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Induced demand as a concept just doesn’t make sense. If demand is “induced” it just means that the supply wasn’t adequate to meet demand. That’s it. It isn’t a

Induced demand as a concept just doesn’t make sense. If demand is “induced” it just means that the supply wasn’t adequate to meet demand. That’s it. It isn’t a large mystery, and there isn’t any logical argument or evidence that greater supply will keep “inducing” demand infinitely. There are a finite number of people and finite minutes in a day, and if they are able to derive value from driving more, then they will do so, but only up to a limit. In return for that driving, they will also gain something for it (the value that motivated them to drive). The phrase “induced demand” is simply a part of the rhetorical war waged by anti car activists. I’m also not sure why we need to create a false dichotomy between roads and bike lanes. I need driving to shuttle between home, work, schools, and other activities in a time efficient way. I also like biking for exercise and leisure, although bike commuting hasn’t been practical for me when I’ve tried it. Have cities considered elevated bike lane networks on pillars built into highway medians or sidewalks, so we don’t have to choose just one or the other? What about cantilevered elevated walk/bikeways? Or perhaps they can have an underground driving network like Chicago does.

kevingadd 5y ago
Do you have evidence to support this? The effect of widening highways used to support "induced demand" typically seems to hold up. You may also want to read up on induced demand in more depth, because it's about where the demand is, not about how many people are driving cars.
- lupire 5y ago
  It's also about altering development patterns (suburbanizating) that spreads stuff out more and forcing everyone to drive more or even buy a car in the first place even if they'd prefer a walkable town.
- sempron64 5y ago
  I'd like to see a study across all road construction whether excessive induced demand is a guaranteed effect. In all articles related to it I only see examples cherry-picked where induced demand negated the effects of adding lanes. However, it's not clear whether this is universally true, true enough to be a rule of thumb, or something that only occurs in specific situations. Anecdotally, removing toll plazas in favor of plate scanners and adding bridge lanes to the Goethals Bridge in Staten Island, as well as widening the Staten Island Expressway, has significantly reduced traffic delays and improved safety for several years. There _are_ more vehicles using the road but not enough more to significantly negate the improvements. https://www.panynj.gov/port-authority/en/press-room/press-release-archives/2020-press-releases/vehicle-crashes-decline-at-new-goethals-bridge-with-wider-lanes-.html https://www.panynj.gov/port-authority/en/press-room/press-re... To me, the case against improving roads is not nearly as open-and-shut as Strong Towns and similar one-sided policy-pushers make it out to be.
  - kiba 5y ago
    It would seems that removing the toll booths dramatically increases capacity and safety without the need to add additional lanes. Also, more vehicles are using the road, true, but you have to remember that it increases over time.
    - sempron64 5y ago
      How fast does demand grow? Does it ever stop or slow down? I know for a fact that far from every highway and road in America is congested: the majority are not. Even many if not most roads in metropolitan areas are not. So you can’t extrapolate demand increases ad infinitum for the current moment.
  - corin_ 5y ago
    I don't know the data (or this area particularly well generally), but intuitively I would expect induced demand to be seen in the majority of cases of roads being updated for increased capacity. Not because of a necessity that any capacity increase must always cause it, but because the decisions of which roads to expand are made by humans who, with the exception of edge cases (maybe the reason for rebuilding was because of the state of the road and increased capacity was a secondary affect rather than the main motivation; maybe corruption led to a poor choice being made; maybe forward looking expecting future demand to increase years later based on other factors like planned new buildings) wouldn't spend money increase capacity unless road traffic has been increasing and looks like it is't about to start trending in the opposite direction soon enough to make expanding the road a pointless short-sighted exercise. Aka if increasing road capacity wouldn't induce more demand, how likely is it to be in a situation where it's considered worthwhile expanding it?
kiba 5y ago
If you expand a road, there will be greater usage because demand soaks up supply. However, cars are big and takes up a lot of space, especially since people regularly drive sedans that seat only one individual with max capacity for four to five people. This requires a lot of space to support cars. Of course, you can continue to expand roads. Problem with that idea is that the roads displace other uses of land such as homes and businesses. Roads increase utility of cars, for sure, but that comes at the expense of everything else.
- fearfulofview4 5y ago
  Don't forget bankrupting municipalities and states by misallocating untold sums of money toward road construction and maintenance and not investment in human capital: schools, healthcare, and other high-ROI public goods.
