Slashdot Mirror
Chaos and Your Everyday Traffic Jam
An anonymous reader writes "What causes these mysterious traffic jams that continually appear throughout the day for no reason whatsoever? Is it simply the fact that most people just don't have a clue how to drive? That's very possible, and in reality there are so many variables involved in something like a traffic jam. But is it possible that the entire traffic jam could be both the continuing and end result of a chain reaction set in motion by a single driver who was in too much of a hurry?"
From TFA:
I like the idea of a single blameworthy agent to bear the brunt of my hideous imprecations: a Christ of traffic, if you will; except I'm the Romans, and it's Mel Gibson's Passion all over again.
Only three comments and already the site seems to have been totally jammed up by a single Slashdot article in too much of a hurry.
"What causes these mysterious traffic jams that continually appear throughout the day for no reason whatsoever?
Too many cars?
it's a blue bright blue Saturday hey hey
Where I live, we don't have traffic jams.
In a community of about 70 people covering 50 square miles, it's not hard to imagine why traffic jams are nonexistent.
I used to live in Houston. After years of moving back here, I've nearly forgotten what traffic jams are like.
Around here, the closest thing to a traffic jam is me. Even the old people think I drive too slow.
There's actually a field of study for this: Traffic Analysis. Of course, this is not to be confused with all of the material out there relating to internet/network/packet analysis.
This mainly deals with optimizing freeways and the like, based on people's behavior in traffic, and the ripple affects.
The troll with karma.
Who was the initial driver
a) old person
b) teenage girl + cell phone
c) teenage girl + friends
d) teenage girl + friends + cell phone
e) teenage boy + camaro or civic
f) mom + kids + ginormous suv + cell phone
g) executive type + cell phone
With Ethernet, as the 'traffic' builds to about 40% of the theoretical capacity, collisions become the norm and the re-tries start to overwhealm the system and it locks. With roadways, as the traffic builds to a certain limit, then awareness of potential collisions magnifies in the drivers, so reactions to situations increases and the road stalls. This is why variable speed limits work, because the road and drivers can cope with more vehicles if there is a lower maximum speed.
rgds,
Richard Rothwell
"All that is required for evil to triumph is that the good keep silent"
...most people just don't have a clue how to drive?
YES! But that's not news, we have known this for over a century now...
Only to idiots, are orders laws.
-- Henning von Tresckow
I fly light planes. Major roads, when VFR, are very good landmarks.
... then the drivers behind (probably following far too close) brake a bit harder, and the drivers behind them brake a bit harder still. The adjacent lanes, in seeing one lane suddenly slow go 'whoa', and someone also brakes in that lane. Pretty soon, just from one person braking a little bit - the braking has propagated down the road with greater and greater severity until one of two things happens: usually, the traffic comes to a standstill, and you get a self-sustaining standing wave of stopped traffic until the amount of traffic on the road reduces to the extent there are fewer cars joining the wave than are leaving. This can take HOURS, especially on the M6 in England. The second thing that may happen in this cascading braking severity is that someone runs into the back of the other. Then chaos ensues for most of the day.
Quite often when it is very busy, you can see a standing wave in the traffic - there's an area where all the cars are stopped - but there is NO obstruction at all. The cars are filling the 'standing wave' from the back as quickly as cars at the front are leaving it - so it becomes self-sustaining.
When the road is full to capacity, moving at 70 mph, all it takes is one person to jab their brakes
The other problem is lorries (large trucks) overtaking lorries with a speed differential of 0.5 mph. It takes them several minutes to get past because they are both speed limited within 0.5 mph of each other, meaning the inside two lanes are 56mph, and the outside lane is 70mph+. When a frustrated driver pulls out into the outside lane after being stuck behind a lorry for "too long", they cause one of the outside lane drivers to brake down to 56 mph quite suddenly. This can easily get the 'braking cascade' started, and before you know it - you have a standing wave traffic jam with no actual obstruction (other than the standing wave itself).
Usually then what happens, is the opposite direction traffic, seeing the stoppage rubber necks for the possible accident. An inattentive driver looking at the other side of the road finally looks back in front and realises he's about to ram a truck in the rear and slams on the brakes. The driver behind him following far to closely has to brake even harder - and there's either a shunt or if they are lucky, ANOTHER standing wave traffic jam starts on this side of the road too.
It's fascinating to watch from the air. Frustrating to be in when driving.
Oolite: Elite-like game. For Mac, Linux and Windows
A pointless story with no data, no analysis, no facts, but lots of conclusions. Don't we usually leave those for Digg?
Around here, traffic jams appear to be caused by very poorly timed lights. When the current light turns green, the next one three blocks down the road is 10 seconds from turning red. It's insane.
A friend of mine once said that the guy who programmed the lights should be set on fire and made to run to the nearest hospital while stopping for every damn red light.
Reduce, reuse, cycle
I have lived in the cities with the worst drivers and the worst traffic and I have seen it time and time again; it's the slow dumbasses that are the real cause of majority of wrecks. It's that asshole who is going 50 in the passing lane and won't move. Or the driver is just going so slow that normal traffic rams into him, or is slowed town greatly.
The people with really fast cars generally drive very well. After all, they don't want to smash up their fancy car.
It's the assholes who don't care that they clogging up the passing lane who really are the cause of most accidents and traffic slowdown.
Oh, I have noticed that traffic patterns and behaviors do vary by location. For instance in New Orleans (pre-katrina) the drivers were extremely agressive and would not let you in no matter what and pretty much there could be aliens landing on the side of the road and nobody would care or slow down. In L.A. the 405 would be backed up forever only to find out that it was slowed down because of ONE car broke down in the emergency lane, with no accident; everyone was slowing down in response to this one car on the side of the road. In San Antonio, TX, everyone is on crack and drives a Ford F450 Dually 100mph, everywhere. Not usually a problem, but the entire city of San Antonio is being redone road wise and it creates choke points almost instantly that can't be foreseen.
"Jeremy, you need to get to an internet cafe and cut and paste some appropriate sentiments about me from the world wide
The phenomenon has also been called the "Spring Effect" because from the aerial view of "Choppper 4", the waves of idiocy propagating back down the line look like the expansion and compression of a spring.
-- You are in a maze of little, twisty passages, all different... --
Isn't it fairly obvious why we get traffic jam?
The only way to get consistent traffic throughput is to have cars that maintain the same speed at all times, do not switch lanes and do not turn left or right at all.
Since all drivers have different destinations, driving techniques, cars and intentions, it is impossible to achieve this. Someone's gonna change to the other lane, delaying the people behind him who have intentions to delay the traffic in some other way, which eventually triggers traffic jam. It's a gigantic chain reaction, really.
Full Tilt
Hey, look, the obvious has made it to the front page of Slashdot disguised as an article again.
If some bonehead makes a bad driving maneuver, he might cause a traffic jam. And whether or not he actually causes a traffic jam is dependent on how many cars are on the road!
This whole thing is just dumb. Yes, if all drivers drove perfectly, then we could push more cars through the same piece of road. But that's not the way it works. Roads don't have a hard capacity. As the number of cars on the road increase, the chances of a traffic-jam-causing event increase. The more cars, the greater probability of a jam. Maybe at 120 cars a minute there's a 50-50 chance of a jam, but at 140 cars a minute a traffic jam is virtually certain.
So, if cars were driven by perfect-driving robots instead of people, we'd could put more cars on the road without traffic jams. Thanks Slashdot!
paintball
A lone butterfly flaps its wings and, thousands of miles away, a lonely slashdotter masturbates furiously at the thought of a new Linux release.
Your sign: .humm... "Dream the pilots with electronic space simulators?"
"Oolite: Elite-like game. For Mac, Linux and Windows [aegidian.org]"
Makes me think..
Why you like Oolite?
Why people like Elite more than Captain blood?
What the Olimphants are?
-Woof woof woof!
