13 ms·

Induced demand is not a useful concept

79 points by telotortium 3y ago

estebank 3y ago
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). https://en.m.wikipedia.org/wiki/Downs%E2%80%93Thomson_paradox https://en.m.wikipedia.org/wiki/Downs%E2%80%93Thomson_parado... Obligatory Not Just Bikes video: https://youtu.be/CHZwOAIect4?si=BR9sFwxYDJSAWYLG https://youtu.be/CHZwOAIect4?si=BR9sFwxYDJSAWYLG
- michaelmrose 3y ago
  You can also tax cars until demand decreases. The obvious challenge is that presently people commute into the city because they can't afford to live in the city or perhaps most aptly cannot afford what they would consider a reasonable lifestyle there. Even if you phase it in you risk simply forcing people to move into the city exacerbating existing housing prices. It feels like you need a very very substantial increase in housing prior to increase in taxes. For instance in cities that have excessive single family housing bulldozing houses to build substantial apartments then phasing in taxes. The alternative is probably pretty ugly because people have a seemingly very high tolerance for bad traffic. They will keep moving to the city and keep driving until driving in the city is beyond untenable.
  - ProfessorLayton 3y ago
    We could also just stop subsidizing as much as we currently do. We hand out so much public land in the form of free street parking, making the roads larger unwieldy to walk in, and bikes have to worry about getting doored. I'm not suggesting we get rid of all street parking, but it's currently at absurd levels. It would be great if some of those subsidies went to something else that lessened the need to own a car in the first place.
    - mitthrowaway2 3y ago
      You're downvoted, but it's a very reasonable point. I'm not sure why you can park a car on the street for hours for free, but not, say, a picnictable with a BBQ, a folding tablesaw, a telescope, a pop-up bookstore, a film projector, and so on.
      - thereisnospork 3y ago
        The short answer is because public parking is in the public interest. Same as bike parking or sidewalks. Think how much space we could save if we got rid of sidewalks! (/s of course)
        adrianN 3y ago
        You grandparent is arguing that there is a desirable level of street parking that is below current levels of street parking. They don't claim that all street parking is bad.
        TulliusCicero 3y ago
        The difference is that car parking is an enormously larger handout. Bike parking probably takes a tenth as much space per "vehicle".
      - melagonster 3y ago
        Before car occupied road, it is possible.
      - maxsilver 3y ago
        > I'm not sure why you can park a car on the street for hours for free, but not, say, a picnictable with a BBQ, a folding tablesaw, a telescope, a pop-up bookstore, a film projector, and so on. I mean, the traditional answer is pretty clear. Roads are public transportation infrastructure. Parking cars (and bikes and scooters) is allowed, because cars move the public around. All these other things are not transportation for the public. People think of parking spots along the streets as "landed property", but they're not, they're more like the overhead bins in a bus or plane. But also, from a practical sense, no one cares about public transportation anymore, so you actually can now park random crap in the street, anytime you'd like? At least in Michigan, restaurants routinely do the "park a picnic table with a BBQ on the side of the road" thing all the time (see https://www.giffelswebster.com/dining-platforms-and-parklets-in-parking-spaces/ https://www.giffelswebster.com/dining-platforms-and-parklets...) -- many of which still persist since COVID assistance ended. And residential/commercial construction workers routinely do get to block off street parking for a tablesaw or any other construction usage at job sites all the time.
  - autoexec 3y ago
    > You can also tax cars until demand decreases. I think punishing drivers is a bad idea. It'd be much better to provide alternatives to driving that are attractive enough that people choose to use them because it actually benefits them to do so. Not many people are looking for their city to hurt them until they have no choice but to make do with things that are worse and less convenient for them. Give people a better option and they'll flock to it naturally. I've spent enough time in places with amazing public transportation that I know it can be the preferred option for 80-90% of my needs. That's what we should strive for.
    - Gibbon1 3y ago
      I agree. The issue with taxing drivers is it assume the driver is mostly culpable. But the infrastructure decisions that force the majority of people to commute by car weren't made by them. You got things like the big boss and his managers all like to live close to each other and close to work. So they commute 5 minutes to the office in Sunnyvale. While the secretary is commuting from Vacaville. Placing a Pigouvian tax on the secretary is kinda a jerk move.
      - michaelmrose 3y ago
        I suggested that housing be substantially expanded FIRST and then phase in increased taxes on cars in the city thereafter. Basically first make it possible for the secretary to have an opportunity to move close to Sunnyvale then years later if its still important to live in Vacaville they can pay increasing taxes representing the actual collective cost.
        autoexec 3y ago
        I suspect you'll run into similar difficulties convincing people to allow their single family homes to be bulldozed and give up their privacy, their equity, and their lawns/gardens so that they can move in with strangers. If you can't offer people a housing situation that's better for them than what they have you'll not get many people signing up to make their lives worse. Try to strong arm them into it and you'll get resistance and resentment. I think we have the ability to give people better, less isolated, housing options that many would find preferable to cookie cutter houses in labyrinth-like subdivisions that cut them off from the rest of the city unless they can drive, but those options will have to minimize the downsides of living in close proximity to many others and come with additional benefits that more than make up for what you're asking people to give up.
  - frankus 3y ago
    It’s worth pointing out that there are lots of ways to get people into and out of a city that don’t involve driving a private car.
  - bluGill 3y ago
    > You can also tax cars until demand decreases. No you can't. If you try you will find yourself voted out of office and replaced with someone who immediately removes those taxes - and everything else you were doing to make alternatives better. If you want to make people not drive you need to start with a better option. Start building great transit. Great transit isn't possible without quantity, so build a lot of it. Make it fast and frequent. Once people have a good (not always better, but it needs to be good) we can talk about how to get the stragglers still driving out of their cars. However very few places in the world have this problem and so it isn't worth talking about.
  - calamari4065 3y ago
    >You can also tax cars until demand decreases Ideas like this disproportionately affects poor people and minorities. Sure, you've reduced traffic, but now only the Right Kind Of People can afford to drive. Not a great look.
    - selectodude 3y ago
      Driving is, in fact, a luxury. Only the right kind of people can vacation in Vail and I don’t see anyone flipping out about that.
      - digging 3y ago
        Not in the vast majority of North America. It's a necessity
        estebank 3y ago
        And the argument is that in cities, it shouldn't be.
        digging 3y ago
        I fully agree but that's 3-4 decades away if it's ever coming for most cities.
        michaelmrose 3y ago
        The vast majority of America by acreage has squirrels and deer, water, or crops by sq ft. 4 in 5 citizen lives in an urban area where one could with sufficient investment live without a car.
        digging 3y ago
