June 18, 2014

"It’s the roads themselves that cause traffic."

"We found that there’s this perfect one-to-one relationship."
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.


Left Bank of the Charles said...

Let's see:

The longer the line, the more people will get on line.

The higher the taxes, the more people will want to pay them.

The larger the grocery stores, the fatter the people who shop in those stores.

The more guns people own, the more bullets people want to fire through them.

John Scott said...

Assuming they're not all out for Sunday drives, more lanes mean more people participating in economic activity. Or at the very least out enjoying life rather than staying home getting fat trolling blogs about imminent John Doe indictments.

The Godfather said...

This isn't a new idea. I heard it from Prof. Edward Banfield at Harvard in 1963 (?). But Banfield didn't explain it the same way. He didn't say that more roads cause more traffic. He said that the lack of adequate roads discourages traffic. In other words, the demand is there, but the the lack of adequate roads prevents the demand from being satisfied.

It's a big difference. The demand for a way to get from Point A to Point B reasonably conveniently reflects the desire of people to engage in economic and social activity. If we refuse to build more roads, these desires will be frustrated. And those who were already willing to endure the inconvenience of clogged roads to conduct their economic and social activities, will continue to suffer the same inconvenience.

Theoretically, the answer is better means of transportation, like subways and monorails (or flying cars). In Washington, DC, they built a subway system for this purpose, and while I lived there I used it as much as I could -- I thought it was great (and I wasn't paying for it). Now, when I go back to DC, I find that the subway is much more crowded than it used to be. I don't think you can build more lanes onto a subway, so I don't know what the solution is.

DKWalser said...

It sounds like there is a lot of pent up demand for more road capacity. With greater capacity, more people use the roads. That's not an argument for fewer roads; it's an argument for more. When road capacity increases and traffic remains the same, you'll know that there are enough roads to meet the demand.

David said...


Except in North Korea.

Because roads need cars to increase traffic.

Nonapod said...

The concept is called induced demand, which is economist-speak for when increasing the supply of something (like roads) makes people want that thing even more... 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.

This certainly makes a good deal of sense. Ask yourself: If an affordable Star Trek-like home teleportation device existed that allowed you to travel to any place on Earth instantly for near zero cost, do you think you would travel a whole lot more or pretty much the same?

I expect that once self driving cars become commonplace traffic will increase an order of magnitude.

Peter said...

No doubt the assertion is true except when it isn't.

If a city has a dense highway network and one highway's capacity is increased then it is to be expected that traffic on that highway will increase.

But what if the region's highways are more linear? At least in this area, widening I-94 in northern Illinois seems to have significantly increased rush-hour traffic speeds there.

Gabriel said...

It's not as implausible as it sounds--if the demand for roads is so high that no practical amount of buildable road will ever satisfy it, then of course new roads will fill as soon as they are built.

Even if traffic moved like water through a pipe, building bigger pipes doesn't necessarily increase flow in proportion, as nineteenth-century sewer engineers found out the hard way.

Original Mike said...

Madison has long operated on the theory that parking spaces cause parking.

Shanna said...

He said that the lack of adequate roads discourages traffic.


Also getting into labor economics, if you are choosing where to work, you are taking factors like the expense and time of commute and weighing them against what you could make if you drive further/what a home would cost close to work and other factors. Say the house an hour's commute from work is 100k less than the house next to the office. That might be worth it if you only have to commute an hour. Two hours you might have to pay more to live closer or give up some of the things you want in a house (or live in an apartment).

Tibore said...

Godfather beat me to it; it seems as though the researchers are presuming that peak demand is already reached and therefore providing more infrastructure creates more demand instead of satisfying that which is pent up. I'd like to see them address the "creation" vs. "pent up" aspect of this. It seems as though the fundamental presumption is towards limiting traffic.

And while I like driving and would hate restrictions on it, I admit to feeling a level of sympathy for that presumption. There's only so much space in a city to handle traffic. While I detest public transportation (yes, I do. Judge me all you want, folks, but I do) I can fully understand why urban planners try to lean heavily on it. It's a bitch to deal with. Whenever I visit Chicago, for example, friends and family always say that driving downtown is a bad idea. I definitely listen to and take their advice.

AJ Lynch said...

Did they adjust the increased traffic for the growth in population? If not, it was not really apples to apples. You'd have to do an analysis that measures miles driven per resident. I think that is the correct way to analyze this.

And lastly I suspect internet traffic responds the same way -it increases when there are more hotspots, internet cafes, broadband, smart phones etc.

tim in vermont said...

