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No comments on emergency situations, but wanted to call out one thing: > You need additional highways (aka: additional offramps) to truly scale day-to-day traf

No comments on emergency situations, but wanted to call out one thing: > You need additional highways (aka: additional offramps) to truly scale day-to-day traffic Additional highways are at-best a stop-gap for day-to-day traffic, never a solution, due to induced demand [1]. You really need large-scale investments in public transportation for this. [1] https://en.wikipedia.org/wiki/Induced_demand#Effect_in_transportation_systems https://en.wikipedia.org/wiki/Induced_demand#Effect_in_trans...

whatshisface 5y ago
I've never understood how inducing demand doesn't count as success. That means people want to use the road, doesn't it? It's almost like saying that releasing new software doesn't do anything to help users, because it increases the demand for software by the virtue of its own utility more than it reduces the demand for software by keeping people busy.
- azylman 5y ago
  It depends what your success criteria is. It's true, you've successfully increased the throughput of the transit network, but you haven't done anything to improve transit times - you just have more people stuck in traffic now. There are other ways you could have spent that same amount of money (public transit) that both increase the throughput of the network _and_ improve transit times.
  - deleted 5y ago
    [deleted]
  - njarboe 5y ago
    Not if you build enough roads. This argument just does not hold up. There was less time wasted stuck in traffic in the past. Go with tunnels underground so as not the create the large problems with having surface roads. If your idea theory is right, why don't we just stop maintaining all roads, shut them down, and save a lot of money, if new roads are useless.
    - tshaddox 5y ago
      In some cases it might be theoretically possible to just outspend the problem. But in most cases the roads have to be going somewhere, and you don't have significant control over where and how big that somewhere is (i.e. you can't easily move a whole urban center, or slice it into chunks and move all the chunks apart from each other a little to fit more roads). If all the roads are ending at the same place, making wider and longer roads to that place will (often) just induce more people to drive to that place from further away. The reason "just shutting down all roads" doesn't make sense is that it doesn't solve the actual problem, which is that people want to both work in places with good jobs (traditionally often dense urban centers) while living in cheaper places that are far away and not spend significant chunks of their lives stuck in traffic. Shutting down all the roads only "solves" the traffic problem in a deliberately ridiculous sense (same as "just kill all humans").
      - Spooky23 5y ago
        Shutting down or tolling chokepoints lowers the opportunity cost of alternatives. I work for a big central business district employer. You can pay $150-250 a month to park or $75/week to take a motor coach bus from your suburban town. Those numbers drive behavior, and make for a better solution as folks who need flexibility can pay for it.
  - mrfusion 5y ago
    But those extra people are choosing to be there so there must be some benefit.
    - seanmcdirmid 5y ago
      > But those extra people are choosing to be there so there must be some benefit. As long as your roads are saturated, they have less throughput, not more. It is kind of like a clog in your toilet: more things are there in your pipes, but not much is getting through.
      - throwaway0a5e 5y ago
        A clogged toilet isn't flowing. More like dumping a 5-gal bucket into a sink . The drain is running at full capacity but any one drop may take a long time to actually clear the sink. The 5-gal bucket is peak demand. Total time to sink clear is how long rush "hour" lasts. Fluid analogies are crappy because fluids flow more when you add pressure and traffic doesn't.
        seanmcdirmid 5y ago
        > because fluids flow more when you add pressure and traffic doesn't. Well, traffic can flow when pressure is added, just not in a way that is very safe.
      - jimmaswell 5y ago
        If your city sewer is clogged, so you widen it, then more people install toilets in their houses and bring the sewer back to capacity, I think that's still a win.
    - tshaddox 5y ago
      They're choosing to be there now, precisely like they were choosing to not be there before you changed the roads. Other people are also choosing to not be there, and instead choosing to live in the woods in northern Canada. I'm not sure how this mode of argument is really demonstrating anything. It seems like you just considering literally any state of affairs other than active physical coercion to be a good state of affairs.
- NikolaeVarius 5y ago
  If the point of adding lanes is to reduce delays, and induced demand prevents that, you have failed in the task.
  - nostromo 5y ago
    The point of adding lanes is to increase throughput.
  - dragontamer 5y ago
    The point of roads, from the city's perspective, is to support additional transportation, which causes growth of the city. More transportation means more trade, more services, and better life for all who live near the roads. It might be in the form of easier-to-get deliveries (Amazon goods), or new jobs that have popped up close by, or new housing developments (aka: homes that previously weren't possible due to the time of transportation, but are now possible thanks to sped up transportation times). ----- It turns out that "individualism" is a crappy reason to do anything. The individual argument must be made because we live in a democracy, and its impossible to get the people to agree to something unless you sell them a story regarding individualism.
    - azylman 5y ago
      It's not correct that cities look at road throughput with no concern for how long that travel takes. The success criteria that city planners use always includes travel times which are impacted substantially by traffic congestion.
    - NikolaeVarius 5y ago
      You are moving the goalpost. The purpose of adding lanes was to REDUCE DELAYS. Not support additional transportation. Your entire post hinges on an incorrect premise
  - bluGill 5y ago
    That means you didn't add enough lanes. You need to get ahead of induced demand, otherwise you city isn't meeting the needs of the people who live there. If you don't want to have many places you can reach in a reasonable amount of time can you can move to a rural area. The point of cities is to give people options to reach lots of places quickly. Get busying being a good city. Note, it can be better to add transit other than lanes of road. Even though I said add lanes, adding lanes is but one possible solution. Good transit may well be better. Figure out how to make your city serve the people who want to get around.