- burlesona 5y ago
  Sedans? Try 5000lb, 7-8 passenger SUVs.
- acdha 5y ago
  It’s easy for people to forget just how spatially inefficient cars are because we’re so used to 30-40% of city space being dedicated to roads and storage. We saw a dramatic example of this next to the bike path I ride to daycare/work: hundreds of new apartments, restaurants & other retail shops, outdoor public spaces, etc. next to a subway station. This was just part of a retail parking lot which broke 50% usage _maybe_ a couple of times a year. The number of people using the space when up by at least an order of magnitude and it’s a lot more consistent economic activity.
- thereisnospork 5y ago
  > If you expand a road, there will be greater usage because demand soaks up supply. This can only occur when there is sufficient latent demand, or phrased differently, the supply of roads (and sufficiently fungible transit modes) is so insufficient that that moderate increases in supply do not create a surplus. This lack of surplus (traffic) representing an economic inefficiency which it can only be desirable to reduce[0]. What is stupifying is how 'induced demand' (read: building more roads will cause more people to perform economic activities facilitated by transit) is contorted into an argument against building roads. [0]Until such point that traffic inefficiency is in equilibrium with others. e.g. I can't see Manhattan widening 5th ave anytime soon, but most of America isn't pressed for real estate.
jochakovsky 5y ago
Based on your tone, it seems like you are critical of the article, but your critique is actually what the article is addressing. Specifically, "Effect 2" demonstrates a unique property of "induced demand" that doesn't fit into traditional discussions of supply and demand.
crazygringo 5y ago
> I’m also not sure why we need to create a false dichotomy between roads and bike lanes. Because there is finite width for existing roads between existing buildings, and so quite literally, adding a bike lane often requires removing a car lane. It's not a false dichotomy at all, it's literally measured in meters. > Have cities considered elevated bike lane networks on pillars... Do you have any idea how astronomically expensive that kind of stuff would be? It's just not even on the table, realistically speaking, for 99.9% of places.
- CorrectHorseBat 5y ago
  Not disagreeing with you, but elevated bike lanes do exist and they are pretty cool.
  - crazygringo 5y ago
    Oh yeah. No, I've seen what that "0.1%" can look like, and they're so fun to ride too... I wish the kind of money was available to put those all over!
- stephen_g 5y ago
  We have some of that in my city, alongside a big freeway (see [1]) and yes, it’s ridiculously expensive. It is great though, and one of the only options given the number of very busy intersections this popular route crosses. But in the inner city, it wouldn’t make any sense. Inside the CBD, they’ve been taking out on-street parking to put in separated bike lanes, and that‘s just as good. They completely removed car traffic from a bridge in the middle of the city also to add an extra bus land and a bike lane, and while some drivers were annoyed, it used to drop you in a extremely congested bit of the city so wasn’t very convenient in the car anyway. 1. https://www.tmr.qld.gov.au/projects/Veloway-1-Pacific-Motorway https://www.tmr.qld.gov.au/projects/Veloway-1-Pacific-Motorw...
lupire 5y ago
Here's a nice articlr thst explains how induced demand is different from latwnt demand: https://www.strongtowns.org/journal/2021/8/24/does-induced-demand-apply-to-bike-lanes-and-other-questions https://www.strongtowns.org/journal/2021/8/24/does-induced-d...
- erik_seaberg 5y ago
  The article ought to do more to distinguish these. Latent demand: Driving more often because we can now actually get to places when we used to give up trying. Induced demand: Driving more miles per day because space for the roads pushed each building farther apart over time. Going to larger stores because small nearby stores failed to compete.
willcipriano 5y ago
I have yet to receive a convincing answer why induced demand does not similarly apply to/or is not a concern for welfare programs, homeless shelters or public transportation. I find it suspect that this theory is apparently only applied to roads, and largely by people who commute by bike.
- sofixa 5y ago
  The article literally discusses that in the second part.
  - willcipriano 5y ago
    I said convincing answer. My read is that by the theory of induced demand the best way to eliminate bike deaths is to eliminate bike lanes and therefore people on bikes.
    - crazygringo 5y ago
      The best way to eliminate car deaths is to eliminate cars, too. But obviously we're not doing that either. I'm not clear what you're trying to accomplish by juxtaposing induced demand with transportation fatalities, when the two concepts don't seem to have any special connection.
      - willcipriano 5y ago
        > The best way to eliminate car deaths is to eliminate cars, too. But obviously we're not doing that either. As far as I can tell that is exactly the outcome the induced demand folks are hoping for, or something close to it.
        crazygringo 5y ago