This is why when in a jam the best thing for people to do is calm down and change their speed slowly to even out the speed. This means trying to predict the average speed ahead of you and do your best to maintain an even speed, even if slow. Yes, impatient drivers will move in in front of you, but they are also most likely to jump back out of in front of you in a bit too. Getting next to a truck doing the same thing helps. Pressing out the waves is what will get traffic moving again for those behind you.
that were spent to produce, sell and maintain those cars, we would be able to make endless lines of light rail-based mass transportation system that would have luxury that would put a 5 star hotel in shame ? and then we would be able to go anywhere we wanted by just leaning back, and faster ?
Read radical news here
The previous theory I heard about in a documentary about traffic in major cities, said that density waves, the same phenomenon that causes many galaxies to have perfectly defined spiral arms, also cause traffic jams, which is to say, the mathematics are the same.
As a sidenote, I once read an anecdotal story about a guy who always got stuck in the road while driving home from work, and one day he thought about how everybody's trying to get home fast yet everybody gets stuck in traffic, so he decided to experiment by driving a bit slower. After a few minutes he was amazed to find how the traffic behind him was neat and orderly, instead of the usual jumble, which implies (I emphasize: anecdotally) that the behaviour of a single car can not only create, but also avoid the creation of density waves.
Lil' Thindime, lilting a lacrimose lament, krashes the kwaint konfines of Kokonino Kounty
I'm not sure if someone hasn't posted it yet but there is an interesting java applet on the web simulation exactly the problem mentioned here. You can find it on http://www.traffic-simulation.de/ My personal favorite is the ring road :)
Can someone catch that dammed butterfly that is causing all those traffic jams?
For the longest time a friend and I have theorized about the reasons for those traffic jams. We've reached the inescapable conclusion that they are the results of a conspiracy.
Don't go your heads a-shaking now. It's really obvious. The oil companies make a bundle of those traffic jams. Every day just before rush hour a small fleet of inconspicuous unmarked vehicles, driven by selected elderly, are leashed upon the major freeways. They are trained to drive in such a pattern that makes it impossible for other cars to bypass them. Soon enough the traffic jam forms. Millions of cars are burning precious fuel while standing still, and the oil barons go cha-ching.
Denying it doesn't make it go away.
-- Arik
When it comes to traffic I've always said that it's throughput that matters, not position. If a car pulls in front of you and sets you back 10 meters, then all you lose is 10 meters. And only you lose it. If someone DOESN'T let you in and you have to slow down 10 m/s for 10 second and then accelerate up to speed again, you and many people behind you lose 100+ meters.
I've always found it ironic that the people who seem in the biggest hurry--the ones who don't let others in--are actually the ones that slow everybody down. So when someone has their signal on, JUST LET THEM IN! Your order in traffic is insignificant (grannies and talkies excepted).
and traffic jams at the SUMO site. You can also use their open source simulation software to create your on
traffic scenarios. I have always seen the creation of a traffic jam as a transition from a high density high flow state meta stable state to a high density low flow state. This can be expressed with a lambda shape curve in a density-flow diagram. The cause for exiting the meta stable state can be a
small disturbance, sometimes simulated by a random factor in CA traffic models, e.g. some guy braking without reason. In reality I don't think you can avoid the transition without maybe the help of computer guided cars.
***Quis custodiet ipsos custodes***
so what this article is trying to explain is that its not the slow, old, asian, female or tired people to blame it on?
All the tailgating idiots who falsely believe that they can drive safely less then two seconds behind the car in front of them are the real cause of this sort of delay.
The fool who taps his brakes is merely the trigger.
Stop the world; I need to get off.
See this Science Hobbyist article from January 1998. It's long and detailed, and suggests practical steps individual drivers can take for breaking up (or causing!) traffic jams. Yes, dear readers, this is a nine-year-old dupe.
This post expresses my opinion, not that of my employer. And yes, IAAL.
Works out to be between 15 and 20 mph, which oddly enough is exactly the speed a cyclist can go.
Next time you're driving in a big city notice how the same guy on the same bicycle passes you over and over again.
This is why. If you slow to the same speed as the bicycle not only will everybody be a bit safer, but you'll be preventing traffic jams too!
-mark____________________________________
-- I beleve you'll like this -->
As anyone who has read Good Omens should know, a major cause of the worst traffic jams is demonic influence in the planning and contruction of roads.
The prime example is the M25 motorway around London, which, due to the work of a certain demon, actually forms the shape of the dreaded sigil Odegra of the ancient black priesthood of Mu (The meaning of the sigil is 'Hail the great beast, devourer of worlds'). The movement of the traffic around the motorway works in much the same way as a prayer wheel, with the added bonus of feeding back its negative energy onto itself in the creation of traffic jams.
[All Your Fish Are Belong To Us]
And this, ladies and gentleman, is why the plethora of speed cameras present on UK roads cause so much traffic chaos. One driver brakes sharply to avoid getting caught in the speed trap, and the domino effect swings into action. You can see this on pretty much any motorway over here with cameras installed all the time.
This informal study has a nice description of how a single good driver can actual reverse the trend by single-handedly "breaking the soliton".
In other words, if you're caught in a traffic jam, let a wide space build in front of you, and try to adopt a constant (slow) speed. While you may not directly benefit from it, the jam will resorb itself for those who follow you.
This page includes simulations in a variety of contexts. While the study is informal, it is still quite convincing from a fluid-dynamics perspective.
Samir: Mother... shitter... Son of an... ass. I just...
[punches steering wheel]
There are no loopholes. It's either legal or it's not.
Government interference is the cause of traffic jams. In a libertarian society, there would be no traffic jams. People would be free to ram or push vehicles out of the way. Each individual's right to own a tank would not be constrained.
I will have a sig when the market demands it.
what I do is, when traffic is moving along too good, I slow right down to about ten miles an hour, this causes a chain reaction where everyone behind me has to slow down and eventually some of them have to stop, and there you go. that spot is the traffic jam for the next tree hours.
I fdo this on the way and from work, why? Its fun. hehe
During rush hour where I live, separation is more like 1/2 a second, if that. That small separation doesn't seem to cause as many problems. I've driven in Houston, TX during rush hour, where 70+mph bumper-to-bumper traffic is considered slow.
I can testify that this is not the most popular reason of traffic jam, because this is not the most common disruptive behavior. Think: why the situation was happening? It is not because just one driver wanted to change the lane, this is because many drivers wanted to do that and one of them was too impatient. That takes off the load of one individual and brings it upon the condition of why the lane was slow?
Most likely the lane was slower because (a) there was a high-inertia-mass truck in front of you or (b) sloppy driver (undercaffeinated, grandma, or just plain unexperienced driver).
This condition could not be helped. The critical condition of the stand-still or bumper-to-bumper traffic jam is caused by concentration of cars increasing certain threshold level. The main factor in this criticality is the distance between cars. How many of us actually follow three-second rule? The tail-gating leads to the high probability of the scenario when the car in front of you breaks and you will be forced to break with the HIGHER deceleration. That leads to lesser control of the final steady speed achieved at the end of the process of deceleration. Needless to say that the chain reaction will continue all the way back with increasing decelaration and decreasing final speeds of deceleration.
The solution to the traffic jam problem is trying to smooth traffic even at very low speeds. To do that we need stricter laws regulating tailgating. It needs to be automatic, the cars should be equipped with automatic sensors, all the entrances to the freeways/highways should be regulated by traffic lights.
Again: the problem with traffic jam is the criticality at certain speed. The only way to lessen this criticality is to increase distance between cars.
The other good way of easing traffic jams is complete abandonment of upper speed limit. That will increase the efficency of the traffic arteries.
Together, tougher tailgating regulation and absence of speed limit, will help the traffic jam situation in the country.
I do not believe in karma. "Funny"=-6. Do good and forbid evil. Yours, Oft-Offtopic Flamebaiting Troll.
...light rail is working in Los Angeles. What's the fastest way to get Downtown? The Red Line. 30 minutes from NoHo to Union Station. Un-freaking-believable.