- kaesar14 5y ago
  Because the metric people care about is traffic on the roads, not how many motorists are able to use the road in a given day. The Big Dig by this metric was a resounding success in Boston, able to dramatically scale up the amount of commuters in and out of the city, but driving still absolutely sucks because of traffic. To the person on the road, the Big Dig solved nothing. Parent comment is saying the only way to scale with higher demand of transportation in a way that feels like an actual improvement to people is public transit, because public transit scales so much better with higher numbers of people commuting.
  - whatshisface 5y ago
    If the metric was really traffic, then that could easily be solved on any road by only allowing even-numbered license numbers to drive on even-numbered days, and vice-versa. If that's an absurd solution, then traffic severity is not the only metric.
    - kaesar14 5y ago
      I mean, I don't see how that's really a fair response to saying what people care about is traffic. Yeah, ability to use the road, sure. I don't think people want a new highway to be built and then told they can't use it because they don't have a new car or something. I as a motorist could not give less of a shit if I'm stuck in traffic for 3 hours a day but the road is able to move hundreds of thousands of cars a day. I'd prefer a road that could only move 20 people a day with 0 traffic. It's the only thing I care about.
      - bagacrap 5y ago
        why would you count that as a win? you almost certainly wouldn't be one of those 20 people allowed on the road
        kaesar14 5y ago
        The example was clearly intended to include the motorist in question, being allowed to be on the road. As long as the motorist got to use the road, it wouldn't matter to said motorist how large the capacity of the road was, if they weren't able to clear through it quickly without traffic. It wouldn't matter if the road in question was servicing large amounts of people, it's only visible impact to the motorists time on the road that matters.
- animal_spirits 5y ago
  The less you invest in public transportation, the more people will drive. The more people that drive, the slower traffic gets. If you just widen the road, all you do is increase the amount of cars that drive. If people can't get to where they are going via public transportation, then they are going to drive instead, increasing congestion. Would recommend watching this video on it: https://youtu.be/RQY6WGOoYis https://youtu.be/RQY6WGOoYis
  - massysett 5y ago
    Yes, if you increase the amount of road and more cars get people to where they are going, the result is increased economic activity. The result also is increased well-being because more people are getting to places where they wish to go - destinations that are improving their lives. This is a success.
    - animal_spirits 5y ago
      You actually see the opposite. Close nit places with more foot traffic and better public transport see higher economic activity and financial resilience. Places with long roads between where people live and where they shop/work/eat _drastically_ harms financial productivity due to higher infrastructure costs. Chuck Mahron makes this point in his TEDx talk. The infrastructure _maintenance_ costs of sprawl dramatically outweighs what a city makes in revenue from taxes they receive. https://www.youtube.com/watch?v=JPbfdcvv0to https://www.youtube.com/watch?v=JPbfdcvv0to
  - criddell 5y ago
    I think generally what you said is true, but there are other factors. Right now we're in the middle of a pandemic. I'm very thankful I don't have to rely on public transportation.
- shkkmo 5y ago
  > I've never understood how inducing demand doesn't count as success. That depends on what you see as the goal. If the goal is reducing congestion, then induced demand means that particular goal is harder to achieve. If the goal is to get more people driving then induced demand is a clear success.
  - tshaddox 5y ago
    Why in the world would "get more people driving" be a measure of success? For industries that directly benefit from that, sure, but I can't imagine how that could be a societal goal.
    - dragontamer 5y ago
      Transportation is directly related to how much your local cities are doing. When you order goods from Amazon, that gets delivered to you. It might be a road, sea, rail, or plane, but its transportation. The more of packages ordered / delivered, the more things are happening in the city. The more jobs being created, the more people will need to transport to-and-from work. The more homes built, the more transportation is needed. Etc. etc. Its a crude measurement with flaws, but generally speaking, the more transportation that's happening, the bigger and better the city is functioning. People wouldn't travel unless they needed to (travel always sucks: traffic accidents, getting stuck, dealing with others on planes/trains/busses, etc. etc.). But we deal with it because without transit, we couldn't do our daily business. Be it a meeting for work, going to school, delivering goods or other such need. ------- Mass transit options, like Rail, get more things done with far less money. But there's a latency issue: rail can be slower for the individual... but its cheaper and more-bandwidth for the city. This conflicts with individual options like roads: it costs a gross amount of money for an individual to buy a car / use it on the highways (plus the cost of highways themselves: rubber tires wear out faster than steel wheels on trains. Asphalt roads need replacing more often than steel rail lines. Gasoline costs much more than the electricity used to move a train). But the individual latency is such an advantage, that the individual will typically prefer car travel.
      - 5y ago
- nostromo 5y ago
  Yeah, they're shifting the goal posts. Here in city (Seattle) most people drive because transit tends to be spotty and slow for most people. So, what's the solution? Make driving worse of course. Speedbumps everywhere. Change 4-lane roads to 2-lanes. Remove parking. Lower speed limits to absurd levels. Make through streets dead ends. Transit still mostly sucks, but now driving sucks too. Success! I love transit and want more of it, but the transit folks realized it's hard to compete with driving, so they've just given up entirely on making transit great. It's easier to ruin driving.
  - robcohen 5y ago
    > I love transit and want more of it, but the transit folks realized it's hard to compete with driving, so they've just given up entirely on making transit great. It's easier to ruin driving. Wow. You just crystalized exactly what I felt was wrong with the argument that induced demand is bad. Thanks.