        I'm sorry, who are "induced demand folks"? What does that even mean? And I'm unaware of anyone proposing the elimination of cars as serious policy. At most it's limiting vehicles in parts of dense pedestrian city centers. People who are generally "left-leaning" on transportation envision a healthy mix between public transportation, cycling, and cars. They simply want car usage to be balanced with alternatives, rather than cars dominating by default. Virtually everyone recognizes that cars are necessary for a wide variety of uses. They're not going away, so I don't think you need to worry about that.
occz 5y ago
Your entire comment leads me to believe that you did not even read the article.
resoluteteeth 5y ago
> Induced demand as a concept just doesn’t make sense. If demand is “induced” it just means that the supply wasn’t adequate to meet demand. That’s it. It isn’t a large mystery, and there isn’t any logical argument or evidence that greater supply will keep “inducing” demand infinitely. There are a finite number of people and finite minutes in a day, and if they are able to derive value from driving more, then they will do so, but only up to a limit. In return for that driving, they will also gain something for it (the value that motivated them to drive). The phrase “induced demand” is simply a part of the rhetorical war waged by anti car activists. Right, it's not surprising but highway expansions are often sold as "reducing congestion" rather than the reality of "causing more people to drive more miles with the same resulting level of congestion." If the actual goal of highway expansions is to make it efficient for people to drive more miles/have longer commutes then there isn't an issue with there being "induced demand," but there may be various reasons why this isn't actually a very good goal. Highway expansions do have benefits to people who end up moving further out (more affordable housing), but there may be better ways to achieve the goals of providing housing to more people around urban areas by increasing density, or to help people get around urban areas by transit, etc.
- tuatoru 5y ago
  > There are a finite number of people and finite minutes in a day, and if they are able to derive value from driving more, then they will do so, but only up to a limit. This is the primary objection I have to self-driving cars. By enabling people to do other things while they are travelling, self-driving cars raise that limit considerably. When self-driving takes off, so will congestion.
  - njarboe 5y ago
    This is very true. Hopefully the Boring company can be successful in reducing tunneling costs by a factor of 10 or 100. Then cities will just have to fined the political will to allow them to be built. Maybe public, self-driving taxies can be made to travel close enough together so that they look like and can be called "trains". Then all the public transport supporters might not try and block them even if the tunnels are open to people's individually owned vehicles also.
caturopath 5y ago
> Induced demand as a concept just doesn’t make sense. If demand is “induced” it just means that the supply wasn’t adequate to meet demand Supply and demand aren't fixed -- they meet at an equilibrium price. There are latent trips that are canceled, change modes, or time-shifted to deal with traffic because of the high cost. > The phrase “induced demand” is simply a part of the rhetorical war waged by anti car activists. Induced demand is a standard transportation engineering concept. You might argue that it's been hijacked by the anti-car folks or whatever, but tramsportation engineers and planners who want to build car-heavy transportation systems are aware of and use it. They taught it to me in a very conservative civil engineering department.
deleted 5y ago
[deleted]
tengbretson 5y ago
Induced demand has never made sense. Does building a hospital create more sick people?
- khrbrt 5y ago
  It increases the number of people getting treated for their sickness, who otherwise would not be.
  - tengbretson 5y ago
    You are describing latent demand.
- martyvis 5y ago
  No, but it can make them visible and willing to be treated. If people cant afford private health care or are unwilling to travel long distances or wait for a long time on a public health waiting list, they might just put up with being untreated. This is quite common for things like joint replacement or chronic dental issues.
- majormajor 5y ago
  If you're only thinking about the already-there population, no. But many hospitals have patients that travel to get there. Building a Mayo Clinic hospital in Arizona results in more sick people traveling there for care than otherwise would have. Seems like there are some natural ways this could cause a loop. Now we hire more doctors and train more new specialists. That burnishes the reputation even more. Now more people want to come! (One thing to note is that it's generally always a localized increase, not an absolute one. The people living in the new suburbs that you built a new shiny road to still would've lived SOMEWHERE in the country. You didn't increase that country's total demand for transit. You just redirected it into "road transit from this particular suburb" from wherever it would've gone in the absence of building that suburb.)
  - thereisnospork 5y ago
    The part I always miss, is how is this a bad thing when it comes to roads? Building 'hospitals'[0] for people to use until there are enough hospitals[0] that people no longer have incentive to flock to the new Mayo Clinic in Arizona seems pretty desirable. [0]Roads

