24 Comments

Agree with the overall points, but I think many who use the term induced demand actually just mean suppressed demand. You are right that suppressed demand is a more accurate way of phrasing it.

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Hot stuff here, very nice. Admittedly, I am less motivated to comment just to say "I agree" vs when I think there's an "umm,, akshually" point to be made, and I think there are maybe a few

- The Lubbock 15 min city, even if facetious, kinda misses one of the understated appeals of a "15 minute city" in that people should not *need* a car (with surprisingly large ongoing costs) to be able to get around normally and live a middle class existence

-- and, at least where I'm at, much of suburbia does have a "viable" density for transit eg every 15 min, 10 min (heck, even after the "streetcar suburb" era), and it is more authorities not budgeting or servicing it. Ie trying to think of it as meeting demand, like seeing if a bridge should be built by counting the number of people coming across (rather than considering suppressed demand)

- The "Atlanta is a Garden City" is a spicy take that feels kinda wrong, but I can't fault except for "the vibe" I guess all I can think of is the "forest" that Atlanta appears to be nestled in is really just suburbs. But, eh, a bunch of leafy suburbs is close enough? to a forest?

- And about the size comparison of Atlanta to Chicago - was Chicago in 1915 really confined to Cook County? I wonder if there were suburbs outside the county boundary that are still functionally suburbs of Chicago (like today, where suburbanisation? urbanisation extends over to Wisconsin and Indiana bythe looks of it)

Insightful to me

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Thank you for these. In turn:

1) Yes that’s a fair point. Of course, it’s easier for me to say this in England because nearly every town and city in the country has neighbourhoods where you can live far free easily if you wish. I would find Lubbock alienating personally. But many love it! And I think the core thing about a 15 min city is the amenities within reach - after all many extend it to 15 mins by bike.

2) I think more investigation necessary here. I gather there are railway suburbs with American (10-20du/ha) densities around the NY metro - and there certainly are around the SE of England. But I suspect most of these services are heavily subsidised in the USA. But you may be right on density. In which case I would suggest that crime/anti social behaviour is the issue and if we could get that down, these Americans would ride transit.

3) It looks basically like a forest from ground level and from space. They are incredibly leafy suburbs. Every single person a patch of garden. Oh I’m sure Ebenezer himself would find a reason to quibble but I think he’d be shifting the goal posts.

4) Unsure on this, but the London in 1870 one is accurate as are the medieval ones. I stole from Thomas Pueyo. This map (of 1900 development suggests yes it was that compact) https://i.pinimg.com/originals/58/1a/c4/581ac42eb1ceb836a3ad70db4cffb0dd.jpg

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I blame the evil tyrant named Kevin Leonpacher for Atlanta's car dependence.

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While induced demand, as typically explained by urbanist, is really just latent demand, I do think induced demand actually exists.

If you build a new freeway though a city, you are are not just providing a road to travel on, you are also creating a roadblock. A person who might be one mile from a store, now has to take a detour to get to the store and might have to travel five miles. That is not only longer travel (induced demand), it might also move the person from walking or cycling into a car (again, induced demand).

The above mentioned freeway will also create more noise, so people moves farther away inducing even more demand.

A new or expanded freeway will not just create more cars on the freeway, but also on side roads. Those roads may become dangerous or unpleasant from increased traffic, again inducing more people to not walk or bike, but go by their own car. Again, induced demand.

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I think the final figure 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 than within 10 miles in LA, so the emissions are way greater in the car-centered places for what advantage?

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+1

You may be able to access more km^2 if you have good roads but the sprawling design with lots of parking means that there is fewer amenities per km^2.

More interesting metrics to me is jobs or amenities accesible in 30 minutes not parking lots and weed filled medians.

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Your first point is garbage and I see no way to salvage anything from it.

By your logic all current forms of traffic are poor substitutes for zero-cost teleportation, which is latently in massive demand. I think this idea is actually possibly defensible in some arcane pure-logic sense (if there was zero-cost teleportation available to me, I would certainly use it over highways or trains) but it is orders of magnitude less useful than the idea of induced demand, which you rail against as "false".

You presuppose that the "latent" demand is specifically for roads, when in reality the demand is for whatever mode gets the traveler from origin to destination in the way that meets their cost/comfort/speed requirements best. The demand is not latent; it is being met by something other than roads. If there is not enough throughput along the busiest corridors, we have the choice to expand access to any one of the currently available modes, which will improve that mode's comfort, cost, and/or speed. This will (say it with me) induce more demand for that mode, and we can (if we want to) choose where we want to induce that demand based on what will be most sustainable long-term.

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I think the thing that always bugged me about induced demand is that, if it were a serious theory, then why would it *only* apply to roads?