    - crowbahr 5y ago
      It's an entirely bad faith and shallow argument. You should probably reconsider what you're thinking is. The goal of transit first infrastructure is to make the majority of trips unnecessary. You shouldn't be required to own a car to participate in American society. This means we need to rezone our residential sprawl to allow for more frequent, smaller grocery stores. We need to increase the amount of mixed zoning, increase density, decrease the insane quantity of land dedicated solely to the movement and storage of privately owned heavy machinery (automobiles) and focus on easily accessible areas of bike & bus friendly infrastructure. The Netherlands was fully capable of transitioning from a nation of car dependent choked cities to a bike first micromobility haven in 30 years. The only thing stopping the USA from doing the same is the enormous government subsidies paid to car owners to keep the roads paved. If the federal government stopped taking 90% of the cost of every road in the US and you had to pay gas tax to support it all do you think you'd still be driving? Do you think you'd support billion dollar bridge extensions and lane additions when it means gas is an extra $5/gallon?
      - 5y ago
- mrfusion 5y ago
  You’re spot on. Plus the argument doesn’t hold water since there are a finite number of potential drivers.
  - asoneth 5y ago
    "Induced demand" doesn't just mean increasing the number of drivers, it means increasing the number of miles driven. In a metro area housing prices are generally correlated with how many minutes it takes to get to a city center. If you add highway capacity then people will choose to move further out to the suburbs. (Though that is great for property values, especially around the periphery of the commuting range.)
- ThrustVectoring 5y ago
  Taking a trip is a cost, not a benefit. It's evidence that the cost of the trip is considered worth taking and that there's some advantage being gained, but more trips in and of itself is a terrible metric.
- tshaddox 5y ago
  In some sense I understand what you're saying, but that mode of argument has limitations. Like, you certainly wouldn't say "I don't understand how increasing medical costs doesn't count as success, that means people want to spend their money on medical care, doesn't it?"
  - twoodfin 5y ago
    If you doubled the number of hospital beds, doctors, nurses, diagnostic equipment, labs … and demand was high enough to keep prices constant, you’ve doubled healthcare access at a rate patients were already willing to pay. “Induced demand” in every other industry is described as “latent demand”.
    - tshaddox 5y ago
      No one is against increasing access to healthcare. But I deliberately chose the example of healthcare costs to be analogous with people experiencing traffic congestion.
      - twoodfin 5y ago
        Right, and I’m suggesting they are, in fact, quite analogous in this context. If there’s latent, unsatisfied demand for healthcare, and you increase the supply, you shouldn’t be surprised or disappointed if the new supply is consumed. More people are getting the healthcare they wanted!
        tshaddox 5y ago
        Yes, but people aren’t complaining that more people drove the route. They’re complaining that congestion was not reduced. And congestion is bad.
        twoodfin 5y ago
        Same congestion, more demand being satisfied seems like a win to me—and to the marginal drivers, who decided to start driving when they weren’t before, or the new capacity would not have become congested. This is such an oddball perspective: EDGE, 3G, LTE mobile networks all became increasingly congested as demand rose to meet supply. But nobody thought building out 5G was therefore pointless.
- mjmahone17 5y ago
  Road usage isn’t necessarily success. For a political region, economic activity is usually considered a success. If by building a larger road through your city, you induce people to live outside of your city instead of in it, then you’ve added costs while reducing your economic activity, while creating more total wasted hours in traffic in the process. Are the trade offs worth it? Sometimes! But induced traffic demand is not by itself a success criteria for regions: it’s only a success if it means more people are able to work and have higher productivity in a region, as opposed to just spreading out the existing workers and reducing their productivity through increased commute times.
  - twoodfin 5y ago
    I’m not sure that tracks: If a new road allows me to build a home where I would not have built a home before, that’s economic activity enabled by the new road.
    - alistairSH 5y ago
      But it's activity somewhere other than where part of the road was built. Take DC and NoVA, typical large suburb next to a large city. If DC wants to increase economic activity, does it want to invest in a new bridge that allows more people to live in NoVA (where most of their retail/commercial activity will occur)? Or, would DC be better off spending that money on redeveloping run-down neighborhoods and adding some light rail (or other transit improvements)?
      - kevinmchugh 5y ago
        Doesn't DC have a height limit on buildings? Seems like eliminating that would be a way for the city to increase economic activity without spending any money
        alistairSH 5y ago
        Yes, that’s a fairly unique rule. IIRC to protect the aesthetics of the downtown monument/lawn zone (which includes the WH and Capitol). Arlington across the river has all the tall office buildings. But I have no idea how much DC “needs” the vertical space for development. It isn’t nearly as dense as NYC - plenty of infill (re)development to be done, I would guess.
- zip1234 5y ago
  If driving demand can be induced by massively subsidizing it with billions as is currently done, so can other forms of transportation.
- bsder 5y ago
  > I've never understood how inducing demand doesn't count as success. More lanes generally improves throughput. However, more lanes often increases latency. City planners may prefer this, but individuals may not.
- Spooky23 5y ago
  The problem is that demand has other consequences. I drive 2-3 times a year from NY to South Carolina or Florida for years, always timing crossing through DC around 5AM. Traffic 15-20 years ago coming into DC extended down to Potomac Mills. When I passed though in 2019 it extended almost 60 miles, well past Fredericksburg! More demand drives more sprawl that drives more demand for roads. Eventually metastasizes into a nightmare like LA or Long Island!
  - IdoRA 5y ago
    Part of the reason there is unusually high traffic in that location is the confluence of two things: one is that local traffic doesn’t have a great alternative to 95 over the Rappahannock river (the local Rt. 17/1 interchange is famously awful) so you take 95, and the other is that there is a large amount of truck traffic between Rt. 17 and 95. Basically over the span of the Stafford/F’burg area 95 sees an additional ~30k cars/day. There are road improvements in progress but they are too little, too late.
