Building Bigger Roads Actually Makes Traffic Worse

[one...two...tree 2,762]

(excerpt)

In 2009, two economists—Matthew Turner of the University of Toronto and Gilles Duranton of the University of Pennsylvania—decided to compare the amount of new roads and highways built in different U.S. cities between 1980 and 2000, and the total number of miles driven in those cities over the same period.

“We found that there’s this perfect one-to-one relationship,” said Turner.

If a city had increased its road capacity by 10 percent between 1980 and 1990, then the amount of driving in that city went up by 10 percent. If the amount of roads in the same city then went up by 11 percent between 1990 and 2000, the total number of miles driven also went up by 11 percent. It’s like the two figures were moving in perfect lockstep, changing at the same exact rate.

Now, correlation doesn’t mean causation. Maybe traffic engineers in U.S. cities happen to know exactly the right amount of roads to build to satisfy driving demand. But Turner and Duranton think that’s unlikely. The modern interstate network mostly follows the plan originally conceived by the federal government in 1947, and it seems incredibly coincidental that road engineers at the time could have successfully predicted driving demand more than half a century in the future.

A more likely explanation, Turner and Duranton argue, is what they call the fundamental law of road congestion: New roads will create new drivers, resulting in the intensity of traffic staying the same.

Intuitively, I would expect the opposite: that expanding a road network works like replacing a small pipe with a bigger one, allowing the water (or cars) to flow better. Instead, it’s like the larger pipe is drawing more water into itself. The first thing you wonder here is where all these extra drivers are coming from. I mean, are they just popping out of the asphalt as engineers lay down new roads?

The answer has to do with what roads allow people to do: move around. As it turns out, we humans love moving around. And if you expand people’s ability to travel, they will do it more, living farther away from where they work and therefore being forced to drive into town. Making driving easier also means that people take more trips in the car than they otherwise would. Finally, businesses that rely on roads will swoop into cities with many of them, bringing trucking and shipments. The problem is that all these things together erode any extra capacity you’ve built into your street network, meaning traffic levels stay pretty much constant. As long as driving on the roads remains easy and cheap, people have an almost unlimited desire to use them.

You might think that increasing investment in public transit could ease this mess. Many railway and bus projects are sold on this basis, with politicians promising that traffic will decrease once ridership grows. But the data showed that even in cities that expanded public transit, road congestion stayed exactly the same. Add a new subway line and some drivers will switch to transit. But new drivers replace them. It’s the same effect as adding a new lane to the highway: congestion remains constant. (That’s not to say that public transit doesn’t do good, it also allows more people to move around. These projects just shouldn’t be hyped up as traffic decongestants, say Turner and Duranton.)

Interestingly, the effect works in reverse, too. Whenever some city proposes taking lanes away from a road, residents scream that they’re going to create a huge traffic snarl. But the data shows that nothing truly terrible happens. The amount of traffic on the road simply readjusts and overall congestion doesn’t really increase.

http://www.wired.com/2014/06/wuwt-traffic-induced-demand/

[GBCW 397]

This has been known for decades.

[Mr. Big Dog 10,747]

Commie green stuff. How you doing Steven?

[one...two...tree 2,762]

Commie green stuff. How you doing Steven?

I'm doing okay. Living the dream here in Portland. How are you doing?

[Teddy B 17,252]

Bring back Mr. Fancypants!!

[Mr. Big Dog 10,747]

I'm doing okay. Living the dream here in Portland. How are you doing?

Life's been treating me well. Not sure how that is even possible with the country going to hell, the economy collapsing and all that but somehow I am doing incredibly well.

[DavenRoxy 1,073]

Life's been treating me well. Not sure how that is even possible with the country going to hell, the economy collapsing and all that but somehow I am doing incredibly well.

Give it a week. After the ebola gets on you, you'll be singing a dentfrent tune, for sure!

[MyLittlePony 340]

Bigger roads will add more dangerous idiot drivers and there are enough of the idiots drivers as is.

[Teddy B 17,252]

Bigger roads will add more dangerous idiot drivers and there are enough of the idiots drivers as is.

Do you have spinners on your F150?

[JohnR! 5,495]

Dude, spinners are so pre-0'bola...

The jig is up. Shyte just got real...

This is how you roll in this post-killary world...

Do you have spinners on your F150?

Edited October 16, 2014 by JohnR!

[MyLittlePony 340]

Do you have spinners on your F150?

Your close i have spinners on a Prius plug in.

[Teddy B 17,252]

Your close i have spinners on a Prius plug in.

You don't strike me as a Prius kind of guy.

[SMR 368]

How come drivers in Omaha, Nebraska, haven't started driving more so that there is as much congestion in Omaha as there is in Los Angeles? If it were really true that drivers just drive more or less depending on how many roads are available and how much congestion there is, then every road everywhere would have exactly the same amount of congestion. People don't just drive because it's fun and don't stop driving just because it sucks. They drive because they need to get somewhere.

Now, of course there is a fair bit of hysteresis, which is what the article is showing. When traffic is bad, people who can avoid driving will. If traffic is tolerable, the people who want to get somewhere but don't absolutely need to will come out of the woodwork. But that doesn't mean we should start getting rid of roads. At the end of the day, people need to get places.

[Mr. Big Dog 10,747]

Give it a week. After the ebola gets on you, you'll be singing a dentfrent tune, for sure!

You got it all twisted, bro. Fact is: Ebola is scared of me.

[Mr. Big Dog 10,747]

Your close i have spinners on a Prius plug in.

Well, well, well. Eric just admitted that that monster C is just a big, fat lie. Everyone knows that you can't fit a monster C into a Prius.