An article about A highway project in the Pacific Northwest caught my attention:
However, the shiny new document omits an essential consideration when it comes to projecting the future impacts of the I-5 expansion in this long-constrained corridor, an omission that would have been far less noticed a decade ago but stands out as a sore thumb now. It almost completely sidesteps the concept of induced demand, which states that additional lane capacity will lead to more trips as road users try to take advantage of faster trips, ultimately negating many of the promised benefits that come from adding that new capacity, with especially the reduction of congestion. .
Opponents of a new and larger bridge connecting Vancouver, Washington and Portland, Oregon argue it would mean more people using the bridge. Supporters of the project assume that the number of cars crossing the bridge will not increase. That seems a bit strange to me.
Consider the following analogy. A cinema is so popular that it is often completely sold out. The management committee is considering an expansion of the cinema. One group claims that a larger cinema would attract more visitors. The other group claims that expanding the theater would not result in an increase in movie attendance. Which of these groups do you expect will support the expansion, and which do you think would be against it? Do you see the problem?
Of course, there are many differences between movie theaters and bridges, and I promise we’ll look at those differences. But first I wanted people to think about how strange it is that the opponents of highway expansion projects are usually the same people who believe it would create more demand for the service.
Supporters of bridge expansion are typically political leaders who want to serve their electorate. There are two types of voters: those who pay attention to the issue of bridge expansion, and those who don’t. I suspect there is a strong correlation between voters who support the bridge expansion and those who already use the bridge, if only because they are likely better informed about the situation than other voters. When proponents of bridge expansion deny that there would be any induced demand, they are implicitly suggesting that all the benefits would go to existing users in terms of reduced traffic congestion. But that outcome seems extremely unlikely because it violates the law of demand. When an increase in supply makes something cheaper (in terms of the opportunity cost of time), it leads to a greater quantity demanded. There would be an induced demand.
Opponents of the bridge expansion also have an incentive to accommodate voters with the most intense interest in the issue. They might want to argue that expanding the bridge would be of no use at all because it would create so much additional demand that traffic congestion would become just as bad as before. But that argument also violates the law of demand! If there were no reduction in traffic congestion, what would motivate new drivers to use the bridge? (To be fair, the author of this article is not claiming that induced demand would prevent congestion reduction, but I have seen others make that claim.)
One side essentially claims that demand curves are perfectly vertical, while the other side implicitly claims that demand curves are perfectly horizontal. In fact, demand curves slope downward.
So what’s the answer? Should the bridge be built?
Elsewhere in the article, the author makes it clear that his opposition to bridge expansion is related to environmental concerns. Ideally, you would want a Pigovian toll that reflects all possible traffic impacts, including congestion, pollution, global warming, suburban sprawl, etc. If that toll existed, it would be easier to assess the project based on the costs/costs. benefit basis.
(Although even in that case there could be other complications, such as indirect effects on the use of other roads that are not subject to a Pigovian toll. So I am not suggesting that a Pigovian toll on the bridge will solve the problem completely, but rather that it makes it easier to assess the pros and cons of a new bridge.)
P.S. In previous posts I suggested that Vancouver, Washington is an attractive place for libertarians. You can work in a state with no income tax (except capital gains) and shop in a state with no sales tax. And the Pacific Northwest is generally quite liberal when it comes to social issues like drugs, abortion and the right to die. So perhaps we should also consider whether this bridge would allow for the expansion of southwest Washington’s little libertarian paradise.
Here’s a photo of Vancouver, with beautiful Mount Adams in the background.