanks, but a bit late.)
What I've noticed, though, is that whenever the signs have a message on them traffic inexplicably backs up around them. I'm convinced that it is because drivers are slowing down while attempting to read the signs. I kind of like the irony that wrecks are going to be caused by people trying to read highway safety information. But it is really annoying.
These signs ought to be used only in the case of a real emergency, because they seriously compromise driving conditions when they are lit up. And it burns me up that someone took my tax money to erect a sign to tell me not to drink and drive (while pretending it was to save kidnapped children). For every drunk person who reads it and decides to stop and call a cab, there are going to be 100 collisions between people trying to sound out the words while simultaneously eating and talking on a cell phone.
5-10% is actually with the correct manufacturer spec'ed tires!
(I researched this a while back. One car I've had was 10% off, my current only 2% but that's quite rare)
it's in my head
I do the "foot off the gas" thing before stopping. My brakes last forever. (100k+ miles) I also get better mileage. When gas got over $2.50/gal, I started driving the limit or slower, and my gas mileage went from 28mpg/tank to 32mpg/tank.
"He's lost in a 'floyd hole"
I already used "DOH!" as a subject line today. And yes it certainly IS the Springfield you're thinking of, as I illustrated in this comment responding a few comments down.
If you're ever in Springfield, mix Paxil and alcohol and you'll REALLY see the cartoons come out (I've been off the Paxil for a few years now but I still love my beer).
mcgrew's razor: Never attribute to stupidity that which can be explained by greedy self-interest
The real problem seems to be that it's in everyone's best interest to not be jerks, but if everyone's not a jerk, any selfish individual can be a jerk and do (marginally) better than everyone else. The situation with traffic we have now is the worst scenario of all... Everyone's being a jerk, causing the worst outcomes for all.
Gas, brake, honk. Gas, brake, honk. Honk, honk, punch. Gas, gas gas!
The Kruger Dunning explains most post on
If we were to automate cars the left two lanes of most freeways would be vacant. I commute on a motorcycle and have observed the ins and outs of traffic (what with my life depending on it and all) and those people are seriously F-ed in the head, I propose a formula for the mathematicians to try that will give the real reason for traffic: Norman Person + oversized vehicle + minor competition = Total Fuckwad. Basically these people should be killed for our national security: 3,620 people die monthly due to automobile accidents, while 2,974 died from 9/11.
The essay on "Traffic Waves" should be required reading for everyone who applies for a driver's license. Here's the link again: http://www.amasci.com/amateur/traffic/traffic1.html
That that is is that that that that is not is not.
This was reported quite a while ago. As a challenge, I try to leave extra distance and look ahead and see if I can't "break the wave" by being the first car not to touch its brake lights off.
I have to admit, vision is probably my biggest reason for SUV bashing. I don't care about that "saving the planet" bullshit. I don't care about somebody else's penis-size compensation, or their deluded feelings about safety. I don't care how much someone else spends on gasoline. Those aren't my problems.
I do care about being able to see. I can't see through large vehicles. It makes me nervous as hell, whether following them, or trying to make a left turn when one of those fuckers is in the opposing left-turn lane.
Either get your huge piece of shit off my street, or build it out of untinted glass, goddammit.
This isn't even old news, it's (un)common sense.
One idiot slows down and starts rubbernecking, and the slowdown propagates at the speed traffic was moving back up the road.
I've seen it happen due to flashing lights on the shoulder, or ironically, those signs designed to warn you that traffic is bad up ahead!
Question everything
"The term you're looking for is standing wave. The problem isn't actually the breaking, it's everyone not giving enough room between themselves and the person ahead of them to absorb small slowdowns."
Intuitively correct, but not completely. In reality while driving on a supersaturated freeway (bumper to bumper @ 30-40 mph) EVERYBODY is tailgating. If some minority of drivers decide to follow the spacing rules they taught in drivers ed, what happens? A gap opens up. That gap will be used opportunistically by other drivers trying to sidestep through traffic. In other words, people will swerve in front of them and cut them off. The gap originally opened up is not large enough for another driver to SAFELY merge into that spot. The end result is even heavier emergency braking by the good Samaritan that tried to leave space. Also a greater chance of a rear end accident than would have been cause by tailgating like everyone else.
Actually driving in gridlock traffic is a variation of the Prisoner's Dilemma and the participants (at least in SoCal) have long ago figured out that the "always defect" strategy works best.
-- your Web browser is Ronald Reagan
Amazing how many Slashdotters are driving broken cars around. In every post, they talk about how their cars are BREAKING.
http://dictionary.reference.com/browse/braking
Incidentally, breaking cars cause traffic jams just as much as braking cars, but for different reasons.
