Comments on: How traffic jams are born

By: digi_owl

digi_owl — Fri, 20 Jan 2012 06:13:00 +0000

Ok Google, how is that car of yours coming along?

By: digi_owl

digi_owl — Fri, 20 Jan 2012 06:12:00 +0000

I am more inclined to remove the human element fully.

By: Antinous / Moderator

Antinous / Moderator — Fri, 20 Jan 2012 04:55:00 +0000

One of the comic (by which I mean tragic) aspects of driving in the desert is that, when it rains or even drizzles, people slow down to one mile per hour because it’s so rare that they’ve forgotten how moisture might affect the road.

By: Antinous / Moderator

Antinous / Moderator — Fri, 20 Jan 2012 04:51:00 +0000

I read an opinion piece decades ago where the author referred to pokey drivers as the Anti-Destination League.

By: Chris Helbling

Chris Helbling — Thu, 19 Jan 2012 16:17:00 +0000

Long ago, 1985, I was interviewing with the NY DEP at Stonybrook, LI, and over lunch we talked about this exact same phenomena, where beyond a certain speed (30MPH) the elasticity of the vehicles (yeah, they aren’t very elastic, but you get my drift) creates a wave front. I first saw an example of this in Toronto as a kid – an explanation of sound waves that involved a Slinky. Holds true with cars (didn’t get the job – too young). (extra credit: go to the kitchen sink, turn on the water, and observe. Same thing.

By: zax

zax — Thu, 19 Jan 2012 15:52:00 +0000

1. It is possible to drive very long distances without braking at all. (long distance is relative, I’m in the UK…but have made it from Lincolnshire to Devon only braking when I need to come to a complete stop. Made it all the way from Birmingham to Plymouth without braking at all!)

2. Tailgating seems to cause a lot of the problems on motorways. I’ve seen cars that are determined to get in front of the next 10 cars by sitting on their ass, constantly braking and accelerating. If folks calmed down a little then maybe there would be less jams.

3. Perhaps it’s time to start teaching people to drive in packs rather than waves. You know what I mean. When waiting at a stop light, each car waits for the one in front to move off, leaving 3-4 seconds between each car starting to move. This long-existing wave method only gets a few cars through the intersection at a time. If each driver was part of a pack and they all moved off at the same time much more traffic could get through (like the ski season methods mentioned above). For this to work properly some kind of automation would need to come into play at intersections with lights I guess…

By: ocatagon

ocatagon — Thu, 19 Jan 2012 15:00:00 +0000

The solution to all our problems is self-driving cars like Google is working on. We should be dumping tons of money into that research. It will revolutionize transportation.

By: Mladen Kalinic

Mladen Kalinic — Thu, 19 Jan 2012 13:53:00 +0000

I once sat in a traffic jam in a 3 lane motorway that wasn’t/barely moving for 2 hrs.

Reason?

They closed 2 lanes to install some cat eyes in the middle of the lane, and people who were about to clear the narrow bit were driving slow so they can see what’s going on.

And I see this almost every time, whenever someone sits in a traffic jam for ages that’s caused by narrowing of the road, their reaction is to drive away slowly once they reach the end of narrow bit, keeping everyone else in there at the same slow pace they are, instead of putting their foot down. In other words (and I’m sorry for swearing): “Fuck everyone else, I’m out of it”.

Typical lowlife selfish behaviour.

A very similar thing happens is when someone is waiting in a long queue, and once it’s their turn, they decide to rest their weary balls on the counter and tell the counter clerk their life story. Anyone who acts that way is scum according to me, and a lesser life form.

Sorry for being so harsh, but such behaviour pisses me off so much.

“If it doesn’t affect me, why should I care.”

By: Red Leatherman

Red Leatherman — Thu, 19 Jan 2012 13:40:00 +0000

I want to know why, every day, while driving at the posted speed with cruise control when there is over 100 yards in front and behind me that a car in the on ramp will inevitably appear directly beside me with the driver glaring at me to move out of his way.

