I usually try to be respectful, but here I have to say it: this article is junk.<p>I did transportation research, and taught it at the masters level, for more than 10 years. His "arguments" against the concept of induced demand are pretty much part of the basic understanding of everyone in the field. There is none of the epiphanies of the author that are not part of a basic transportation planning class.<p>"Induced demand" is tightly linked with urban sprawl, which the author seems to have just discovered. The critique of induced demand is pretty much centered on the fact that urban sprawl is widely considered as bad, which the author does not seem to even aknowledge. I could write an answer long as a book, but this would be giving this article too much weight.<p>Do yourself a favor and just ignore this.<p>I would concede that the wording is not great, but this is unfortunately often the case with concepts that develop over decades.
Traffic will get worse until taking alternative means transportation is faster and then teach equilibrium. Even if you love driving, if driving takes an hour and the train 45 minutes, most people will just take the train, until traffic speed lowers enough that a balance is reached. If there's no alternative (like in many American cities), the traffic will just continue worsening indefinitely (or at least until people give up on the area and move somewhere else that is more livable). <a href="https://en.m.wikipedia.org/wiki/Downs%E2%80%93Thomson_paradox" rel="nofollow">https://en.m.wikipedia.org/wiki/Downs%E2%80%93Thomson_parado...</a><p>Obligatory Not Just Bikes video: <a href="https://youtu.be/CHZwOAIect4?si=BR9sFwxYDJSAWYLG" rel="nofollow">https://youtu.be/CHZwOAIect4?si=BR9sFwxYDJSAWYLG</a>
He claims roads are efficient. I'm not so sure. Even a small 2-seater has a lot of space around the (typically) single occupant. To say nothing of the wasted space between vehicles when traveling at speed. When riding a motorcycle you can easily ride between cars laterally as well.<p>Of course, train tracks are also vacant almost all of the time, but when there is a train, the passengers are packed much closer together than in a typical road vehicle.<p>He also equates space with comfort but doesn't seem to consider the 2nd-order consequences. More roads, more space on roads, more space between things, and more infrastructure to accommodate cars shifts people from walking and cycling and so on, to cars, because the distances become greater. It's a kind of zero sum game. I wonder if the author would consider THIS demand-shifting to be "induced demand"?
This article does a poor job of representing induced demand so it's can't be trusted to critique it. Traffic and congestion is defined by (number of trips) * (distance traveled). So, if 10 people take 1 mile trips every day, or 5 people take 2 mile trips every day, the traffic congestion will be the same.
Induced demand says that by building roads, you enabled people to buy a cheaper house further out of the city, and drive further, thus congestion stays the same. This is true for other trips as well. You might drive further to Costco to get cheaper groceries rather than to your neighborhood store if there is a fast road there.<p>I think there is a legitimate criticism of induced demand that it usually doesn't provide a tradeoff for when you have enough roads. 0 roads in all size cities isn't the answer. At some point a city has enough roads and should focus on mass transit or other transportation. I've never seen an induced demand argument attempt to define this threshold and why.
Exactly! If building a new lane doesn't immediately ease congestion then demand hasn't been "induced" it's just that the <i>already existing</i> demand has been demonstrated as being insufficiently addressed.<p>That's the case most of the time anyway. There are situations where making travel along a road better does improve the situation at first, but it leads to attracting the development of new destinations along that route which can increase the demand for travel on that same road.<p>For most places the amount of redesign required to fix our terrible traffic infrastructure is going to be a huge problem, but there's hope for new developments and growing cities to avoid these problems and provide amazing public transportation, bike lines, walkable spaces, and better zoning.
> <i>Induced demand is not a useful concept – the demand is always there, latent</i><p>Latent demand and induced demand are distinct:<p>> <i>The technical distinction between the two terms, which are often used interchangeably, is that latent demand is travel that cannot be realised because of constraints. It is thus "pent-up". Induced demand is demand that has been realised, or "generated", by improvements made to transportation infrastructure. Thus, induced demand generates the traffic that had been "pent-up" as latent demand.[6][7][8][9]</i><p>* <a href="https://en.wikipedia.org/wiki/Induced_demand#In_transportation_systems" rel="nofollow">https://en.wikipedia.org/wiki/Induced_demand#In_transportati...</a><p>Though some folks say that it is a distinction without a difference.