        > The vast majority of America by acreage has squirrels and deer, water, or crops by sq ft. Very clever, you sure got me. > 4 in 5 citizen lives in an urban area where one could with sufficient investment live without a car. Most definitely not. Americans living in a typical suburb have no option except to drive or walk for perhaps hours (often with no sidewalks) to get basic necessities. Even within the vast majority of US cities, typically it's a minority of neighborhoods well serviced by walkable amenities and transit, and the rest are still car-dependent. Again, walking 45+ minutes for basic errands is not a reasonable ask. Bike infrastructure is usually lacking or absent and is forbiddingly dangerous to people who aren't strong and confident bicyclists.
- autoexec 3y ago
  > Traffic will get worse until taking alternative means transportation is faster Alternate modes of transportation don't even have to be faster, it just can't be substantially worse. I'd gladly add an extra 10-15 to my travel time if I can spend that trip relaxing in a comfortable and well-maintained train and not have to deal with traffic, other drivers, parking, etc. People will still want cars, and in many cases still need them, but a huge percentage of our driving could be eliminated as long as public transportation was made the more attractive option.
  - bluGill 3y ago
    I always tell people I want them to get rid of a car - most people live in a family situation where there is more than one driver. If there was a good transit system they could keep one car (to tow the boat or whatever it is that transit can't do), and save a large pile of money. As you say, better can mean a little slower, but not a lot slower. Creating a better transit system is expensive, but still cheaper than cars.
    - dboreham 3y ago
      > but still cheaper than cars Overall for society yes, but in most places where transit is widely used, it is quite costly. E.g. a season ticket between Reading and London is 512UKP/mo. For the individual traveler it may not be cheaper especially if they already need to own a car to go to Tesco etc.
      - pessimizer 3y ago
        https://en.wikipedia.org/wiki/Impact_of_the_privatisation_of_British_Rail https://en.wikipedia.org/wiki/Impact_of_the_privatisation_of...
      - TulliusCicero 3y ago
        Meanwhile, when I was living in Munich a few years back, an annual pass covering the whole city was like 500 EUR. For the year. That plus a bike made for great urban transportation.
- waveBidder 3y ago
  it almost feels like the njb video was specifically a reaction to this, the exact misunderstandings this article has are what he's responding to.
  - bluGill 3y ago
    I didn't see the video (I find NJB annoying so I rarely watch his stuff), but it is a common misconception in the transit world that induced demand is a bad thing. Cities should be inducing demand for getting around. The only question is what demand - build a great transit system and you will induce demand for more transit and places to live close to transit. Have a bad transit system and you will induce demand for more roads.
    - zeendo 3y ago
      It sounds more like people use "induced demand" with negative connotations when referring to "induced driving demand" rather than truly meaning that any source of induced demand is bad. i.e. it's just a conventional shorthand?
      - bluGill 3y ago
        I have only seen induced demand used with clearly negative connotations in my life. This article (and a couple others) are the rare exception and they are only using it in context of explaining why it isn't bad (as opposed to using it in a neutral form)
        waveBidder 3y ago
        the vast majority of urbanists are referring to induced driving demand when they bring up the topic. njb is definitely a jaded man, can see why it'd potentially be offputting.
    - throw0101c 3y ago
      > Cities should be inducing demand for getting around. This is mentioned in the latest NJB video, "More Lanes are (Still) a Bad Thing": > The difference for induced demand for cars, and induced for other modes of travel, is that cars are a extremely space inefficient. You can absorb a lot more induced travel demand on a subway line, tram line, or bicycle path, than you can in a car lane. * https://www.youtube.com/watch?v=CHZwOAIect4&t=15m54s https://www.youtube.com/watch?v=CHZwOAIect4&t=15m54s The Oh The Urbanity! channel has a good video on this, "What People Get Wrong About Induced Demand": * https://www.youtube.com/watch?v=8wlld3Z9wRc https://www.youtube.com/watch?v=8wlld3Z9wRc Cars have (AFAICT) the lowest hourly through-put of any transportation mode: * https://en.wikipedia.org/wiki/Passengers_per_hour_per_direction https://en.wikipedia.org/wiki/Passengers_per_hour_per_direct...
- steveBK123 3y ago
  The induced demand memes always show the crazy west coast mega highways. Meanwhile east coasters have roughly the same HOV-less, 2-3 lane highway infra in the suburbs that we had 50 years ago when the population in some areas was 1/2 of what it is today. Worse yet, we also have roughly the same transit infra we did then too. You can tax cars/roads, you can make trains free, but at the end of the day.. you need to build SOMETHING. If you want your economy to grow as your population grows, you need to grow your infra. It's a sorry state in the NYC metro area because we are not. You can't just keep slicing up the existing infra pie differently, you need to grow the pie. Otherwise you are just reallocating winners & losers, and unlikely to make the overall situation any better. Thinking we will simply increase the pain of driving until the existing state of trains is tolerable is idiotic, but I see plenty of this in the alt-transit movement. Make trains great, make them awesome, make me want to take them.. make me regret having to drive when I do!!
  - eppp 3y ago
    We don't NEED to build something. Maybe NYC is big enough and people need to consider going elsewhere with better policies. We need to stop this narrative that growth must continue indefinitely.
    - TulliusCicero 3y ago
      Those people don't cease to exist if they're not in NYC, you realize? If they're not there, they're probably somewhere more sprawly, that uses more energy and cuts more space out of the environment.
      - steveBK123 3y ago
        This guy gets it
        TulliusCicero 3y ago
        A lot of NIMBYs seem to lack object permanence. If dastardly "newcomers" have to move elsewhere, they chalk that up as a victory for degrowth, as if those people poof out of existence as soon as they leave the metro area.
- jakderrida 3y ago
  > 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). While it's incredibly hard to believe, it is true. If you look at population statistics for Philadelphia up to the 1980s, it fell to 4/5ths its peak in less than a couple decades. Driving from river-to-river, or from city-to-suburbs or vice versa was a nightmare, according to everyone older than me. Driving "through" or "to" the center city's impassable traffic grid was hopeless. Then, in 1984, they took advantage of the government buying all the bankrupt railroads and used that property to create a below-ground highway Vine-Street Expressway for river-to-river traffic and connected Penn Railroads Center-city terminal with Reading's system through an underground commuter tunnel and turned Reading's terminal into the Convention Center instead of a giant mess off railroad track interlockings leading into Reading Terminal making traffic even worse. If not for that, I have no doubt it would be 3/5ths the peak population. I could write a 50-page paper on all the things it fixed and I was only 2 when it was all built.
adrianN 3y ago
More roads lead to more sprawl in the mid term and hence more traffic. The problem is that cars don't scale.
- Scoundreller 3y ago
  I always wonder what impact on traffic larger vehicles have because they take up more space and people cognitively give more space to larger objects (hopefully?). The impacts on unsegmented linear street parking are obvious. Dunno why monthly/yearly permits for those aren’t by the (square) foot/metre.
  - sokoloff 3y ago
    Presumably length (as parked) matters more than area for parking consumption. Whether my car is 5 feet wide or 6.25 feet wide doesn’t meaningfully change the amount of street parking it consumes.
    - mitthrowaway2 3y ago