For security, the MD5 hash of this message and sig is 09f911029d74e35bd84156c5635688c0.
(a/b+3.5)*2^10 = Get off your cell phone and stop tailgating.
"Always forgive your enemies; nothing annoys them so much." - Oscar Wilde
Courtesy of a course I audited at MIT on discrete mathematics, about 20 years ago, which included a fascinating section on the mathematics of traffic...
(1) They're not really standing waves, which are composed of traveling waves going both forward and backward (and waves can't propagate forward in traffic). They're ordinary traveling waves. The best analogy is to the flow of a compressible gas in a pipe. You can easily get strong shock waves at various densities and flow rates when you introduce obstructions or change the flow rate at various branch points.
Part of the problem in our expectations is that we (unreasonably) expect traffic flow to be more like the flow of an incompressible fluid like water, where, generally speaking, more pressure simply equals faster flow. It's the presence of compressibility that makes gas flow in certain critical regions much more complicated than water flow, so that, for example, an increase in pressure (e.g. an increase in cars entering at a given on-ramp, or a constriction due to an accident) can result in drastic decreases in flow. The compressibility comes about in traffic because the density of cars is quite variable.
(2) Along those lines, the density per se -- the space between the cars -- really has very little to do with the peculiarities of traffic. It's the fact that the density can change locally which makes the "car gas" compressible, and allows for density waves (traffic jams, stop-n-go traffic, etc.).
But the reason the density changes locally is not because people don't leave enough space between their car and the car ahead, but because of human reaction time. If the car spacing (i.e. density) changes here at time t, human reaction time means it cannot propagate very fast -- it will change there at some time t' significantly later than t. That is, a density wave must propagate. Under the right conditions, it's quite easy for such a density wave to grow in amplitude as it goes. Hence, a very small initial perturbation in the density -- one driver slamming on the brakes -- can grow much larger as it propagates, so that at some distance away large numbers of cars must come to a halt.
The only real solution is to make the car "gas" much less compressible, and that requires greatly raising the speed at which density fluctuations can propagate, in other words, tremendously shortening the time it takes for cars to respond to slight changes in spacing. Presumably, that suggests computer control of cars.
Do you even need a study to know the conclusion? Of COURSE people on cell phones are mucking up traffic, because they aren't paying attention to their surroundings (#1 cause of traffic jams and accidents).
This was shown in a time-lapse sequence in a movie called Koyaniskatsi (or some spelling similar to that)
Produced about 20 or 30 years ago.
Cool movie.
If anyone can find it or confirm the proper spelling, I'd appreciate an update.
Part of the problem is that brake lights themselves only have "on" and "off" modes. They could be designed to convey so much more information than that, by utilizing the entire spectrum ranging from:
Brake lights glowing dimly: indicates the car is decelerating slightly. (And not necessarily due to active braking by the driver. Perhaps the driver has merely begun to coast, or does not have the accelerator sufficiently depressed while driving up a steep hill. It would be a good idea to communicate these scenarios to other drivers too.)
Very bright accompanied by a rapidly flashing strobe: indicates the car is braking maximally; antilock braking system is fully engaged. (At times like this, the car should do everything possible to get the attention of other drivers.)
That that is is that that that that is not is not.
That's one of the main reasons I drive a manual transmission: I can adjust my speed without having to use my brakes. Makes the brake pads last longer too.
I swear, we could reduce the amount of idiots on the road by making two things mandatory for new drivers: (1) learn on a manual transmission first, and (2) make parallel parking part of the driver's test (again).
Will draft for food...
Little kid runs out in front of my car. I slam on the brakes. Car decides that hitting the brakes that hard might cause backup miles behind and limits the braking force. Kid gets splattered all over the front of my car and I have to scrape the brain matter off my windscreen.
I hate scrapping brain matter of my windscreen.
It doesn't take a rocket-science mathematician to analyze the flow of traffic. The Queue data structure has been around forever, and many people take advantage of it for every day analysis; just visit your local news web site, and more often then not, they will have a fancy real-time traffic diagram.
Right but you had to go slower at some point to leave that gap. Plus you will have to let that gap shorten during breaking to smooth the traffic but then what do you do when you go again? That's right, you speed up later. Thereby creating the same damn standing wave you so stupidly tried to eliminate. This shit doesn't work.
If the universe is mathematical, then everything can be explained with maths, so I'm not surprised :)
We call these due to "fear of flaming death".
