Japanese Researchers Search for Solution to Traffic Jams
Now, researchers from several Japanese universities are studying the so-called "shockwave" effect in hopes of learning how to prevent traffic jams. According to The New Scientist, "shockwave" is a concept that has been around for a while and describes the way a single driver slowing down can cause a chain reaction that eventually halts traffic. The researchers were the first to create a full-scale experiment to test the theory.
To do so, they had 22 vehicles drive around a 230-meter one-lane circle, then watched how the drivers reacted. Sure enough, a shockwave eventually mired the circuit in gridlock every time.
The researchers attributed the cause of the shockwave to simple human error. If robots were allowed to control the cars, they could maintain consistent speed and intervals with ease, but unfortunately it turns out we humans are far too … well, human.
We get distracted or nervous and slow down our car, which in turn begins to slow traffic in the rearview mirror. Before you know it, you have a full-scale traffic jam. Isn't it funny to think that the maddening gridlock that makes you want to blow open a vein might be caused by nothing more than a driver tapping the break to change the CD?
Shockwave Traffic Jam Recreated for First Time (The New Scientist via Slashdot)
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Sounds really simple except they missed one thing.
Take a mile of road with three+ lanes and a speed limit of 65mph, then fill it with cars going 75+mph with 2 car lengths between them.
Here's what they missed, add 2 on ramps pumping out one car every 10 seconds into the mix and have them merging at the same speed as the current traffic.
All the cars are maintaining the same speed. The flow is great except you start to get 1 car length between cars as more vehicles join the flow. Pretty soon there's no more space for more incoming vehicles.
This is what happens on any freeway in California at 4pm. The volume exceeds the road capacity. I'm not sure how a robot would make this situation better since spacing and speed are affected by the volume increase.
It's time to ration the freeways. You are only allowed to drive on certain days, depending on your license plate number. The other days you find mass transit or car pool. Congestion solved. Of course that would be unneccessary if people exercised some common sense and lived near where they work, and didn't do the 40 mile one-way commutes.
Highways are designed on the concept of fluid dynamics. It's all about flow. Stop lights and intersections are impediments to flow.
This is not a new idea. Studies of emergent phenomenon in traffic flow have been around for years.
Even in a relatively sparsely populated road you can get a phase transition between the "free" state and a "congested" state from pretty much any minor input. The automobiles will then coalesce into this denser state in a wave traveling backward through the traffic at a certain speed. Pretty much anything can serve as an input; an accident, an onramp, an offramp, someone changing lanes, a drop in speed limit, even an increase in speed limit.
As a result of this, simple fluid dynamics does not properly address the mechanics of traffic flow. There is no order parameter in fluid dynamics, and each automobile does not behave autonomously in a sort of geometric brownian motion neglecting an overall potential difference. Studies have been done both using real world data and computer simulations and they agree. I haven't heard of a controlled test before, so I guess that's where this study is novel. Unfortunately this has yet to provide us with a solution to the problem, but understanding what the problem is, is a step in the right direction.
It happens every single day I get off from school. Everytime I pass that very same part of the trip, there is a backup for no reason whatsoever, and people just stops there. Bunch of idiots. It gets worst when it is a snow day. They would jam their brakes for no reason. Don't they understand that by slamming the brakes hard will actually cost them the control of the vehicle?
I am sure that there are places where you can't avoid traffic jams but in many places it can be easily avoided. All you need is a common sense. Drivers are the Problem. Many times you have these places where couple on-ramps come in with the good number of cars and everything goes to a stop and go. The reason is because every driver is trying to get ahead. They try to go 75 in 55. They switching lanes right and left, they speed up and then they must brake. Every car behind start to react and as result it all stops.
But what if they would approach this part of the road with the speed below limit, switching to the left lane as needed to let others to get in and stop accelerating and braking, just drive steady and below. Don't change lane with purpose of passing.
I am sure that many times you can create a flow. not 75mph flow but 35mph instead of speed and brake.
Another day I was driving in such situation. And I saw my cousin driving parallel to me. We opened windows and say "Hi" to each other. In front of us there was a mile of cars bumper to bumper. While keeping our cars leveled to be able to speak we fell about 10 yards behind the stop and go 3mph cars. And guess what? The driver behind blew the horn, like if we were slowing anything there. This is exactly reason why most jams occur. People just want take the road for themselves without consideration of others. I can only suggest to read a drivers manual, which says:
1. Driving is a privilege, not right
2. Driver must drive in the right lane of two or more lanes roads at all times unless this driver drives faster then cars in the right lane
3. Driver must not cross any whole lines, only dashed lines are crossable and some can be crossed only in one direction
4. Driver merging into traffic can’t drive with the speed greater then cars on the road into which this driver is merging
I can find more.
Driver's manual? What is that, something published by the government.