      It does if the road needs to be made wide to accommodate such vehicles, or for how wide the stalls in a parking lot are. On my small side street, there are two people who own Ford Raptors with the wide tires, and if they happen to park across from each other it becomes nearly impossible for an Amazon delivery van to drive down the remaining width of road.
    - Scoundreller 3y ago
      The hypotenuse might be the most sensible here. Wider needs more space to get in/out of a spot.
  - carlosjobim 3y ago
    The impact is exponential. A motorcycle is about 1/4 the size of a car, but needs less lanes to have a good traffic flow, or: Have a thousand motorcyclists going down a two-lane highway, their traffic will be smoother and faster than a thousand cars going down a four lane highway.
bluGill 3y ago
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.
autoexec 3y ago
Exactly! If building a new lane doesn't immediately ease congestion then demand hasn't been "induced" it's just that the already existing demand has been demonstrated as being insufficiently addressed. 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. 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.
- waveBidder 3y ago
  that's called latent demand, not induced. induced demand is people changing e.g. housing in response. like all those businesses that start around train stations.
  - thereisnospork 3y ago
    I would argue that is still latent demand, just on a geographically larger scale. If demand were met (globally) then adding a train line (or highway, or stroad) would have a neglible impact on traffic and business development patterns - because everyone can already get to their needs and wants in a timely and economic fashion and therefore has at most casual incentive to use the new infrastructure. For instance a literal "road to nowhere" may 'induce demand' but only because there is unmet demand elsewhere.
    - deleted 3y ago
      [deleted]
  - bluGill 3y ago
    Even as the world population starts to decline (expected in the 2080s according to the UN), cities are likely to expand for a while as people move out of rural areas. Which means that just population projections for your lifetime imply that your city will be growing in population for your lifetime. Therefore there will be more demand for travel over time (unless you build so much that you get ahead - good luck as this is expensive)
light_hue_1 3y ago
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. 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. 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. 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.
SoftTalker 3y ago
Better roads leads to more economic opportunity, which leads to more jobs, which attracts more people to the area, which creates more traffic.
- sagarm 3y ago
  Building housing attracts people, expanding the economy of the metro area. Expanding highways supports and enables building sprawl instead of infill. Sprawl is very expensive to maintain due to the per-capita infrastructure costs; eventually the growth slows and the infrastructure starts requiring maintenance, and the property taxes can't cover it.
  - randomdata 3y ago
    > Building housing attracts people Eh, not really. Sure, if people cannot find anywhere to live, building a house in place X might push them towards place X. But if everyone already has somewhere to live, building a house in place X is not going to attract people to place X. Someone already attracted to place X may hinge their move on housing availability, but you need the attraction first for the houses to matter. Building a bunch of houses on the North Pole isn't really going to compel people to move there. > expanding the economy of the metro area To a limited degree, but an insular economy does not have much growth potential. For example, let's say place X has gold. But if you can't get the gold out then you can only trade gold between the local residents – who are probably also in the business of gold. Why are they going to trade for your gold with you when they already can get gold themselves? That leaves little economic opportunity. But if you build a road, then you can ship the gold off to places where gold isn't locally available. Now you've got people who are keen to trade with you.
  - ryathal 3y ago
    Building houses only attracts people to where they want to live. A 30-story condo building in Anchorage isn't going attract people, that same building in San Francisco would likely have a waitlist.
- zip1234 3y ago
  Have you noticed that all the projections used to justify the cost of adding more lanes to roads are always wrong? Maybe there is some economic growth but almost never enough to justify the cost of such sprawl.
Analemma_ 3y ago
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. The "induced demand" being criticized is fake 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.
hughesjj 3y ago
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 > 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’. This has been debunked and rebuked to death. 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 2. Some people will absolutely take trips they otherwise wouldn't when more throughput is available 3. Leisure driving is absolutely a thing 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" Also, > 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’? 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. Did the author get a proofreader or editor before posting this or is it just an independent blog post?
- randomdata 3y ago
  As commonly defined, latent demand and induced demand are effectively the same thing, albeit observed at different points in time. With respect to highways, latent demand describes the potential demand before the improvements are made. Induced demand describes the shift from potential to actual demand after the improvements have been made.
  - ryathal 3y ago
    While they may measure the same thing the connotation is different and often only applied to cars like the article says. We don't say more low-income housing created demand for low-income people. We don't say building a school created demand for children. Flipping cause and effect for expansion of roads is wrong.
deleted 3y ago
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aero142 3y ago
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. 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.
- bluGill 3y ago
  Economics should define that threshold. There are things you cannot do on mass transit - get the lumber to build a new house/apartment for example. There are things you don't want on mass transit (I don't want you to take your smelly garbage to the dump via the train even though this is possible). Thus a small town will need to build roads. However as the town grows to a city eventually the minimum road to all lots is not enough. At this point we need to ask what is more cost effective: building transit in this town or building more lanes. Unfortunately transit depends on the whole system (this applies to roads too, but we started with them!), which means long term transit might have been a better answer, but right now more roads are cheaper.
rconti 3y ago
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. 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. 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"?
- estebank 3y ago
  There's an additional problem: traffic congestion isn't caused by the number of lanes, but the number of intersections. You can widen the highway all you want, but if the traffic still needs to be absorbed by a city with a handful of sliplanes into the city grid, the backup will continue to exist. When crossing the San Francisco Bay Bridge, the places where the highway has congestion is on the exits. You could even improve traffic on the bridge if you removed a lane and used that for buses, bikes or just emergency vehicles, because you're giving more time to the city to absorb the incoming traffic.
  - trgn 3y ago
