traffic
I’ve been reading and enjoying Tom Vanderbilt’s book Traffic, which led me to his interesting blog, which led me to this terrific story on Wired:
If humans took their cues from ants, they might spend less time in traffic.
When opposing streams of leafcutter ants share a narrow path, they instinctively alternate flows in the most efficient way possible. Studying how ants manage this could provide the basis for a system of driverless cars running on ant traffic algorithms.
“They never get stuck in traffic,” said Audrey Dussutour, a University of Sydney entomologist. “We should use their rules. I’ve been working with ants for eight years, and have never seen a traffic jam — and I’ve tried.” . . .
Dussutour’s team found that ants leaving the colony automatically gave right-of-way to those returning with food. Of the returning ants, some were empty-mandibled — but rather than passing their leaf-carrying, slow-moving brethren, they gathered in clusters and moved behind them.
This seemingly counterintuitive strategy — when stuck behind a slow-moving truck, are you content to slow down? — actually saved them time. . . .
If ants in the experiment behaved like the average human driver, they’d routinely run head-first into each other, causing insect versions of pile-ups and gridlock. Dussutour’s team calculated that patience reduced the average delay experienced by an individual ant crossing a crowded three-meter bridge from 64 to 32 seconds.
“One dominating factor in human traffic is egoism,” said University of Zoln traffic flow theorist Andreas Schadschneider. “Drivers optimize their own travel time, without taking much care about others. This leads to phantom traffic jams which occur without any obvious reason. Ants, on the other hand, are not egoistic.”
The Wired story, in its inevitable technophilic way, suggests that the proper lesson to be learned from this research is that we should create a system that would drive our cars for us according to the leafcutter-ant algorithm. Not sure whether even this President and this Congress could come up with a stimulus package big enough for that, which raises the question: is there any other way to prompt people to learn these lessons? Or is unthinking, reflexive egotism invincible? It seems to me that the prime problem here is that the leafcutter approach only works if pretty much everyone applies it. I’m not sure that partial compliance would have much effect.
UPDATE: I should have added here Reihan’s tribute, a year ago, to Hans Monderman. Seems relevant, since what Monderman discovered was ways to encourage good behavior without legal or technological compulsion.
I wish I could give you a citation, but years ago I heard a traffic engineer talking about traffic as an organism, with roadways as its natural habitat. His theory went something like this:
Like any other organism, traffic population will grow until it fills the available habitat. Once the habitat is full to capacity, the population will level off at the carrying capacity of the habitat. He went on to say that any increase in carrying capacity (adding more lanes to highways, increasing the efficiency of the use of existing lanes, or building more roads) will offer only temporary relief from congestion, and that the traffic population will eventually grow to whatever the carrying capacity of the habitat; and that the only way to reduce traffic was to reduce the available habitat.
For myself, I hate being stuck in traffic almost more than anything else. At this instant I can’t think of anything that make me feel more foolish or wasteful or lacking in foresight. The longest regular commute I’ve ever had was about 1/2 mile by bicycle, and I go to (probably irrational) lengths to avoid making trips to anywhere at the same time that everyone else has to make the same trip.
— Tony Comstock · Feb 11, 03:29 PM · #
Obligatory xkcd: Highway Engineer Pranks
— Mike S. · Feb 11, 03:51 PM · #
Fascinating. And in response to your (possible rhetorical) question about possible alternatives to “reflexive egoism,” I immediately thought of a piece in last Sunday’s Times about nudging.
— Maureen Ogle · Feb 11, 05:48 PM · #
Thanks, Maureen — I had known about Nudge but, being a non-wonk, had forgotten.
— Alan Jacobs · Feb 11, 10:19 PM · #
Well, when the day comes that cars drive themselves (I can’t decide if that’s 10-20 years from now or 50…), manufacturers might manage to work out some system like this. There’s a lot less of a coordination problem when you’re talking about 10 major companies than 100 million Americans.
I also wonder if egoism precisely the term for what happens. My experience is that I’m much more concerned about traffic and having to slow down when I am driving. I think it’s something to do with having to actively direct the car while being frustrated from doing so in the way that comes naturally for me. As a passenger, my response is “meh” unless the traffic is absolutely terrible. I lose the same amount of time either way, but it only gets to me if it’s my own activity of driving that is impeded.
— Justin · Feb 11, 11:35 PM · #
Another peeve of mine is following distance, and I wonder where might fit into the conversation.
As best I can, I try to observe generous following distances. There’s simply no reason to ever hit the car in front of you. But try as I might, when driving on the LIE in crowded conditions, other drivers will “fill in” the space I try to maintain between my vehicle and the vehicle in front of me. There’s nothing quite like the heady thrill of running bumper to bumper at 75 mph, a thrill I hate very very much.
The whole thing reminds me of Talebe’s 10,000 barrel Russian Roulette analogy in “Fooled by Randomness”: incidence is not the same thing as consequence. You can pay for half a lunch, but you can’t pay for a 1/10,000 of a bullet to your brain.
Anyway, we already know how much pain the average person is willing to endure for the “freedom” of driving their own car to work. Look at any metro area and it’s clear that the threshold is high. Unless or until the willingness, nay eagerness to sit in bumper to bumper traffic (or worse, fly along at 80 mph!) changes, no amount of technology will change things.
— Tony Comstock · Feb 11, 11:51 PM · #
I am not sure if the ant approach could work when it comes to human traffic. The main aim of what the ants do, it seems to me, is that they maximize the gains for the group as a whole. So how will huddling behind a slow moving truck help me get to where I want when I want?
— scritic · Feb 12, 01:53 AM · #
“I am not sure if the ant approach could work when it comes to human traffic. The main aim of what the ants do, it seems to me, is that they maximize the gains for the group as a whole. So how will huddling behind a slow moving truck help me get to where I want when I want?”