- Ajedi32 5y ago
  There was an article[1] posted here a while back which changed my perspective on this issue. Indeed, there's nothing wrong with induced demand on its own. In any other market, more demand induced by lower costs (whether those costs be monetary or in the form of commute times) would almost certainly be a good thing. The only reason it's a potential issue for roads is that road use is an externality. Building and maintaining efficient roadways comes at a significant cost, but our current system of road construction funded primarily by income taxes means road users don't pay that cost in a manner proportional to their use of those roads. Road construction is "free" from their perspective, so there's no incentive to use alternative means of transportation even if those alternatives would be superior overall once road construction and maintenance costs were factored in. Because of this it's hard to be sure whether the demand induced by increased supply of roadways is worth the cost in any particular instance. It could be a worthwhile increase in utility, or it could just be a waste of money. [1]: https://news.ycombinator.com/item?id=28320834 https://news.ycombinator.com/item?id=28320834
  - efxhoy 5y ago
    The canonical economist solution to this is to introduce road tolls. Make drivers pay at point of use to fund the road.
    - ravel-bar-foo 5y ago
      We already have this in the form of gas taxes. However, increasing them is politically untenable.
      - bobthepanda 5y ago
        Gas taxes are becoming less of this, though, partially because cars have become more fuel efficient, partially because some cars don't even use gas, and partially because the gas tax has not been raised since 1993 and so has not covered full road spending for a long time. The most "fair" way to do it would be to charge according to road wear and tear, which would look something like axle load ^2 * miles driven, but this would be hard to implement and also widely unpopular with huge swathes of the population (truck driver is the most common profession in many states)
- JPKab 5y ago
  Just to be clear (I lived in DC/northern Virginia for 10 years, and witnessed induced demand over and over), if the goal of widening a highway is to ease traffic congestion, induced demand quickly makes this a failed strategy. In northern Virginia, every project to widen 66 or 95 has always been sold to taxpayers as a move to ease congestion. But the result of that is temporary. As soon as the congestion is eased, cheapish land opens up for new development and more affordable housing. People flock to these new developments, and the cycle repeats. It does result in growth for an area, but quality of life stagnates. The traffic in northern Virginia/DC/Maryland is at a point where it noticeably affects the mood of a bulk of the people who live there. Spending 90 minutes each way day after day after day fucks people's heads up.
  - kmeisthax 5y ago
    90 minute commutes not only fuck with people's heads, it also creates Stockholm syndrome where people start talking about how cars are freedom. This isn't directly caused by the commutes. It's more that car-dependent suburbs also can't support transit infrastructure, so not having a car at all is still worse than 90 minutes of lost time.
- VintageCool 5y ago
  Expanding highways is sold as "making traffic better", or "scaling to day-to-day traffic" as the grandparent poster put it. However, what expanding highways actually accomplishes is incentivizing people to move out of the city because they can have a commute which is longer in miles but shorter in minutes. That lasts until enough people move to the suburb that the commute is now longer in miles AND equal time or longer in minutes. You haven't made traffic any better, you've just made sprawl worse and you've increased the vehicle miles traveled to accomplish the same result of getting people where they want to be. The message of the New Urbanists is that we should make our cities more livable and build/allow more housing units within the cities so that more people can live where their commutes are short (in terms of miles) and the increase in density will make providing transit more cost-effective.
- jimmytidey 5y ago
  Fascinating that this has generated so many answers, from so many different perspectives. Induced demand is a terrible name for the real issue here. Perhaps the "one more lane fallacy" would be better. The "one more lane fallacy" is not universal, it only applies in cities and other densely populated areas. Imagine you are sitting in a suburban traffic jam, getting slowly more and more annoyed. It's easy to imagine adding marginally more road capacity would put an end to traffic jam. That thought is the 'one more lane fallacy'. That, admittedly attractive, idea is wrong because adding more capacity leaves the traffic jam exactly the same, with more lanes and more cars in them - because of induced demand. The kicker is that in a densely populated area, there is often no realistic prospect of adding enough road capacity to end traffic jams, simply because of there is not enough space. I suspect that in most cases, road building achieves political support through the expectation of ending traffic jams. Nearly always, this expectation will not be met. This is the essence of the induced demand problem - it is not as obvious as is sometimes made out. So, even if you are die hard driver, if you want to reduce traffic jams, you should advocate for other people to use transport methods that are more space efficient than driving. Of course, you might want to live in an area dominated by constantly congested roads, in which case, induced demand isn't a problem.
  - benf76 5y ago
    So why bother build any roads larger than one lane?
    - jimmytidey 5y ago
      You need some road capacity for ambulances and Deliveroo.
- imgabe 5y ago
  The goal of building new roads is to decrease congestion and reduce travel times. If you build a new road and it gets just as congested and it takes just as long to travel from A to B, then what did you accomplish? The number of people who want to use a road is not the metric we're trying to optimize here. If we wanted to do that we should build as few roads as possible. Then there would be tons and tons of people who want to use each road. Hooray! Success!
- megablast 5y ago
  It is. If you work for an oil company. Or love pollution. Or hate the planet. Getting more people driving is awesome!!
animal_spirits 5y ago
Correct, The Downs-Thomson paradox [1] is a known issue in urban planning stating basically unless you improve public transportation car congestion will continue to get worse. > the equilibrium speed of car traffic on a road network is determined by the average door-to-door speed of equivalent journeys taken by public transport. NotJustBikes has a good introduction to it [2] [1] https://en.wikipedia.org/wiki/Downs%E2%80%93Thomson_paradox https://en.wikipedia.org/wiki/Downs%E2%80%93Thomson_paradox [2] https://youtu.be/RQY6WGOoYis https://youtu.be/RQY6WGOoYis
andrewflnr 5y ago
I don't understand why public transit doesn't have exactly the same induced demand problem as highways. If there's enough people to fill up new highways, they'll also fill up the public transit... Unless the plan is to make public transit miserable enough that only outside with no better options will use it, in which case it seems like it's all going according to plan already.
