4 ms·

Induced demand is good. People just complain about it with cars due to what they claim are excessive environmentally detrimental externalities.

• stephen_g 2y ago
  Apart from the environmental externalities, the problem with induced demand and cars is that cars take up too much physical space on the road for the number of people they tend to carry, so induced demand in any reasonably populated area (like a city) will always produce excessive congestion, and you can basically never build enough lanes to fix that (especially because intersections are often a bigger problem). Whereas with more space-efficient transit, like trains, trams (streetcars) and buses, you can often increase capacity on existing lines or build more capacity for reasonable cost and space, so induced demand isn't as much a problem.
  • Vecr 2y ago
    That's not bad though, by the preferences of the people driving the cars. I've done a couple very informal low sample count surveys, and as far as I can tell the result of pricing in the externalities and building what mass transit is realistic (not much, in certain places) would lead to at least a short-term reduction in satisfaction.
    • Y_Y 2y ago
      > pricing in externalities .. would lead to ... reduction in satisfaction [for those paying] I agree with everything you said and would add > That's not bad though Of course people who aren't paying something would rather not pay it. In the case of externalizing those costs, they're getting an effective subsidy from society at large for something they disproportionately participate in! I think the complaint about induced demand for roads is that it induces demand in those who have the means and motive to drive. The land those roads are on (and the environment the cars may pollute) is also demanded for other uses like green space or railway or housing. It's a rivalrous finite resource and the part of society that doesn't benefit from more roads may be the larger part.
    • iknowstuff 2y ago
      To be clear, this is what happens when you pander to car commuters and build out car infrastructure instead of livable cities: https://ggwash.org/view/4315/houstons-cars-vs-rotterdams-bombs https://ggwash.org/view/4315/houstons-cars-vs-rotterdams-bom... Google some more before/after car infrastructure photos: https://www.google.com/search?q=before+after+car+infrastructure https://www.google.com/search?q=before+after+car+infrastruct... So you see it’s NOT just about the environment. It’s about cities being pleasant or dreadful.
    • DiogenesKynikos 2y ago
      People's preferences are heavily influenced by what is available. Ask the average person in a car-centric American city with no (or barely any) public transit, and of course they prefer to drive. Ask that same question of someone who lives in a city with great public transit (e.g., pick any major city in East Asia, or many cities in Europe) and congested roads, and their answer will be very different.
  • toast0 2y ago
    The whole concept of induced demand is really a misunderstanding of the problem. Congestion indicates transportation capacity is below demand. But once the medium is congested, you can't measure what the demand is; only how long it's congested. You can reduce congestion by increasing capacity, or decreasing demand. If you have a pandemic and encourage people to stay at home, you'll find that the transportation networks that are still operating have plenty of capacity. If you add another lane to the 405 in LA, you'll find the duration of congestion has a step change reduction, but as population continues to grow, congestion duration will also continue to grow. If you add mass transit capacity, highway congestion duration will likely be reduced too. When it's a real situation, the question is usually what intervention allows for the most additional transportation capacity given realistic funds availability. Somewhere like the LA area usually takes an all options approach: there is investment in mass transit as well as highways that service mass transit, individual transportation and commercial shipping. Although intentionally reducing population could work too :p
    • lazide 2y ago
      Eh, I think that’s a misstatement of market dynamics. Yes, congestion is stating that demand is exceeding capacity. However… Congestion is a pushback signal that reduces actual demand, by reducing quality/utility of the actual ‘product’. Congestion is demand being throttled through the mechanism of reduction in quality/availability, instead of some other mechanism, like increases in pricing (tolls), or reduction in customers (aka population decreases or exclusionary rules) through the natural usage of the system. Due to induced demand. Because there is almost always more ‘low quality’ demand, than ‘high quality’ demand. It’s a type of tragedy of the commons. In any ‘free’ system, it almost always ends up this way (see crazy long wait times in nationalized health systems!) precisely because the other options are excluded. Just like on free ways.
    • matsemann 2y ago
      > Congestion indicates transportation capacity is below demand. But once the medium is congested, you can't measure what the demand is; only how long it's congested. But congestion is also part of what controls the demand. It's not a "true" demand that you're just not seeing because of congestion. Once the congestion is solved, the demand will increase as that changes the attractiveness of driving. Since driving then for some people will outcompete bus, cycling, trains etc., they will then shift over to driving even though they had no demand for it earlier. It will then reach a new equilibrium, not far off the old congestion.
• ggm 2y ago
  Cars are a bad metaphor for radio physics. Car congestion is a bad metaphor for RF channel collision because of a number of things including TDM and the non fatal quality of what we call a collision in radio space.
• unethical_ban 2y ago
  Induced demand is not inherently good or bad.