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This article repeats a common flaw, which is citing the theory of “induced demand”. This is merely rhetorical framing. Demand isn’t induced, but fulfilled. And

This article repeats a common flaw, which is citing the theory of “induced demand”. This is merely rhetorical framing. Demand isn’t induced, but fulfilled. And it is a good thing, because that’s what those drivers want - to make their trips easily, which is what road infrastructure enables. The notion that increased road infrastructure will magically hold congestion steady or worsen it is laughable. It just means demand hasn’t been satisfied yet. Clearly a 1000 lane highway would not be congested, so there is some finite and lower number where demand balances out with supply. This is no different than supply and demand in any other situation, which is why the label of “induced demand” is without meaning and simply a rhetorical device.

adrianN 6y ago
You're missing the fact that more space allocated to roads and parking moves the things people actually want to do farther apart, increasing the need for more roads and parking. People don't want to drive, they want to get to places. That's the actual demand that needs to be satisfied. Cars don't scale very well to do so. You can't realistically build roads in cities that can move the same number of people as a subway line. If you did you wouldn't have a city anymore, you'd have a parking lot with some buildings sprinkled across it.
- AnthonyMouse 6y ago
  > You're missing the fact that more space allocated to roads and parking moves the things people actually want to do farther apart, increasing the need for more roads and parking. But if this is your concern then the thing that really moves the things people actually want to do farther apart is low density zoning requirements. Which is also the thing that keeps mass transit from being viable, because it needs enough population density to fill the vehicles while still offering frequent enough service to be competitive.
  - emn13 6y ago
    That's too simplistic; you can't pin the blame on a singular effect like that nor choose to disregard other factors to conveniently support some conclusion. It is incidentally clear that low density zoning requirements are not the singular driving factor for sprawl simply because the sprawl occurs even in places without those rules (e.g. houston). Furthermore, effects like these have complex feedback loops. Zoning laws are entirely politically motivated - so the public's support is critical. You can be sure that public support would be affected if it became clear they led to crippling congestion that would not be solved by more road infrastructure; and conversely sprawl-encouraging zoning laws also encourage sprawl-enabling transport investments. Other factors to consider are parking availability (and rules concerning that), and probably more. The correlation between these effects means that you should be careful blaming just one factor, and certainly cannot conclude anything meaningful if you intentionally and artificially exclude related factors from your analysis.
  - anonymoushn 6y ago
    In downtown Austin, many uses are placed next to each other and density is fairly high, but half of the blocks are allocated to parking. So somehow the things people actually want to do are moved far apart by factors other than low density zoning.
wahern 6y ago
> This is no different than supply and demand in any other situation It's different because highway usage is free. Demand is induced because you're giving away something for free. Demand plateaus when the costs (i.e. traffic) rise to the previous levels. Image if SpaceX started giving away free rides to Mars. Millions of people might go. But what if they charged a price equal to the actual costs--manufacture of the spaceship, fuel, etc? The cost would be ridiculously high and only a tiny handful of the richest people would go. Those handful of people represent actual demand where it meets the supply curve. The difference between those willing and able to pay, and all those willing to go if free, is the induced demand.
- 01100011 6y ago
  That's not practically the case though. Road usage costs gas, including taxes, and maintenance.
  - jacobush 6y ago
    Depending on where you live, you might already eat most the car associated costs as part of living. EVs are only going to make it worse, with higher fixed costs and lower marginal.
    - TeMPOraL 6y ago
      A complete tangent, but when I read "you might already eat most the car" I mentally put a full stop here and realized that this is true to an extent: if you live close to a place with large traffic, you're quite literally eating (or at least breathing in) cars, in the form of tire and brake dust. So that's another, non-monetary, cost of living you have to pay.
  - wahern 6y ago
    Sure, and going to Mars has its own costs, like cancer risk or forgoing a trip to Disney Land, even if a ticket is free. The point is that to the extent people don't have to internalize the actual cost of the product or service, demand will be higher. And this difference is what's being referred to as induced demand in the context transportation policy. None of this means that new infrastructure can't create a richer, more productive environment.[1] Obviously the real world is more complex. But the pathological phenomena of induced demand in especially clear and substantial for highway construction because of the process for choosing, designing, and budgeting projects. And to the extent the actual costs are born by the individuals voting for and using a new highway, the linkage is particularly weak and distant and so the costs don't moderate the demand as should normally happen in well-functioning markets. When you try to bring them closer, say through tolling, people become apoplectic; "That's what my taxes are paying for!", etc, ignorant of the point that costs don't moderate consumption very well unless the relationship is clear and obvious--usually the more immediate, the better. [1] Though that's why the article criticizes reliance on modeling, because at the end of the day the choice is less about planning for an inevitable future than picking & choosing among potential futures, each with costs & benefits that are difficult to quantify independent of policy goals--equity, sustainability, mobility, etc.
sideshowb 6y ago
This isn't physics and it isn't an exact equilibrium, but within the range of highway sizes we actually have (not your 1000 lane hypothetical) it seems to hold. Not only do people drive more, but more origins and destinations get built to take advantage of new transport links.
- AnthonyMouse 6y ago
  That's because the existing demand is highly under-satisfied, as evidenced by the existing traffic congestion. In theory you could actually satisfy all of it by building a thirty lane triple-decker highway and it would work. Of course, that's still stupid, because what you should do is build a normal highway (e.g. add a lane or two) to absorb some of the demand, and absorb more of it in other ways, as with mass transit or increasing zoning density so that people can live closer to their destination.
  - anonymoushn 6y ago
    Increasing zoning density doesn't help much if it's still illegal to build a grocery store or a coffee shop anywhere near an apartment complex (and the other way around, too)
- iso947 6y ago
  A 1000 line highway would take tens of minutes, maybe upto an hour, to drive to the outside lane, it would have its own interesting traffic problems.
  - TeMPOraL 6y ago
    I can imagine you'd want to split it e.g. into 250 4-lane tracks, with the leftmost track being reserved for people going all the way to the end of the highway, rightmost track for people who're about to exit the highway, and the middle tracks for people traveling to various points along the highway path, sorted left-to-right by distance, descending. Otherwise it would be just one huge mess.
doktorhladnjak 6y ago
This overlooks that roads take up space and other resources. If you build or expand a road, that's something else you can't build or expand (housing, offices, parks, schools, etc.) there. Moreover, who wants to live next to a busy freeway? Noise and air quality aren't great. In the 1000 lane situation, people can get where they want, but where is it that they're going to if the fraction of space is mostly roads? You can see the practical limits of pushing for more, wider roads at scale clearly in Los Angeles. A massive grid of wide freeways. Long commutes. Bad traffic even outside rush hour. Auto dependency. Air pollution. High household transportation costs.