Why doesn't it apply to other transport infrastructure too? Wouldn't building extra rail capacity just magic new commuters out of the ether, and leave our trains just as crowded as they were before? After all, you're inducing a lot of demand for those trains...

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The first part to the answer to that question is that it's not about one level deep. I explain that more here: https://www.bensouthwood.co.uk/p/why-induced-demand-is-fake/comment/84007592

The second part is that the next levels for cars vs. transit are totally different. Cars demand more parking, are associated with more zoning restrictions, and as side-effects of those demands degrade every other type of useful transportation. Transit integrates with walking much more seamlessly, does less to demand zoning restrictions (though many cities have made some big mistakes there even when they do have good transit).

If you choose to look at this only directly.. i.e. a road can't "induce" traffic directly, you'll be correct in an academic sense, but also totally ignorant of anything important. Low density induces longer trips, which induces more traffic (which reoccupies the capacity you built). Wider roads induce lower density (a bit more complex relationship.. but hard to argue with observations of correlation there).

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Nov 9Edited
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“We should” who exactly is this “we”? Our local council has repurposed an old railway line locally as a cycle/ pedestrian route into our city. It is used by a tiny number as a serious route into the city but by quite a few as a purely leisure facility. It’s used by virtually no one on rainy cold days for either activity.

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This is a good insightful assessment. It is certainly not a foregone conclusion that road travel speeds at any time period are doomed to stay down at some inefficiently low level. Now we have GPS-based travel data such as TomTom, we can see there is a wide range of travel speeds across the data for cities. There doesn't seem to be much analytical effort being expended on working out the reasons why. There seems to be a prevailing ideological barrier to identifying and maximizing the gains from automobility itself, instead it is assumed that "making people drive less" is the objective.

Buried in all the confusion, is the factor of "co-location" which is surely the one that will make the most difference. The way that central planners think they can get us there, is by rationing the overall land supply and upzoning and building high density. But there is no data that shows any success via such approach. Hong Kong has extraordinary density but "co location efficiency" is elusive; monster commutes are the norm.

Contrary to planners assumptions, forcing density by rationing land supply pushes up the urban "land rent" curve and this results in the "pricing out" of the most possible people. Housing is demonstrably NOT more affordable even as the size of homes shrinks and they become more stacked and packed. The price of land embodied in their cost is higher, not lower, in spite of the very much smaller footprint per unit. The price of land varies by a factor of tens, or hundreds or even thousands. The lowest land prices are found in the free-sprawling cities and this price is so low that the size of lots cannot push the price of housing up anywhere near the high-land-price cities.

The basic economics underlying this, is that prices can be derived "differentially" or "extractively". The latter involves consumers paying the very maximum they can stand, for a necessity. This applied to almost everything, including food and housing, back in Victorian times. Food and almost all consumer goods came to be priced "differentially" when transport, refrigeration and free trade rendered the supply effectively superabundant, so no owners of resources could charge "extractive" prices for the product of their resources.

Housing came to be also priced "differentially" when automobility rendered the supply of land on which "urban" populations can live, superabundant. The change from Victorian era housing markets, to that of the mid 20th century, is so blindingly obvious that it is extraordinary that there is so much hate for the process that enabled it. What we do by curtailing that supply of land in very low value uses - farmland is $10,000 per acre almost everywhere - is flip urban land markets back to "extractive" condition. The price of sites is worked out backwards - even developers can candidly tell you this - from what the end consumers of housing can be gouged to pay for it. The greater the allowed density, the higher the site value, and this elasticity is exponential. The price of land can be tens, hundreds, or even thousands of times higher, as you cram more people in. The result is not only housing cost stresses, but "pricing out" effects delivering the opposite of the intended co-location efficiencies.

If we simply allowed sprawl and low land prices but provided other incentives for people to reduce their travel distances by co-locating more efficiently, we would actually achieve the best of both worlds, rather than doing nothing but harm.

In all the factors that create "demand for travel", the big one that the official experts do not notice is "escape from land rent gouge". In the third world, as people get motor scooters, their slums spread out and become more spacious. No "highway subsidies" are necessary to drive this process. Even Frank Lloyd Wright, not an economist, saw that it was simple escape from rent gouges in old legacy city centres, that drove "sprawl" in his time, and he applauded it. The Leavitt Brothers were students of his.

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Not sure why you think monster commutes are the norm in Hong Kong. One of the lowest among major cities.

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I must admit I haven't seen data on it for years, it was the worst in the data set I saw at one time. What data have you seen?

I am very familiar with methods of data collection that give quite disparate results. It is necessary to survey the workers, not the residents. Hong Kong has a significant proportion of the workforce who live in Shenzhen and commute from there.