    > traffic congestion isn't caused by the number of lanes, but the number of intersections. I wish people understood this more. Parallel travel lanes really just create reptile-brained jostling for position, push-pull accordion effect. it's one thing on highways, but I absolutely can't stand it in city traffic. That constant rush to get to the next intersection, the weaving in&out of lanes just to gain a car length, that mindless churn that when there is a gap it needs to be filled. Like being surrounded by mindless automatons in a weird fill-the-next-gap game of life at best, by insecure typeA losers at worst. Drivers are a lot more calm and considerate when they just chug along in single file. And it doesn't even impact total travel time! The weird thing is. It is absolutely impossible to explain this to anybody. There's always the immediate reaction, but see more lanes, more lanes is better, more cars in more lanes. Intuition really fails here, it's an emergent property of drivers being 90% id the second they step in a car, and then throwing these dumb beasts in a system that doesn't curb their instincts.
hayst4ck 3y ago
> 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’? 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. Globally, induced demand is not useful, but for the person who bought 10% more food in a particular city it is very useful. So the argument that the author is trying to makes is wrong. Induced demand is true, locally. Induced demand is less useful when things are addressed globally. 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.
up2isomorphism 3y ago
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.
dehrmann 3y ago
> Strictly, it is false, and we shouldn’t let it stop us building more roads 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.
- Qwertious 3y ago
  Counter-intuitively, ripping out roads empirically can reduce traffic.
  - bluGill 3y ago
    Only if there are good alternatives. Otherwise it just gets you voted out of office and those roads restored.
    - hughesjj 3y ago
      Literally no, you can reduce traffic by removing roads in certain circumstances. This is an approachable video describing the mathematics behind such if you're concerned from a theoretical/first principles ground https://youtu.be/Cg73j3QYRJc?si=PqKI6XSeTTbrPc1D https://youtu.be/Cg73j3QYRJc?si=PqKI6XSeTTbrPc1D
- adrianN 3y ago
  Tearing out existing roads gets you to pleasant walkable neighborhoods like those people like to visit on vacations.
- erehweb 3y ago
  Well, sure, if you tear out all roads, that gets you to a silly place, just as building as many roads as possible would. But that doesn't say anything about whether taking out some of the currently existing roads would be better. In many cases, it has been - e.g. SF removing the Embarcadero Freeway https://www.cnu.org/what-we-do/build-great-places/embarcadero-freeway-removal https://www.cnu.org/what-we-do/build-great-places/embarcader...
- 3y ago
miamowers 3y ago
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... The author seems to seriously underestimate if not ignore the incredible negative externalizaties of car infrastructure.
TheCoelacanth 3y ago
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.
jonnycat 3y ago
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!" 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.
- ravetcofx 3y ago
  > but obviously that doesn't scale ad absurdum 28 lanes in Texas say otherwise
Scriddie 3y ago
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?
throw0101c 3y ago
> Induced demand is not a useful concept – the demand is always there, latent Latent demand and induced demand are distinct: > 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] * https://en.wikipedia.org/wiki/Induced_demand#In_transportation_systems https://en.wikipedia.org/wiki/Induced_demand#In_transportati... Though some folks say that it is a distinction without a difference.
aftoprokrustes 3y ago
I usually try to be respectful, but here I have to say it: this article is junk. 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. "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. Do yourself a favor and just ignore this. I would concede that the wording is not great, but this is unfortunately often the case with concepts that develop over decades.
- throwanem 3y ago
  Since you're in the field, I'll ask: do you know a good 101-level treatment of the subject? Looking for broad rather than deep, something that gives a good overview and directions for further study. Thanks!
  - gensym 3y ago
    I'm not in the field, but I highly recommend Tom Vanderbilt's Traffic. Not a textbook, but an excellent one (and I've had people in the field speak highly of it to me).
- sapiogram 3y ago
  > 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 acknowledge. Isn't this exactly what the author's point #2 ("More and better infrastructure lets us spread out and enjoy more space") was about?
  - sebstefan 3y ago
    It misses the core point of the people spouting "induced demand", which is that if you were to satisfy the demand for cars, there won't be a city to drive to or to park in at the end They just take too much space "More and better infrastructure lets us spread out and enjoy more space" only works to the point where you can still get to the centers of activity in your city within a reasonable time, and past a certain point you either have to bulldoze the center to make space for the vehicles of the suburbanites, or densify It is insane to me that they decided to write an entire blog post about something like that if they didn't even address this So honestly I agree, it's a trashy piece
agentultra 3y ago
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. 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.
xyzelement 3y ago
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. 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." 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.
- johnkpaul 3y ago
  I'm exactly the dad in this scenario and I 100% do not feel like I had an option here. I am pretty frustrated with the house, the space and I don't feel any more safe or higher quality of life. I did this only because I could not afford the number of bedrooms I need for surprise triplets in the city I was basically born and raised in. From my anecdata of peers, pretty much everyone who lived in an urban environment for most of their lives would like to stay there but cannot afford it. I suppose I could see the "family is better off" statement being valid but it is not because of the list you mentioned, it is purely affordability for me. My parents were able to afford a 3 bedroom apartment and I cannot.
  - xyzelement 3y ago
    I hear you and congrats on the triplets. In the pure economic sense you are obviously making a choice "I don't love the burbs but this is my best path vs what I can have in the city" which is obviously only possible because those burbs have roads etc. So you're in line with my point here.
    - johnkpaul 3y ago
calvinmorrison 3y ago
Anyone who says "induced demand" when talking about roads needs a brain transplant. 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. 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. 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! 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. 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? Let us unleash the economic power of Philadelphia by INDUCING GREAT ECONOMIC GROWTH. EMBRACE THE DEMAND! MEET THE DEMAND! SUCCEED THE DEMAND!
- eppp 3y ago
  You are missing the forest for an unhinged rant. The lie that is fed to everyone is that traffic will be improved by expanding roads. It is simply a lie. Tell the truth about what these projects are for and you can start having a legitimate discussion. You are simply distorting the actual truth of what happens. Trains also don't induce demand in the middle of the routes the same way because there aren't exits to build more garbage. If you want to talk about building expressways from city to city without exits then you have a more apt comparison.
theptip 3y ago
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. 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.
zip1234 3y ago
The author states that widening the M-25 only achieved a 10% increase in throughput. This is not good and the definition of diminishing returns.
deleted 3y ago
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kmeisthax 3y ago
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.