You're trucking along at rush hour, 10 feet between cars, and going 90 MPH. Everything is going 20 MPH too fast and there are 4x more cars per mile than there should be for safety, and everyone is on edge and hyper-alert.
Then one guy drifts a bit too close to the guy in front of him, and touches his brakes, the guy behind him sees brake lights and puts on his brakes hard; the people farther back have to pretty much stand on their brakes. If there's long visibility, people a mile back put their brakes on when they see hundreds of sets of brake lights up front go on at once. Within seconds traffic is stopped. A standing wave like that can take hours to clear, because traffic was so dense and fast to start with that within the time it takes for the traffic in the front to get back up to speed (a minute or so), the density wave is several miles thick.
Yeah.... I tried this for several weeks. Except everyone took the opportunity to sneak in front of me so they could play a game of changing lanes repeatedly to snake their way through traffic faster.
That is the problem. You can do what is best for the group, but then selfish individuals abuse that for their own gain which hurts the group more.. A better way to look at it is that it's a system which seeks equilibrium. Traffic density will tend to stay relatively even. Just like in nature, if you allow a "vacuum" to open up in front of you, the tendency will be for traffic to fill it. What these homespun amateur traffic engineer types like the GP poster fail to really understand is that you cannot change traffic density. "If enough people would just leave a larger space in front of them" is simply an unreasoned way of saying "if only there were fewer cars on the road". You can fit 5 ten foot cars with a 10 foot interval into 100 feet of lane. You can only fit 4 with a 15 foot interval. A larger interval between cars translates to fewer cars per 100 lane feet. That "extra" car has to go somewhere, and where it goes is into the previous 100 feet of lane. Multiply by the number of 100 foot segments of road in the jammed area...
There's just no way around it. Slowing down more carefully and "leaving a bigger gap" just cannot get around the fact that only so many cars can coexist on the roadway at a given speed, and the speed varies inversely with that number. When you cram 5 lanes of cars into 4 lanes, it will slow down. When you pour X number of cars per mile via onramps onto an already crowded roadway, it will slow down. It's really very, very simple. The specific optimums of traffic flow are quite complicated, but the basic "X is slower, Y is faster" isn't.
If a job's not worth doing, it's not worth doing right.
It's just you being Americans. Deal with it, or become Europeans, like me :)
I want to play Free Market with a drowning Libertarian.
I posted exactly the same statements, without the math, in a response here on /. several months ago. I want my credit for prior publication.
It wasn't even my original work. The same example was used in a workshop at the Santa Fe Institute that I attended almost a decade ago.
The math is trivial. It's decremental time delay applied to acceleration according to position in a rate varying flow. If it were 2 or 3 dimensional, you'd see turbulence. In fact you do see close to 2 dimensional turbulence when people try to drive on the roadside or median strip, or turn around in the traffic.
If they can get this published despite the prior widespread use of the same concepts and math, then perhaps I should just buckle down and invent calculus.
"I may be synthetic, but I'm not stupid." -- Bishop 341-B
Driving in Calgary can be an adventure during peak traffic times. Compared to most big cities traffic flows relatively well (There are about 4 hours of "rush hour" traffic per working day typically). However, literally the majority of major thoroughfares still exceed 100% of their design capacity for sever hours a day and it is very obvious that very small distruptions can trigger one of those traffic waves for several km in those cases.
Traffic jams are caused by idiots.
It gets worse when you put all different sorts of idiots together in one place. That is a distinctive characteristic of motorists in Calgary--the majority of them were not born in the city it seems, and in fact a great many of them moved here after learning to drive elsewhere...so you get all sorts of *different* idiots, who react differently to the same events. Here are some prominent examples:
* The British Columbian: Officially the laws regarding your indicators are consistent throughout Canada--you use them a few seconds prior to making a turn or changing lanes so as to let other drivers know your intention and to leave the area clear for you to manoeuvre. The ACTUAL convention on the "left coast" (mostly in urban areas), from what I can tell through observation, is to alert the driver behind you that the area to that side of your automobile is clear but might not be for long, so you should immediately speed up and pull into the unoccupied space. Given this unique BC convention regarding indicators it is thus standadrd practice to avoid using your indicators at all costs prior to turning or changing lanes, as doing so would risk luring drivers into the unoccupied space, thus impeding you from making your intended turn.
* The Torontonian: Posted speed limits back in their native Toronto are generally considered MINIMUM acceptable speeds, not maximums. It is quite important to be the first in queue at red lights. The road 5 car lengths fore and aft, along with the space immediately adjacent on either side, for the moment the Toronto driver is at that point, is OWNED by said driver (along with the airspace and mineral rights within). Other drivers are allowed within that space only out of the kindness of the "owner's" heart, thus if you are in this driver's way you'll be subject to their discontent, be it an evil look, an upraised finger or a sustained, purposeful sounding of the horn.