kevingadd 5y ago

Do you have evidence to support this? The effect of widening highways used to support "induced demand" typically seems to hold up. You may also want to read up on induced demand in more depth, because it's about where the demand is, not about how many people are driving cars.

lupire 5y ago
It's also about altering development patterns (suburbanizating) that spreads stuff out more and forcing everyone to drive more or even buy a car in the first place even if they'd prefer a walkable town.
sempron64 5y ago
I'd like to see a study across all road construction whether excessive induced demand is a guaranteed effect. In all articles related to it I only see examples cherry-picked where induced demand negated the effects of adding lanes. However, it's not clear whether this is universally true, true enough to be a rule of thumb, or something that only occurs in specific situations. Anecdotally, removing toll plazas in favor of plate scanners and adding bridge lanes to the Goethals Bridge in Staten Island, as well as widening the Staten Island Expressway, has significantly reduced traffic delays and improved safety for several years. There _are_ more vehicles using the road but not enough more to significantly negate the improvements. https://www.panynj.gov/port-authority/en/press-room/press-release-archives/2020-press-releases/vehicle-crashes-decline-at-new-goethals-bridge-with-wider-lanes-.html https://www.panynj.gov/port-authority/en/press-room/press-re... To me, the case against improving roads is not nearly as open-and-shut as Strong Towns and similar one-sided policy-pushers make it out to be.
- kiba 5y ago
  It would seems that removing the toll booths dramatically increases capacity and safety without the need to add additional lanes. Also, more vehicles are using the road, true, but you have to remember that it increases over time.
  - sempron64 5y ago
    How fast does demand grow? Does it ever stop or slow down? I know for a fact that far from every highway and road in America is congested: the majority are not. Even many if not most roads in metropolitan areas are not. So you can’t extrapolate demand increases ad infinitum for the current moment.
- corin_ 5y ago
  I don't know the data (or this area particularly well generally), but intuitively I would expect induced demand to be seen in the majority of cases of roads being updated for increased capacity. Not because of a necessity that any capacity increase must always cause it, but because the decisions of which roads to expand are made by humans who, with the exception of edge cases (maybe the reason for rebuilding was because of the state of the road and increased capacity was a secondary affect rather than the main motivation; maybe corruption led to a poor choice being made; maybe forward looking expecting future demand to increase years later based on other factors like planned new buildings) wouldn't spend money increase capacity unless road traffic has been increasing and looks like it is't about to start trending in the opposite direction soon enough to make expanding the road a pointless short-sighted exercise. Aka if increasing road capacity wouldn't induce more demand, how likely is it to be in a situation where it's considered worthwhile expanding it?

kiba 5y ago

If you expand a road, there will be greater usage because demand soaks up supply. However, cars are big and takes up a lot of space, especially since people regularly drive sedans that seat only one individual with max capacity for four to five people. This requires a lot of space to support cars. Of course, you can continue to expand roads. Problem with that idea is that the roads displace other uses of land such as homes and businesses. Roads increase utility of cars, for sure, but that comes at the expense of everything else.