I think the final figure in the article is very misleading. Sure, the total area accessible by care may be large in many US cities, but at the same time these cities are sprawling so one has to go very far to find the same range of places/services. One could probably find as many shops and restaurants within 1 mile in Paris as within 10 miles in LA, so the emissions are way greater in the car-centered places for what advantage?
I am not an economist (actually I guess I kinda am) so I won't split hairs about the exact definition of induced demand, but what I do find is that in common experience, the folks that use the term "induced demand" generally use it to shit on things they don't like rather than actually thinking about the total utility generated.<p>Eg the "cars are evil" crowd sill say something like "oh they built another lane from the burbs into the city, but traffic is still slow because more people now moved from the city into the burbs and are driving in that lane."<p>You never hear them say, though "I guess that means there was demand for people to move out to the burbs for greater space/safety/quality of life." So even if dad now gets a longer commute, he's clearly choosing to do that because his family overall is better off. To the extent that building the extra lane enabled this, the world is better off even if eventually that lane itself is as saturated as the existing ones.
I think induced demand actually is a useful concept, but I've also always wondered about its absolute and uncritical application: somebody says "we should add a road here", and gets shut down with "but adding a lane only adds traffic!"<p>Sure, sometimes - but obviously that doesn't scale ad absurdum. So at some point you need to take a more nuanced position on what the actual latent demand is (as this article discusses), what the actual bottleneck is, and what the alternatives are to solve it.
All of the authors arguments for car infrastructure are also arguments for transit infrastructure. And Transit infrastructure investment is more efficient in basically every way. So the conclusion should be... don't invest in car infrastructure...<p>The author seems to seriously underestimate if not ignore the incredible negative externalizaties of car infrastructure.
> Strictly, it is false, and we shouldn’t let it stop us building more roads<p>The clue that this is the case is that if no new roads are good, then tearing out existing roads must be better. This gets you to a silly place rather quickly. At least an abundance of roads stops at some point.
the annalisys starts right, but misses on critical fact: for the amount of X moved roads are expensive. Thus most cfties could save a lot of money by building a great transit system.
At least in NYC the major factor contributing to traffic jam is not from induced demand but the ever deteriorating public transportations. It is more expensive, less safe, less efficient and punctual than before. But government still managed to persuade a large amount of people that the drivers caused this.
ITT: Confused Americans try to explain to everyone else why choosing when you sit in traffic for five hours is preferable to waiting 15 minutes for an hour long train ride.
This is not a good post. This guy is addressing the cliff-notes one-sentence summary of the theory of induced demand, not the full thing, and hence this post is a pretty bad case of attacking a strawman. The more complete version goes like this: building more and bigger roads is a hidden subsidy to sprawl, since it allows people to live further away and in lower-density areas without having to pay the true costs of those areas. For details, see the many, many Strong Towns articles about how many suburbs and exurbs are functionally bankrupt because they never took their true costs of maintenance into consideration.<p>The "induced demand" being criticized is <i>fake</i> demand, because this hidden subsidy is lowering the true price, and as any economist will tell you, demand goes up when the price goes down.
> Imagine a city with acute food shortages and controlled prices (e.g. Caracas, Pyongyang). People join long queues before bakeries daily, and still only average half their calorie needs. The supply of bread then improves so that they average 60% of their calorie needs instead. Would we really expect the queues to wither away? Of course not. They might not even get discernibly shorter. Does this mean that demand for bread is in some peculiar and distinctive sense ‘induced’?<p>Section 1 ceases to make sense if a local frame of reference is chosen rather than a global frame. If you have a country where every city in the country is able to supply 50% of the caloric needs of it's citizens, and then one city is able to satisfy 60% of the calories of it's citizens, you would expect people to want to move to that city until the caloric satisfaction approaches a new equilibrium.<p>Globally, induced demand is not useful, but for the person who bought 10% more food in a particular city it is very useful.<p>So the argument that the author is trying to makes is wrong. Induced demand is true, <i>locally</i>. Induced demand is less useful when things are addressed globally.<p>If a city housed every single homeless person their city, you would expect homeless people from other cities to migrate. In the global sense demand is not induced, but in the local sense it is.
