Traffic waves
 

http://www.amasci.com/amateur/traffic/traffic1.html

Might as well start its own thread rather than hijacking again.

Since I read the above piece, I drive the Schuylkill Expressway differently. I use the principles the guy talks about.

And I feel great about it, and I'm absolutely certain that I'm making a difference.

I don't drive in traffic jams very often, because I'm a public transportation kind of guy, but when I do, I try to do the same thing. It works out well.

(from the article)

Rolling barriers made of State Troopers

OK, so here's how to dissolve a major interstate traffic jam. Start many miles upstream from the jam. Put a row of State Trooper vehicles across the road and have them drive towards the jam. They drive perhaps at 55 rather than 70 as everyone else had been driving. Nobody can get by them, and so all the traffic behind the State Troopers is moving at 55 or so. In front of them a vast space opens up. After many minutes, the traffic which had been feeding into the city traffic jams simply stops arriving. There is no new traffic for many minutes. The huge jam trickles away. Just as the last of it is gone, the row of State troopers and the 55-mph traffic arrives, and the jam has been transformed into miles and miles of slightly slow traffic upstream from the old location of the jam.

This actually happened years ago in MD. I was driving along I-695 towards the city, and suddenly the traffic slowed down, and everyone seemed to be rolling along at the same speed. This continued all the way to the I-95 exit split to go to Baltimore City (north) and Washington, D.C. (south). As I was bearing off to the BC 95N exit, I looked to my left at the traffic that was continuing on I-695 S. I saw that there had been a state trooper in each lane going exactly 55MPH (when it was 55mph..it's now 65mph). Later on that day, I heard about the new "rolling roadblocks" that the MD state troopers were trying out. Funny thing...I only remember it that one time and not hearing about it after that...strange...

I thought it was kinda sneaky, but clever. :D

I wish we had a viable mass transit here in LA. I take the metro trains whenever I can, but the system is not very useable yet. It doesn't go many places, is expensive, and the trains are almost an hour apart.

-sm

Aren't every two points in LA about an hour away from each other by car anyway?

i didnt have to read the link to know what it said. ask jinx. i've been commenting on this effect for years. one asshole can spill his coffee, and there will be waves for hours. i try to keep a steady speed to "erase" the waves when i can. i love the gif on the top of the page, it looks just like i imagined it in my little pea sized mind.

it's about cumulative reaction time lag. i try to look at the car in front of the one i'm following for my cues. keeping a peripheral focus on the one right in front for any unexpected idiocy, of course ( is that an oxymoron when the topic is traffic?...."unexpected idiocy", that is)

that's what I call "protecting and serving" way to go, cops.

IIRC, tw brought this up some time ago...and russotto refuted it. Where are those 2?

I think they tried the rolling roadblock concept on the PA Turnpike between Ft Washington and King of Prussia during one of the construction phases.

The 55mph Maryland rolling roadblocks were for speed enforcement. Didn't last too long, probably when Maryland realized they weren't getting any revenue from it. Anyway, they caused massive traffic tie-ups behind them.

Anyway, you can try to eat traffic waves on the Schuylkill expressway, but it probably won't work. #1, Schuylkill drivers will pull in front of you as soon as you leave a gap. #2, the waves on the Schuylkill are generally caused by physical features (curves and interchanges). As for his other techniques -- use them, and you're contributing to a jam behind you even as you may alleviate the jam in front of you.

Wave def'n: A disturbance traveling through a medium by which energy is transferred from one particle of the medium to another without causing any permanent displacement of the medium itself.

Just to be anal :D it's not a wave, because the cars (the medium) are moving permanently down the line. For it to be a wave, and it would be a longitudinal wave because you're describing compressions and rarefactions, the cars would have to drive forward, shift into reverse, and repeat!

To redeem myself from this brash attempt at being technical, check out this traffic simulator

Bam!

My concern in driving 270 and 495 around D.C. is that people will swerve in front of you whenever you leava a space. I have enough of this as it is because (defensive driving) I always leave a bit more space between me and the car in front so that I have time to react to anything the driver in front might do, and people cut in front of me.

