5 ms·

Traffic is induced demand. Traffic is induced demand. Traffic is induced demand.

throwawaysea 8y ago
This whole notion of "induced demand" seems like a suspicious artificial label used to position roads as a negative. The reality is that roads provide something people want - the ability to get around quickly, on one's own terms, without dealing with waiting times or trip planning, and without some of the unsavory experiences that can sour public transit (e.g. https://www.sfgate.com/crime/article/BART-takeover-robbery-50-to-60-teens-swarm-11094745.php https://www.sfgate.com/crime/article/BART-takeover-robbery-5...). Building roads doesn't "induce" demand. Rather, it _fulfills_ demand. There is a limit to that demand - it's not like supplying infinitely more of something would infinitely scale the associated behavior. There are only so many humans and only so many trips they are willing to make in a day. And an area that is 100% roads obviously would not have any destinations worth traveling to (leaving aside edge cases like race tracks).
- devriesp 8y ago
  Agreed, a lot of pieces that talk about "induced traffic" throw claims out like "look, we closed this road and ppl dealt with it... no problem, let's close more". Yes lets.. Reductio ad absurdum .. let's close 50% of the roads b/c apparently people will just "adapt" and we could save a ton of money :) The reality is people get some marginal benefit from each extra trip the road system allows. People do tend to apparently undervalue their time though.. so there's some point where building more road capacity doesn't make real economic sense. But I don't think we are anywhere close to that point in Seattle...
- so33 8y ago
  >The reality is that roads provide something people want - the ability to get around quickly, on one's own terms, without dealing with waiting times or trip planning, and without some of the unsavory experiences that can sour public transit (e.g. https://www.sfgate.com/crime/article/BART-takeover-robbery-5... https://www.sfgate.com/crime/article/BART-takeover-robbery-5...). Build public transit out enough, and you get that as well. And funny enough, cities in developed nations other than the United States don't have issues with crime on public transit. Is it a problem inherit to public transit or is it systematic underinvestment? >Building roads doesn't "induce" demand. Rather, it _fulfills_ demand. There is a limit to that demand - it's not like supplying infinitely more of something would infinitely scale the associated behavior. There are only so many humans and only so many trips they are willing to make in a day. And an area that is 100% roads obviously would not have any destinations worth traveling to (leaving aside edge cases like race tracks). First of all – building roads absolutely does induce demand. In fact, _any_ sort of transportation infrastructure, _including public transit_, induces demand. This is pretty well-known. Induced demand isn't about creating larger trips - it's about creating demand through trips that were once not possible. For example, a new train line or highway out in the suburbs will induce people to move close to that piece of infrastructure. This is a well-documented phenomenon, and it happens even for public transit. The problem is that roads for one-person cars don't scale. Downtown Seattle, in particular, is constrained by Elliott Bay on one side and Lake Washington on the other. Amazon is building out tons of towers in the last bit of open land near downtown Seattle. If every Amazon worker were to commute by driving alone, it just wouldn't work because there's no place to put in new highways! Public transit (or living close to where you work, or not commuting at all and teleworking) simply scales better.
- oasisbob 8y ago
  It sounds like you're caught up on the terminology, do you disagree with the underlying concept? https://www.ibtta.org/sites/default/files/Generated%20Traffic%20and%20Induced%20Travel.pdf https://www.ibtta.org/sites/default/files/Generated%20Traffi... Coming from a chemistry background, the idea of traffic and travel choices being an equilibrium process is a very natural and easy concept to grok.
  - TeMPOraL 8y ago
    Equilibrium is traffic jams. What we want is for roads to be underutilized, because 100% utilization is a synonym for gridlock. A saturated solution, in chemical terms. I like the term "latent demand" more, because "induced" sounds like demand was suddenly created, whereas "latent" implies it's already there, but can't be fulfilled just yet. A saturated solution with more soluble material waiting at the bottom of the flask. If you add a drop of solvent, a little bit of material from the bottom will dissolve - just like if you add another road, you'd only eat into the latent demand. But the fix to this problem isn't "don't build new roads because induced demand". It's "build even more roads", up until you eat up all that demand, in the same way you could add more and more solvent until you dissolve all the remaining material, and then some more, to keep the solution unsaturated.
busboybus 8y ago
It's urban planning and infrastructure and social policy. The once common walkable and street car serviced urban areas were destroyed by "civil rights" and public education taxation. The deliberate decision to federally fund highway infrastructure at the expense of local solutions also played a big role.
tomcam 8y ago
Can you explain what that means? Can you explain what that means? Can you explain what that means?