79 points by telotortium 3y ago

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). https://en.m.wikipedia.org/wiki/Downs%E2%80%93Thomson_paradox https://en.m.wikipedia.org/wiki/Downs%E2%80%93Thomson_parado... Obligatory Not Just Bikes video: https://youtu.be/CHZwOAIect4?si=BR9sFwxYDJSAWYLG https://youtu.be/CHZwOAIect4?si=BR9sFwxYDJSAWYLG

michaelmrose 3y ago
You can also tax cars until demand decreases. The obvious challenge is that presently people commute into the city because they can't afford to live in the city or perhaps most aptly cannot afford what they would consider a reasonable lifestyle there. Even if you phase it in you risk simply forcing people to move into the city exacerbating existing housing prices. It feels like you need a very very substantial increase in housing prior to increase in taxes. For instance in cities that have excessive single family housing bulldozing houses to build substantial apartments then phasing in taxes. The alternative is probably pretty ugly because people have a seemingly very high tolerance for bad traffic. They will keep moving to the city and keep driving until driving in the city is beyond untenable.
- ProfessorLayton 3y ago
  We could also just stop subsidizing as much as we currently do. We hand out so much public land in the form of free street parking, making the roads larger unwieldy to walk in, and bikes have to worry about getting doored. I'm not suggesting we get rid of all street parking, but it's currently at absurd levels. It would be great if some of those subsidies went to something else that lessened the need to own a car in the first place.
  - mitthrowaway2 3y ago
    You're downvoted, but it's a very reasonable point. I'm not sure why you can park a car on the street for hours for free, but not, say, a picnictable with a BBQ, a folding tablesaw, a telescope, a pop-up bookstore, a film projector, and so on.
    - thereisnospork 3y ago
      The short answer is because public parking is in the public interest. Same as bike parking or sidewalks. Think how much space we could save if we got rid of sidewalks! (/s of course)
      - adrianN 3y ago
        You grandparent is arguing that there is a desirable level of street parking that is below current levels of street parking. They don't claim that all street parking is bad.
      - TulliusCicero 3y ago
        The difference is that car parking is an enormously larger handout. Bike parking probably takes a tenth as much space per "vehicle".
    - melagonster 3y ago
      Before car occupied road, it is possible.
    - maxsilver 3y ago
      > I'm not sure why you can park a car on the street for hours for free, but not, say, a picnictable with a BBQ, a folding tablesaw, a telescope, a pop-up bookstore, a film projector, and so on. I mean, the traditional answer is pretty clear. Roads are public transportation infrastructure. Parking cars (and bikes and scooters) is allowed, because cars move the public around. All these other things are not transportation for the public. People think of parking spots along the streets as "landed property", but they're not, they're more like the overhead bins in a bus or plane. But also, from a practical sense, no one cares about public transportation anymore, so you actually can now park random crap in the street, anytime you'd like? At least in Michigan, restaurants routinely do the "park a picnic table with a BBQ on the side of the road" thing all the time (see https://www.giffelswebster.com/dining-platforms-and-parklets-in-parking-spaces/ https://www.giffelswebster.com/dining-platforms-and-parklets...) -- many of which still persist since COVID assistance ended. And residential/commercial construction workers routinely do get to block off street parking for a tablesaw or any other construction usage at job sites all the time.
- autoexec 3y ago
  > You can also tax cars until demand decreases. I think punishing drivers is a bad idea. It'd be much better to provide alternatives to driving that are attractive enough that people choose to use them because it actually benefits them to do so. Not many people are looking for their city to hurt them until they have no choice but to make do with things that are worse and less convenient for them. Give people a better option and they'll flock to it naturally. I've spent enough time in places with amazing public transportation that I know it can be the preferred option for 80-90% of my needs. That's what we should strive for.
  - Gibbon1 3y ago
    I agree. The issue with taxing drivers is it assume the driver is mostly culpable. But the infrastructure decisions that force the majority of people to commute by car weren't made by them. You got things like the big boss and his managers all like to live close to each other and close to work. So they commute 5 minutes to the office in Sunnyvale. While the secretary is commuting from Vacaville. Placing a Pigouvian tax on the secretary is kinda a jerk move.
    - michaelmrose 3y ago
      I suggested that housing be substantially expanded FIRST and then phase in increased taxes on cars in the city thereafter. Basically first make it possible for the secretary to have an opportunity to move close to Sunnyvale then years later if its still important to live in Vacaville they can pay increasing taxes representing the actual collective cost.
      - autoexec 3y ago
        I suspect you'll run into similar difficulties convincing people to allow their single family homes to be bulldozed and give up their privacy, their equity, and their lawns/gardens so that they can move in with strangers. If you can't offer people a housing situation that's better for them than what they have you'll not get many people signing up to make their lives worse. Try to strong arm them into it and you'll get resistance and resentment. I think we have the ability to give people better, less isolated, housing options that many would find preferable to cookie cutter houses in labyrinth-like subdivisions that cut them off from the rest of the city unless they can drive, but those options will have to minimize the downsides of living in close proximity to many others and come with additional benefits that more than make up for what you're asking people to give up.
- frankus 3y ago
  It’s worth pointing out that there are lots of ways to get people into and out of a city that don’t involve driving a private car.
- bluGill 3y ago
  > You can also tax cars until demand decreases. No you can't. If you try you will find yourself voted out of office and replaced with someone who immediately removes those taxes - and everything else you were doing to make alternatives better. If you want to make people not drive you need to start with a better option. Start building great transit. Great transit isn't possible without quantity, so build a lot of it. Make it fast and frequent. Once people have a good (not always better, but it needs to be good) we can talk about how to get the stragglers still driving out of their cars. However very few places in the world have this problem and so it isn't worth talking about.
- calamari4065 3y ago
  >You can also tax cars until demand decreases Ideas like this disproportionately affects poor people and minorities. Sure, you've reduced traffic, but now only the Right Kind Of People can afford to drive. Not a great look.
  - selectodude 3y ago
    Driving is, in fact, a luxury. Only the right kind of people can vacation in Vail and I don’t see anyone flipping out about that.
    - digging 3y ago
      Not in the vast majority of North America. It's a necessity
      - estebank 3y ago
        And the argument is that in cities, it shouldn't be.
        digging 3y ago
        I fully agree but that's 3-4 decades away if it's ever coming for most cities.
      - michaelmrose 3y ago