I hope AJ will correct me if I’m wrong, but it seems that lurking under the surface of many of AJ’s posts is the gentle suggestion that we’re arrived at a point where some re-thinking of priorities and perspectives might be in order.
You’ve asked “How will huddling behind a slow moving truck help me get where I want when I want?” I think AJ is asking “Are I getting where I want when I want? If I’m not, what might I do differently? A different mode of travel? A different destination?”
— Tony Comstock · Feb 12, 04:22 PM · #
The Brits have a great roads sign in their repertoire: “Changed Priorities Ahead”!
— Johnny Sagan · Feb 12, 04:34 PM · #
Road sign—I hate a typo!
— Johnny Sagan · Feb 12, 04:35 PM · #
Tony may be right about my secret agenda — I’ll never tell! — but scritic, note that the summary of the research suggests that even the wholly self-interested should follow this practice: “ Dussutour’s team calculated that patience reduced the average delay experienced by an individual ant crossing a crowded three-meter bridge from 64 to 32 seconds.” See? Good for you, good for everybody!
— Alan Jacobs · Feb 12, 06:10 PM · #
“ Good for you, good for everybody!”
Tragedy of the Commons.
I just wanted to say it before anybody else did.
— Tony Comstock · Feb 12, 06:22 PM · #
Alan, I’d have to see the original article, but I think you’re misreading that quote. It doesn’t say that a driver in a system where everyone else is driving selfishly can save time by driving like an ant. I think it’s saying that if everyone drove like ants, everyone’s delays would be reduced.
Furthermore, I wouldn’t be surprised if it turned out that, if everyone else were driving like ants, an individual driver could save even more time by driving selfishly.
— Michael Straight · Feb 12, 07:55 PM · #
It doesn’t say that a driver in a system where everyone else is driving selfishly can save time by driving like an ant. I think it’s saying that if everyone drove like ants, everyone’s delays would be reduced.
Well, yeah — that’s the clear message. As I say in the post, “It seems to me that the prime problem here is that the leafcutter approach only works if pretty much everyone applies it.” So I don’t understand your comment.
— Alan Jacobs · Feb 12, 10:27 PM · #
Perhaps it would work to simply put up roadsigns containing the applicable game theory matrices…with the Nash Equilibrium points helpfully highlighted in safety orange.
— Ethan C. · Feb 13, 01:55 AM · #
Alan, you said in the comments: the summary of the research suggests that even the wholly self-interested should follow this practice
The summary does not suggest that and I highly doubt the research itself supports it either.
Will I get there faster if everyone else is driving like an ant? Yes. If everyone else is driving like an ant, will it benefit me to also drive like an ant? You seem to be saying “Yes,” but the article doesn’t say, and my guess is that the research would say, “No.”
— Michael Straight · Feb 13, 08:05 PM · #
The summary does not suggest that and I highly doubt the research itself supports it either.
Michael, here’s my reasoning: I assume that the wholly self-interested drivers will want to reduce the time they spend in traffic; the Leafcutter Strategy, widely or universally followed, reduces the time everyone spends in traffic; therefore wholly self-interested drivers should follow the Leafcutter strategy. So yes, I think the summary of the research absolutely and straightforwardly says that if everyone else is driving like an ant, it will benefit me to also drive like an ant — at least if I think that cutting my commuting time in half is a benefit!
What you are saying is that there might be some other approach that would benefit me even more than the one that cuts my commuting time in half. Could be — but I doubt that we can find enough rebellious leafcutter ants to provide the evidence we need for testing that speculation.
Now, it may be that what someone wants is not so much to cut his own absolute time in traffic but rather to cut his time in traffic relative to other drivers. (Studies suggest that, in relation to income anyway, people care more about relative than absolute success.) So maybe that person would be happy to reduce his own commute by only ten percent if other people failed to reduce their commute at all. I would say that such a person has refused a real benefit in favor of a largely fictitious one, and that such a choice is not rational.
— Alan Jacobs · Feb 13, 09:59 PM · #
“ I would say that such a person has refused a real benefit in favor of a largely fictitious one, and that such a choice is not rational.”
Story of my fucking life!
— Tony Comstock · Feb 14, 05:58 AM · #
Well, mine too, if it comes to that. . . .
— Alan Jacobs · Feb 14, 01:51 PM · #
Alan, if this is like other traffic studies I’ve seen, the way you drive mostly effects the traffic for the people behind you. A selfish driver will realize that it doesn’t matter one way or the other how he himself drives, his traffic is determined by the people ahead of him, so he might as well drive however he pleases.
Or are you thinking of the extremely marginal tit-for-tat benefit (the selfish driver thinking, “If I drive like an ant today, maybe some of the people behind me who benefit might be more likely to drive like ants tomorrow, and some of them may be ahead of me.”)? The tit-for-tat strategy works pretty well if it’s just two parties, but if you’re one of thousands on the road, it’s hard to believe you’d get enough benefit to make it worth your while to change your driving habits.
A much more effective strategy would be to loudly and publicly (e.g. on one’s blog) insist that even selfish drivers will see a personal benefit from the Leafcutter strategy, hoping a majority of drivers will come to believe this, even if you yourself know it’s not true.
— Michael Straight · Feb 16, 09:37 PM · #
Alan, it does sound like a classic prisoner’s dilemma case. You’re better off cooperating than both being selfish, but being the single selfish person might be better than cooperating. The selfish thing to do is to cooperate only if you think your cooperation is causally relevant to other people’s cooperation.
As Michael says, it’s natural to think that your own selfish behavior would primarily slow down people behind you (you change lanes often and cut them off, forcing them to slow down, etc).
— Justin · Feb 17, 06:47 AM · #