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Experiment Shows Traffic 'Shock Waves' Cause Jams
Galactic_grub writes "Japanese researchers recently performed the first experimental demonstration of a phenomenon that causes a busy freeway to inexplicably grind to a halt. A team from Nagoya University in Japan had volunteers drive cars around a small circular track and monitored the way 'shockwaves' — caused when one driver brakes — are sent back to other cars, caused jams to occur. Drivers were asked to travel at 30 kmph but small fluctuations soon appeared, eventually causing several vehicles to stop completely. Understanding the phenomenon could help devise ways to avoid the problem. As one researcher comments: 'If they had set up an experiment with robots driving in a perfect circle, flow breakdown would not have occurred.'"
You're missing the point of the experiment. Yes, in reality, something like that is incredibly likely. But the idea here is to study the effects other humans have on each other in dense driving situations.
Non impediti ratione cogitationus.
Actually if you're following at the correct distance you shouldn't need your brakes in all but the most extreme situations like getting cut off. I know I try to minimize breaking most of the time and in non-gridlock situations I can keep from touching my break pedal probably 80% of the time when the car in front of me touches theirs. It requires looking several cars ahead and easing off the gas well ahead of the ripple location but if more people drove like this I bet most of those stupid sudden stop points could be eliminated.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
It's a combination of people who ride slow in the left-hand lane and speeders. The people (whom I'd like to shoot) that pull over to the passing lane and then drive the same speed as the car to their right cause rolling road-blocks. When faster-moving traffic inevitably catches up to them, it can't pass, so it builds up into a massive pack of slow-moving crap. Then, sooner or later, someone taps his brakes, and then the one behind him does it just a bit longer, and so on and so forth, until there's a stop for no reason. Meanwhile, the jerk-off in the left hand lane at the head of this rolling traffic jam is still doing just fine at 50 MPH.
If police would enforce rules against driving too slowly (generally defined as being passed on the right (because if traffic is passing you on the right, then you need to get the fuck over)) as they do aggressive driving, the problem would be much less prevalent. Then, the faster moving traffic could pass the slower moving traffic, keep on going, and there wouldn't be any problems. Sadly, though, that's not the case in any metro-area I've dealt with. Instead, the jerkoff Sunday Driver creeping along at 50 in the passing lane just has to be dealt with, usually by getting around him in the right hand lane, then speeding up to 90 and cutting in front of him so you can pass the traffic on the right.
The louder he talked of his honour, the faster we counted our spoons. -- Ralph Waldo Emerson
Tailgating is THE problem.
I try to stay far enough behind the car ahead of me so that when he brakes, I merely have to remove my foot from the accelerator so I don't convert my kinetic energy to heat. Of course, some dipshit always sees the three car length hole in the thirty mph traffic (you're supposed to maintain 1 car length for every 10mph anyway but none of the fucktards in Springfield do) and fills it in.
If people maintained a reaonable distance (the 1 car lenhgth for each 10 mph) you wouldn't have this effect, or if it occurred it wouldn't be so bad.
Every time you touch your brake for any reason whatever you throw fuel away as waste heat.
<jk>(global warming comes from the hot air blowing out of the world's capitols)</jk>
-mcgrew
mcgrew's razor: Never attribute to stupidity that which can be explained by greedy self-interest
I really hope that this isn't truly a "new" discovery. If someone sits and thinks about it it should be really obvious. I have posted a basic explanation as a comment to a number of blogs and I'm not a traffic engineer.
Once traffic reaches a point of saturation ANY change is flow will bring traffic to a halt. This includes things like a road feature that makes people accelerate, a merging or diverging ramp, or a hill or corner that allows people to see farther ahead inducing them to adjust their speed.
Any change in relative speed will at some point cause a person to slow down. If they are accelerating they will slow when they get close to the car in front. If they are slowing then that is obviously a slow down. Each car behind this change reacts to it after a delay. The longer the delay the more they have to react. People tend to react much slower then they normally would because very few drivers focus primarily on driving. They only use the minimum attention that is necessary. This just makes the problem worse. It only takes a few cars for a subtle adjustment to become a complete stop. The length of time each successive car is stopped will become longer and longer.
To make the problem worse the same 1 to 2 second delay in reaction applies to the acceleration of the vehicles after the slowdown/stop. Every fraction of a second that a person delays accelerating is adding to the stacking of the delay.
To look at another aspect of a slowdown...
If you have a smooth flow of traffic at a fixed speed you will have a certain number of cars passing a point on the road per minute. If you have a slowdown you will reduce the number of cars passing per minute. But the traffic was already at a capacity flow so the number of cars feeding into this situation continues unabated. It is obvious that the flow of traffic is done until the quantity of vehicles feeding into the situation is drastically slowed to less then the flow of traffic at the restriction. (In Orange County, CA that means waiting till after 6:30PM for a situation that started at 3:00PM.)
What can be done about this without building a vastly increased number of lanes? (The I-405 is already 14 lanes in central Orange County. Increasing it to 20+ lanes would cost billions and in 20 years when they are done we would need 30+ lanes...)