- meheleventyone 5y ago
  Improving public transport absolutely does induce demand and that’s part of the point of making it better. In particular because it’s much more space efficient it also reduces congestion as people switch to it. Same thing with improving cycling facilities. It’s just inducing demand on an already overused system like private cars doesn’t fix the system being overused unless you can get beyond the desired capacity.
- azylman 5y ago
  The way that public transit scales to meet higher demand is different than roads. Whereas roads require more lanes, public transit such as trains can scale by either adding more train cars to existing trains or adding more frequent service. More frequent service, in addition to improving throughput, also helps everyone else using the system by making it more convenient. And, if it "induces" people to move from roads to trains, that also reduces congestion on the roads. So induced demand for rail lines is a good thing. If induced demand is high enough even that, too, may not be enough - but then building a new rail line is at least no harder than adding a new highway lane (in most cases), and can support substantially more throughput with equal or lower travel times.
  - njarboe 5y ago
    Before COVID, BART in the Bay Area was completely full during peak hours. You had to wait for multiple trains to finally pack into the car. That, or take the train the opposite direction for a few stops from downtown and then get back on in the other direction. They are starting to remove more and more seats to pack in more people, but eventually if use keeps increasing you will have to build a new subway and who knows how much that will cost or how long it will take. It is probably not really possible right now. See the failure of California's bullet train.
njarboe 5y ago
Most people prefer individual transport systems for many good reasons. "Induced demand" is just more people using new roads because they get to do what they need/want to do. If we build enough roads (maybe using tunnels underground, a la The Boring Company) for everyone to go where they want, when they want, with up to 40 tons of cargo with them, there won't be any traffic congestion. This happened when the interstates were first built in the US and we could have that again if we decided to build thousands of miles of new tunnels. That would be a true national infrastructure project that would make everyone's lives much better. Sitting in traffic is a scourge on humanity. These tunnels could also have buses and groups of buses (trains?) in them for people who would rather travel with strangers, following a schedule set by someone else, and not carrying many objects with them. Could constructing this system also be called large-scale investment in public transportation then we could get everyone on board? Win-win solutions in society are still possible I hope.
- bluGill 5y ago
  individual transport vs shared is a matter of compromise. Human drivers only go fast (when there is no congestion the autobahn with no speed limit doesn't in practice move any faster than US freeways for the majority of users of each). Trains today have the ability to go faster than human drivers. Trains carry far more people than cars. Thus replacing most trips with train trips would be faster and cheaper for most people. Note that I said most trips there. If you don't have a system useful enough that most people use it most of the time then people still need cars to get around and that changes the calculation. it can be very hard to get there.
adventured 5y ago
> never a solution, due to induced demand That's false. The mistake universally made by people repeating that claim is a failure to account for the fact that vehicles and population are finite. In the US there isn't much population growth, except for in a select few urban areas. It's baffling that it gets repeated so often as though it's always true, when it's not. You can swamp the amount of induced demand with additional roads, it all depends on the number of vehicles you're dealing with. Which is to say, it depends on context and it's incorrect to suggest matter-of-fact that induced demand defeats additional roads. You'd need to run a study on the traffic potential and local + regional population growth to know one way or another what additional roads might do as it pertains to inducing demand over time and whether you can overcome the expected increased demand. The demand doesn't just keep rising forever as you build more roads.
- _dain_ 5y ago
  >You can swamp the amount of induced demand with additional roads, it all depends on the number of vehicles you're dealing with Do you realize just how extravagantly expensive that would be?
dave_aiello 5y ago
HOV lanes, special toll lanes, driverless vehicles, new alternative means of transportation that never quite materialize, etc., don’t cut it and never did.
rayiner 5y ago
I grew up in Northern VA. Public transit here is a solution looking for a problem. The job centers and commercial are too spread out for public transit to make any sense. Most of the population and jobs in the DC metro area aren’t in DC but spread around in Tysons, Loudoun, Reston, Arlington, Bethesda, etc. The state spent billions building the Silver line out to Tysons, Reston, and Loudoun, and ridership was disappointing even before COVID. (And it’s approximately zero now.) In a traditional hub-and-spoke city like Chicago, heavy rail can bring tons of commuters down to where the jobs are in the core. But when the jobs are spread out all over the spokes, that model breaks down. It’s impossible to take Metro to Reston from most of the surrounding residential areas (all the ones except the narrow slice on the Silver line itself). And it’s a huge pain in the ass to do the spoke-hub-spoke commute and take Metro from a different suburb to Reston. And for married couples, it’s a real roll of the dice whether both your jobs will be easily accessible via Metro. Rail transit is an anachronism, best suited for the 1950s when life involved a woman staying home with the kids while dad took the train into the city for work. I did that for a year before my wife started her job and it was lovely (took Metro North down from Westchester to Manhattan every day). But in a modern family with two jobs in two locations, plus kids with daycare and school and after school activities, it’s not scalable. My wife and I are “city people.” We really tried to scale the transit lifestyle. We lived in downtown Baltimore for two years and took Amtrak to work each day. We lived in downtown DC and took Metro. We’ve commutes in the Silver line, Orange line, Blue line, MARC, etc. And every year the service got worse, and every time we had another kid the equation got harder to balance. Eventually we threw in the towel, moved to a red county, and bought an SUV that gets 13 mpg. And we’ve never looked back. You want to know what the future of America looks like? Go to the Dallas suburbs. That’s where all the immigrants with kids are, and where the next generation of Americans are being raised. It’s a glorious place. And it doesn’t involve public transit.
