“Building bigger roads actually makes traffic worse,” asserts Wired magazine. “The reason you’re stuck in traffic isn’t all these jerks around you who don’t know how to drive,” says writer Adam Mann; “it’s just the road that you’re all driving on.” If only we had fewer roads, he implies, we would have less congestion. This “roads-induce-demand” claim is as wrong as Wired‘s previous claim that Tennessee fiscal conservatives were increasing Nashville congestion by banning bus-rapid transit, when actually they were preventing congestion by banning dedicated bus lanes.
In support of the induced-demand claim, Mann cites research by economists Matthew Turner of the University of Toronto and Gilles Duranton of the University of Pennsylvania. “We found that there’s this perfect one-to-one relationship,” Mann quotes Turner as saying. Mann describes this relationship as, “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.” If this were true, then building more roads doesn’t make traffic worse, as the Wired headline claims; it just won’t make it any better.
However, this is simply not true. Nor is it what Duranton & Turner’s paper actually said. The paper compared daily kilometers of interstate highway driving with lane kilometers of interstates in the urbanized portions of 228 metropolitan areas. In the average metropolitan area, it found that between 1983 and 1993 lane miles grew by 32 percent while driving grew by 77 percent. Between 1993 and 2003, lane miles grew by 18 percent, and driving grew by 46 percent.
That’s hardly a “perfect one-to-one relationship.”
The paper also calculated the elasticities of driving in relationship to lane kilometers. An elasticity of 2 would mean a 10 percent increase in lane miles would correspond with a 20 percent growth in driving; an elasticity of 1 would mean that lane miles and driving would track closely together. The paper found that elasticities were very close to 1 with standard errors of around 0.05. Even though this is contradicted by the previously cited data showing that driving grew much faster than lane miles, this is the source of Turner’s “perfect one-to-one relationship.”
The Antiplanner has a serious problem with this conclusion, mainly because my analysis of driving and highway capacity data for the 101 largest urban areas from 1982 through 2011 produces very different results. Yes, there is a correlation between an increase in road capacity and an increase in driving. But (as illustrated in the table below for the top 30 urban areas) the correlation is far from perfect and it is very far from one-to-one.
-Growth in Lane Miles vs. Driving<_center>
| Lane Miles 83-93 | Driving 83-93 | Lane Miles 93-03 | Driving 93-03 | |
|---|---|---|---|---|
| New York | 15.0% | 39.0% | 8.6% | 33.7% |
| Los Angeles | 14.8% | 52.4% | 15.7% | 19.3% |
| Chicago | 31.3% | 65.2% | 6.3% | 27.0% |
| Miami | 26.7% | 108.1% | 12.5% | 43.3% |
| Philadelphia | 34.2% | 49.0% | 12.7% | 44.8% |
| Dallas-Ft. Worth | 20.3% | 53.8% | 23.0% | 50.3% |
| Houston | 53.3% | 55.0% | 32.7% | 46.5% |
| Washington | 50.8% | 80.4% | 7.4% | 29.0% |
| Atlanta | 40.9% | 80.5% | 18.4% | 58.1% |
| Boston | 0.8% | 35.5% | 17.6% | 26.4% |
| Detroit | 12.4% | 67.6% | 7.9% | 13.8% |
| Phoenix | 209.1% | 226.5% | 94.9% | 152.3% |
| San Francisco-Oakland | 7.2% | 36.1% | 8.5% | 18.0% |
| Seattle | 14.3% | 67.9% | 11.9% | 20.6% |
| San Diego | 12.5% | 64.7% | 11.4% | 31.8% |
| Minneapolis-St. Paul | 22.4% | 71.5% | 2.3% | 32.2% |
| Tampa-St. Petersburg | 86.5% | 111.3% | 67.0% | 75.8% |
| Denver | 25.8% | 41.1% | 14.0% | 38.7% |
| Baltimore | 52.8% | 94.9% | 11.3% | 44.5% |
| St. Louis | 35.0% | 48.1% | 24.7% | 31.2% |
| Riverside-San Bernardino | 19.9% | 101.5% | 16.6% | 49.7% |
| Las Vegas | 62.5% | 322.7% | 94.2% | 112.2% |
| Portland | 20.2% | 80.2% | 8.0% | 25.5% |
| Cleveland | 8.5% | 41.7% | 13.6% | 16.7% |
| San Antonio | 42.6% | 58.6% | 10.4% | 58.7% |
| Pittsburgh | 37.6% | 53.0% | 6.8% | 30.6% |
| Sacramento | 11.1% | 67.4% | 3.6% | 35.2% |
| San Jose | 32.7% | 44.5% | -11.8% | 0.1% |
| Cincinnati | 15.4% | 51.1% | 24.1% | 40.4% |
| Kansas City | 28.4% | 65.8% | 12.1% | 35.5% |
Looking at the same years as Duranton & Turner, in more than 90 percent of urban areas, driving grew far faster than lane miles. On average, driving grew more than twice as fast as lane miles. But the range was from 0.6 (meaning driving grew only 60 percent as much as capacity) to nearly 50 (meaning driving grew nearly 50 times faster than capacity). This suggests that, not only are Duranton & Turner’s elasticities wrong, their standard errors (that is, the range of results) are far too low. (You can check my results by downloading Texas Transportation Institute data for 101 urban areas.)