adrianN 6y ago

You're missing the fact that more space allocated to roads and parking moves the things people actually want to do farther apart, increasing the need for more roads and parking. People don't want to drive, they want to get to places. That's the actual demand that needs to be satisfied. Cars don't scale very well to do so. You can't realistically build roads in cities that can move the same number of people as a subway line. If you did you wouldn't have a city anymore, you'd have a parking lot with some buildings sprinkled across it.

AnthonyMouse 6y ago
> You're missing the fact that more space allocated to roads and parking moves the things people actually want to do farther apart, increasing the need for more roads and parking. But if this is your concern then the thing that really moves the things people actually want to do farther apart is low density zoning requirements. Which is also the thing that keeps mass transit from being viable, because it needs enough population density to fill the vehicles while still offering frequent enough service to be competitive.
- emn13 6y ago
  That's too simplistic; you can't pin the blame on a singular effect like that nor choose to disregard other factors to conveniently support some conclusion. It is incidentally clear that low density zoning requirements are not the singular driving factor for sprawl simply because the sprawl occurs even in places without those rules (e.g. houston). Furthermore, effects like these have complex feedback loops. Zoning laws are entirely politically motivated - so the public's support is critical. You can be sure that public support would be affected if it became clear they led to crippling congestion that would not be solved by more road infrastructure; and conversely sprawl-encouraging zoning laws also encourage sprawl-enabling transport investments. Other factors to consider are parking availability (and rules concerning that), and probably more. The correlation between these effects means that you should be careful blaming just one factor, and certainly cannot conclude anything meaningful if you intentionally and artificially exclude related factors from your analysis.
- anonymoushn 6y ago
  In downtown Austin, many uses are placed next to each other and density is fairly high, but half of the blocks are allocated to parking. So somehow the things people actually want to do are moved far apart by factors other than low density zoning.

wahern 6y ago

> This is no different than supply and demand in any other situation It's different because highway usage is free. Demand is induced because you're giving away something for free. Demand plateaus when the costs (i.e. traffic) rise to the previous levels. Image if SpaceX started giving away free rides to Mars. Millions of people might go. But what if they charged a price equal to the actual costs--manufacture of the spaceship, fuel, etc? The cost would be ridiculously high and only a tiny handful of the richest people would go. Those handful of people represent actual demand where it meets the supply curve. The difference between those willing and able to pay, and all those willing to go if free, is the induced demand.