This is why when the price of gas went up, and people actually tried the Red Line and Metrolink and other parts of our old/new (most of the right-of-ways are old Pacific Electric right-of-ways) light rail infrastructure, people started talking about how nice it would be to have the Wilshire spur of the Red Line finally take its intended trip to Santa Monica. The Expo Line between USC and Culver City (with an extension to Venice on the drawing board) is being built now. It links with the oldest of our light rail lines, the Blue Line, which goes down the Alameda corridor through some of the nastiest neighborhoods in LA. And yet: the Blue Line gets a lot of use. Why? It's the easiest way to get to Long Beach.
We have our ill-advised lines too: the Green Line which boneheadedly does not go all the way to LAX, and the Gold Line which is a good route into Pasadena from Downtown but is slowed to a crawl by nervous NIMBYs who don't have the good sense to tell their kids to GIVE RAILROAD RIGHT-OF-WAYS A WIDE BERTH. "Oh, those Blue Line trains go so fast and we see lots of people killed on the 6:00 news...oh please, City Councilperson, make 'em run the trains at 15 miles per hour in our neighborhood!" Dumbasses. You can't outrun a train, either on foot or in your freaking car. Grow a freaking brain.
We need light rail. It made sense when they put the Pacific Electric in back in the day, and it makes even more sense now. With Peak Oil on the horizon it's time. When gasoline hits $5 a gallon maybe even the NIMBYs will have a nice warm cup of STFU and get on board.
Knowledge is power. Knowledge shared is power multiplied.
Ten cars streaming across that, that freeway, and what happens to your own personal lane? I just the other day got... a car was driven by my staff at 10 o'clock in the morning on Friday, it got in yesterday. Why? Because it got tangled up with all these things going on the freeway commercially. They want to drive vast numbers of cars on the freeway. And again, the freeway is not something you just dump something on. It's not a big truck. It's a series of tubes. And if you don't understand those tubes can be filled and if they are filled, when you put your car in, it gets in line and it's going to be delayed by anyone that puts into that tube enormous numbers of cars, enormous numbers of cars.
I spend my commute times on a road that is fairly busy but usually the traffic flows well and it's all good. Of the observations I've made, an interesting one is what happens when one lane is blocked for construction or what have you. Often, in the case of construction, there are warning signs way in advance instructing drivers to get in the left/right lane. In the case of an accident, no signs and while you can't see what the problem is, you can easily tell which lane the problem is in because it's the lane that's moving quickly. It seems ironic but as you get closer and begin to see the problem, the lane in question flows faster and faster relative to the lane into which everyone has to eventually merge. From a politeness perspective, it seems like I should just merge at my earliest opportunity and wait my turn like everyone else but from a flow perspective, it seems like I should blast on ahead and find a space to merge as long as I can find some way to do it without creating a standing wave... Unfortunately, in the latter case, everyone is justified in not opening a space to let me in and indeed, when I see someone blast on ahead and then wait right in front of the problem area, I don't make them a space, but invariably, someone always puts on the brakes, comes to a full stop and waits while the idiot driver wakes up and begins to creep into traffic, thus exacerbating the whole problem. Of course, if everyone was able to make their vehicle accelerate quickly, stop on a dime, and were fully alert, as well as fully conscious of just where each corner of their vehicle was relative to the rest of the world, we wouldn't have traffic jams. It's humans that are the problem. Lets get the humans out from behind the wheel.
I believe I've seen the other side of this "equation", namely what goes on when there are few cars. Recently traveled to Florida on I-75 on Christmas Eve. That's pure desolate, much like a desert. Nobody, nothing, I'm the only driver on the interstate. Wait a minute, there's another car out here? No wait, several cars. A group or "pod" if you will, of 10-15 cars approach behind me at 70-80 mph. They pass, and disappear ahead of me over time. The phenomina repeats over and over. By daylight, I estimate that approximately 200 cars passed by me in groups of 10-20 cars every hour. What, these drivers are all "family" or are they afraid to break out away from mama? Very strange, although I believe I was witness to some form of herd instinct, I can't believe that I was the only driver out there not traveling in a pack.
If drivers maintained proper distance between their vehicle and the one in front, there would be room for minor braking and the accordian effect would be reduced if not eliminated.
If drivers maintained proper distance. . .
Yeah, right.
What?
hummer is not capitalized.
Unless you meant he was driving an SUV.
Is it just my observation, or are there way too many stupid people in the world?
try motorbikes, four wheeled sissies ;)
In our area, there is a twice-daily traffic jam that has been understood for years, but fixing the road to take away the problem would be ungodly expensive.
There is, actually, nothing technically wrong with the road. The road in question is I-87 (the Northway), and the pinch point is where it crosses the Mohawk river. The Twin Bridges have a slightly narrower shoulder than the highway leading up to them in either direction, but the shoulder, on both sides of each bridge, is still every bit as wide as any of the three lanes going in either direction.
Compounding the problem is that the bridges are (hope this is the right term) truss bridges. There are two convex bowed beams that go over each side of each bridge, and a construct of triangular trusses between them. These are the reason why a change would be ungodly expensive, because you would have to rebuild the bridges.
Anyway, people come to the bridges and slow down because they perceive that the road has gotten narrower, while failing to perceive that this fact is irrelevant. This slowing down leads to the accordion effect that was described in TFA, where successive cars have to apply more and more braking in order not to hit the car in front of them. By the time you are a mile north of the bridge in the mornings (south in evenings), traffic is basically stopped.
The construct that causes all of this trouble can be seen here (along with some Google wierdness in the construction of the image).
www.wavefront-av.com
The subject sounds very much like William Beaty's texts from 1998: Traffic Waves - sometimes one driver can vastly improve traffic, except Beaty's text is way more enlightening...
Unselfish actions pay back better
Construction zone. Lanes have to merge, large flashing signs have been telling ou that the left lane is closed 2 miles ahead, 1 mile ahead, 3/4 mile ahead, 1/2 mile ahead, 1000 feet ahead. Orderly drivers have long since taken the opportunity to merge without disrupting the flow. And then, zoom, there goes some dick in a BMW (it seems to be a BMW more than any other model, to me). Runs right up the gap we all worked to create to facilitate our transit of the construction zone, right up to the final inch before the cones cut him off and he forces his way in.
Driving a big SUV (hey, we've got 6 people plus gear in the car!) we often ride in that lane at the pace of the merged traffic to help prevent this, and 99.9% of the time folks recognize the tactic and "save" our slot for us. But we've had people (usually in BMW's) go right around us in the median.
We give way to the semis who do this job much better than we can by driving 2-abreast or even 3 or 4 abreast. I have seen one BMW driver try to run down the emergency lane to squeeze past a semi, which promptly closed the gap and virtually pinned the BMW against the concrete wall. I figure that BMW guy had to get new pants.
One thing I'd do when I became the benevolent dicatator is raise revenue off these pricks. Put a detail of troopers at construction zones. Anyone who zips right up to the merge point...$1000 fine. Second offense, $5000 and lose your license.
Reading this and related articles, I'm convinced nearly all traffic jams are cause by some selfish idiot who tried to save 2 seconds on *his* commute by tailgating, running up merge areas, abrupt lane changes, etc.
Everybody is busy pointing out the "first causes" of traffic jams without noticing that every one of these causes is caused by interaction with the roads in the first place.
The real "first cause" of traffic jams is differences in driving decisions and style. If everyone drove at 120mph, or everyone drove a 30mph, or everyone could anticipate exactly what the other driver would do before they did it, and adjust accordingly in advance, there would be no traffic jams.
Traffic jams happen because one guy is driving 45 mph thinking "look at all these damn idiots driving too fast for this weather and this level of congestion, well not me, I'm a good driver" and the guy behind him steps on the gas and passes at 80 mph thinking "look at all these damn idiots impeding the flow of traffic, well not me, I'm going to pass so that others behind me can pass afterward" and the guy in the next lane over is thinking "jesus, look at these idiotic fast and slow drivers passing each other and holding up traffic, I'm going to stay in my lane and not accommodate any of them or let them use my lane to pass, since they're all rotten-ass drivers."
It's the conflicting intentions and behaviors in similar situations that lead to brake-slamming, passing, swerving, wrecks, and the other causes of the density patterns that characterize traffic jams.