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Daily Miles of Driving Per Lane Mile<_center>
| 1983 | 1993 | 2003 | 2010 | |
|---|---|---|---|---|
| New York-Newark NY-NJ-CT | 11,048 | 13,345 | 16,431 | 15,693 |
| Los Angeles-Long Beach-Santa Ana CA | 16,976 | 22,552 | 23,248 | 22,911 |
| Chicago IL-IN | 12,523 | 15,756 | 18,810 | 17,882 |
| Miami FL | 8,957 | 14,709 | 18,734 | 19,423 |
| Philadelphia PA-NJ-DE-MD | 10,332 | 11,468 | 14,728 | 13,132 |
| Dallas-Fort Worth-Arlington TX | 10,678 | 13,652 | 16,677 | 16,818 |
| Houston TX | 15,072 | 15,247 | 16,824 | 16,606 |
| Washington DC-VA-MD | 12,901 | 15,432 | 18,537 | 18,079 |
| Atlanta GA | 11,292 | 14,469 | 19,323 | 16,677 |
| Boston MA-NH-RI | 10,888 | 14,640 | 15,738 | 14,463 |
| Detroit MI | 10,984 | 16,384 | 17,277 | 15,215 |
| Phoenix-Mesa AZ | 13,795 | 14,574 | 18,868 | 17,324 |
| San Francisco-Oakland CA | 14,663 | 18,610 | 20,242 | 20,252 |
| Seattle WA | 11,092 | 16,298 | 17,564 | 14,503 |
| San Diego CA | 11,229 | 16,449 | 19,460 | 18,465 |
| Minneapolis-St. Paul MN | 9,579 | 13,415 | 17,346 | 15,310 |
| Tampa-St. Petersburg FL | 12,423 | 14,072 | 14,815 | 14,537 |
| Denver-Aurora CO | 11,547 | 12,950 | 15,754 | 15,257 |
| Baltimore MD | 10,278 | 13,113 | 17,026 | 17,090 |
| St. Louis MO-IL | 11,667 | 12,796 | 13,465 | 11,836 |
| Riverside-San Bernardino CA | 9,993 | 16,798 | 21,579 | 20,749 |
| Las Vegas NV | 6,063 | 15,769 | 17,228 | 16,111 |
| Portland OR-WA | 10,044 | 15,058 | 17,493 | 15,566 |
| Cleveland OH | 9,435 | 12,318 | 12,647 | 12,220 |
| San Antonio TX | 9,662 | 10,749 | 15,451 | 15,030 |
| Pittsburgh PA | 7,188 | 7,991 | 9,768 | 8,905 |
| Sacramento CA | 9,746 | 14,686 | 19,172 | 18,577 |
| San Jose CA | 14,974 | 16,310 | 18,508 | 18,886 |
| Cincinnati OH-KY-IN | 10,259 | 13,433 | 15,203 | 14,222 |
| Kansas City MO-KS | 7,188 | 9,283 | 11,214 | 10,519 |
If it were true, as Mann claims, that capacity generates its own demand, then freeways would be equally congested all over the country. Yet this is far from true. As shown above, while Los Angeles freeways support more than 22,000 daily miles of driving per lane mile, Pittsburgh freeways host less than 9,000 miles per lane mile. Nor are the numbers consistent over time within an urban area, as Duranton & Turner’s elasticities would predict. Instead, many urban areas, including Miami, Las Vegas, and Sacramento, saw miles of driving per lane mile more than double between 1983 and 2003; the average growth was 50 percent, and some grew less than 20 percent, which again suggests that both elasticities and standard errors are much different than found by Duranton & Turner.
So Duranton & Turner’s numbers appear to be wrong, and Wired overstated those numbers anyway. But let’s say it were true that there is a perfect one-to-one relationship between driving and highway capacity, and further stipulate that increasing capacity leads to increased driving (rather than the other way around, which is equally credible if highway engineers are trying to keep up with demand). Is that a bad thing?
