Flashback Sunday: Does building roads harm the economy?

Every weekend we dig into the archives. This post by Matt was originally published in January 2014.

Most proposals to build new roads or widen existing ones seem to boil down to an ultimate belief that it will “help the economy”. Whether it’s by improving freight reliability or getting people to their jobs faster or helping business travel or whatever, there seems to be a fundamental belief among many that quite a strong relationship must exist between building more roads and improving the economy.

Clearly this is a contestable assumption, and some recent research in the USA details some pretty interesting trends – as reported on in Planetizen:

University of Minnesota professor David Levinson has written in the past that, because of the relative completeness of our national highway network and the cost of construction, the return on investment for additional mileage is approaching zero. One study estimates the return on investment for highway construction was just 14% between 1990 and 2000.

I recently decided to follow up on this line of research, so I dug through some Census data. What I found was shocking, though not altogether surprising. It seems that, besides wasting billions of taxpayer dollars, road-building may actually be holding back economic growth overall: from roughly 2000 to 2010, states that built the fewest urban road miles grew an average of 64 to 94 percent faster than their asphalt-enamored neighbors. Rather than increasing productivity through increased mobility and reduced congestion, as politicians and lobbyists so often promise, all this mindless road-building could be depressing statewide economic growth!

Let’s look at the details a bit more:

Looking at the numbers in aggregate, we see some interesting trends that seem to hold up just about any way you slice the pie:

• States that increased their urban road mileage by less than 30% grew by an average of 14.40%, while those that increased mileage by greater than 30% grew by an average of just 8.77%.
• If we set the cutoff at 20% mileage growth, states that built less grew by 17.97%, and states that built more grew by 9.24%.
• At a 10% cutoff, states that built less grew by an impressive 20.70%, compared to just 10.66% for those that built more.

Statistically, analyzing the correlation between road-building and economic growth gives us an r-score (correlation coefficient) of -0.34, which implies that about 10% of a given state’s economic growth can be explained by how much urban road-building they did over this time period. Many things influence the overall health of any economy, obviously, so we shouldn’t expect the quantity of roads to wholly predict statewide economic growth by itself, but this does indicate a negative correlation between the two variables: more roads equals less growth. (As always, please remember that correlation does not imply causation.)

And for a graphed comparison:

The post’s author, Shane Phillips, doesn’t think that these results are particularly surprising:

None of this should be particularly surprising. While politicians and advocates love to tout the job-creating value of new road and highway capacity, congestion reduction rarely lasts more than five years and widened roads ultimately only succeed in extending the boundaries of wasteful, unproductive sprawl. In the case of road widenings, it’s entirely possible that the disruption caused during the construction phase completely erases — or even exceeds — the fleeting benefits of reduced congestion.

Then there’s the opportunity cost: think of all the good that could have been done with the hundreds of billions of dollars spent on roadways over that period: more responsible transportation spending, education, renewable energy … take your pick.

I think it’s probably unlikely that building roads directly harms the economy, but there are logical reasons to think that it might cause indirect harm: particularly due to it not the best use of public funds and encouraging dispersed land-use patterns which undermine agglomeration. New Zealand’s heavy dependency on private vehicles also forces us to spend a lot of money each year importing cars and oil – basically cancelling out wealth that we create from exporting dairy to the the world.

The next version of the Government Policy Statement will be released some time later this year. If it’s anything like the current version it will stress the importance of transport’s role in improving the economy and then make a giant leap of faith in assuming that building more roads is the best way for transport to improve the economy. It’s time to fundamentally question that assumption.

Share this