[hn_throwaway_99]

I completely disagree. Not from a "you are wrong, he is right" perspective, but from the perspective that you're basically arguing that his opinion is not valid.

You say "His "arguments" against the concept of induced demand are pretty much part of the basic understanding of everyone in the field." That may all be well and true, but it is definitely not the understanding of many laypeople who frequently spout the phrase "induced demand" as some sort of evidence for an "if you don't build it, they won't come" mindset.

That is, I see all the time on the Internet (especially since I'm in Austin, TX, which has notoriously bad traffic, and tons of Austinites are trying to shut down the state-mandated expansion of the major highway through the city), people using an argument of induced demand as to why no more roads should be built.

Thus, you may differ on the exact definition, but I think an article like this is useful for pointing out the benefits of building additional road capacity, even if it does get "filled up".

[aftoprokrustes]

My main problem is not someone disagreeing with the consensus in the field. I actually love when someone sheds a new light on something everyone agrees on.

I also have no problems with "laypeople" not being aware of the research and having only a half-informed opinion. Even experts cannot be familiar with everything. This is actually something I love about HN, that people with general curiosity come to discuss about topics they are not always experts in.

My problem is that, before boldly stating that everyone in the field is wrong, he does not seem to have taken the time to get familiar with what they actually say. But he can write, and _sounds_ informed. I consider this a dangerous combination.

I do not think anyone serious ever said "no more roads should be built". But no one builds roads just for the sake of it: one builds roads, in very broad terms, to the benefit of society and the economy. What transportation planning research is about is pretty much to try to understand (i) what is actually of benefit to society, as far as the transportation infrastructure is concerned, and (ii) how to actually achieve it. And to be honest, no one really agrees on either point.

[ravetcofx]

Do you have honest arguments for why TDOT should continue with the expansion? I haven't seen any that are coherent.

[pixl97]

We can make Austin into Houston with a 26 lane highway. We can see that huge highway solved traffic over there.

[bigDinosaur]

There's nothing more tiresome than someone from the states arguing that actually, what you need is more or wider roads. Go ahead and build them, it's thankfully not my tax money (and few places are as bad as the US when it comes to basically exclusively funding roads).

[seadan83]

The arguments are so vacuous against induced demand that the author is left with just opinion. I'm making a strong statement there, but I think I can defend it.

At its core, the author argues that "induced demand" is strictly false, posits that it's all "latent demand" instead, and then from there effectively ignores the concept of "induced demand" entirely.

Now, for the sake of definitions, "latent demand" is demand that only exists when a given means is made more attractive. "induced demand" is demand that exists, but is using alternatives. In other words, "induced demand" are people using the best option of multiple choices, "latent demand" is people choosing no option because the best option is not worth choosing at all.

When doing things like improving infrastructure, the increase in usage is a mixture of both "latent" _and_ "induced" demand. At what ratio between the two is context dependent.

So, let's go through the examples:

(1) UK highway goes from 3 lanes to 4, sees 10% total increase in volume

The citation does not look at what ratio of that 10% are people that are changing their mode (or time of day) for their transport vs those that are not making the trip entirely. The author argues that the 10% is 100% latent demand, that every single one of those trips would not have happened otherwise. The citation does not provide that evidence, it just says 10%, but does not say why or where that 10% came from. This example does not disprove or prove induced demand.

(2) more subsidized housing would result in more subsidized housing being used

Arguably "living somewhere" is something that 100% of us do, unless we don't, in which case we are talking about a dead person. If we build more subsidized housing, and that means more people can choose to live there instead of in a tent - that's induced demand. This is an example of induced demand......

Let's be more charitable though and say those living in a tent are completely unhoused (and thus represent latent demand). Is there any data that more subsidized housing would not also lead to people switching their non-subsidized apartment for a subsidized one?

Arguably housing is 100% induced demand, you live somewhere and are choosing the best of several options. Being more charitable, again, we are not seeing an example that says anything one way or another about induced demand.

(3) Length of a line for subsidized bread

Let's consider this example a bit differently. Let's say the bread is free, and the line is non-existent. At that point, I would probably go and get some bread. Though, at some point the long will be long enough where I'd just buy some bread instead of waiting for it (an example of induced demand). Alternatively, I might choose to go without bread entirely because I do not want to wait for it, and maybe there is none available to be purchased (this would now be an example of latent demand).

That's the last example, in all cases the examples don't support the hypothesis that induced demand is strictly false. I think the fatal flaw of the article is that it does not go on to address induced demand at all, basically takes the hypothesis as a given. I would expect there to be refutation of the explanations that induced demand is at play. Basically something along the lines of "if this were induced demand at play, then we should see X, but we see Y instead, which fits better with an explanation of 100% latent demand."

> people using an argument of induced demand as to why no more roads should be built.

I suspect people are using induced demand as an example of why some roads should not be built. The reason for expanding many roads is that it will reduce travel time. That reason does not always hold water, specifically induced demand. If all things were taken into account, then perhaps spending 50% of that road expansion money on say better buses - would be more effective for reducing travel times. It depends on context, generally though US civil engineers do not take into account induced demand (AFAIK; my impression is US civil engineers treat traffic as if it were purely 100% a flow of water, a fixed amount that is independent of the piping).

> Thus, you may differ on the exact definition, but I think an article like this is useful for pointing out the benefits of building additional road capacity, even if it does get "filled up".

While that could be very well true in some cases, there could be even greater benefits for committing those resources to alternative means of transport than additional road capacity. It is context dependent. At the same time, when the "benefits" are not as great as claimed, at some point it becomes snake-oil and we are left stuck in a traffic jam.