We know that every car on the road has someone in it who is going somewhere that is important to them. Increasing the number of cars on the road means more people are getting to do things that are important to them. Provided we aren’t subsidizing that travel (and, as I’ve shown before, subsidies per passenger mile are small and probably zero for freeways), then increasing highway capacity leads to net economic benefits because it generates travel that wouldn’t have taken place otherwise.
By comparison, building expensive transit systems aimed at getting people out of their less-expensive cars generates zero economic benefits if it generates no new travel. Only new travel generates economic benefits, so people who argue that new roads induce new travel are actually arguing that new roads create economic benefits.
If congestion is the issue, then–as Mann briefly mentions–the solution is congestion pricing. But Mann doesn’t understand the difference between true congestion pricing and New York City’s proposal for cordon pricing. Cordon pricing is more a way of raising revenue to fund urban boondoggles than a way of relieving congestion.
Even New Urbanist Robert Cervero believes that the induced demand argument is “wrong headed.” “Road investments by themselves do not increase volumes,” he says. “Only by conferring a benefit, like faster speeds, will traffic increase.” Provided that benefit is greater than the cost–something that could be assured, Cervero says, through proper pricing of roads–then it is a good thing.
That’s why the Antiplanner supports, not new road construction, but better road pricing. If freeways are congestion-priced and revenues exceed costs, including the costs of maintenance, the extra revenues should be spent building new highway capacity. This will help restore America’s transportation system to be, as it once was, the best in the world.
This is one of the zombie claims here – every time you think it’d dead it rises to try and bite someone.
DS
Planners are institutionally trained to lie & obfuscate, so it is no surprise that a government planner dropped by to lie and obfuscate.
The only thing worse I suppose than a “gummit planner” is an Internet troll. Take that any way you like, Metrosucky you troll.
The Antiplanner left out one huge item in his criticisms of Mann. Mann pretty much comes to the same conclusion as The Antiplanner: congestion pricing plus parking surcharges. So both are not nearly in as much disagreement as the The Antiplanner implies.
If congestion is the issue, then–as Mann briefly mentions–the solution is congestion pricing.
I wonder why authors for popular publications always soft-peddle the solution, which obviates all of the incorrectly-performed ‘induced demand’ studies. Guess that would make for a pretty short article, wouldn’t it?
To get the full picture of induced demand one would also need to know how many lane-kilometers of arterials were added in each urban area, plus the daily kilometers driven on such roadways. Some indicator of local population and growth and ongoing suburbanization would also provide a much clearer picture.
It’s also important to remember that correlation does not prove causation. Even if you could show that increased highway capacity is correlated to additional traffic it would not prove induced demand. These studies look at a bunch of different cities, each one with differing conditions. It some cases increased traffic may have encouraged additional highway construction. In others, third factors may have encouraged both additional travel and highway construction.
As I grew up every time the city of Portland added a new freeway, it moved nearly all of the congestion problems in the neighborhoods, to the freeway. Making neighborhoods more livable and driving more pleasurable.
Because people don’t drive just to drive, they are going to work, doing businesses or visiting friends and family and taking kids to youth activities.
sprawl,
the exact opposite is happening now. As freeways and arterials suffering crushing congestion, people drive on surface streets and take shortcuts through neighborhoods, mowing down pedestrians and endangering residents.
Planners don’t care because they are so obsessed on punishing drivers for using their cars to safely & conveniently do the things they need to do. They’ve even invented this preposterous myth of “induced demand”, pretending that people drive more just for the hell of it, without any reason at all. The real reason recently expanded roads see more traffic is because there was pent-up, latent demand for the capacity, and now drivers can take the high speed arterial or freeway instead of neighborhood streets.
But reality is as foreign to planners, as being sober is, to a drunk. And planners are drunk on power.
Mr. O’Toole astutely contradicts induced demand claims. Of course the data also shows that increases in capacity have done virtually nothing to reduce congestion. Alas, the solution: price poor people out of driving to free up the roads for the wealthy.
Bennett,
at least you can look at it as increased capacity has prevented congestion from being worse. And in areas where substantive increases in capacity are made to keep up with population growth, such as Phoenix, traffic flows quite smoothly, versus areas where planners have conspired to prevent arterials and freeways from being built or expanded.
“As freeways and arterials suffering crushing congestion, people drive on surface streets and take shortcuts through neighborhoods, mowing down pedestrians and endangering residents. ”
We must give in to drivers’ demands or they’ll keep killing innocent people. Sort of like terrorists.