The US Supreme Court weighed in on the matter (in the 1970 if I remember correctly). Driving is a hybrid privilege-right. Not everyone can hold that right, you need eyes that work [I am sorry blind people], ears that can hear [I am sorry deaf people], and an inner ear accelerometer [I am sorry people with vertigo]
and either the people have forgotten, or were never told. With rights come responsibility. You don't monopolize the road system, you don't drop nails onto the roadway, you don't spill oil and other fluids onto the center of the road [think of motorcycles]
Tony:
"In front of us there was a mile of cars bumper to bumper. While keeping our cars leveled to be able to speak we fell about 10 yards behind the stop and go 3mph cars. And guess what? The driver behind blew the horn, like if we were slowing anything there. This is exactly reason why most jams occur."
yes, too many idiots cannot see that if there is a stoppage ahead (however brief), it simply MAKES NO SENSE to rush up and have to brake.
i am always immediately OFF the gas and coasting as soon as i see i will have to stop. having slowed, it does take more time to traverse the empty road to that point. BUT, in that extra time, the need to stop may be gone, and i OFTEN NEVER HAVE TO MAKE A FULL STOP.
sometimes an impatient driver will pass me as i coast down, only to have to come to a full stop. if i'm fortunate to still have my lane clear, i will ZIP RIGHT PAST him, never having to make a full stop, still CARRYING MOMENTUM and re-accelerating more easily, burning less fuel.
i end saving engine and brake wear, AND GAS. i actually get better mileage LOCALLY driving in this manner, than on trips where i often sustain 65 -75 mph and my engine is constantly running at higher speeds. a difference of ~7 mpg. and i don't even drive a Hybrid!
thots more related to this blog subject:
with a goal of keeping the whole line in motion (even at a very low speed), vs. a jerky constant stop, go, creep, stop, go, repeat-- i have found that the most effective way to help this occur, is to have EVEN SPACING.
every time i come up on two or more cars that i know i will not be able to pass, i adjust my speed so as to maintain the SAME DISTANCE to the car ahead, as it is maintaining to the next car further ahead. the next car behind me will often tend to follow the pattern.
this allows the maximum space for ALL cooperating drivers to accelerate OR decelerate together, if/when the leading vehicle changes speed.
if this is happening on a multi-lane highway and we are all going "bumper to bumper at 75 mph," people WILL NOTE in their mirrors that the person behind is as confident (and presumably as competent) as they are, in close quarter driving, and will tend NOT TO MIND someone as close to their rear bumper as they are to that of the car ahead. drivers in adjoining lanes will NOT be tempted to squeeze in.
any driver NOT competently maintaining the same close distance, WILL TEND to have someone cut into the larger gap he keeps in front. then another, and another, and he will fall back in the line. and hopefully OUT of this fast moving lane, eventually.
so a WHOLE BUNCH of cooperating drivers moves UNIFORMLY fast, in a compact group. until they come up to some idiot IMPROPERLY sitting in the fast lane and slowing the whole line.
i have not done a formal study, but imho, this is the KEY to fast, high volume movement.
theoretically, ideally, ALL DRIVERS in the fast lane NOT CONFIDENT having a following driver close to their rear bumper, should GET OUT OF THAT LANE!
drivers who are not uncomfortable, should SPEED UP to a pace at which they can still be fairly comfortable. and, it goes without saying, maintain a certain level of ALERTNESS. the following driver will often TEND to do the same, at an elevated speed comfortable to both. other drivers also comfortable at that higher speed in close quarters, could latch on. anyone NOT comfortable (or simply having an exit coming up) would simply leave that 'express lane.'
so ideally, the leftmost lane contain ONLY fast, alert drivers comfortable and COMPETENT to drive in close quarters at say, 85 - 90+ mph.
the next lane over, just drivers who are comfortable and competent at 75 - 85. the third lane, for 65 - 75. and the 4th lane, a MINIMUM of 60-65, except for entering and exiting traffic.
theoretically, this will allow for MAXIMUM VOLUME at a MIX of speeds at which drivers sort themselves out, according to level of competence/confidence.
and NO LANE would be obstructed by a single driver who is NOT comfortable/competent and in the WRONG lane for his/her preferred speed.
to make this IDEAL HIGH FLOW freeway system work, traffic officers would have to re-focus their efforts at enforcing MINIMUM speeds and LANE DISCIPLINE. enforcing totally arbitrary limits at the top side, is actually COUNTER productive. after all, today's car are perfectly capable of running at 90 - 120 mph speeds in PERFECT SAFETY.
the above scheme would still leave lanes open for the dawdlers who won't go above 65. the latter just need to STAY IN the lanes designated for them.
until this most sensible scheme can be implemented, we can all informally adopt it NOW. simply follow this basic rule:
If you are not comfortable with someone hanging on your bumper, MOVE OVER to the right. OR SPEED UP. (if necessary, do both.)
If people do understand, why would they accelerate just to decelerate?
When I am riding with my dad while he drives on the minimum speed limit. I often see people exiting the highway speed up on the exit ramp right after riding on my dad's ass for a mile. What's the point?
I agree with J, its silly. Even when people can plainly see they're going to stop soon, they often floor it. People need to chill out and stop trying to speed up to gain nothing.