STOP . AMERICA . NOW
Not at all, you could have the best drivers everywhere , and
if you live in an area where the government is so poorly run ( as we have here in montreal)
the poorly laid out construction plans make for some serious delays regardless or not of accidents.
The people who make the construction plans arent even engeneers or even live in our area to know
how to set up grids in order to keep the traffic moving while one street is closed.
Also our construction gets done about every year for certain streets because our government
thinks it to be smarter to pay the least possible to the worst contractors who cut corners everywhere they can and have to do this every year, instead of getting much better workers who actually know what they are doing and that the streets paved and laid down would actually last minimum 10 years as they do in lets say ontario.
The problem arises from all the corruption in our political system especially in quebec
where they all line their pockets while in office!!!
"Until they bring back LOBO make mine Marvel!"
http://www.amazon.com/Turtles-Termites-Traffic-Jam s-Explorations/dp/0262680939
I remember discussing this in my engineering dynamics class in 1983 (my prof did research into traffic patterns)
The very act of observation causes the cars ("particles") to clump up. Conversely, if everyone drove blindfolded, there would be no traffic jams.
This is a subject I've spent a great deal of time conjecturing about, and I've come up with a few root causes:
1) Lane movement: I have found that the number of drivers changing lanes has an incredible effect on the speed and density of traffic. This is usually exacerbated by poorly designed onramps/offramps. I commuted from Baltimore toward DC every day for about 6 months. Some of the exchanges there are remarkably short, try and accomdate cars both getting off and on 295 (Baltimore DC Parkway), and there is very little in the way of a usable viewshed (lots of trees). That single interchange caused more traffic then I care to think about
2) Similar to the lane movement is lane reduction. On the same road back into Baltimore, "construction" forces 3 lanes to 2, then 2 to 1 (left to right). End result: People in the left most lane get into the middle lane, causing a bit more congestion, then those people try to get into the right most lane, joining the cars already there. Once the right most lane becomes clogged, people don't want to wait in that lane, and fly by in the now open (but closing ahead) left lane(s). The effect is similar to ramming a funnel of BBs into a tube. If the BB's are already lined up, they flow smoothly. If the are being funneled, they will congest.
3) Rubbernecking. Self explanatory
4) Accidents. Again, self explanatory. Many could be avoided with a bit of caution.
5)Tailgaiting: If one follows too closely to the car in front of them, the car behind will tend to break more quickly, and frequently, thereby causing the cars behind them to roughly do the same (depending on how closely the cars behing the tailgater are following). I've seen this happen, the break lights all light up in a row, with a moment break between each car in the series.
6)Similarly, brake riding. If a "lead" car (relative) applies to breaks too frequently, the car behind them will most likely do the same, all the way down the line. Butterfly effect.
Traffic moves like a worm, not like a string. Even in heavy traffic situations, traffic will not clear with there is no obstruction. Cars in the middle will lurch forward a bit, then stop, the cars behind will move similarly.
The average driver is concerned with one person, themselves. If this average driver would be reminded that driving is a communal activity (on the whole), and adjust driving habits, I would like to think that the majority of traffic in this country could be aleviated.
Unfortunately, that is too much credit to give the average driver.
- Now the individual in charge of it, James Pond, provided me with a succient answer as to why it was impossible. "We won't do it".
:)
There are many factors that lead to delays. Here they widened the roadway and inserted a barrier- we now have only 'protected' left turns. Of course they do permit some U-Turns, and when people perform one they CRAWL thru the intersection at 5mph because they're afraid their front wheels will fall off. That reduces the number of vehicles down to 4, maximum, that will get thru a left turn arrow.
Of course, there are always 13 cars making left turns. That means.... TRAFFIC JAM!
ANd it's so easy to see it forming. After 3 signals the turn lane fills up. It spills into the left most lane. That shuts that lane down. At some point vehicles try to merge out of the lane while traffic is still approaching- which shuts down / slows down the center lane.... until those poor saps get panicky and emergency lane shift into the right lane. Which shuts down the right lane.
Why? Because most people are too scared to go 10 to 15mph with their wheels cranked all the way to the left to get thru the turn arrow.
Trying to make the 'traffic analysis/engineering' people see this is impossible. They refusee to come out and witness the actions, instead relying on sensors and counters. I drive the route every day at different times and can do a pretty good job at explaining each set of circumstances which triggers the resulting backup.
My favorite now is trying to get them to modify the left turn arrow to 'blink' red after 7pm. They refuse, of course, because waiting at a red light for 2 minutes while there is NO ONCOMING TRAFFIC is not an invonvience. I should bill them the $150/hr per instance. We have a 'slugs' of traffic that are always held up by series of lights, and always arrive in a single 'slug' of cars. After that slug passes it's about 2.5 minutes to the next 'slug' of cars. The lights are set to trigger at some time short of the trumpet shout- yet we can't get them to up the frequency for some reason.
Apparently there is a limit on the number of cars per hour - 200 CPH- that triggers different timing signals for the lights. I haven't seen the rules yet but this is just what I've been able to glean from conversations with Jim. He doesn't like me
There are a number of contributing factors to this phenomenon. For every 1 minute that an incident is blocking, it takes 3 minutes to recover and for traffic to flow normally again. Blocking incidents can include, buses that are stopped, police pulling over a vehicle, emergency vehicles, wrecks, obstructions (trees, water over road way, etc.) This paired with driver inattention, causes several traffic delays. Also when you have just 1 lane blocked you loose 60% of you capacity for that roadway. So now on an already congested route you have just decreased efficiency by 60%. And the fact that everyone is in a hurry adds a significant time delay as people are not as focused on the conditions that are present on the roadway because of the stress of a slow commute, so the either try to do other things while driving (read a book or magazine, apply makeup, do their taxes, everything but drive) and therefore are not paying the appropriate attention and then get rear ended or rear end someone else, therefore crating an additional blocking incident, compounding the problem. Then there are the people that want to change lanes and no one will let them over so the stop in the lane that they are currently in and hold up all the traffic behind them while waiting to switch lanes. Then there are some people that are not very adept at driving in the first place and are scared to drive the speed limit, and therefore cause backups, this had roughly the same effect as a blocking incident. Failure to properly merge has this same effect as well. These are just some of the factors that can contribute. There are several others, but these are the most common
...and when you try to push too many cars through the pipes, they get clogged up.
Nice find.
So a 2 second gap is 205 feet.
2/5ths of a second then equates to 41 feet.
That leaves 205 - 41 = 164 feet left to stop, which is 6 feet less than the number cited for the average modern vehicle to stop. So the two second rule is deficient by about 3.5% for the average modern vehicle.
On a side note, modern isn't exactly defined, but I don't think my '87 station wagon (with no ABS) qualifies.
except, instead of an SUV it's a full size pickup truck with a trailer in tow with an SUV on top of the trailer.
a conservative estimate would be rolling right around 15,000lbs total
I don't care if i'm doing 30over, there's always a jackass right behind me tailgating the trailer making it look like i'm going too slow.
taping the brakes dosen't do anything but agravate the guy behind you. if i can maneuver my land-train out of my current lane to avoid a stopped car infront of me, but the driver behind can't. who's at fault here? that's right, the guy that was tailgating the trailer.
i hate people in small cars that have a hate for large vehicles on the road. they cause a whole lot of road rage
I drive a standard car and the thing that drives me insane is people who ride the damn brake. If you watch while driving in traffic, you'll see one idiot tap the brake, then another person will tap there, and eventually you'll be stopped in traffic for no reason at all.
Recently I drove my brothers car which is automatic because of bad weather. now please understand, I have driven a standard car for the past 5 years and haven't even driven an auto once in that whole time. My experience was terrible! I can not believe how difficult it is to control your speed without tapping the brake. Yes large volumes of traffic will create a traffic jam, but most of the times if traffic moves I don't really care. It's when people RIDE the brake is when the real shit happens.
If everyone drove standard I suspect it would still be an issue, but it wouldn't be as severe. So remember everyone! DON'T RIDE THE BRAKE! Or tailgate !