        The vast majority of America by acreage has squirrels and deer, water, or crops by sq ft. 4 in 5 citizen lives in an urban area where one could with sufficient investment live without a car.
        digging 3y ago
        > The vast majority of America by acreage has squirrels and deer, water, or crops by sq ft. Very clever, you sure got me. > 4 in 5 citizen lives in an urban area where one could with sufficient investment live without a car. Most definitely not. Americans living in a typical suburb have no option except to drive or walk for perhaps hours (often with no sidewalks) to get basic necessities. Even within the vast majority of US cities, typically it's a minority of neighborhoods well serviced by walkable amenities and transit, and the rest are still car-dependent. Again, walking 45+ minutes for basic errands is not a reasonable ask. Bike infrastructure is usually lacking or absent and is forbiddingly dangerous to people who aren't strong and confident bicyclists.
autoexec 3y ago
> Traffic will get worse until taking alternative means transportation is faster Alternate modes of transportation don't even have to be faster, it just can't be substantially worse. I'd gladly add an extra 10-15 to my travel time if I can spend that trip relaxing in a comfortable and well-maintained train and not have to deal with traffic, other drivers, parking, etc. People will still want cars, and in many cases still need them, but a huge percentage of our driving could be eliminated as long as public transportation was made the more attractive option.
- bluGill 3y ago
  I always tell people I want them to get rid of a car - most people live in a family situation where there is more than one driver. If there was a good transit system they could keep one car (to tow the boat or whatever it is that transit can't do), and save a large pile of money. As you say, better can mean a little slower, but not a lot slower. Creating a better transit system is expensive, but still cheaper than cars.
  - dboreham 3y ago
    > but still cheaper than cars Overall for society yes, but in most places where transit is widely used, it is quite costly. E.g. a season ticket between Reading and London is 512UKP/mo. For the individual traveler it may not be cheaper especially if they already need to own a car to go to Tesco etc.
    - pessimizer 3y ago
      https://en.wikipedia.org/wiki/Impact_of_the_privatisation_of_British_Rail https://en.wikipedia.org/wiki/Impact_of_the_privatisation_of...
    - TulliusCicero 3y ago
      Meanwhile, when I was living in Munich a few years back, an annual pass covering the whole city was like 500 EUR. For the year. That plus a bike made for great urban transportation.
waveBidder 3y ago
it almost feels like the njb video was specifically a reaction to this, the exact misunderstandings this article has are what he's responding to.
- bluGill 3y ago
  I didn't see the video (I find NJB annoying so I rarely watch his stuff), but it is a common misconception in the transit world that induced demand is a bad thing. Cities should be inducing demand for getting around. The only question is what demand - build a great transit system and you will induce demand for more transit and places to live close to transit. Have a bad transit system and you will induce demand for more roads.
  - zeendo 3y ago
    It sounds more like people use "induced demand" with negative connotations when referring to "induced driving demand" rather than truly meaning that any source of induced demand is bad. i.e. it's just a conventional shorthand?
    - bluGill 3y ago
      I have only seen induced demand used with clearly negative connotations in my life. This article (and a couple others) are the rare exception and they are only using it in context of explaining why it isn't bad (as opposed to using it in a neutral form)
      - waveBidder 3y ago
        the vast majority of urbanists are referring to induced driving demand when they bring up the topic. njb is definitely a jaded man, can see why it'd potentially be offputting.
  - throw0101c 3y ago
    > Cities should be inducing demand for getting around. This is mentioned in the latest NJB video, "More Lanes are (Still) a Bad Thing": > The difference for induced demand for cars, and induced for other modes of travel, is that cars are a extremely space inefficient. You can absorb a lot more induced travel demand on a subway line, tram line, or bicycle path, than you can in a car lane. * https://www.youtube.com/watch?v=CHZwOAIect4&t=15m54s https://www.youtube.com/watch?v=CHZwOAIect4&t=15m54s The Oh The Urbanity! channel has a good video on this, "What People Get Wrong About Induced Demand": * https://www.youtube.com/watch?v=8wlld3Z9wRc https://www.youtube.com/watch?v=8wlld3Z9wRc Cars have (AFAICT) the lowest hourly through-put of any transportation mode: * https://en.wikipedia.org/wiki/Passengers_per_hour_per_direction https://en.wikipedia.org/wiki/Passengers_per_hour_per_direct...
steveBK123 3y ago
The induced demand memes always show the crazy west coast mega highways. Meanwhile east coasters have roughly the same HOV-less, 2-3 lane highway infra in the suburbs that we had 50 years ago when the population in some areas was 1/2 of what it is today. Worse yet, we also have roughly the same transit infra we did then too. You can tax cars/roads, you can make trains free, but at the end of the day.. you need to build SOMETHING. If you want your economy to grow as your population grows, you need to grow your infra. It's a sorry state in the NYC metro area because we are not. You can't just keep slicing up the existing infra pie differently, you need to grow the pie. Otherwise you are just reallocating winners & losers, and unlikely to make the overall situation any better. Thinking we will simply increase the pain of driving until the existing state of trains is tolerable is idiotic, but I see plenty of this in the alt-transit movement. Make trains great, make them awesome, make me want to take them.. make me regret having to drive when I do!!
- eppp 3y ago
  We don't NEED to build something. Maybe NYC is big enough and people need to consider going elsewhere with better policies. We need to stop this narrative that growth must continue indefinitely.
  - TulliusCicero 3y ago
    Those people don't cease to exist if they're not in NYC, you realize? If they're not there, they're probably somewhere more sprawly, that uses more energy and cuts more space out of the environment.
    - steveBK123 3y ago
      This guy gets it
      - TulliusCicero 3y ago
        A lot of NIMBYs seem to lack object permanence. If dastardly "newcomers" have to move elsewhere, they chalk that up as a victory for degrowth, as if those people poof out of existence as soon as they leave the metro area.
jakderrida 3y ago
> 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). While it's incredibly hard to believe, it is true. If you look at population statistics for Philadelphia up to the 1980s, it fell to 4/5ths its peak in less than a couple decades. Driving from river-to-river, or from city-to-suburbs or vice versa was a nightmare, according to everyone older than me. Driving "through" or "to" the center city's impassable traffic grid was hopeless. Then, in 1984, they took advantage of the government buying all the bankrupt railroads and used that property to create a below-ground highway Vine-Street Expressway for river-to-river traffic and connected Penn Railroads Center-city terminal with Reading's system through an underground commuter tunnel and turned Reading's terminal into the Convention Center instead of a giant mess off railroad track interlockings leading into Reading Terminal making traffic even worse. If not for that, I have no doubt it would be 3/5ths the peak population. I could write a 50-page paper on all the things it fixed and I was only 2 when it was all built.