The falsest conclusions on the low side always come from surveying the residents in the centre of the city. Of course they have short commutes; they wouldn't be paying premiums for locating in the centre of the city if they didn't work there. However, even in their own workplaces, there will be a majority of people who have come from afar.

I shouldn't even have to raise these questions, but yes, one sees so called experts trumpeting "findings" to the heavens in support of their ideological position on urban planning, when those "findings" suffer from this most basic flaw of logic.

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The happy medium is a society where the norm is a one-car household. Adults can work, get the kids to school, and run errands with one car, supplemented with robust biking, walking, and transit networks. People need and like cars: roadtrips, hauling groceries, etc — but we need to recognize that they are space hogs and an expensive pain in the butt for most households (not to mention a leading cause of death and disability, and finding parking is a huge time suck). Latent demand exists for biking and transit as well - at the end of the day, people just want a safe and fast way to get from A to B.

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That may be a happy medium for you but the proliferation of two and three car households where I live suggests that others disagree. Our second car enables my wife and I to follow our separate interests without conflict and the ongoing cost of the 11 year old reliable second car is minimal.

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Do you actually prefer that, or is that choice forced upon you because you don’t have any good alternatives to get around? Most households don’t spend tens of thousands of dollars on an extra car because they want to, they do it because there’s no other way to get to work, go to school, etc. Society has forced that on us, and without infrastructural changes we’re helpless to get out of the bind.

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Ben, are you any of the following?:

1. a NIMBY

2. a fossil fuel industry shill

3. an auto industry lobbyist

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Insofar as I am known for anything, it is for being a YIMBY who loves walkable neighbourhoods!

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Renaming induced demand as suppressed demand makes sense, although both terms are equally value-laden. The unaddressed question is why roads are the best way to meet that demand - and especially why roads built for private cars are best, which every example cited assumes.

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There are forms of demand that fits the literal meaning of "induced" in this context though. Minimum lot sizes, parking requirements, height restrictions, they all would fit the definition of inducement you take issue with, and all of them were part of the conversation about why there was always someone to fill up a new lane.

Besides those simple points, there's a more nuanced one that was part of the original framing of induced demand in respect to roadways. For the sake of simple discussion, think of a city in 3 zones, inner, outer, and outside, where the inner is the core city that's driving agglomeration value, outer is the edge, and outside if the area you've not yet developed. If you build a bigger highway through an outer area, it will degrade the value of that outer area. Yes, it opens up the outside area, but it ultimately degrades another part and doesn't enable more trips, but extends existing ones. Spend some time looking at almost any US city and you'll find that pattern repeated. You don't even need population growth to fuel it.. it's often worse when population is flat, as there is no opportunity for the formerly "outer" area to create some agglomeration value of their own. This effect of degrading the value of a closer area (which at the same time is locked into a particular zoning pattern), is also inducing demand to move farther away, which is thus an inducement for traffic.

There might be places where "suppressed" would be more correct, but overall, it's often wrong and you can't know without delving deeper into those other details which you haven't done. The original framers of the term did think about all these aspects you've not yet done, and I'd suggest you need to engage with them a bit more deeply before declaring it a not useful concept.

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You guys, or ought I say guys like you are sooo ….what is the word….. arrogant…self centered (in the sense that you think that because an ‘opinion’ is yours it must be right, and helpful, and true , and worth sharing (imposing) …..)….it is beyond belief… have you heard the story about the American who had returned to the home country to seek out his ancestral roots… lost, and driving along a country lane and sees an old farmer leaning on a gate chewing on a piece of straw…. ‘Excuse me my friend, I wonder if you could give me directions to the village of Ballybanock.’ ‘I certainly could young man, but if I were you I wouldn’t start from here.’ Have a look at where you are starting from…. more wealth does not make any one of us, or the people, or the country, nation or whatever you want to call it, ‘happier.’ And anyone who still thinks it does is ill. Diseased. On all levels, physically, emotionally, psychologically, humanly. Of course, abject poverty, which is entirely unnecessary anywhere on the Earth today May make one forlorn, sad, possibly to feel hopeless and even maybe unhappy. But more wealth per se never has, and never will make anyone happier. Don’t start from here. Think again.

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Why do you use “gouged” for the price developers can charge? Developers are price takers and use their assessment of the potential selling price and building costs to set the maximum price they will pay for land. Speaking as an “evil” developer I’m more than fed up with the moronic assumption that developers are intrinsically evil.

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I think there is something to the dynamic where State DOT’s highway work program seem to be limited by budget, their leaders are not elected, can sometimes exempt themselves from environmental regulations/review, not necessarily sensitive to public pushback versus building development, limited by regulation, sensitive to local resident/elected political interests, driven by capital.

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