* The Montrealer: Observes the speed limit in a manner similar to that of a Torontonian, but without the "personal space" issues. In fact, personal space is seen as an inefficiency that can be eliminated when the mood suits (I'm not following too close...the bumpers aren't touching yet). Traffic lights have different meanings. Amber is equivalent to green--it just means that the end of green is near so speed up more to get through. Red in Montreal is like amber everywhere else, at least for a few seconds (ie. proceed with caution, or what passes for caution on Montreal roads). You don't cross the street in Montreal until you count to 5 after the lights change unless you are a risk taker. The exception is the red light at turns--a Montrealer can't seem to ditch the habit of waiting for a green to turn right. Also, in much of Quebec, the roads have two more lanes than elsewhere--in other places they're called "stall lanes" or "service lanes" and are where you park when you have car problems, or where you walk when you hitchhike, or where you ride your bicycle. In Montreal, they are "overflow lanes"--if traffic is not moving to your satisfaction, you pull into these lanes and sprint up to your destination.
* The Prairie Dog: Until moving to Calgary "the Big City" meant Regina or Saskatoon--each have about 200k or 250k in population and wide streets downtown that permit angle parking. Thankfully they often make them selves known with green "Rider Pride" bumper stickers or other visual indicators of their undying devotion to their native province's football team so you have early warning. Another indicati
1: Cop sitting on the side of the road causes drivers to slow down.
2: Those electronic signs on the highway cause everybody to slow down so they
can read some useless message that doesn't apply to them.
3: People slowing down to rubberneck and take a peek at a dead animal on the side of the road.
[citation needed]
I can't even find this claim on the internet, let alone evidence for or against it. There is mention that speedometers are often slightly off (here, for instance), but no claim that they're biased too low.
Ob. XKCD comic.
[[A car is stopped at a traffic light.]] / Driver: This light always takes forever. / Driver: I'd like to smack the idiot who designed this intersection.
[[Seen closer, the car now has another person crouching on the hood.]] / Engineer: Hi. / Driver: Who the hell are you? / Engineer: I designed this intersection.
Engineer: You're right--I should have just made the light shorter! Never mind the hours of simulation and testing I did. Never mind that this intersection interacts with its neighbors in a complicated way and it took me a week to work out timing sequences that avoided total jams.
Engineer: Clearly, I'm a crappy engineer and you have a better solution. / Engineer: Go on. Show me your proposed timings.
Driver: Get the hell off my hood before I start driving and fling you into traffic.
Engineer: You can't. Light's red. / Driver: Well, when will it change? / Engineer: Tuesday.
{{alt: You can look at practically any part of anything manmade around you and think 'some engineer was frustrated while designing this.' It's a little human connection.}}
http://xkcd.com/277/
Nouvelles de jeux et technologies en français. TC
While your comment is excellent, you assume that each person's reaction time is a function only of those immediately in front of them. The problem is that I can see farther than adjacent cars. I could see that someone 5 cars ahead has hit the brakes, and I can start to slow down before the "shock wave" gets to me. Human reaction time is plenty if human attention span is sufficient.
:(){
Here in Austin, TX, that is definitely what is going on. There are many times when a few patrol cars will just park in the left lane, and set up cones, but never do anything else. Narrowing a highway to 1 or 2 lanes from 3 or 4 is what kills traffic. That and the assholes who wait until the last possible second to try and switch lanes instead of getting over safely a half mile back.
We've always just called it a 'traffic memory' because the backlog (read: traffic jam) can take hours to clear, long after the initial cause is gone. I didn't know we needed a mathematical model of what I consider to be common sense.
- I voted for Nintendo and against Bush
Your solution to slow traffic is to - slow down -?
This is good if you are trying to avoid that next fender bender rear end collision - but the guys behind you are delayed by the gap in front of you - which in my neck of the road means someone from the next lane is getting in front of you - pushing your lane back a car - which means now you have to slow down again to get your cushon back in place. GOTO 10.
Speed up? Drive closer together? Can't do that either because you need a little buffer for reaction time.
Humans have this wet thing in their head that makes them do all kinds of crazy things. One of the key things here is that we tend to slow down when we get closer together. Not only in cars, but in walking down the street, running in a marathon, escaping a burning building... Think I'm wrong? Check your distance at heavy traffic and then try to do that same distance at normal traffic - It's called tailgating. Try the 3 second rule (1-2 seconds around here) and you will see that speed and distnace between cars is directly proportional.