MrJynx
It would help to cut down on the standing waves if people applied the 'join slowly, leave quickly' rule.
This is true. And you can see this principle in use by truck drivers, who are forced to act this way due to the sheer mass of their vehicles. What originally got me thinking about this were the long lines of traffic into Boston before the Central Artery tunnel was finished. Four lanes of traffic would narrow into one, not just causing a bottleneck, but also making the entire road serial, thus amplifying the 'elasticity' of the traffic. But anytime there was a truck in front of you, like a giant 16-wheeler, traffic would be a much more tolerable slow crawl. Drivers with standard transmissions also help to limit these standing waves somewhat, since it is a lot of work (and damaging to your clutch) to continually stop and go again.
As another poster mentioned, what defeats this technique somewhat are the impatient drivers in adjacent lanes who accelerate into the gap that you just created. The one-lane example above was unique in that the road was a single lane on an elevated highway, which made 'accelerating into the gap' impossible.
Anyhow, this phenomena would completely disappear if we could remove humans from the job of actually piloting the vehicle. I'd love to see something like personal rapid transit, but I think the American public would complain too loudly about their loss of 'freedom', even if it meant that traffic delays and traffic fatalities would virtually disappear.
I'm also greatly frustrated by traffic, and have spent a fair portion of my spare IQ trying to make sense of it, going as far as coding up elaborate simulations as I'm sure others have done before me. Sadly I have no magic solution. The big problem with driving is that just about anyone can get a license, but only a very small portion of those people are skilled enough to really drive. Sure, they know where the controls are and what they do, but they don't have the brains to do watch all the vehicles around them, while figuring out where they're going and real-time physics processing all at once. My favorite analogy for this one is painting: Just because you can tell red from blue, and you know how to hold a paintbrush, doesn't make you an artist.
:) I can only hope he'll learn from that lesson.
One thing I hope everyone can relate to is the "invisible choke point". It seems every city has at least one of these, where everyone slows down for no reason whatsoever. Traffic just plain stops at rush hour, and you expect to see a nasty accident blocking two lanes with an idiot cop blocking the 3rd, but instead you just find that people go back to full speed a quarter-mile later with no event.
Then there's the left-lane hogger. I ran into one last night on a half-hour drive. The little bastard was the only car in the left lane, doing about 95 in a 100 zone (kilometers not miles), where most people do 130 or more. Traffic was too dense in the other lanes because of the holiday craze so everyone was stuck because of him. After a few miles of this nonsense, I drove right up to him and tailgated like a murderous psychopath for less than a minute until he finally moved over and let me through. I kept an eye on my rear-view and sure enough, the instant I passed him, he shimmied right back blocking everyone else. My response to that passive-aggressive pansy-boy was to give him a taste of his own medicine, hopefully making him realize how frustrating and dangerous his disrespectful driving had been. I slowed down right in his face forcing him to hit the brakes just a couple feet away from hitting me, then cruised along for a bit until he changed lanes to try and pass me on the right, then I moved in front of him again while everyone else sped through like they were escaping from prison. He was effectively trapped behind me with a long line of angry speeders on either side. Payback's a bitch
I'd say a big part of the problem is that driving requires cooperation. As a driver, your are responsible for the safety of everyone around you, just as they are responsible for yours. You can't go out there, driving selfishly as if you were the only car on the road and expect things to go smoothly. One thing I noticed moving from a smallish city to a bigger one, is the lack of courtesy on the road. You could have your car practically sideways trying to do a left turn, NOBODY will slow down to wave you over, actually they will floor it to cut you off, so you end up waiting a few minutes and holding up the line of cars behind you. Driver A saved 5 seconds by cutting you off instead of letting you turn, but cost the other side of the road 2 minutes each, times 15 cars. Now if Driver A could appreciate that half the time, he's the one wasting his time in a jam and he'd really like it if the incoming assholes would slow down and give him a chance to pass.
Where I live, driving lessons involve 3 evenings of classroom lectures about road signs and safe driving, and 10 hours of driving practice. I think it would be immeasurably beneficial to spend a few extra nights in the classroom, talking about cooperation and respect on the road. Hammer it in people's heads that they're driving a 3000 pound hunk of metal. Hostile driving turns that vehicle into a deadly weapon, and well I wouldn't want to live in a neighborhood where all my neighbors are madly twirling a 3000 lb baseball bat at each others' head.
-Billco, Fnarg.com
Why are people in a hurry? Because they're not having fun. Why? Because they're told how fast (slow) to drive. Ever try actually going the speed limit? I do now that I've gotten a number of speeding tickets. I drive 25 in a 25, and I end up with a looong line of cars behind me. But... I'm at the speed *LIMIT*!
So you're driving along, all normal, you look down and low and behold you're going quite a bit over the limit. You didn't feel out of control, but father government says its not safe.
Now you must slow down to a speed that is uncomfortably slow. You may do as I do, rubberneck (because you're mind is going numb watching things crawl by).
I've never thought velocity the cause of any accident (or it is the cause of EVERY accident b/c you wouldn't have gotten in an accident of you were going 0mph).
Or just do as I do, smoke a bowl... then you don't care if you're doing 45mph in the fast lane.
Brakes usually aren't the limiting factor in slowing a vehicle down. larger brakes won't slow a vehicle down any faster - why - because usually it is a function of tire grip. Most any vehicle can lock up its brakes and skid. Larger and better brakes won't help anything to slow down faster, it will only help prevent brake fade.l #
As to large trucks slowing down faster than cars - LOL. Yes trucks have larger contact patches, but they weigh oh so much more (80 tons fully loaded and 10 brakes only- not 18), and have a higher mass to contact are ratio than do cars (2.5 TONS AND 4 BRAKES) - which means longer braking distances. General quoted stopping distances for a truck are about 40% longer.
http://www.thetruckersreport.com/truck_facts.shtm
..........FULL STOP.
Basically they said that in a crowded condition, one bad decision can domino up to a traffic jam. Obviously, if there is sufficient space between the cars, this doesn't happen, (one domino does not 'hit' the other if it is far enough away). The original problem was one car cutting off another, not coming to a full stop.
If were were being totally honest with each other, the fact that humans had problems stopping in this situation means they were ALREADY driving too close to each other for the speed they were going. As such, this was a 'supersaturated' solution of cars in the road, just waiting to crystalize into a traffic jam. You could in fact say that that the jam already existed, it was just a matter of being triggered by either a safe slow down or an accident.
We could in fact THANK the one obnoxious driver that cut off people, because his actions safely crystalized the road into a traffic jam instead of experience a catastrophic crystalilization called a multi-car pile-up.
The proper solution to removing the jam is not to blame or eliminate the obnoxious driver, but instead to limit the number of people getting on the road once it has reached the super-saturated state.
excitingthingstodo.blogspot.com
I still amazes me that here in the Bay Area, the following lead to immediate gridlock:
-Exits. Even if it's on the right of a seven lane freeway, half to people slow down to 20, a quarter tries to exit by cutting across six lanes, and the rest stops to ask for directions.
-Parallel parking. Four lane city street, parkee swings out into left lane (or the first of the opposite lanes), backs up to the curb at right angle, hits the curb, gets out of the car--which now blocks both lanes causing other drivers to pass across the center divider effectively shutting down both directions--to assess the situation, asks a few pedestrians for their opinion, gets back into the car, maneuvers back and forth a bit more, gives up, and cedes the spot to a city bus which fits easily.
-45 degree parking. Should be easy, right? Well, most Cali drivers miss the spot on the first few tries necessitating backing up across two lanes of traffic a couple of times.
Some newer cars have dynamic cruise control that maintains a certain distance behind the car ahead of you. Cars with this technology conteract the domino effect of each car braking harder than the previous one because it initiates the braking very quickly and brakes slightly less aggresively than the car ahead, allowing the inter-car gap to close as the vehicles slow. This has a dampening effect on the entire reaction.