I like to observe how little difference it makes if you lane change.
While it may seem that the lane next to you is going along faster, it soon slows and you pass the cars that had passed you. Though I have seen some really agressive lane changers who seem to work their way ahead by shifting to another lane, then shifting back again. Accident waiting to happen.

The Front Range of Colorado is as bad as any place. My second favorate "worst" commute is the stretch on I-25 between Colorado Springs and Denver. Forget about safe following distances - the other drivers won't allow you to create one. The moment you create a safe distance between you and the car in front of you, someone else switches lanes and fills it. So there we all are, a speeding wall of metal objects filling both lanes of the I going 80mph bumper to bumper and this wall is 60 miles thick (distance between the two towns). I make that drive with every one of my senses on red alert, constantly eying the cars behind me and to my left or right as well as trying to keep an eye on the traffic up ahead for those tell tale red break lights, meaning that in just 3 seconds we are all going to be collectively standing on our brakes, and I hope all the members of the team of the moment are up to their game today.

In number one spot for driving thrills is the stretch of I-70 from near Vail to Denver. Its an extremely mountainous part of I-70 with plenty of sharp curves and fairly steep grades and Vail is about where the congestion starts. Once again its bumper to bumper, 80mph all the way in to Denver. The fun starts if its after dark and raining. You'd think folks would slow down under these conditions but NO- oh! Try and slow down yourself and you're likely to be rear- ended by drivers coming up from behind. So there we all are, like a pack of crazed Mario Andretti's taking those slick, wet mountain curves at 80 mph with extremely limited visibility all the way into Denver. I guess its Colorado's answer to population control since there have been quite a few traffic fatalities due to this mass driving technique.

my worst driving experience
 

The Pacific Coast Highway. California. Four lanes of bumper to bumper moving at 70mph (55 zone). Sheer dropoffs to the left and high, steep mountains to the right. Wife is reading aloud a news story about trucks with bad brakes. I point out the stream of logging trucks (ever seen a loaded one?) coming down the mountain roads to the right at 65mph or so with NO MERGE AREA!

Wife about pisses herself and forces me to take an alternate route home. I myself was not pleased about the mentality of those drivers although in fairness, they were more or less courteous and seemed to know what they were doing. It was more like being a cow in a stampede....everyone going in the same direction at the same speed and no fair trying to change anything suddenly. Turns and lane changes had to be set up miles in advance.

Brian

Yeah, I've seen 'em. We've got them here in Colorado (logging trucks), and they REALLY have them in Idaho where I lived for a year once. I think it must be a mandatory requirement to get a job driving one of those things that you be hopped up on methampetamines at all times. Those guys are CRAZY!

The highway is the medium, the cars are the particles.

Actually this is exactly analogous to sound waves. Sound consists of layers of greater and lesser compression in the air.

No, there is no medium AND set of particles

The particles ARE the medium. The road has absolutely no displacement, and thus is not part of the wave. Think of a sound wave in oxygen; the "particles" are the oxygen atoms, what would the medium be...?

And it's similar to sound waves, but definitely not analogous. In sound waves, the compressions and rarefactions are caused by the back-and-forth motion of air particles, NOT the permanently-forward motion of cars.

could the reaction time of the drivers be analogous to a medium?

there may not be physical contact between the medium and the particles, but the fact that the drivers will not allow the cars to collide(if possible) ensures a medium 'like' response within the wave. In other words, the drivers each maintain their own medium for their particle, so it doesn't really matter that there "IS" no medium. an imaginary one sufices.


how's 'at?

But...I wave doesn't have a distinct medium and particles! No wave does!

The particles are always the medium! The definition of medium is "a whole whack of particles"!

And when you think about it, it makes no difference that the cars don't crash into each other. Whether you smash your car into the other one, or maintain 1 foot of separation before smashing, you're still mimicking the same motion.

ok, i don't know about all that book larnin' stuff, but all i'm saying is that although there is no physical component of a traffic wave that is analogous to the physical components of a real live wave, be it a soundwave or waves in water, or whatever, the time between the cars acts in an analogous fashion. the back and forth motion could be akin to the variance in different drivers' reaction times to stressors like brake lights, or the image of the car in front of you accelerating. if driver b reacts to driver a in 1 second, but driver c reacts to driver b in 1/2 a sec, then you get your "reverse effect" between b and c.

whatever the analogy, the observable data is similar to ripples in water, but linear instead of circular.