So - we can establish that when traffic slows down, we get closer - and stay slow and closer until traffic speeds up again. Or - to flip this around - traffic will be fine until someone/something slows us down and we get closer together and slower, and will remain so until traffic speeds up and spreads out.
Your 'solution' is based on spreading out - but not speeding up - which will compound the traffic behind you by taking up more volume of driveable road than other cars, and keeping a reduced speed - thereby occupying the same distance of road for a slightly longer period of time (because speed = distance over time).
One factor that seems to be key is traffic volume and additional traffic coming into the freeway. If the road is at capacity and additional traffic is trying to get in, there will be a slowdown at the merge point. Simply speaking - you are putting an additional car inbetween every car already on the road. And if the cars already on the road are slow and close together, they have no choice but to slow down to make space to accomodate the oncoming traffic. After the cars are merged together, spaces between the cars and speeds both rise and the traffic congestion eases until the next merge point. These are usually predictable places where traffic is always bad.
Next - the mystery of the random slowdown. You sit in traffic and then later it suddenly goes away and you see no cause. Coming from a family of firefighters and police, there are often times when an accident will block a lane because the car is disabled or the occupants are too dim to pull over to the shoulder (or better - off the freeway) to exchange information. So they sit in a traffic lane and look at the damage and write down information - creating a jam from people having to merge into another lane to get around them. And sometimes another car will crash into them, creating a bigger mess and great risk to the people standing outside in the middle of the freeway writing down a license number and insurance information for a fender bender. I used to teach and I had a student of mine killed in this exact scenario - minor fender bender in a car pool lane, got out to look at the damage and exchange info, stood between the two cars and then a 3rd car plowed into them, killing my student. But I digress - Around here (let's call it Los Angeles) traffic accidents are everpresent. Take a look here for current info: http://cad.chp.ca.gov/ And typically an accident blockinglanes will be moved to the shoulder or off the freeway in about 10-20 minutes. So if it is a minor fender bender, the people get out IN LANES to look at the damage, then agree to pull off the freeway to exchange info, you could easily sit in traffic and then have it suddenly evaporate by the time you get around the bend.
The CHP will also get reports of a traffic hazard (usually a ladder) in the lanes and run a traffic break where they get in front of the free fl
http://Communityville.com - A free place for new and old neighborhood webmasters to hang out.
While I did research this myself (easy, use either a GPS unit or time between markes that are on many roads in some countries) it's also logical that they're biased too low. What would happen if the car makers produced cars that showed a legal speed to the driver while the actual was over the speed limit?
Better safe than sorry, which fits with what I found.
OTOH - this search (in Swedish) shows the 4-5 first hits saying exactly the same as I'm writing. The first is to a science mag, the third gave me a link to the Swedish "road authority" which actually says in clear text that a speedometer MUST never show a value below the real speed.
Query:
http://www.google.com/search?q=hastighetsm%C3%A4tare+visar+f%C3%B6r+l%C3%A5g+hastighet
Road authority manual (in Swedish) chapter 33 paragraph 5 is the interesting one with a formula, and paragraph 6 says the maximum error is 10%.
http://www20.vv.se/vvfs/htm/2003nr022%20.htm#_Toc38872870
This could of course be an "only in Sweden" thing, but I doubt it.
it's in my head
Wow. I can't believe this even made it to /.
In related news, their next paper will be on the effect of check writing on supermarket lines.
-William Shatner can be neither created nor destroyed.
I think I will try to talk about "car gas" instead of traffic from now on, that is quite awesome, but very nerdy.
"The car gas was quite thick this morning"
"Smog?"
"No, lots of cars going slowly"
If I have nothing to hide, don't search me
... in MI3 ? Probably the only interesting thing about that movie IIRC ...
I've heard of stop-go traffic called "The Centipede Effect" in essence each leg cannot pass the one ahead of beind it but may only open and close gaps around it.
I've found typically the faster drivers go, the sooner they encounter Centipede Effect traffice backups.
Lane weavers exacerbate the situation, and were ticket-able a few decades ago in Michigan (clearly someone knew the cause and effect of lane weaving) Place a few police cars in the mix and amazingly everyone immediately behaves and traffice moves right along.
A feeling of having made the same mistake before: Deja Foobar
If you start late to leave more room, then the person in back of you does as well , and so on and so on. This results in more people waiting to start, or waiting to go faster. More traffic continues to pile up in back of you propagating the traffic jam.