I've read that once a certain percentage of vehicles have this technology, it will eliminate these traffic jams. I don't remember what that percentage was, but I remember it surprised me at how low it was, something like 25% or less.
This is a neat simulator a guy in Germany developed. Its fun to play with the dynamics. In some case increasing the speed limit can actually slow down the traffic! Java required, enjoy.
t ml
http://141.30.186.11/~treiber/MicroApplet/index.h
putting the 'B' in LGBTQ+
Never. It's physically impossible.
Light rail moves groups of people. Cars move individuals.
http://kinetic.seattle.wa.us/prt.html
Deleted
If you plot carrying capacity of a road vs speed of traffic you will find a maximum around 40 miles/hour (65 kph). Lets start with an empty road and begin adding cars with everyone going 70 mph. Eventually traffic will begin to slow down. Remember that the carrying capacity is density of cars multiplied by their speed. As more cars are added the carrying capacity increases as more cars can be added to make up for the slower speeds. However once you reach a critical point about 40 mph then the carrying capacity goes down causing a traffic jam. Think about it this way once the speed goes below the critical speed (tipping point, if you like that term) then traffic will be feeding into a jam much faster than it can leave the jam.
This is why once the speed has dropped below the critical point all hell breaks loose on a crowded road. You can sense this when you are driving on a crowded interstate and feel that anything or idiot can cause everything to come to a halt.
I have lived in Orlando, FL for about five years now and I deal with traffic jams on I-4 constantly. To me, it's just another reason to embrace intermodal transportation. Roads do not scale well. I remember a few years ago FDOT installed some useless speed limit signs along I-4 that changed the speed limit based on traffic congestion. Which would help the situation -- if anyone bothered to heed it. But of course drivers ignore it. Human behavior is the root cause. No one element of an intermodal transportation system is a panacea but Orlando plans to build a light-rail system by 2009 and I am all for it. But again, if no one uses the alternatives the problem won't go away.
buff3r
1: People hitting the brakes causes a standing wave as other posts mention. I do this for fun BTW, a second tap on the brakes does it.
2: It takes longer to exit a road than it does to travel down it. If cars travel 2 seconds apart and it takes 5 seconds to park your car it's obvious that congestion is going to develop. It's lack of high bandwidth parking which causes congestion rather than lack of roads.
Deleted
The main thing I noticed on the roads is that a driver who drives differently than the local norm is always a major pain. It can be a driver who is going 20Mph faster or slower than the surrounding traffic on a highway, a hesitant driver obviously lost in a busy city street, an overly aggressive driver on the main street of a small town, a driver who thinks rules are for others in an area where people tend to follow them or someone who follows the rules strictly in an area where most drivers fudge them quite a bit.
Essentially, most people drive badly; people in an area just have to drive badly the same way and things go much more smoothly. When someone drives badly in a different way (i.e. when someone non-local uses a different style of driving), then you have problems.
When in Rome, drive badly as the Romans.
De gustibus et coloribus non est disputandum
Simply put, most people lack the necessary awareness, mindfulness and spatial sense to drive. It is why they are driving in the first place. You can't fight that kind of stupidity, and there is no sense stressing about it. It costs us all millions every day, its just a fact of life. Eugenics is not an acceptable solution and natural selection has been replaced by sexual selection in western civilisation, so I see no end to it.
I maintain that good grades in high school physics (at a bare minimum) should be prerequisite to even considering a candidate for a driving exam. Fat chance that will ever happen.
If we implemented the concepts of forward and backward congestion notification on freeways, nobody would be getting in traffic jams because of following too closely. The ideas behind frame-relay work well on networks and if we had changing speed limits 10 miles before a major accident, it wouldn't be a mess when the cars all got there. Just think about what that would clear up. You could have hundreds of cars all riding eachothers asses and then you could tell the ones in front to accelerate to 90 mph. It's just about leaving room in front of yourself. Everybody loses in a traffic jam. For cars entering the road, just leave a few carlengths for them to get in.
than you claim (2/5 sec. = 0.4 sec).
The average driver's reaction time on the freeway is between 2 seconds and infinity (they don't react at all). Presence of a cell phone or an active conversant in the front seat with a teenage driver increases reaction time.
I can't count the number of times I've seen cars fly into another vehicle at full speed fully 5 to 20 seconds after the first vehicle was stopped, with unimpaired visibility, clear weather and no excuse. This is the infinite reaction time scenario.
In one instance there was an accident in an intersection and a woman driver (who had plenty of time to stop) approached the intersection at about 35 mph and, when she saw the accident, threw her hands up in the air and opened her mouth in astonishment. She had plenty of time to stop, but she didn't brake, she didn't swerve, she did nothing but plow full-speed into the accident scene. Luckily no one was hurt.
This is the typical driver. And I'm not talking about old drivers, who usually drive slowly and carefully, but young and middle-aged drivers who aren't paying attention to what's in front of them.
The question as to what takes a road a saturation and pushes it over the edge is meaningless. It can be anything. Someone trying to go too fast, someone hitting the breaks a bit too hard, someone changing lanes.. any little blip can start things off. As many people have noted, once the road is at saturation, eventually something will push it over the limit.
The real question here is "How do we stop traffic jams?"
The answer is simple: don't saturate the road. Trying to avoid traffic jams on saturated roads is like trying to dodge raindrops.
A road below saturation has room enough between cars to handle little impulses. The impact of someone slowing traffic will be absorbed and dampened by the extra space instead of amplified. Roads that are built with excess capacity do this naturally so one way to achieve this is to simply make roads bigger. Most roads are built so far below the load that would naturally be put on them though that it would require a massive (2-3x) increase in their capacity to make this work.
A similar solution is to simply have more highways. Right now they only account for about 2% of the roads in the US and handle about 25% of the traffic. Taking land to build roads is always controversial but every second you sit in a traffic jam should bring you one second closer to understanding why it has to happen.
Other methods would include things like blocking access to the highway when it is near capacity. There have been failed attempts at this in California but they weren't designed to keep the roads under the saturation point so they were doomed to fail. A correct solution would have to outright deny access to people if the road is near saturation until it dropped below. This solution would probably be more annoying than the problem though.
set softtabstop=4 shiftwidth=4 expandtab nocp worlddomination
There's a lovely clip which crops up from time to time on those "Police action!" style programs. Filmed from a police car it shows a a small car (metro or Renault 5 or similar) in lane three which resolutely fails to notice the jam sandwich on its tail, despite the sirens, red lights, blue lights and oscillating headlights. The police car is trying to get to an earlier accident which is ahead on the motorway and is being held up by the small car. Then as they approach the blocked road the police car slows, which gives the appearance of the small car suddenly accelerating away (although it isn't) and then it finally smashes into the back of the stationary traffic queue. The driver of the small car had 20 to 30 seconds to bring his or her attention to bear on the odd things happening around, and failed miserably.
A two second gap is the absolute minimum that any sane driver would contemplate in fast heavy traffic. Unfortunately there are a lot of insane drivers around.
The Slashdot audience is supposed to be at least moderately technically minded. What engineer thinks that a 25 % (if that calculation had actually been correct!) safety margin suffices when lives are at stake?! Safety is 'stupid'? Don't get me wrong: you're very welcome to risk your own neck, but there happen to be other people on the road.
I'm curious, do people in the US actually aim for a mere two second interval? In the Nordic countries, we recommend at least a three second margin. Which is really far too little when the roads are icy and the sun is in your eyes during the long twilight. Nevertheless, even here, there always seems to be some optimist with a poor sense of maths, physics and psychology, who compensates with an inflated sense of his driving ability, sniffing at your tailpipe, just waiting for a chance to slam into you... which kinda makes you reluctant to slam on the brakes yourself, increasing the safety distance even more.
But of course I'm being silly: packing the highways solid to maximize road utilization is far more important than saving lives -- nor would such packing ever have any adverse effects such as complete highway gridlocks! Waves of compression and rarefaction...
Let me start by saying that I live in the suburbs of atlanta and work in Midtown, so I have had some experience with traffic.