A big improvement could be made through driver training (Yeah right...). Teaching people how to merge can reduce the constant forced slowdown from cars merging onto a freeway at less then freeway speed. The correct speed to merge at is 5 to 10 MPH FASTER then the flow of traffic. A car won't accelerate quickly but it will slowdown quickly so you simply drive down the on ramp picking the hole in traffic you will merge into and brake into that hole matching speeds. This minimizes the disruption. "Freeway Meters" on an onramp actually make this problem worse on a freeway that is still flowing at a reasonable speed because they reduce the distance that a car has to accelerate insuring that they enter the roadway at a reduced speed causing traffic to slow down for them.
Teaching people to slowdown after they are on an offramp will also help reduce the disruption to traffic flow. Most drivers slow down a minimum of 10mph before the exit the roadway causing large backups for open free flowing offramps.
To reduce the effect of slowdowns you can teach people to look past the car in front of them and try to slowdown before the car in front of them, which can reduce the quantity of speed they have to scrub off. If they look ahead and start to accelerate earlier this will cause a similar improvement in reduction of traffic impediment.
(Truth is that you will never be able to teach people to change their driving habits because their cell phone, their coffee, and their daydreams are way more important then driving the 1-1/2 tons of steel they are sitting in.)
I like the 3 second rule better than the car length rule. Regardless of your speed you should be 2-3 seconds behind the next car.
And yes. Tailgating certainly is a HUGE problem. What's most astonishing to me is how many people shrug it off as no big deal or even justify their own tailgating behavior by saying something like: "Well, it's much worse and more dangerous to be driving slow on the freeway." This is of course utter nonsense. Tailgating is insanely dangerous, leads to a huge number of accidents, and in my mind is the equivalent of pulling a knife on someone for taking too long getting their wallet out at the grocery store.
(I would love to see widespread police crackdowns on tailgating, but I'm guessing it's just easier to prove speeding in court so that's where the tickets go. Anyone know if that's it?)
http://nerdcartoons.com/
Well of course you're going to need your brakes. The point is using them as little as possible. If the light ahead is red, take your foot off the gas! The idiots who live here race from red light to red light. I'm always amused when some moron zooms past me as I coast along, only to pass him as he's starting from a dead stop at the now green light.
That as well as maintaining a reasonable following distance, traffic permitting.
Your post gave me visions of Frank Drebin hitting trash cans as he pulled up to a curb.
mcgrew's razor: Never attribute to stupidity that which can be explained by greedy self-interest
Right. In the area I'm in, I see that kind of behavior all the time. And you're right that it's a mentality and habit that follows the driver everywhere. I've had people tailgating me through 20mph school zones. For that matter, I've had people tailgate me in parking lots.
Another interesting aspect of the problem is how many people who aren't these kind of habitual tailgaters will become tailgaters when speeds drop, e.g., on exit ramps. They maintain a safe distance until the speed gets down to 50 or 40mph. Then it's as if they forget that much past 30mph is fatal crash territory, and they plant themselves one foot off the next car.
I think the root cause for all this is a lack of respect for how potentially dangerous driving is in general. You won't find large numbers of gun owners who play with guns like toys (though they're out there), but you can find plenty of people who treat driving with all the care and attention they put into watching TV. There just isn't enough respect for driving. If there were, accident rates would plummet. I'm just going to hold out hope for a day when reckless driving is rare.
http://nerdcartoons.com/
Your self righteous attitude is the cause of hundreds of lost hours of time for people all over the world. Instead of trying to be a one-sided-Buddha, teaching everyone patience, why not express some compassion and move over for faster moving traffic. Plus, if you are as patient as you wish other people to be you won't mind hopping into the slow lane for a few seconds.
Of course if you are motivated by some other less honorable sentiments you will continue to act as you do and feel justified and prideful about it.
Also, be aware that there are varying circumstances that may cause someone to drive faster than you. Your statement that it is because of some dissolusioned consumer fantasy belies your presupposition that the people who drive faster than you are somehow inferior to you. Believing a lie and then becoming irrationally angry with you because you show them the truth of the world makes an easy straw man to flatten. However, consider that you might be stopping someone from reaching an important destination in an appointed time. Like the time my father was in the hospital. His respiratory doctor called me and said he was not breathing without assistance and that I had very little time to get there to see him before the DNR orders took effect. I was across town at work and had no idea if I was going to get to see my father alive ever again. I cannot tell you how frustrating it was to deal with people *just* *like* *you* as I made my way to see if my father was still alive, to talk to me one last time.
But hey, one thing I have learned is that people act as they feel they must. Compelled is a good word. People who drive faster than me, I move over for them. People who drive slower than me, I just wait till I can pass them. Understanding that they have their own internal motivations that I probably do not understand makes it easier to live and let live. When I catch myself assigning characteristics, thoughts, and motivations to people driving near me I just take a deep breath and realize that I don't know why they are doing what they are doing and it is best to work cooperatively with people, even if I have never met them.
When the only tool you have is a claw hammer every problem starts to look like the back of someone's skull.