..........FULL STOP.
I wonder if they still teach the old "1 car length for each 10 mph" rule.
No, these days they teach the two second rule. There should be two seconds of empty road between you and the car in front of you. The way to gauge this is to watch for a mark on the pavement (an oil stain, or a crack, or something) to emerge from underneath the vehicle in front of you. It should take two seconds before that mark disappears below your hood. This gives you lots of reaction time, and there's no math involved.
There's an interesting website concerning traffic waves and "anti-traffic" that I came across a few years ago. It really works.
When our name is on the back of your car, we're behind you all the way!
I think even Ethan Hunt knew that as a cover up story for his "boring real job". Maybe the mathematicians solved the mystery of Maxis' pathfinding mechanism! One can only hope the guys at Maxis don't get all inspired and make the traffic simulation even messier.
^[:wq!
Yes, don't stop at just varying the brightness. The brake lights should also begin to blink when you reach moderate braking intensity, and blink more and more rapidly as the braking intensity increases.
The brightness should also be calibrated by an ambient light sensor. Take the case were the car is decelerating gently, and you therefore want other drivers to perceive that the brake lights are glowing dimly. At night (or in a tunnel), you don't need to apply much voltage to the lamps to accomplish this, but during the day, you'd need to apply significantly more voltage to achieve the same "glowing dimly" perception. The ambient light sensor would take care of that.
With sophisitcated LED displays, you could change the shape and color of the display: smooth, rounded, and cheerful yellow for gentle deceleration, transitioning to angular, "angry," and fiery red for rapid deceleration.
There are all kinds of ways to better convey information to other drivers!
That that is is that that that that is not is not.
I'm not a math person, but I'll solve traffic jams with math anyway:
Double the speed limit, and cars are on the road half the time. Doubling the speed limit automatically doubles the capacity of the road. Why are there jams at cities? Because the speed limit goes from 70 to 55, increasing the density of the traffic. That's why in Germany, where there are no speed limits, and a denser population, there are fewer traffic jams.
If you think doubling (or best, just eliminating) the speed limits is less safe, you are wrong, it actually makes the road more safe. Google it, there's no need for me to explain it here.
The way to have the least jams is to have no speed limits at all. It would also get rid of the nazi pukes that sit in the left lane at the artificial revenue generating speed limit with smug expressions.
Over 10 years ago, a study was done by Cal Trans (the State of California Transportation Department) using traffic cameras and they discovered the same thing that mathematicians have just now discovered. Cal Trans did it the old fashioned way: by studying hours of video and doing a little brain work...
...this research has been ongoing for the better part of 20 years. I worked on some of this when I worked for Honda R&D. The formulas have existed for years, and widely available computer models have existed since 95...probably sooner. Sorry this simply isn't news.
There are 2 groups of people you can make fun of on the Internet without fear of attack. The illiterate, and the Amish.
the average person isn't smart enough to figure that out.
And in response to your sig: Yeah, you may only save 59 seconds over 8 miles... but on a 500 mile trip, that adds up to an hour.
The meek may inherit the earth, but the strong shall take the stars.
Intuitively known, perhaps, but not mathematically. There's a universe of difference between the two.
If everyone doubled the distance between themselves and the car in front of them, then the road capacity at a given speed would be cut in half. This is because the volume (in cars per unit time) is a given. Due to fixed speed limits, the road would hit maximum capacity at half the volume of the tailgating driver model. Once maximum capacity is hit, stuff starts to fall apart. If the drivers stay polite, then the on-ramps become parking lots. If the drivers start to close the gaps between each other, then they start to slow down due to micro-mistake being made more frequently. Interestingly, this slowing down doesn't reduce capacity, it just allows the road to "buffer" more cars. The buffering is necessary to keep the surface streets clear. So, your strategy will get you home faster, but will delay the guy behind you because he can't get on the road. If the 30 thousand people in front of you followed the same strategy you do, then you'd be just as late, but you'd spend most of the time trying to get on the freeway, then very little time getting the rest of the way home.
The only way to make the situation better is to have a better trained driving population. Better trained drivers are able to drive fast while packed tightly without making many mistakes. Drive on the 405 in L.A. some day and you'll see 1 million people doing a pretty good job of not clogging up the road. Drive the 95 between NY and Boston and watch the idiot drivers cause backup after backup at a lower volume. All you people who live in LA are going to tell me I'm nuts and you drive with idiots every day. Trust me, the rest of the country drives far worse than your local idiots.