- vjust 5y ago
  Right on. I lived literally next to Dulles International Airport - ~8 miles. Yet, to get to Dulles (or Reston/Herndon) by Public transit, would've taken me 2 hours perhaps, or more.
  - 5y ago
trhway 5y ago
public transportation doesn't work for people with pets, in many situations for people with children, people with various health issues.
- enragedcacti 5y ago
  they can still drive?
- acdha 5y ago
  > public transportation doesn't work for people with pets, in many situations for people with children Do you mean the millions of people who do this every day don't exist? You might personally prefer that and it's certainly an opinion which has been lavishly subsidized in the U.S. but this is a lifestyle choice, not a truth. > people with various health issues. How many of the people who cannot take transit are capable of safely driving cars? Public transportation — whether bus/rail mass transit or on-demand access services — is key for a large number of people who cannot drive themselves and a large number of people who could but are not affluent enough to afford the $10K/year or more that personal car ownership (considerably more if you need a vehicle customized with assistive technologies). Again, you obviously have an opinion on this issue but that doesn't make such blanket statements less incorrect.
  - trhway 5y ago
    It isn't a preference nor choice. It is direct experience. More than half of my life i was using public transportation in USSR/Russia, no issues, we'd take our cats/dogs when needed. Not the case in US. >How many of the people who cannot take transit are capable of safely driving cars? It doesn't matter how many (though a lot of people for example develop back issues by mid age and beyond so prolonged walking/standing is much harder than sitting in the car especially after a workday). The point is you just dismiss them. And this is why those tone-deaf public transportation proponents like you aren't going anywhere - you dismiss all those supposedly small groups and thus as a result left with pretty much no support. And just a bit of meta to illustrate the point - notice that i'm telling you about the issues with your approach and instead of addressing them, you're dismissing them outright as supposedly just "my preferences".
AnthonyMouse 5y ago
> Additional highways are at-best a stop-gap for day-to-day traffic, never a solution, due to induced demand This continues to be wrong every time someone brings it up. If you have insufficient road capacity, you have congestion, and congestion suppresses demand. If you increase capacity, some of the congestion goes away, and then some of the demand comes back. What this looks like is that you currently have enough cars to require three lanes but have two lanes, so you build a third lane. The reduction in congestion causes you to have enough cars to require four lanes, leading to the fool's conclusion that adding enough lanes is impossible. But that's not it. It's that you needed four from the beginning to handle the amount of traffic that occurs there in the absence of congestion, but you only had three, or two. Sometimes building a four (or five or six) lane highway isn't the best solution. Sometimes it's better to build more housing near the jobs so people have shorter commutes, or build mass transit etc. Sometimes you just need a wider road. Pretending that's never the case is preposterous. If that was true then why do we keep multi-lane highways open instead of closing all but one of the lanes? Wouldn't that improve traffic, under this theory?
- azylman 5y ago
  > Sometimes you just need a wider road. Pretending that's never the case is preposterous. If that was true then why do we keep multi-lane highways open instead of closing all but one of the lanes? Wouldn't that improve traffic, under this theory? You're setting up this strawman where the argument is "improve roads" vs. "do nothing". That's obviously not the case. The argument is "improve roads" vs. "improve public transit". Demonstrably, improving roads is worse than improving public transit. You refer to this as a "fool's conclusion" yet this has been a well-known fact in the field for almost a century. The wikipedia article I linked has some good information on this if you'd like to learn more.
  - AnthonyMouse 5y ago
    > Your setting up this strawman where the argument is "improve roads" vs. "do nothing". Your claim is this: > Additional highways are at-best a stop-gap for day-to-day traffic, never a solution, due to induced demand That claim is false and is not a straw man because you actually claim it. Improving mass transit might work as an alternate solution, sometimes, in specific contexts. That doesn't prove that adding more lanes wouldn't also work, and it's also not universally true. A large fraction of the traffic on I-95 is trucks. How many semi truck drivers and their loads can you fit on a public bus? Many highways are congested at a specific choke point. You could make a completely free thousand mile an hour bullet train to transport people from one side of the choke point to the other and solve nothing because people would get to the other side without a car and be unable to get the last ten miles to their destination. But once you get past the choke point, the traffic diverges in every direction and there is no longer enough density to justify a mass transit route. Sometimes you just need a wider road.
mrfusion 5y ago
I love how people think induced demand is an iron clad argument against any road building. What about the induced demand of going from 0 lanes to 1 lane?
- yifanl 5y ago
  Depends on where that 0 lanes is initially I guess. You can bulldoze a housing block to add a new lane, that's not necessarily an economic success.
  - asdff 5y ago
    It is if destroying those ten houses relieved a trucking bottleneck at the train yard.
erik_seaberg 5y ago
“People drive more instead of giving up and staying home” is latent demand being met. “People drive more because building the highways made everything farther apart” is induced demand being created.
wyager 5y ago
There is no economical way for public transportation to cover the kind of transit patterns serviced by highways. If I had to take buses from Bozeman, MT to Boise, ID, any plausible bus network would take 5x as long to get me from A to B. Making everyone ride busses and bicycles in a country with the geography of America is a fantasy, even if you buy the premise that this is otherwise desirable. I don't even buy the premise, because things that are valuable to me include: 1. Expediency 2. Comfort 3. Not being subject to timetables decided by other people 4. Not having to deal with homeless or crazy people while transiting 5. Sanitation. Public transit and pandemic mitigation measures are mutually incompatible While driving, I only have to deal with one network topology (the road system) instead of two (the bus network on top of the road network), leading to vastly shorter travel times in practice. My vehicles are customized to my comfort. I don't have to get permission or wait on someone else to use them. I don't have to share them with anyone. I can keep them as clean as I please.
yuliyp 5y ago
Is there really that much induced demand in rural interstate highways? They're congested rarely enough and still almost everywhere the standard 4 lane interstate can handle things without seeing demand fill the available capacity. Certain corridors see increased demand at times but that's because of the surrounding communities happening to grow (and thus need more goods delivered / ability to ship goods) more than the highways necessarily inducing that growth. I understand that induced demand is a thing in sprawling metropolis where transport is the bottleneck preventing growth in certain areas, but this feels like a different situation.
massysett 5y ago
The idea that highways are “never” a solution due to induced demand is an utter falsehood. It may well be that the expense of sufficient highway capacity is, in some cases, more than society is willing to bear. But that does not mean that highway construction is “never” a solution.