adrianN 3y ago

More roads lead to more sprawl in the mid term and hence more traffic. The problem is that cars don't scale.

Scoundreller 3y ago
I always wonder what impact on traffic larger vehicles have because they take up more space and people cognitively give more space to larger objects (hopefully?). The impacts on unsegmented linear street parking are obvious. Dunno why monthly/yearly permits for those aren’t by the (square) foot/metre.
- sokoloff 3y ago
  Presumably length (as parked) matters more than area for parking consumption. Whether my car is 5 feet wide or 6.25 feet wide doesn’t meaningfully change the amount of street parking it consumes.
  - mitthrowaway2 3y ago
    It does if the road needs to be made wide to accommodate such vehicles, or for how wide the stalls in a parking lot are. On my small side street, there are two people who own Ford Raptors with the wide tires, and if they happen to park across from each other it becomes nearly impossible for an Amazon delivery van to drive down the remaining width of road.
  - Scoundreller 3y ago
    The hypotenuse might be the most sensible here. Wider needs more space to get in/out of a spot.
- carlosjobim 3y ago
  The impact is exponential. A motorcycle is about 1/4 the size of a car, but needs less lanes to have a good traffic flow, or: Have a thousand motorcyclists going down a two-lane highway, their traffic will be smoother and faster than a thousand cars going down a four lane highway.

bluGill 3y ago

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.

autoexec 3y ago

Exactly! If building a new lane doesn't immediately ease congestion then demand hasn't been "induced" it's just that the already existing demand has been demonstrated as being insufficiently addressed. 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. 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.

waveBidder 3y ago
that's called latent demand, not induced. induced demand is people changing e.g. housing in response. like all those businesses that start around train stations.
- thereisnospork 3y ago
  I would argue that is still latent demand, just on a geographically larger scale. If demand were met (globally) then adding a train line (or highway, or stroad) would have a neglible impact on traffic and business development patterns - because everyone can already get to their needs and wants in a timely and economic fashion and therefore has at most casual incentive to use the new infrastructure. For instance a literal "road to nowhere" may 'induce demand' but only because there is unmet demand elsewhere.
  - deleted 3y ago
    [deleted]
- bluGill 3y ago
  Even as the world population starts to decline (expected in the 2080s according to the UN), cities are likely to expand for a while as people move out of rural areas. Which means that just population projections for your lifetime imply that your city will be growing in population for your lifetime. Therefore there will be more demand for travel over time (unless you build so much that you get ahead - good luck as this is expensive)

light_hue_1 3y ago

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. 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. 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. 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.

SoftTalker 3y ago

Better roads leads to more economic opportunity, which leads to more jobs, which attracts more people to the area, which creates more traffic.

sagarm 3y ago
Building housing attracts people, expanding the economy of the metro area. Expanding highways supports and enables building sprawl instead of infill. Sprawl is very expensive to maintain due to the per-capita infrastructure costs; eventually the growth slows and the infrastructure starts requiring maintenance, and the property taxes can't cover it.
- randomdata 3y ago
  > Building housing attracts people Eh, not really. Sure, if people cannot find anywhere to live, building a house in place X might push them towards place X. But if everyone already has somewhere to live, building a house in place X is not going to attract people to place X. Someone already attracted to place X may hinge their move on housing availability, but you need the attraction first for the houses to matter. Building a bunch of houses on the North Pole isn't really going to compel people to move there. > expanding the economy of the metro area To a limited degree, but an insular economy does not have much growth potential. For example, let's say place X has gold. But if you can't get the gold out then you can only trade gold between the local residents – who are probably also in the business of gold. Why are they going to trade for your gold with you when they already can get gold themselves? That leaves little economic opportunity. But if you build a road, then you can ship the gold off to places where gold isn't locally available. Now you've got people who are keen to trade with you.
- ryathal 3y ago
  Building houses only attracts people to where they want to live. A 30-story condo building in Anchorage isn't going attract people, that same building in San Francisco would likely have a waitlist.
zip1234 3y ago
Have you noticed that all the projections used to justify the cost of adding more lanes to roads are always wrong? Maybe there is some economic growth but almost never enough to justify the cost of such sprawl.

Analemma_ 3y ago

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. The "induced demand" being criticized is fake 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.

hughesjj 3y ago

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 > 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’. This has been debunked and rebuked to death. 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 2. Some people will absolutely take trips they otherwise wouldn't when more throughput is available 3. Leisure driving is absolutely a thing 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" Also, > 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’? 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. Did the author get a proofreader or editor before posting this or is it just an independent blog post?

randomdata 3y ago
As commonly defined, latent demand and induced demand are effectively the same thing, albeit observed at different points in time. With respect to highways, latent demand describes the potential demand before the improvements are made. Induced demand describes the shift from potential to actual demand after the improvements have been made.
- ryathal 3y ago
  While they may measure the same thing the connotation is different and often only applied to cars like the article says. We don't say more low-income housing created demand for low-income people. We don't say building a school created demand for children. Flipping cause and effect for expansion of roads is wrong.

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aero142 3y ago

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. 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.

bluGill 3y ago
Economics should define that threshold. There are things you cannot do on mass transit - get the lumber to build a new house/apartment for example. There are things you don't want on mass transit (I don't want you to take your smelly garbage to the dump via the train even though this is possible). Thus a small town will need to build roads. However as the town grows to a city eventually the minimum road to all lots is not enough. At this point we need to ask what is more cost effective: building transit in this town or building more lanes. Unfortunately transit depends on the whole system (this applies to roads too, but we started with them!), which means long term transit might have been a better answer, but right now more roads are cheaper.

rconti 3y ago

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. 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. 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"?