Dude, righteous.

I'm merely being a physics sick-up-my-ass about the situation.

You're totally in the clear with that statement.

Thought about this thread this morning while navigating the usual 202 North - 30 Bypass merging bottleneck...

Basically, it's common-sense stuff; if you act in ways that makes merging easier, it'll ease the flow of traffic in general.

My pet aggravation on the highways isn't the guy who won't let people merge in front of him, however -- it's the guy who has no clue how to merge properly.

Quick description for out-of-towners: The 30 Bypass is two lanes that feed into 202 North (the major highway, which is also two lanes) from the right. So 202 goes from two lanes to four, then to three, then to two within the space of a mile or so. In the morning when everyone's rushing towards the Great Valley corporate parks and the Schuylkill Expressway, all four lanes are typically packed.

(Pause now while I act proud of myself that I spelled Schuylkill correctly on the first try without looking it up.)

The reduction to three lanes isn't typically a big problem, but the third (merging) lane ends up with a lot of traffic. There's a decent stretch of straightaway before that lane closes, plenty of time for people to find a gap and merge to the left. I tend to leave such a gap as often as possible, particularly when trucks and other large/slow vehicles are to my right.

When I see vehicles in the merging lane IGNORE such gaps and zoom ahead, determined to use up every last inch of asphalt in the merging lane (and often a fair amount of shoulder after that), roaring up to the very last possible place to merge and forcing traffic to halt so that they can rejoin traffic, I want to throw grenades out my window at those responsible.

And even they're not the biggest idiots on the road. Those would be the bozos who are in Lane 2 (the right-hand straight lane) and MOVE INTO the merging lane on the right, knowing that they're going to have to merge back in half a mile, but that they'll be able to speed up and move a whole three car lengths ahead by doing so.

All you Americans are hilarious.

Try commuting to Toronto during rush hour, along any of the highways that go into Toronto.

401 is the busiest highway in North America. It has a stretch that is considered the world's longest piece of 12+ lane highway.

On a drive that would normally take 25-30 minutes with no traffic, you can expect between 1 and 3 hours to drive.

Big deal; the Philadelphia area Surekill Distressway can manage that with only four lanes.

Ah, but can you manage an 87-car crash?

http://www.drivers.com/article/324/

Aw, I went expecting to see pictures... what a ripoff.

Here are the photos:

http://www.ctscoxons.com/job.htm

8 people died, which is hard to believe.

We do ok. :)

Heck, no. We're crazy, not stupid. Once the first half-dozen or so are finished crashing, the rest pretty much stop. A few minor collisions occur in the backup, of course.

When visibility goes down to ONE metre on 10 lanes of highway, 100km/h speed limit, I don't think it's stupidity that causes people to crash. I think it's inevitability.

In studies of drivers in foggy conditions, a rather surprising result. When the fog got thicker, some drivers would actually drive faster. Furthermore, those drivers would claim they had not increased their speed.

Yeah, but even an American visiting Toronto has enough sense to stay the hell off of 401 during rush hour. Toronto is a grid city and alternatives abound. I started to say "stupid" American but then realized that I don't become stupid till I leave Ontario and cross over into Quebec :)

Come to Washington DC, the most retarded traffic circulation system in North America and see how long it takes to get to DC from the hinterlands of Virginia or Maryland. Oh, and you only have ONE road to choose from - if its blocked, bend over and "crack" open a jar of vaseline. Even if you have advance notice of a backup, there are no alternates. Toronto, on the other hand, has many alternates for any given route.

I think you're a little mistaken. Maybe for a dozen kilometres within the city core, the 401 can be circumvented...we even built a toll-highway specifically for that purpose...but if you're going anywhere else, there is no other option. The 400 series highways are main arteries in Ontario, there's really no alternative in many cases.

And when there is, it's usually a 50km/h speed limit road with stop signs every block...try driving 200km on that!