In telephony the term "offered traffic" is the total number of calls that would use a circuit if it had an infinite carrying capacity.

Basically, it has long been accepted that one has to guess at the number of discouraged callers because they are impossible to measure, but one can guess at it in terms of phone traffic, since there are billions of cases and thousands of studies on the subject as well as scientific research, as well as the ease of adding and subtracting 'lanes' from a phone circuit.

I suspect there is no way to know the hidden demand for traffic without building eight lane highways in the middle of nowhere.

In the movie "Captain Phillips," the captain drives between Underhill, VT and the Burlington airport, a trip where there may be as many as five traffic lights, once you get to Burlington, none on the Underhill to Burlington route, which takes ten or twenty minutes to drive and you are more likely to be held up by a wandering cow than a traffic jam of more than eight cars.

In the movie, there is a huge highway with more cars on it than there are cars in all of Underhill, or probably the whole Northeast Kingdom to the east, driving each way.

Build that kind of highway and you will find out the actual traffic demand unconstrained by bottlenecks.

traditionalguy said...

That is more Malthusian moaning, that when more people that are happy and healthy, the worse it is for good people.

The assumption is a limited resource that never grows. They turn that into a mandatory rule because they hate happy people beating the zero sum games they enjoy using to defeat others.

Tom said...

Junk expands to fill available space, traffic expands to fill available roads. It's a law of the universe.

Sam Hall said...

The roads fill until the pain caused by the traffic is balanced by the people willing to suffer that level of pain. There are many more people that would drive if there were less pain by adding more lanes.
They have no idea what the true demand for lanes is because we have never had enough.

Michael K said...

Rain is the result of wet streets. That's easy.

The Murray Gell-Mann Amnesia Effect:

“Briefly stated, the Gell-Mann Amnesia effect is as follows. You open the newspaper to an article on some subject you know well. In Murray’s case, physics. In mine, show business. You read the article and see the journalist has absolutely no understanding of either the facts or the issues. Often, the article is so wrong it actually presents the story backward—reversing cause and effect. I call these the “wet streets cause rain” stories. Paper’s full of them.
In any case, you read with exasperation or amusement the multiple errors in a story, and then turn the page to national or international affairs, and read as if the rest of the newspaper was somehow more accurate about Palestine than the baloney you just read. You turn the page, and forget what you know.”

— Michael Crichton

rhhardin said...

The more birdhouses I put up, the more House Sparrows I have.

NotquiteunBuckley said...

As it feeds, the appetite grows.

That's biblical yo.


John Lynch said...

Wow, so... infrastructure limits economic growth? Who knew?

Joe said...

Traffic does not equal congestion.

Where I live the state rebuilt and widened the main freeways. Traffic very likely increased, but congestion markedly decreased.

Gene said...

One thing I notice here in L.A.--the bike lanes are never full. If you have to physically work to get somewhere people naturally limit how much they travel. People who travel by car on the other hand won't be happy till we pave over the planet.

lgv said...

The Godfather explained it well.

If you give away tax subsidized "free food" and all it gets even. You increase the amount of free food by 10% and consumption of the free food increases by 10%. Why is this surprising. As highways to the burbs expand, more housing is built in the burbs.

I shocked at such cause and effect. Shocked, I tell you.

tim in vermont said...

You know what we really have to worry about? Headstones in graveyards. Every time you see one, and the exceptions are exceedingly rare, there is a dead body right nearby, if not dozens or hundreds, or even thousands of them.

Sam L. said...

Nonapod, just THINK of the number of customs officials needed to check the passports and visas at all those transporter stations! And all government employees!

Sam L. said...

Nonapod, just THINK of the number of customs officials needed to check the passports and visas at all those transporter stations! And all government employees!

Just Mike said...

What, the people in those cars didn't exist until the roads were built? By the way this is exactly the theory believed by the (then young) Governor Moonbeam in CA during the 70's. When elected, he and his DOT appointees scrapped all plans for new freeways that had been planned since the 60's apparently thinking that the opposite would be true and fewer roads would mean less traffic. Huh...didn't happen. Now he's back and they want to build a bullet train - which will obviously (we now know) lead to train congestion.

mkh said...

What idiots.
Maybe the highway planners looked at demographics and predicted traffic growth and planned highway capacity to match? Isn't that what they are paid to do?

Now lefties want to assume that we randomly expand roads and people suddenly feel the need to drive?

Maybe the "road to nowhere" would have disproved this.