My theory regarding the reason for most accidents / traffic jams is simple. People generally are stupid. Now before you discredit my theory consider this. I have studied some user interface design and I am aware that humans can process 7 +/- 2 pieces of data in short term memory. Yes, we humans routinely handle more information than that but that has to do with our ability to group stimuli / data. Many accidents / traffic jams occur at places on the interstate / road with signs that have 2 or more pieces of information to convey. People can't process 2 pieces of data. Additionally, when a person comes to an intersection or exit they are forced to make a decision. For example: Should I get on I-675 or stay on I-285? People can't make decisions.
Now to leave you with one final thought. I know that generalizations are always bad. (well not so much in programming but that's another topic).
Sure, the standing wave deal, and the lone idiot concept, and the slow truck(s) ideas are all valid, but the biggest thing I've seen is road design, as in slope. There are two places in my commute where traffic is constantly backing up - and both of them are at the top of a hill, or ridge. I'm pretty sure it's a visibility thing, and not an impact on the cars thing, as the slopes really aren't that significant, but there's a definite "peak" and you' can't quite see what's on the other side. One is the new Leverett Connector off ramp from I93 in Boston. A lot of people blame the 2 to 1 lane drop, but if you get there at the right time (~6am), you'll see that traffic starts backing up at the peak of this elevated roadway, a few hundred meters after the lane drop. Again, once passed the peak, normal speed resumes. I know there are guidelines(?) about the slopes of highways, etc., but I don't know how it addresses peaks like this. The Leverett Connector is just poorly designed (part of the Big Dig), the other peak I refer too is more landscape based, but seems it should have been addressed when the road was built.
I'll save them a lot of time. Here is how to build a freeway:
-Build more lanes then you think you will need. It will pay off later when you don't have to tear down a bunch of overpass and transition bridges just to add a few lanes.
-Build Transition Bridges and Overpass Bridges with more space on either side of the freeway then you are using now. (Reason: See above)
-Prevent forced merging at all costs! If one freeway transitions to another then give those people transitioning a new lane on the freeway. This way traffic can flow. I don't care how much it costs to build it now. It will cost even more later when you have to tear down a bunch of bridges because you didn't plan ahead.
-Use transitional bridges as opposed to joining two freeways and forcing all traffic to merge to get where it is going. Bridges are more expensive but they are also more efficient. Do NOT use a single transition to go in multiple directions on the same freeway. Each direction needs it's own transition.
-If a lane must be forced to merge, only force outside lanes to merge. Do not force the leftmost or inner lanes to go away if possible.
-Put signs 1 mile earlier then you think they need to be as long as they will not contradict other signage. This way people can merge earlier to get where they need to go.
-Avoid steep inclines or tight turns at all costs
Do these things and you will have a well flowing and efficient freeway.
Energy is proportional to mass times the square of your velocity -- an average car at 70 MPH/110 kph has a lot of momentum.
Which is a valid point except for two things, 1)Kinetic Energy isn't conserved 2)Momentum is proportional to the velocity not the square of the velocity(K.E. is). Oh the irony of "bad maths"
I laughed at the weak who considered themselves good because they lacked claws.
Top Ten (need a couple more) of the problems with backups on major highways in the North East:
1. Highways not designed for city bypass, dedicated truck lanes, buses,etc.
2. On and Off ramps not consistant on same side where drivers out of the area know the best lanes to enter and exit
3. Driver preparation prior to entering and exiting highway
4. Visitors
5. Sunday drivers
6. I got my hooptie piece of trash (insert car of choice) , talk on my cell phone, pimpin my bling bling watch, driving in the left hand lane mutha.
7. I cant judge the distance or tell what speed the car in front is going so I am going to put on my breaks mutha.
8. I dont like people driving close behind me when I drive slow in the left lane mutha so I put on my breaks.
I can tell you that I was impressed with the way European roadways are (Italy at least) where the drivers know what a passing lane is.
Happy Holidays
true driving nirvana is reached only when you accept that everyone else on the road is an asshole and realize that you get to your destination at the same time regardless of what speed or style of driver you are. Slow down. Let the asswipe in the SUV cut you off. you'll take the same exit within 20 seconds of them 30 minutes further down the highway and will live a much happier life in the process with which to spend laughing at the stupid padoin in the SUV.
about the jerk who always tailgates for that extra microsecond. It's the weird attitude of not letting anybody ahead of you that makes it impossible to move about freely. It's very simple. Leave adequate space in front of you and the jam-ups will disappear. Follow too close, and you deserve whatever happens. Leave three seconds!
What?
If merging at the end was the right solution then there would be no need for a merge lane at all. There would be only one place to merge.
We have merge lanes so that drivers can merge wherever they do so most smoothly. This may be near the start, near the end, or somewhere in between. If you ignore early opportunities and wait until then end, you will often have to brake and/or force yourself into the through lane. Neither is any good for traffic flow. You also really hack off those of us were ahead of you, smoothly executed our merge and are now stuck behind the traffic jam you created.
Any, y'know, um, kinda' relevant objections to my main point of respecting velocity and the inadequacy of monkey genes on a highway? Otherwise, I'll just pull over here at the next stop and let you brave gentlemen drive on to your indubitable glory...
Following distance is very important. People keep describing a situation where a driver has to hit the brakes even harder than the driver in front of him, where any small event leads to people standing on their brakes. That's all tailgating. If you ever hit your brakes harder than the guy in front of you, you were tailgating pure and simple.
Unfortunately, over-capacity roads lead to defensive tailgating, where if I don't tailgate, the tweaker/crackhead/cellphone/drunk behind me will pass me on the right, cut me off, and slam on his brakes 'cause he's too close in front. I don't mind that much, except that bad drivers keep being bad drivers. He'll nod off and slow down to 50 in no time, only waking up when I try to get around him. If I pass with a 20+ mph differential, they usually don't have time to notice and go back into hyperaggressive mode before I'm out of range (I don't care who's in front, but I just don't want to be near a bad driver) but that accelleration requires space.
The rule for tailgating is this: If you're regularly using your brakes on the freeway, you're probably tailgating.
Space cushion. Remember that from driver's ed? Oh yeah, we decided driver's ed was too expensive for public schools, so now we pay for that decision every day on the roads. There are plenty of non-obvious rules that make driving safer. Drivers really are worse than they used to be.
I watched a show about this on National Geographic about a year ago. I was determined to stop tapping my brakes for the slightest of reasons in an attempt to do my civic duty of not taking part in being a congestion agent. If only we could get the news out to everyone!
The legality of speed of the driver in the outside lane is no concern of yours. That's for the police or the camera to decide.
What matters is whether you - as the driver executing the manoeuvre - can do so safely and without causing other vehicles to change speed or course.
If you cannot or do not correctly judge the closing speed of a vehicle in your mirror, and you pull into their path, then you're at fault.
Whether you think it's right or wrong (and the police certainly don't prosecute for speed alone under 85MPH - although I have heard of automated enforcement pinging people for 81MPH), the de facto speed limit on the British motorway network is around 80MPH, not 70.
FWIW, I drive a BMW 528i, do a lot of motorway miles (20K plus per year) and frequently encounter people pulling out from behind wagons into lane 3. This makes their speed differential with respect to me unsafe. It doesn't stop them. They don't seem to realise that the gap they saw as they glanced in their mirror is about to be filled by nearly two tonnes of car travelling at a speed that will merit a visit from Mr Ouchies should contact be made.
This might sound patronising. That's OK - it is. You clearly need to be patronised a bit, because by your own admission, your motorway driving habits are dangerous.
I've noticed that despite best efforts (sign after sign), etc. people simply will not merge into lanes before they are forced to by the lane cutting off. While driving out to the western portion of PA I encountered numerous delays along construction points, every single one followed the same pattern:
1) Sign says "right lane ending in __ miles, merge left"
2) As I go into the left lane, people continue to pass me on my right at egregious speeds.
3) The traffic (except for in some proportion the ending right lane) slows to a crawl.
4) Upon encountering the source of the delay, it turns out the people in the right lane, refusing to merge for miles and miles, instead have slowed everyone else down in their attempts to merge at the last minute.