By: hxa7241

hxa7241 — Thu, 19 Jan 2012 13:26:00 +0000

Also a phenomenon to be seen on London Underground escalators.

People walk up on the left, but then often stop just before stepping off. With enough people behind, a jam spreads back down the escalator.

Leave a gap in front of you as you walk– be a jam-buster.

By: Antinous / Moderator

Antinous / Moderator — Thu, 19 Jan 2012 05:54:00 +0000

Unfortunately, the car companies bought the government planners six decades ago and people now live fifty miles from where they work. So unless you have an extremely powerful magic wand, it’s not that simple.

By: EssEffOh

EssEffOh — Thu, 19 Jan 2012 05:38:00 +0000

for the love of christ people. get the f*ck out of your cars and stop crying about traffic jams.

By: knappa

knappa — Wed, 18 Jan 2012 03:17:00 +0000

What you are saying is roughly that, if everyone drove at exactly 30mph, then whatever spacing pattern the cars started with would simply rotate around the circle. While that’s true, it misses the point. The important feature that you are missing is that the drivers can see the distance to the car ahead of them and will slow down in order avoid hitting it.

By: pjcamp

pjcamp — Wed, 18 Jan 2012 03:10:00 +0000

In astronomy, we call this a density wave and it is what makes the lovely swirly characteristic of spiral galaxies.

By: Maggie Koerth-Baker

Maggie Koerth-Baker — Tue, 17 Jan 2012 23:53:00 +0000

Up here, we have visiting Californians gawking at loons, fall colors, and the presence of snow on the roadway.

By: jephary

jephary — Tue, 17 Jan 2012 23:38:00 +0000

Emergent traffic jams are a kind of hidden ecology that most of us recognize, tolerate or not. But from my experience drivers of the same sections of road or highway are as attuned to the ecology of traffic as any good hunter is to the signs of game in the woods. Is it past 3:15? Watch for that exit ramp and merge lane combo. Is it late after a ball game? (Or hockey in my neck of the woods) then expect a number of high speed mergers coming off the on ramp. We complain secondarily to witnessing and experiencing.

By: israel

israel — Tue, 17 Jan 2012 23:24:00 +0000

I’m with you on all counts, sir. I drive a truck for a living (although a local route rather than over the road), and have done a decent amount of driving trips longer than a couple thousand miles, and I agree how much people tend to suck at interstate driving.

Mostly though I like the idea of less autonomous, more efficient transpa to get our sorry asses to work and back (or walking/bicycling). That way we can have enough dino juice left to run our fewer remaining cars for fun on occasion. And I guess breathable air would be a benefit too.

By: lecti

lecti — Tue, 17 Jan 2012 23:05:00 +0000

Shooting drivers that keep feathering the brakes on freeway will be a permanent fix. They are beyond help.

By: Antinous / Moderator

Antinous / Moderator — Tue, 17 Jan 2012 23:00:00 +0000

A computer-driven car could stay very close to a constant 30 MPH

Does the speedometer even go that low?

By: exoskeletor

exoskeletor — Tue, 17 Jan 2012 22:50:00 +0000

“caused by one person braking” aha! interstate trolls!

By: exoskeletor

exoskeletor — Tue, 17 Jan 2012 22:48:00 +0000

ejection seats?

By: Stephan Wehner

Stephan Wehner — Tue, 17 Jan 2012 22:46:00 +0000

For another study of traffic jam patterns, see Traffic Zoology:

* http://www.trafficlife.com/page92.html

in my Traffic Life book!

Cheers,

Stephan

By: Antinous / Moderator

Antinous / Moderator — Tue, 17 Jan 2012 22:39:00 +0000

I live in a resort that fills up with Minnesotans and Manitobans every winter. Here it’s: “Slow down, Floyd! There’s a palm tree!”