There’s a more obvious criticism of this idea that you can never build a highway big enough to handle the demand it’ll generate. We’ve done it. And done it nearly everywhere. The vast, vast, vast majority of highway miles in America are virtually never congested (and if they are it’s only because of a catastrophic failure like an accident, a natural disaster, etc.). That just flat out disproves the idea that you can’t build a highway system large enough to accomodate everyone who wants to drive on it.
Building freeways as the populations grows always works. Adding density and not adding road capacity, always increase congestion on the freeways and in our neighborhoods.
FantasiaWHT sez:
There’s a more obvious criticism of this idea that you can never build a highway big enough to handle the demand it’ll generate. We’ve done it. And done it nearly everywhere. The vast, vast, vast majority of highway miles in America are virtually never congested (and if they are it’s only because of a catastrophic failure like an accident, a natural disaster, etc.). That just flat out disproves the idea that you can’t build a highway system large enough to accomodate everyone who wants to drive on it.
Yes, because somewhere north of 90%+ of the road network is outside urbanized areas. No one, not even Metrosucky, has ever claimed that “gummit planners” (sic) have claimed vast congestion outside urbanized areas.
“Rural congestion” tends to happen in very specific circumstances, such as Yosemite Valley, Malibu or the Big Sur coast on summer weekends. And surely no one is advocating building freeways in such places, not even the most religious “auto creationism” apologist (there were plans for freeways along the California coast between San Francisco and Santa Cruz and through Malibu and in West Marin, but those ideas were even too much for 1950’s and 1960’s California when automania was at its height).
I think there’s an error in the first table, which appears to indicate that San Jose lost 11.8% of its lane miles 1993-2003.
Building freeways as the populations grows always works. Adding density and not adding road capacity, always increase congestion on the freeways and in our neighborhoods.
This makes a lot of sense to people with their head screwed on right, but planners aren’t normal. They come from the same lineage that slaughtered millions to accomplish dubious political goals.
We must give in to drivers’ demands or they’ll keep killing innocent people. Sort of like terrorists.
We should blame planners here. They deliberately mix pedestrian, bicycle, and automobile traffic, and are to blame for the resulting chaos. They gloat over gigantic traffic jams as if that’ll show evil car drivers for daring to use cars instead of the glorious transit boondoggles that have been offered to them.
Gilfoil is obviously some planner, probably from Portland, who gets paid a nice salary to make residents’ lives miserable and a few contractors extremely rich.
The fact remains that if urban planners did their job, and were responsible public servants they would have “planned” for increased motor vehicle traffic and roads would have been built and expanded to serve the increased demand for road capacity as urban populations expand. Metrosucks is right – but he doesn’t go far enough when he says “Planners are institutionally trained to lie & obfuscate, so it is no surprise that a government planner dropped by to lie and obfuscate.” I’ve been to the meetings – they lie – urban planners say anything it takes to impose density, and theuir vision on us, whether we want it or not including and not limited too, reducing road capacity, and vilifying drivers, which includes squeezing us into ultra-dense housing, on substandard size lots, because they – the planners – are incompetent. If you need proof jump onto any of the Interstates listed above and experience it, because if they were good – competent – at their craft traffic congestion would be minimal and these antagonists we refer to as “planners” would not be center of our universe that they have become or be receiving the attention they have not earned or deserve.
Alas, the solution: price poor people out of driving to free up the roads for the wealthy.
Yes, we should avoid the one policy that might have the best chance at providing last congestion relief because…equity!
Nevermind that the evidence on priced roadways in urban areas indicates that a substantial number of low and moderate-income travelers willingly use priced facilities when those facilities offer them a significant time savings. Surprisingly, they are very often able to make decisions about tradeoffs just like the rest of us. Of course, in the vast majority of cases, even those who are ‘priced off’ the roads typically have close substitutes available to them — nearby unpriced routes or even other modes — to mitigate the effects of pricing.
And of course if you actually are serious about the welfare of low-income travelers, you can earmark a share of the revenues from pricing for direct assistance. Given transportation planners’ frequent invocations of the rubric of ‘choice’, I would think this would be a welcome option. But I’ve been wrong before about that, too.
MJ suggested: “And of course if you actually are serious about the welfare of low-income travelers, you can earmark a share of the revenues from pricing for direct assistance. Given transportation planners’ frequent invocations of the rubric of ‘choice’, I would think this would be a welcome option.”
I actually think this is a great trade off and one I would support. However, in today’s political climate any concession to the “takers” will get you tossed out by the wackadoodles on the right. Just ask Eric Cantor.
bennett, well than you are part of the problem! “Pay them”? There you go again, you are incompetent as a planner, and as an American because you are willing to pay people to not reach their full potential? I don’t find that acceptable, essentially “pay” people to settle for, and be happy living in mediocrity? What a mantra of failure!