whatshisface 5y ago

I've never understood how inducing demand doesn't count as success. That means people want to use the road, doesn't it? It's almost like saying that releasing new software doesn't do anything to help users, because it increases the demand for software by the virtue of its own utility more than it reduces the demand for software by keeping people busy.

azylman 5y ago
It depends what your success criteria is. It's true, you've successfully increased the throughput of the transit network, but you haven't done anything to improve transit times - you just have more people stuck in traffic now. There are other ways you could have spent that same amount of money (public transit) that both increase the throughput of the network _and_ improve transit times.
- deleted 5y ago
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- njarboe 5y ago
  Not if you build enough roads. This argument just does not hold up. There was less time wasted stuck in traffic in the past. Go with tunnels underground so as not the create the large problems with having surface roads. If your idea theory is right, why don't we just stop maintaining all roads, shut them down, and save a lot of money, if new roads are useless.
  - tshaddox 5y ago
    In some cases it might be theoretically possible to just outspend the problem. But in most cases the roads have to be going somewhere, and you don't have significant control over where and how big that somewhere is (i.e. you can't easily move a whole urban center, or slice it into chunks and move all the chunks apart from each other a little to fit more roads). If all the roads are ending at the same place, making wider and longer roads to that place will (often) just induce more people to drive to that place from further away. The reason "just shutting down all roads" doesn't make sense is that it doesn't solve the actual problem, which is that people want to both work in places with good jobs (traditionally often dense urban centers) while living in cheaper places that are far away and not spend significant chunks of their lives stuck in traffic. Shutting down all the roads only "solves" the traffic problem in a deliberately ridiculous sense (same as "just kill all humans").
    - Spooky23 5y ago
      Shutting down or tolling chokepoints lowers the opportunity cost of alternatives. I work for a big central business district employer. You can pay $150-250 a month to park or $75/week to take a motor coach bus from your suburban town. Those numbers drive behavior, and make for a better solution as folks who need flexibility can pay for it.
- mrfusion 5y ago
  But those extra people are choosing to be there so there must be some benefit.
  - seanmcdirmid 5y ago
    > But those extra people are choosing to be there so there must be some benefit. As long as your roads are saturated, they have less throughput, not more. It is kind of like a clog in your toilet: more things are there in your pipes, but not much is getting through.
    - throwaway0a5e 5y ago
      A clogged toilet isn't flowing. More like dumping a 5-gal bucket into a sink . The drain is running at full capacity but any one drop may take a long time to actually clear the sink. The 5-gal bucket is peak demand. Total time to sink clear is how long rush "hour" lasts. Fluid analogies are crappy because fluids flow more when you add pressure and traffic doesn't.
      - seanmcdirmid 5y ago
        > because fluids flow more when you add pressure and traffic doesn't. Well, traffic can flow when pressure is added, just not in a way that is very safe.
    - jimmaswell 5y ago
      If your city sewer is clogged, so you widen it, then more people install toilets in their houses and bring the sewer back to capacity, I think that's still a win.
  - tshaddox 5y ago
    They're choosing to be there now, precisely like they were choosing to not be there before you changed the roads. Other people are also choosing to not be there, and instead choosing to live in the woods in northern Canada. I'm not sure how this mode of argument is really demonstrating anything. It seems like you just considering literally any state of affairs other than active physical coercion to be a good state of affairs.
NikolaeVarius 5y ago
If the point of adding lanes is to reduce delays, and induced demand prevents that, you have failed in the task.
- nostromo 5y ago
  The point of adding lanes is to increase throughput.
- dragontamer 5y ago
  The point of roads, from the city's perspective, is to support additional transportation, which causes growth of the city. More transportation means more trade, more services, and better life for all who live near the roads. It might be in the form of easier-to-get deliveries (Amazon goods), or new jobs that have popped up close by, or new housing developments (aka: homes that previously weren't possible due to the time of transportation, but are now possible thanks to sped up transportation times). ----- It turns out that "individualism" is a crappy reason to do anything. The individual argument must be made because we live in a democracy, and its impossible to get the people to agree to something unless you sell them a story regarding individualism.
  - azylman 5y ago
    It's not correct that cities look at road throughput with no concern for how long that travel takes. The success criteria that city planners use always includes travel times which are impacted substantially by traffic congestion.
  - NikolaeVarius 5y ago
    You are moving the goalpost. The purpose of adding lanes was to REDUCE DELAYS. Not support additional transportation. Your entire post hinges on an incorrect premise
- bluGill 5y ago
  That means you didn't add enough lanes. You need to get ahead of induced demand, otherwise you city isn't meeting the needs of the people who live there. If you don't want to have many places you can reach in a reasonable amount of time can you can move to a rural area. The point of cities is to give people options to reach lots of places quickly. Get busying being a good city. Note, it can be better to add transit other than lanes of road. Even though I said add lanes, adding lanes is but one possible solution. Good transit may well be better. Figure out how to make your city serve the people who want to get around.
kaesar14 5y ago
Because the metric people care about is traffic on the roads, not how many motorists are able to use the road in a given day. The Big Dig by this metric was a resounding success in Boston, able to dramatically scale up the amount of commuters in and out of the city, but driving still absolutely sucks because of traffic. To the person on the road, the Big Dig solved nothing. Parent comment is saying the only way to scale with higher demand of transportation in a way that feels like an actual improvement to people is public transit, because public transit scales so much better with higher numbers of people commuting.