01100011 6y ago
That's not practically the case though. Road usage costs gas, including taxes, and maintenance.
- jacobush 6y ago
  Depending on where you live, you might already eat most the car associated costs as part of living. EVs are only going to make it worse, with higher fixed costs and lower marginal.
  - TeMPOraL 6y ago
    A complete tangent, but when I read "you might already eat most the car" I mentally put a full stop here and realized that this is true to an extent: if you live close to a place with large traffic, you're quite literally eating (or at least breathing in) cars, in the form of tire and brake dust. So that's another, non-monetary, cost of living you have to pay.
- wahern 6y ago
  Sure, and going to Mars has its own costs, like cancer risk or forgoing a trip to Disney Land, even if a ticket is free. The point is that to the extent people don't have to internalize the actual cost of the product or service, demand will be higher. And this difference is what's being referred to as induced demand in the context transportation policy. None of this means that new infrastructure can't create a richer, more productive environment.[1] Obviously the real world is more complex. But the pathological phenomena of induced demand in especially clear and substantial for highway construction because of the process for choosing, designing, and budgeting projects. And to the extent the actual costs are born by the individuals voting for and using a new highway, the linkage is particularly weak and distant and so the costs don't moderate the demand as should normally happen in well-functioning markets. When you try to bring them closer, say through tolling, people become apoplectic; "That's what my taxes are paying for!", etc, ignorant of the point that costs don't moderate consumption very well unless the relationship is clear and obvious--usually the more immediate, the better. [1] Though that's why the article criticizes reliance on modeling, because at the end of the day the choice is less about planning for an inevitable future than picking & choosing among potential futures, each with costs & benefits that are difficult to quantify independent of policy goals--equity, sustainability, mobility, etc.

sideshowb 6y ago

This isn't physics and it isn't an exact equilibrium, but within the range of highway sizes we actually have (not your 1000 lane hypothetical) it seems to hold. Not only do people drive more, but more origins and destinations get built to take advantage of new transport links.

AnthonyMouse 6y ago
That's because the existing demand is highly under-satisfied, as evidenced by the existing traffic congestion. In theory you could actually satisfy all of it by building a thirty lane triple-decker highway and it would work. Of course, that's still stupid, because what you should do is build a normal highway (e.g. add a lane or two) to absorb some of the demand, and absorb more of it in other ways, as with mass transit or increasing zoning density so that people can live closer to their destination.
- anonymoushn 6y ago
  Increasing zoning density doesn't help much if it's still illegal to build a grocery store or a coffee shop anywhere near an apartment complex (and the other way around, too)
iso947 6y ago
A 1000 line highway would take tens of minutes, maybe upto an hour, to drive to the outside lane, it would have its own interesting traffic problems.
- TeMPOraL 6y ago
  I can imagine you'd want to split it e.g. into 250 4-lane tracks, with the leftmost track being reserved for people going all the way to the end of the highway, rightmost track for people who're about to exit the highway, and the middle tracks for people traveling to various points along the highway path, sorted left-to-right by distance, descending. Otherwise it would be just one huge mess.

doktorhladnjak 6y ago

This overlooks that roads take up space and other resources. If you build or expand a road, that's something else you can't build or expand (housing, offices, parks, schools, etc.) there. Moreover, who wants to live next to a busy freeway? Noise and air quality aren't great. In the 1000 lane situation, people can get where they want, but where is it that they're going to if the fraction of space is mostly roads? You can see the practical limits of pushing for more, wider roads at scale clearly in Los Angeles. A massive grid of wide freeways. Long commutes. Bad traffic even outside rush hour. Auto dependency. Air pollution. High household transportation costs.