5) After the merger is over, traffic then continues normally.
Which leads me to say, as always, wow, people are stupid.
Judges and senates have been bought for gold; Esteem and love were never to be sold.
Not at all. From my experiences the target interval seems to be closer to 0.15 seconds
(1 car length at 70 miles per hour (113km/h)).
Frequently I find people unable to keep quite this much distance between themselves and
the car in front of them, though I fail to understand precisely why.
Another problem is most of the people I know are suprised when you tell them they should
be 2 seconds behind the car in front of them, they all seem to think that 2 car lengths
is what the test said, and that it was just a recommendation.
A worldwide demonstration, to all the s***heads out there, what it would be like if everyone drove like that.
C'mon, you know you want to.
I suggest May 14. Not for any particular reason, it's just not taken by anything else I know of yet. If anyone has a better idea, I'm all ears.
I've observed this "ripple effect" of brake lights many, many times. I blame the modern automatic transmission...ok, actually, I blame the drving laziness/stupidity that has been espoused by the auto tranny.
Back in the old days (and in the modern days for those of us who still drive cars with clutch pedals), learning to drive included understanding that lifting your foot off the accelerator is the preferred method for gradual speed reduction. The brake pedal should only be used in cases where you are intending to bring your car to a complete stop, or when you need to drop a whole lot of speed in a hurry.
If you are driving prudently and with good situational awareness, you should almost never need to use your brake pedal during highway driving. Note that this doesn't (necessarily) mean driving at grandma speeds and trying to leave 5-second following distances. It primarily means having your head cut-in to what's going on around you, maintaining mental "escape" plans for any situation, and understanding how your actions are likely to affect drivers around you.
9 times out of 10, the driver braking in front of me is doing so unneccessarily...this includes morons who seem to believe it necessary to brake because a driver two lanes over and slightly ahead of them did so, as well as those annoying asshats who just seem incapable of driving without touching the brake pedal every few seconds. How I cringe for their passengers and the uncomfortable ride they must be enduring.
I seem to be in the smallest of minorities, but my immediate reaction to seeing the brake lights illumninated on a car ahead of me is to double-check my escape route...that means I already know of a way around the guy stepping on his brakes (such as a lane change), but now is the time to glance around and make sure it's still open. Most of the time, the person braking has done so for no good reason and has already released their brake. If this isn't the case and they're still braking and/or my escape route isn't open, then I'll take my foot off the accelerator pedal and re-evaluate what's happening. Only in the rarest of instances am I ever in the situation where I am required to use my brake pedal.
I have a couple of ideas on how to discourage "brake pedal dependency": (intended to be tongue-in-cheek)
1 - Implement a one-quarter to one-half second delay between pedal actuation and signal illumination. This wouldn't do much for the ride comfort of folks who have been condemned to be chauffeured by a brake-tapping jackass, but it might soften their effect on other drivers.
2 - Deliver a mild electric shock to the driver every time she touches the brake pedal. The voltage should be modulated by a learning computer that analyzes the driver's braking patterns, ramping up the intensity on morons who "ride" the brake for long distances or repeatedly "tap" the pedal without actually slowing down, and reducing the shock when the pedal is firmly depressed.
I personally think that cyclists can (and should be able to) eat their cake and keep it. One of the great things about cycling is that you can hop off at a pedestrian zone, walk to the other end, and hop back on. Or hop off at the red lights, walk around, and hop back on on the other side. There is nothing at all wrong with this (except for annoying car drivers who feel slighted at being passed by a cyclist). If you are walking next to a bicycle, you are a pedestrian.
(Of course, if you are still riding, you are not a pedestrian - which I acknowledge is what you and others were moaning about and I agree entirely.)
Phukko here, sorry about the AC post, but y'all need to visit: http://vwisb7.vkw.tu-dresden.de/~treiber/MicroAppl et/
to see a most excellent set of simulations
The 'in a hurry driver' could have just as well been the idiot on the cell phone repeatedly applying his brakes for no reason, or the idiot who is staring at an accident in the other lane, or the idiot who isn't in a hurry but pulls out into the fast lane in front of a lot of people who are, or the idiot who keeps braking to maintain his 'safe distance' because he doesn't understand how to properly coast and doesn't realize that the real danger is not his 'safe distance', but the guy behind him who might be looking away for a brief moment when the idiot brakes for no good reason but his 'safe distance'...
In other words- its not caused by someone in a hurry or someone who wants to drive fast. Thats not it at all. Its caused by someone who causes braking!!! Thats usually not the guy who just wants to go fast....it can be if he is swerving in and out of lanes, but speed itself isn't the issue!!! People who drive fast are not the problem, its people who drive slow in the fast lane that are the problem! Get out of our way and stop traffic jams!!
But No! In a world where slowpokes are revered, we've got to pick on the fast drivers.
Have gnu, will travel.
I've had one or two times when I've been very glad that I use some sense with following distance. The thought process in these situations is something like this: "OK, I need to slow down now...... Oh, I really need to slow down now!"
I sure hope people aren't locking up their brakes (or engaging ABS) every time they see brake lights in front of them.
Are you sure? I get 98 feet.
70miles/hour * (60minutes/hour) * (60seconds/minute) * (5280 ft/mile) = 48 feet/second.
double it for 2 seconds of space ==> 98 feet.
They don't teach driving in high school.
You want a license in Europe, you need to spend big money on real driving classes and pass rigorous driving tests. You don't see as many idiots on European roads because the idiots don't get licenses to drive.
paintball
Google's Super Secret Search Algorithm: SELECT @search_results FROM internet WHERE @search_results = 'good'
I've driven my mother's wagon before and had no trouble merging. Why would you cut off a grocery getter?
Driving a friend's Mercedes, on the other hand, meant no one would let me merge.
They don't grade fathers, but if your daughter's a stripper, you fucked up. --Chris Rock
I spent 6+ hours driving from Manchester to London to catch a flight back to Boston yesterday; a 180 mile, a 3hr trip as predicted by the nav system. In fact, it took about as long to drive that 180 miles than it did to fly the 3250 miles to the US! What a mess, there was no good reason for the traffic, it was just stop and go all the way down the M1, then again on the M25, during a "holiday week" also. We only just made the flight.
The UK is a highly overcrowded, congested and polluted place. What with all of the cameras and taxes, I don't know why anyone wants to live there!
otherwise it stays quite conserved, thank you very much, right up to the point it starts to be used to deform the front, the engine, and your knees.
Except modern vehicles are designed to deform and therefore shed energy in the form of heat, well before the energy is transmitted into the occupant of the vehicle. Also most accidents occur through either distractions or velocity differentials. So you should pull over anyways.
I laughed at the weak who considered themselves good because they lacked claws.
Spot on, and Mr Bernoulli established the principles some time back, as I recall. Cars on roads are just another form of particle flow.
:)
To absolutely confirm the single twit driver effect on traffic flow in this discussion - back in the mid sixties I used to fly traffic watch for a local radio station. Once a year a tiny picturesque race track in the Adelaide hills would put on a gala race day. Every man & his dog turned up. The road into the race course was one lane each direction. From 1,500' at going home time you cwuld observe a fast flowing smooth laminar flow of rational drivers, until, that is, a single moron would decide to try travel faster than the mean speed, and pass cars ahead.
The entire traffic stream would be disrupted, with clearly visible waves of congestion expanding out in BOTH directions, forward and back.
The interesting thing was that the moron who had disrupted the flow was incredibly quickly locked up in the snarl, the snarl that he/she/it had personally caused
I've told that story for the last 40 years. From it I leant that if you are in a flow of traffic that appears to bogging down, the very best way to rectify things is to drop to a low gear, pick a rev/speed that seems to be about the current average traffic flow speed (even idle revs in low - but you must keep flowing/moving), and totally ignore everyone else. Within a kilometre you will see the traffic >aheadyou will be back up to speed, and you'll drag the rest of the traffic with you.
Until, of course, the next impatient moron decides to buck the flow.
Bernoulli rules, OK?