fearfulofview4 5y ago
Don't forget bankrupting municipalities and states by misallocating untold sums of money toward road construction and maintenance and not investment in human capital: schools, healthcare, and other high-ROI public goods.
burlesona 5y ago
Sedans? Try 5000lb, 7-8 passenger SUVs.
acdha 5y ago
It’s easy for people to forget just how spatially inefficient cars are because we’re so used to 30-40% of city space being dedicated to roads and storage. We saw a dramatic example of this next to the bike path I ride to daycare/work: hundreds of new apartments, restaurants & other retail shops, outdoor public spaces, etc. next to a subway station. This was just part of a retail parking lot which broke 50% usage _maybe_ a couple of times a year. The number of people using the space when up by at least an order of magnitude and it’s a lot more consistent economic activity.
thereisnospork 5y ago
> If you expand a road, there will be greater usage because demand soaks up supply. This can only occur when there is sufficient latent demand, or phrased differently, the supply of roads (and sufficiently fungible transit modes) is so insufficient that that moderate increases in supply do not create a surplus. This lack of surplus (traffic) representing an economic inefficiency which it can only be desirable to reduce[0]. What is stupifying is how 'induced demand' (read: building more roads will cause more people to perform economic activities facilitated by transit) is contorted into an argument against building roads. [0]Until such point that traffic inefficiency is in equilibrium with others. e.g. I can't see Manhattan widening 5th ave anytime soon, but most of America isn't pressed for real estate.

jochakovsky 5y ago

Based on your tone, it seems like you are critical of the article, but your critique is actually what the article is addressing. Specifically, "Effect 2" demonstrates a unique property of "induced demand" that doesn't fit into traditional discussions of supply and demand.

crazygringo 5y ago

> I’m also not sure why we need to create a false dichotomy between roads and bike lanes. Because there is finite width for existing roads between existing buildings, and so quite literally, adding a bike lane often requires removing a car lane. It's not a false dichotomy at all, it's literally measured in meters. > Have cities considered elevated bike lane networks on pillars... Do you have any idea how astronomically expensive that kind of stuff would be? It's just not even on the table, realistically speaking, for 99.9% of places.

CorrectHorseBat 5y ago
Not disagreeing with you, but elevated bike lanes do exist and they are pretty cool.
- crazygringo 5y ago
  Oh yeah. No, I've seen what that "0.1%" can look like, and they're so fun to ride too... I wish the kind of money was available to put those all over!
stephen_g 5y ago
We have some of that in my city, alongside a big freeway (see [1]) and yes, it’s ridiculously expensive. It is great though, and one of the only options given the number of very busy intersections this popular route crosses. But in the inner city, it wouldn’t make any sense. Inside the CBD, they’ve been taking out on-street parking to put in separated bike lanes, and that‘s just as good. They completely removed car traffic from a bridge in the middle of the city also to add an extra bus land and a bike lane, and while some drivers were annoyed, it used to drop you in a extremely congested bit of the city so wasn’t very convenient in the car anyway. 1. https://www.tmr.qld.gov.au/projects/Veloway-1-Pacific-Motorway https://www.tmr.qld.gov.au/projects/Veloway-1-Pacific-Motorw...

lupire 5y ago

Here's a nice articlr thst explains how induced demand is different from latwnt demand: https://www.strongtowns.org/journal/2021/8/24/does-induced-demand-apply-to-bike-lanes-and-other-questions https://www.strongtowns.org/journal/2021/8/24/does-induced-d...

erik_seaberg 5y ago
The article ought to do more to distinguish these. Latent demand: Driving more often because we can now actually get to places when we used to give up trying. Induced demand: Driving more miles per day because space for the roads pushed each building farther apart over time. Going to larger stores because small nearby stores failed to compete.

willcipriano 5y ago

I have yet to receive a convincing answer why induced demand does not similarly apply to/or is not a concern for welfare programs, homeless shelters or public transportation. I find it suspect that this theory is apparently only applied to roads, and largely by people who commute by bike.

sofixa 5y ago
The article literally discusses that in the second part.
- willcipriano 5y ago
  I said convincing answer. My read is that by the theory of induced demand the best way to eliminate bike deaths is to eliminate bike lanes and therefore people on bikes.
  - crazygringo 5y ago
    The best way to eliminate car deaths is to eliminate cars, too. But obviously we're not doing that either. I'm not clear what you're trying to accomplish by juxtaposing induced demand with transportation fatalities, when the two concepts don't seem to have any special connection.
    - willcipriano 5y ago
      > The best way to eliminate car deaths is to eliminate cars, too. But obviously we're not doing that either. As far as I can tell that is exactly the outcome the induced demand folks are hoping for, or something close to it.
      - crazygringo 5y ago
        I'm sorry, who are "induced demand folks"? What does that even mean? And I'm unaware of anyone proposing the elimination of cars as serious policy. At most it's limiting vehicles in parts of dense pedestrian city centers. People who are generally "left-leaning" on transportation envision a healthy mix between public transportation, cycling, and cars. They simply want car usage to be balanced with alternatives, rather than cars dominating by default. Virtually everyone recognizes that cars are necessary for a wide variety of uses. They're not going away, so I don't think you need to worry about that.