By: tomrigid

tomrigid — Tue, 17 Jan 2012 22:20:00 +0000

In the case of this particular experiment there might be a simpler explanation: a zero upper-bound. Since cars can’t go faster than 30 MPH by the rule, but can always go slower (and often must), the average speed of the circular system must get dragged down.
A computer-driven car could stay very close to a constant 30 MPH, which would reduce (though not eliminate) this inevitable reduction.

note: above idea not edited for wrongness.

By: etherist

etherist — Tue, 17 Jan 2012 22:14:00 +0000

Growing up in L.A. I used to listen to “The Car Show” on the local Pacifica radio station. For a while, the hosts would close the show by saying “don’t lift” (makes sense if you do any high performance driving, relates to weight transfer) and “look down the road”.

I think drivers’ failure to “look down the road” contributes to these traffic waves.

No one obeys the tw0-second rule (supposed to be 3 or 4 seconds if road/traffic conditions are bad), and nobody is aware of anything that happens more than three car lengths ahead of them.. Hence multicar pileups in rain/fog/smoke. Maybe one driver in 20 uses cruise control on the open road.

Won’t be fixed until human nature is fixed.

By: Comedian

Comedian — Tue, 17 Jan 2012 21:55:00 +0000

Way back in the late 1980s I took a civil engineering survey course to fulfill a required out-of-major elective.

One third of the class was about traffic flow & controls, and I remember this effect being covered pretty well even back then.

They even used the term “shock waves” to describe the compression of cars traveling away from where it began.

http://www.fhwa.dot.gov/publications/research/operations/tft/chap5.pdf

More modern reference, but look though the references, many dating from the 1980s and before.

I imagine a lot of topics are like this. Casual web browsers operating outside of their areas of specialization think something is new, while specialists in the topic are so far removed from the conversation that they don’t bother to engage in a dialog.

(Ah, the benefits of a classical [engineering] education.)

By: Lagged2Death

Lagged2Death — Tue, 17 Jan 2012 21:53:00 +0000

It’s really interesting that even though the science is explicitly and accurately summed up with “Once you have enough density of cars on a road, jams are inevitable,” some of us here still comment as though blame can be assigned to someone, somewhere. To some class of habit, to some style of behavior, to some demographic of drivers, etc.

But there’s no mystery here. If you’re in a traffic jam, it’s your fault; you are part of the density that made the jam happen. You knew it was a possibility when you got behind the wheel; be an adult and stop blaming other people for your stupid first-world problems. Jesus.

By: lorq

lorq — Tue, 17 Jan 2012 21:41:00 +0000

I remember noticing this effect about 20 years ago in, of all things, a shot of moving traffic in “Koyaanisqatsi”. It wasn’t one of that film’s many time-lapse shots, but rather a normal-motion shot in which the camera gradually tilts upward to reveal a long line of cars on a freeway. Quite by accident, the shot happens to capture a slinky-effect shock-wave traveling slowly up the line of traffic. I remember noticing the wave and saying, “Of course! That would have to be how a traffic slow-down works!” So for the last 20 years — as others have indicated here in their posts — I have kept a generous distance between me and the car in front of me, while maintaining as near a constant speed as I can. (It takes some restraint, since you have to decouple your own car speed from that of the one in front of you, and resist the urge to close the gap when it starts receding from you.)

By: Mike Birtwistle

Mike Birtwistle — Tue, 17 Jan 2012 21:36:00 +0000

Hey Kids, there’s Buckingham Palace!

By: andygates

andygates — Tue, 17 Jan 2012 21:31:00 +0000

Be interesting to see a repeat with superhuman reflexes (ie, robocars). I’d assume a robo carousel.

…and
a repeat with a mixed driver cohort. Can one lone human screw up a robo carousel? Would a minority of humans do it? Half-and-half? Or could a mere salting of robocars nudge the density of condensation up so the jams happen less?