This whole notion of "induced demand" seems like a suspicious artificial label used to position roads as a negative. The reality is that roads provide something people want - the ability to get around quickly, on one's own terms, without dealing with waiting times or trip planning, and without some of the unsavory experiences that can sour public transit (e.g. https://www.sfgate.com/crime/article/BART-takeover-robbery-50-to-60-teens-swarm-11094745.php https://www.sfgate.com/crime/article/BART-takeover-robbery-5...). Building roads doesn't "induce" demand. Rather, it _fulfills_ demand. There is a limit to that demand - it's not like supplying infinitely more of something would infinitely scale the associated behavior. There are only so many humans and only so many trips they are willing to make in a day. And an area that is 100% roads obviously would not have any destinations worth traveling to (leaving aside edge cases like race tracks).

devriesp 8y ago
Agreed, a lot of pieces that talk about "induced traffic" throw claims out like "look, we closed this road and ppl dealt with it... no problem, let's close more". Yes lets.. Reductio ad absurdum .. let's close 50% of the roads b/c apparently people will just "adapt" and we could save a ton of money :) The reality is people get some marginal benefit from each extra trip the road system allows. People do tend to apparently undervalue their time though.. so there's some point where building more road capacity doesn't make real economic sense. But I don't think we are anywhere close to that point in Seattle...
so33 8y ago
>The reality is that roads provide something people want - the ability to get around quickly, on one's own terms, without dealing with waiting times or trip planning, and without some of the unsavory experiences that can sour public transit (e.g. https://www.sfgate.com/crime/article/BART-takeover-robbery-5... https://www.sfgate.com/crime/article/BART-takeover-robbery-5...). Build public transit out enough, and you get that as well. And funny enough, cities in developed nations other than the United States don't have issues with crime on public transit. Is it a problem inherit to public transit or is it systematic underinvestment? >Building roads doesn't "induce" demand. Rather, it _fulfills_ demand. There is a limit to that demand - it's not like supplying infinitely more of something would infinitely scale the associated behavior. There are only so many humans and only so many trips they are willing to make in a day. And an area that is 100% roads obviously would not have any destinations worth traveling to (leaving aside edge cases like race tracks). First of all – building roads absolutely does induce demand. In fact, _any_ sort of transportation infrastructure, _including public transit_, induces demand. This is pretty well-known. Induced demand isn't about creating larger trips - it's about creating demand through trips that were once not possible. For example, a new train line or highway out in the suburbs will induce people to move close to that piece of infrastructure. This is a well-documented phenomenon, and it happens even for public transit. The problem is that roads for one-person cars don't scale. Downtown Seattle, in particular, is constrained by Elliott Bay on one side and Lake Washington on the other. Amazon is building out tons of towers in the last bit of open land near downtown Seattle. If every Amazon worker were to commute by driving alone, it just wouldn't work because there's no place to put in new highways! Public transit (or living close to where you work, or not commuting at all and teleworking) simply scales better.
oasisbob 8y ago
It sounds like you're caught up on the terminology, do you disagree with the underlying concept? https://www.ibtta.org/sites/default/files/Generated%20Traffic%20and%20Induced%20Travel.pdf https://www.ibtta.org/sites/default/files/Generated%20Traffi... Coming from a chemistry background, the idea of traffic and travel choices being an equilibrium process is a very natural and easy concept to grok.
- TeMPOraL 8y ago
  Equilibrium is traffic jams. What we want is for roads to be underutilized, because 100% utilization is a synonym for gridlock. A saturated solution, in chemical terms. I like the term "latent demand" more, because "induced" sounds like demand was suddenly created, whereas "latent" implies it's already there, but can't be fulfilled just yet. A saturated solution with more soluble material waiting at the bottom of the flask. If you add a drop of solvent, a little bit of material from the bottom will dissolve - just like if you add another road, you'd only eat into the latent demand. But the fix to this problem isn't "don't build new roads because induced demand". It's "build even more roads", up until you eat up all that demand, in the same way you could add more and more solvent until you dissolve all the remaining material, and then some more, to keep the solution unsaturated.

busboybus 8y ago

It's urban planning and infrastructure and social policy. The once common walkable and street car serviced urban areas were destroyed by "civil rights" and public education taxation. The deliberate decision to federally fund highway infrastructure at the expense of local solutions also played a big role.

tomcam 8y ago

Can you explain what that means? Can you explain what that means? Can you explain what that means?