Traffic waves - Page 2

dar512 · 06-11-2004, 05:03 PM

Quote:

Originally posted by Carbonated_Brains
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 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!

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.

Carbonated_Brains · 06-11-2004, 11:31 PM

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.

lumberjim · 06-11-2004, 11:58 PM

Quote:

Originally posted by Carbonated_Brains
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?

Carbonated_Brains · 06-12-2004, 12:05 AM

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.

lumberjim · 06-12-2004, 12:42 AM

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.

Carbonated_Brains · 06-12-2004, 12:48 AM

Dude, righteous.

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

You're totally in the clear with that statement.

vsp · 06-14-2004, 08:22 AM

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.

Carbonated_Brains · 06-14-2004, 09:07 AM

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.

russotto · 06-14-2004, 01:43 PM

Quote:

Originally posted by Carbonated_Brains

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.

Carbonated_Brains · 06-14-2004, 01:56 PM

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

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

Clodfobble · 06-14-2004, 01:59 PM

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

Carbonated_Brains · 06-14-2004, 02:30 PM

Here are the photos:

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

8 people died, which is hard to believe.

xoxoxoBruce · 06-14-2004, 02:40 PM

We do ok.

russotto · 06-16-2004, 09:08 AM

Quote:

Originally posted by Carbonated_Brains
Ah, but can you manage an 87-car crash?

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

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.

Carbonated_Brains · 06-16-2004, 09:11 AM

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.

06-12-2004, 12:42 AM	#20
lumberjim I can hear my ears Join Date: Oct 2003 Posts: 25,571	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. __________________ This body holding me reminds me of my own mortality Embrace this moment, remember We are eternal, all this pain is an illusion ~MJKeenan Last edited by lumberjim; 06-12-2004 at 12:54 AM.

06-14-2004, 02:40 PM	#28
xoxoxoBruce The future is unwritten Join Date: Oct 2002 Posts: 71,105	We do ok. __________________ The descent of man ~ Nixon, Friedman, Reagan, Trump.

06-11-2004, 11:31 PM	#17
Carbonated_Brains Does it show up here when I type? Join Date: Oct 2003 Location: Between the smoky layers of a prosciutto sandwich! Posts: 355	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.

06-12-2004, 12:05 AM	#19
Carbonated_Brains Does it show up here when I type? Join Date: Oct 2003 Location: Between the smoky layers of a prosciutto sandwich! Posts: 355	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.

06-12-2004, 12:48 AM	#21
Carbonated_Brains Does it show up here when I type? Join Date: Oct 2003 Location: Between the smoky layers of a prosciutto sandwich! Posts: 355	Dude, righteous. I'm merely being a physics sick-up-my-ass about the situation. You're totally in the clear with that statement.

06-14-2004, 08:22 AM	#22
vsp Syndrome of a Down Join Date: Jun 2001 Location: West Chester Posts: 1,367	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.

06-14-2004, 09:07 AM	#23
Carbonated_Brains Does it show up here when I type? Join Date: Oct 2003 Location: Between the smoky layers of a prosciutto sandwich! Posts: 355	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.

06-14-2004, 01:56 PM	#25
Carbonated_Brains Does it show up here when I type? Join Date: Oct 2003 Location: Between the smoky layers of a prosciutto sandwich! Posts: 355	Ah, but can you manage an 87-car crash? http://www.drivers.com/article/324/

06-14-2004, 01:59 PM	#26
Clodfobble UNDER CONDITIONAL MITIGATION Join Date: Mar 2004 Location: Austin, TX Posts: 20,012	Aw, I went expecting to see pictures... what a ripoff.

06-14-2004, 02:30 PM	#27
Carbonated_Brains Does it show up here when I type? Join Date: Oct 2003 Location: Between the smoky layers of a prosciutto sandwich! Posts: 355	Here are the photos: http://www.ctscoxons.com/job.htm 8 people died, which is hard to believe.

06-16-2004, 09:11 AM	#30
Carbonated_Brains Does it show up here when I type? Join Date: Oct 2003 Location: Between the smoky layers of a prosciutto sandwich! Posts: 355	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.

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