occz 5y ago

Your entire comment leads me to believe that you did not even read the article.

resoluteteeth 5y ago

> Induced demand as a concept just doesn’t make sense. If demand is “induced” it just means that the supply wasn’t adequate to meet demand. That’s it. It isn’t a large mystery, and there isn’t any logical argument or evidence that greater supply will keep “inducing” demand infinitely. There are a finite number of people and finite minutes in a day, and if they are able to derive value from driving more, then they will do so, but only up to a limit. In return for that driving, they will also gain something for it (the value that motivated them to drive). The phrase “induced demand” is simply a part of the rhetorical war waged by anti car activists. Right, it's not surprising but highway expansions are often sold as "reducing congestion" rather than the reality of "causing more people to drive more miles with the same resulting level of congestion." If the actual goal of highway expansions is to make it efficient for people to drive more miles/have longer commutes then there isn't an issue with there being "induced demand," but there may be various reasons why this isn't actually a very good goal. Highway expansions do have benefits to people who end up moving further out (more affordable housing), but there may be better ways to achieve the goals of providing housing to more people around urban areas by increasing density, or to help people get around urban areas by transit, etc.

tuatoru 5y ago
> There are a finite number of people and finite minutes in a day, and if they are able to derive value from driving more, then they will do so, but only up to a limit. This is the primary objection I have to self-driving cars. By enabling people to do other things while they are travelling, self-driving cars raise that limit considerably. When self-driving takes off, so will congestion.
- njarboe 5y ago
  This is very true. Hopefully the Boring company can be successful in reducing tunneling costs by a factor of 10 or 100. Then cities will just have to fined the political will to allow them to be built. Maybe public, self-driving taxies can be made to travel close enough together so that they look like and can be called "trains". Then all the public transport supporters might not try and block them even if the tunnels are open to people's individually owned vehicles also.

caturopath 5y ago

> Induced demand as a concept just doesn’t make sense. If demand is “induced” it just means that the supply wasn’t adequate to meet demand Supply and demand aren't fixed -- they meet at an equilibrium price. There are latent trips that are canceled, change modes, or time-shifted to deal with traffic because of the high cost. > The phrase “induced demand” is simply a part of the rhetorical war waged by anti car activists. Induced demand is a standard transportation engineering concept. You might argue that it's been hijacked by the anti-car folks or whatever, but tramsportation engineers and planners who want to build car-heavy transportation systems are aware of and use it. They taught it to me in a very conservative civil engineering department.

deleted 5y ago

[deleted]

tengbretson 5y ago

Induced demand has never made sense. Does building a hospital create more sick people?

khrbrt 5y ago
It increases the number of people getting treated for their sickness, who otherwise would not be.
- tengbretson 5y ago
  You are describing latent demand.
martyvis 5y ago
No, but it can make them visible and willing to be treated. If people cant afford private health care or are unwilling to travel long distances or wait for a long time on a public health waiting list, they might just put up with being untreated. This is quite common for things like joint replacement or chronic dental issues.
majormajor 5y ago
If you're only thinking about the already-there population, no. But many hospitals have patients that travel to get there. Building a Mayo Clinic hospital in Arizona results in more sick people traveling there for care than otherwise would have. Seems like there are some natural ways this could cause a loop. Now we hire more doctors and train more new specialists. That burnishes the reputation even more. Now more people want to come! (One thing to note is that it's generally always a localized increase, not an absolute one. The people living in the new suburbs that you built a new shiny road to still would've lived SOMEWHERE in the country. You didn't increase that country's total demand for transit. You just redirected it into "road transit from this particular suburb" from wherever it would've gone in the absence of building that suburb.)
- thereisnospork 5y ago
  The part I always miss, is how is this a bad thing when it comes to roads? Building 'hospitals'[0] for people to use until there are enough hospitals[0] that people no longer have incentive to flock to the new Mayo Clinic in Arizona seems pretty desirable. [0]Roads