This article misses the point. It assumes that adding lanes doesn't lead to any other changes. And it totally misses the point of why people are willing to spend money on highways.<p>When you make travel to a destination easier more people will want to live and work there. Soon, that capacity will be used up and everything will go back to being congested.<p>If you told voters: your commute will not get better at all, but we want to spend $1B to enlarge this highway so other people can benefit, no one would ever expand a highway again.<p>So the article is right, as long as you have the wrong model for how cities work and you have the wrong model for why anyone would build a highway.
I don't buy that it's not a useful concept. Space is limited in geographic areas so it seems like a zero-sum game to me. Adding more lanes means there is more space to be utilized by cars, taking away space to be used for other productive means of transportation.<p>The demand to travel is still there, as the author asserts, but it's how we use the space we have to provide it that matters. If you add another lane you induce demand for more cars since there is less useful land to build on for other purposes and you make it harder to get around by other means.
When you give something away for free that costs a lot of money to produce (i.e. road capacity) that creates demand that would not exist at price that would actually pay to supply that demand.
I disagree with the author's premise that Induced demand is not a useful concept, as I think his "suppressed demand" alternative is a bit myopic<p>> The demand is not really ‘induced’: it’s more true to say that it was always there – when the roads don’t exist to accommodate it you could call it ‘suppressed demand’.<p>This has been debunked and rebuked to death.<p>1. The suppressed (latent would have been a better word for what he's claiming but i digress) demand is not for cars, it's for fast transportation<p>2. Some people will absolutely take trips they otherwise wouldn't when more throughput is available<p>3. Leisure driving is absolutely a thing<p>When I think of "suppressed" demand, I think of economically useful demand that needs to exist. Perhaps that's my own bias on the semantics of these words, but if so that's just another reason why I think "induced" is more accurate-to-reality than "suppressed" or "latent"<p>Also,<p>> If we offer more subsidised social housing, more people tend to live in it – would we then say that demand for social housing has been ‘induced’?<p>Yes, yes I would. The demand is for housing, and only a subset (which I would bet is minor) would prefer social housing over detached housing. However, social housing is much more economically efficient (similar to buses and trains and public transit in general), so of course the excess demand will fill up social housing when it comes available.<p>Did the author get a proofreader or editor before posting this or is it just an independent blog post?
I generally agree with the observation that most folks get induced demand wrong, and miss the “more people get to use the road which is good” angle.<p>But I also think this observation misses the degree to which most people are uninterested in raising abstract utility for anonymous strangers. If the new road doesn’t make _my_ life better, it’s a waste.
Anyone who says "induced demand" when talking about roads needs a brain transplant.<p>You see it all the time, idiots, mostly civil engineers, with the intent of removing all roads from the map of earth, claim that adding lanes to 76 will cause some sort of apocolyptic end times scenario. As if Daniel's dreams weren't about Babylon but a stretch of crucial highway transit.<p>The phrase "induced demand" induces a headache every time. Truly these people seem to think "demand" is something bad. The truth is the lack of development on 76 has caused many Billions of dollars of damage to our region. The best those fat-on-the-government-teet engineers can give us is a 5 billion dollar, 8000 foot extension to a unused 'high speed rail line'. MORONS.<p>Should we build a railway to connect to the west coast? NO! That would Induce Demand and that's bad! Should we build a road to connect Rome to Constantinople? No! Road are bad! the Silk road was evil!<p>Demand is good. There is almost endless untapped demand that won't get released into economic dollarydoos because 76 is a parking lot of traffic.<p>With a double decked 8 lane each way, people could easily work in the city and live in the suburbs. With a double decked 8 lane each way we could have MORE economic integration between the city and suburbs. Imagine the tens of thousands people move easily, to live in Cherry Hill and commute to KoP, or have a second office, these city-slut-mongors are obsessed with making transit, not easy as they claim, but literally so impossible we are all stuck in the shithole. Plus who likes city taxes?<p>Let us unleash the economic power of Philadelphia by INDUCING GREAT ECONOMIC GROWTH. EMBRACE THE DEMAND! MEET THE DEMAND! SUCCEED THE DEMAND!