I've seen no less than six posters stating some variation of "such and such a study proved this X many years ago". I know this is going to earn me a troll rating, but: is the average slashdotter so reliant on mathematical models and scientific studies that he can't just look at the evidence in front of him? [There's a free +5 Funny mod to the first person who snips out that line and makes a one-liner like "Yes."]
You can literally /see/ this wave of traffic back-propagating from any road that isn't a sharp curve to the inside. And I do mean see it -- one person makes a brief tap, the next person taps for an instant longer; the next person is on the brake for a second, then two seconds, in a exponential increase of duration. [Some people even see this coming and slow down without using their brakes, in an attempt to reduce the effects of the inevitable.]
There's a lot to be said for proving something mathematically, and for scientific studies. But sometimes, one can learn things by looking at the road ahead -- literally, in this situation. In this particular case, it's rather disturbing to see that so many folks are /not/ looking past the end of their bumpers to see this for themselves -- because failing to do so usually means that they're a contributor to this specific problem.
Well, the same moron who sneak in front of you is usually the same moron who quickly disappear from your front, so the bad impact of that moron on you become less. Anyway, the key is too keep closer distance so that only the bravest moron will cut you, while keeping it farther enough to allow smooth breaking.
If you delay pleasure infinitely, the pleasure will be infinite. (YM)
As previously noted, a cooperative approach, California style driving will put more cars closer together than some east coast (Washintgon DC) locations.
Or even a (manual) bicycle. I live in Oxford, England and since it's such a small, dense city, everything is easier to get to by bicycle than by car. Most people I know (including most full Professors) ride a bike rather than drive a car.
A bicycle has a further advantage over cars and motorbikes in that if I'm stuck in really heavy traffic with no room to manoeuvre on the road, or at an interminable stop light, I can just get off my bike and carry it!
Phoenix, Boston, Little Rock, see a pattern?
This is news - it has been known for a long time. I think the real news, which you can read between the lines, is that they have actually made some measurements, run some simulations and clarified some details - perhaps the most important part is the simulation, which means they have a good, working, mathematical model.
And instead of putting funny devices in people's cars, a simple and much safer solution to most traffic jams is to ban lorries from overtaking. Lorries seem mostly to drive 60 mph - when one overtakes another, you suddenly have 2 lanes that can only move at 60, where most cars would have been driving at 70 or more (in UK much, much more, but let us just assume that people drive at the legal speed limit) - that is the most common cause for traffic slowdowns. It doesn't help a lot either that it take 10 minutes to overtake in a lorry, because the difference in speed is about 0.1 mph.
This has been tested in several places, with great success. The one I remember best was in Denmark, where one particular road was almost constantly congested. When they banned lorries from overtaking, the problem all but disappeared, just like that.
According to the Smith System, in a normal car, you should allow 5 seconds between your vehicle and the one ahead of you. Best-case reaction time is 3 seconds, and that's assuming you're not distracted, and that you immediately recognize the situation and the need to brake. If you're driving a larger, heavier vehicle, you need to allow even more time.
You should not go by distance, because distance is difficult to judge, and gets harder to judge as your speed increases. You should choose an object ahead of you, and count the time that passes between the vehicle in front of you passing it and your vehicle passing it. This method always works, regardless of your speed; you don't even have to look at your speedometer.
"Those who consume the bulk of goods are those who make them. We must never forget this secret of our prosperity."
The model described in the summary is old news; there has also been a lot of work on finding ways of avoiding the resulting traffic jams (for real-world driving, it turns out that it's quite important that drivers don't just look at the car in front of them but look several cars ahead).
Maybe these mathematicians happened to also figure out something new, but if they did, it's not mentioned in the summary.
You mean a bunch of people went through all that trouble to come up with a mathematical explanation for stupidity. The problem is between the steering wheel and the seat. These are the same people that cause the keyboard/chair errors on computers. Better known as the ID-10-T Error.
All these drivers, even here on Slashdot, admit to breaking while driving! They should get more reliable cars. No wonder the roads are jammed with all these breaks. I'll admit to braking sometimes to look at breakdowns.
Sorry, but I think your model is rather simplistic.
For one thing, roads never really reach full capacity at a given speed, because other effects such as those you mentioned cause everyone to slow down first. This increases the effective capacity, because less space is necessary between vehicles.
For another thing, you are completely ignoring the effects of the accidents caused by people following too close. I'm doing a fair bit of long distance driving at the moment, in some pretty nasty weather conditions some days. I've been stuck for hours in freezing temperatures on major roads that have been completely closed, all because one idiot couldn't be bothered to leave enough space and then had nowhere to go in an emergency and hit someone else.