estebank 3y ago
There's an additional problem: traffic congestion isn't caused by the number of lanes, but the number of intersections. You can widen the highway all you want, but if the traffic still needs to be absorbed by a city with a handful of sliplanes into the city grid, the backup will continue to exist. When crossing the San Francisco Bay Bridge, the places where the highway has congestion is on the exits. You could even improve traffic on the bridge if you removed a lane and used that for buses, bikes or just emergency vehicles, because you're giving more time to the city to absorb the incoming traffic.
- trgn 3y ago
  > traffic congestion isn't caused by the number of lanes, but the number of intersections. I wish people understood this more. Parallel travel lanes really just create reptile-brained jostling for position, push-pull accordion effect. it's one thing on highways, but I absolutely can't stand it in city traffic. That constant rush to get to the next intersection, the weaving in&out of lanes just to gain a car length, that mindless churn that when there is a gap it needs to be filled. Like being surrounded by mindless automatons in a weird fill-the-next-gap game of life at best, by insecure typeA losers at worst. Drivers are a lot more calm and considerate when they just chug along in single file. And it doesn't even impact total travel time! The weird thing is. It is absolutely impossible to explain this to anybody. There's always the immediate reaction, but see more lanes, more lanes is better, more cars in more lanes. Intuition really fails here, it's an emergent property of drivers being 90% id the second they step in a car, and then throwing these dumb beasts in a system that doesn't curb their instincts.

hayst4ck 3y ago

> 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’? 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. Globally, induced demand is not useful, but for the person who bought 10% more food in a particular city it is very useful. So the argument that the author is trying to makes is wrong. Induced demand is true, locally. Induced demand is less useful when things are addressed globally. 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.

up2isomorphism 3y ago

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.

dehrmann 3y ago

> Strictly, it is false, and we shouldn’t let it stop us building more roads 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.

Qwertious 3y ago
Counter-intuitively, ripping out roads empirically can reduce traffic.
- bluGill 3y ago
  Only if there are good alternatives. Otherwise it just gets you voted out of office and those roads restored.
  - hughesjj 3y ago
    Literally no, you can reduce traffic by removing roads in certain circumstances. This is an approachable video describing the mathematics behind such if you're concerned from a theoretical/first principles ground https://youtu.be/Cg73j3QYRJc?si=PqKI6XSeTTbrPc1D https://youtu.be/Cg73j3QYRJc?si=PqKI6XSeTTbrPc1D
adrianN 3y ago
Tearing out existing roads gets you to pleasant walkable neighborhoods like those people like to visit on vacations.
erehweb 3y ago
Well, sure, if you tear out all roads, that gets you to a silly place, just as building as many roads as possible would. But that doesn't say anything about whether taking out some of the currently existing roads would be better. In many cases, it has been - e.g. SF removing the Embarcadero Freeway https://www.cnu.org/what-we-do/build-great-places/embarcadero-freeway-removal https://www.cnu.org/what-we-do/build-great-places/embarcader...
3y ago

miamowers 3y ago

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... The author seems to seriously underestimate if not ignore the incredible negative externalizaties of car infrastructure.

TheCoelacanth 3y ago

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.

jonnycat 3y ago

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!" 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.

ravetcofx 3y ago
> but obviously that doesn't scale ad absurdum 28 lanes in Texas say otherwise

Scriddie 3y ago

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?

throw0101c 3y ago

> Induced demand is not a useful concept – the demand is always there, latent Latent demand and induced demand are distinct: > 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] * https://en.wikipedia.org/wiki/Induced_demand#In_transportation_systems https://en.wikipedia.org/wiki/Induced_demand#In_transportati... Though some folks say that it is a distinction without a difference.

aftoprokrustes 3y ago

I usually try to be respectful, but here I have to say it: this article is junk. 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. "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. Do yourself a favor and just ignore this. I would concede that the wording is not great, but this is unfortunately often the case with concepts that develop over decades.

throwanem 3y ago
Since you're in the field, I'll ask: do you know a good 101-level treatment of the subject? Looking for broad rather than deep, something that gives a good overview and directions for further study. Thanks!
- gensym 3y ago
  I'm not in the field, but I highly recommend Tom Vanderbilt's Traffic. Not a textbook, but an excellent one (and I've had people in the field speak highly of it to me).
sapiogram 3y ago
> 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 acknowledge. Isn't this exactly what the author's point #2 ("More and better infrastructure lets us spread out and enjoy more space") was about?
- sebstefan 3y ago
  It misses the core point of the people spouting "induced demand", which is that if you were to satisfy the demand for cars, there won't be a city to drive to or to park in at the end They just take too much space "More and better infrastructure lets us spread out and enjoy more space" only works to the point where you can still get to the centers of activity in your city within a reasonable time, and past a certain point you either have to bulldoze the center to make space for the vehicles of the suburbanites, or densify It is insane to me that they decided to write an entire blog post about something like that if they didn't even address this So honestly I agree, it's a trashy piece

agentultra 3y ago

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. 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.

xyzelement 3y ago

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. 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." 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.

johnkpaul 3y ago
I'm exactly the dad in this scenario and I 100% do not feel like I had an option here. I am pretty frustrated with the house, the space and I don't feel any more safe or higher quality of life. I did this only because I could not afford the number of bedrooms I need for surprise triplets in the city I was basically born and raised in. From my anecdata of peers, pretty much everyone who lived in an urban environment for most of their lives would like to stay there but cannot afford it. I suppose I could see the "family is better off" statement being valid but it is not because of the list you mentioned, it is purely affordability for me. My parents were able to afford a 3 bedroom apartment and I cannot.
- xyzelement 3y ago
  I hear you and congrats on the triplets. In the pure economic sense you are obviously making a choice "I don't love the burbs but this is my best path vs what I can have in the city" which is obviously only possible because those burbs have roads etc. So you're in line with my point here.
  - johnkpaul 3y ago

calvinmorrison 3y ago

Anyone who says "induced demand" when talking about roads needs a brain transplant. 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. 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. 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! 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. 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? Let us unleash the economic power of Philadelphia by INDUCING GREAT ECONOMIC GROWTH. EMBRACE THE DEMAND! MEET THE DEMAND! SUCCEED THE DEMAND!

eppp 3y ago
You are missing the forest for an unhinged rant. The lie that is fed to everyone is that traffic will be improved by expanding roads. It is simply a lie. Tell the truth about what these projects are for and you can start having a legitimate discussion. You are simply distorting the actual truth of what happens. Trains also don't induce demand in the middle of the routes the same way because there aren't exits to build more garbage. If you want to talk about building expressways from city to city without exits then you have a more apt comparison.

theptip 3y ago

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. 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.

zip1234 3y ago

The author states that widening the M-25 only achieved a 10% increase in throughput. This is not good and the definition of diminishing returns.

deleted 3y ago

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kmeisthax 3y ago

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.