Better trained drivers are able to drive fast while packed tightly without making many mistakes.
That's true to an extent, but not that great an extent. A better trained/more experienced driver will generally anticipate potential hazards significantly sooner than a novice, allowing them to make better use of whatever space is available, but when you're driving a ton or two of metal around, it still takes a significant distance to stop or change course when driving at speed, and your visibility in the dark or poor weather is still limited.
The Italians have an interesting alternative: their culture is very much to drive right up close (and I mean close) even at speed, and driving is basically a game where everyone tries to cut in front of everyone else, in between lanes, overtaking anywhere they can get. They're actually surprisingly safe in terms of major accidents, because in the end, it's variations in speed that cause accidents, and everyone there tries to maintain their speed relative to other vehicles no matter what. Italian driver training is pretty heavy and, despite their apparently crazy behaviour to our eyes, objectively their drivers are almost uniformly very attentive and very aware of the size of their vehicle and what's going on around them. They do have a hideous number of minor accidents, though: walk through the streets of any Italian town and you'll find probably half the cars have substantial damage to their bodywork.
If you disagree, post your argument. (-1, Overrated) isn't your personal censorship tool for views you don't like.
Why is it that some mathematical endeavors simply explain in complex terms what we all already understand in simple terms? Who in the hell didn't already know that breaking sequences on a congested freeway often causes a ripple effect throughout the traffic behind it? This is less about the accomplishments of mathematicians regarding traffic and more about a cleaver way of extracting grant money.
The thing is, if you do leave the proper distance between your car and the one in front of you, a tailgater will see it as a place he can shoehorn into.
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SVM, ERGO MONSTRO.
Think about it for a second... If a highway has a carrying capacity of 400 cars per minute and you try to push 500 cars per minute through it how many cars per minute will end up sitting and waiting somewhere?
People seem deeply perplexed by this problem of "who is responsible" for them having to sit in traffic and for some reason always expect it to be some drivers fault. Unless the traffic jam you are in lasts about 10 seconds, or there is a real accident, then odds are the trigger event for the slowdown is irrelevant. The slowdown was inevitable.
Your road isn't big enough. It's operating at near or over saturation. Any road that is being pushed over its saturation point will buckle and traffic will stop, plain and simple. The trigger for the slowdown can be a person hitting the breaks, a momentary breakdown, even someone deciding they need to play it safe and leave a little more room between them and the next car can start the wave that ends up in a traffic jam. But the question isn't how the wave starts.. that question is meaningless. The question is why doesn't it dissipate like all the other waves and that answer is saturation. If the road wasn't saturated, the wave that got started when the guy hit his breaks too hard would have lasted a few cars and then dissipated as people worked around it and space between cars was compressed. Traffic would have absorbed the shock and kept moving.
Instead of tinkering with exotic breaking systems why not simply build more and bigger roads to accommodate the traffic. Better yet.. make tax incentives for companies who have employees work from home so less people are actually on the road.
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Sadly, I would say that a reduced death rate on the highway would not be an improvement for the gene pool. It's true that about half the people killed on the road are innocent, or at least in the wrong place at the wrong time, but the other half are instigators and poor drivers that make the world a dangerous place through their inability to make good decisions. Since we can't just up and kill someone for needin' it anymore, the highway is the last place we can expect those folks to pass on without living for another 70 years, and ruining the world for the rest of us.
JH
ps. For the humor impaired, the above is at least 70% tongue in cheek. I'd welcome a good law allowing us to vote people dead, though.
Any connection between your reality and mine is purely coincidental.
Owning and operating cars make sense where the population density falls below a certain threshhold, say in the country,
I live about 17 miles from work.
In a perfect world, I'd be able to bike to and from, thus saving money and fossil fuels, reducing traffic congestion, etc. In reality, I would have to be suicidal to try and bike it (over half of it would be without sidewalks, across very busy streets), not to mention the extra 3 (or so) hours it would probably take out of my already jam-packed day, not to mention the fact that I need to drive around town occasionally on official business and my boss wouldn't tolerate the wait.
We do have a few bus stops, but this isn't the big city (it's "medium city", if there is such a thing) and the buses don't run around my schedule, nor do they let me off where I need to be (would require at least 3-5 miles of biking, I think.)
This is my situation, and I have a job in an adjacent town. MANY people who live here commute to the biggest city in the area (Orlando), which makes busing/biking pretty much impossible.
And I don't think our city is very unusual. The sad fact is, America's urban/suburban population density is a lot lower than that of most of Western Europe, and that makes public transportation not an option for most of us.