- whatshisface 5y ago
  If the metric was really traffic, then that could easily be solved on any road by only allowing even-numbered license numbers to drive on even-numbered days, and vice-versa. If that's an absurd solution, then traffic severity is not the only metric.
  - kaesar14 5y ago
    I mean, I don't see how that's really a fair response to saying what people care about is traffic. Yeah, ability to use the road, sure. I don't think people want a new highway to be built and then told they can't use it because they don't have a new car or something. I as a motorist could not give less of a shit if I'm stuck in traffic for 3 hours a day but the road is able to move hundreds of thousands of cars a day. I'd prefer a road that could only move 20 people a day with 0 traffic. It's the only thing I care about.
    - bagacrap 5y ago
      why would you count that as a win? you almost certainly wouldn't be one of those 20 people allowed on the road
      - kaesar14 5y ago
        The example was clearly intended to include the motorist in question, being allowed to be on the road. As long as the motorist got to use the road, it wouldn't matter to said motorist how large the capacity of the road was, if they weren't able to clear through it quickly without traffic. It wouldn't matter if the road in question was servicing large amounts of people, it's only visible impact to the motorists time on the road that matters.
animal_spirits 5y ago
The less you invest in public transportation, the more people will drive. The more people that drive, the slower traffic gets. If you just widen the road, all you do is increase the amount of cars that drive. If people can't get to where they are going via public transportation, then they are going to drive instead, increasing congestion. Would recommend watching this video on it: https://youtu.be/RQY6WGOoYis https://youtu.be/RQY6WGOoYis
- massysett 5y ago
  Yes, if you increase the amount of road and more cars get people to where they are going, the result is increased economic activity. The result also is increased well-being because more people are getting to places where they wish to go - destinations that are improving their lives. This is a success.
  - animal_spirits 5y ago
    You actually see the opposite. Close nit places with more foot traffic and better public transport see higher economic activity and financial resilience. Places with long roads between where people live and where they shop/work/eat _drastically_ harms financial productivity due to higher infrastructure costs. Chuck Mahron makes this point in his TEDx talk. The infrastructure _maintenance_ costs of sprawl dramatically outweighs what a city makes in revenue from taxes they receive. https://www.youtube.com/watch?v=JPbfdcvv0to https://www.youtube.com/watch?v=JPbfdcvv0to
- criddell 5y ago
  I think generally what you said is true, but there are other factors. Right now we're in the middle of a pandemic. I'm very thankful I don't have to rely on public transportation.
shkkmo 5y ago
> I've never understood how inducing demand doesn't count as success. That depends on what you see as the goal. If the goal is reducing congestion, then induced demand means that particular goal is harder to achieve. If the goal is to get more people driving then induced demand is a clear success.
- tshaddox 5y ago
  Why in the world would "get more people driving" be a measure of success? For industries that directly benefit from that, sure, but I can't imagine how that could be a societal goal.
  - dragontamer 5y ago
    Transportation is directly related to how much your local cities are doing. When you order goods from Amazon, that gets delivered to you. It might be a road, sea, rail, or plane, but its transportation. The more of packages ordered / delivered, the more things are happening in the city. The more jobs being created, the more people will need to transport to-and-from work. The more homes built, the more transportation is needed. Etc. etc. Its a crude measurement with flaws, but generally speaking, the more transportation that's happening, the bigger and better the city is functioning. People wouldn't travel unless they needed to (travel always sucks: traffic accidents, getting stuck, dealing with others on planes/trains/busses, etc. etc.). But we deal with it because without transit, we couldn't do our daily business. Be it a meeting for work, going to school, delivering goods or other such need. ------- Mass transit options, like Rail, get more things done with far less money. But there's a latency issue: rail can be slower for the individual... but its cheaper and more-bandwidth for the city. This conflicts with individual options like roads: it costs a gross amount of money for an individual to buy a car / use it on the highways (plus the cost of highways themselves: rubber tires wear out faster than steel wheels on trains. Asphalt roads need replacing more often than steel rail lines. Gasoline costs much more than the electricity used to move a train). But the individual latency is such an advantage, that the individual will typically prefer car travel.
    - 5y ago
nostromo 5y ago
Yeah, they're shifting the goal posts. Here in city (Seattle) most people drive because transit tends to be spotty and slow for most people. So, what's the solution? Make driving worse of course. Speedbumps everywhere. Change 4-lane roads to 2-lanes. Remove parking. Lower speed limits to absurd levels. Make through streets dead ends. Transit still mostly sucks, but now driving sucks too. Success! I love transit and want more of it, but the transit folks realized it's hard to compete with driving, so they've just given up entirely on making transit great. It's easier to ruin driving.
- robcohen 5y ago
  > I love transit and want more of it, but the transit folks realized it's hard to compete with driving, so they've just given up entirely on making transit great. It's easier to ruin driving. Wow. You just crystalized exactly what I felt was wrong with the argument that induced demand is bad. Thanks.
  - crowbahr 5y ago
    It's an entirely bad faith and shallow argument. You should probably reconsider what you're thinking is. The goal of transit first infrastructure is to make the majority of trips unnecessary. You shouldn't be required to own a car to participate in American society. This means we need to rezone our residential sprawl to allow for more frequent, smaller grocery stores. We need to increase the amount of mixed zoning, increase density, decrease the insane quantity of land dedicated solely to the movement and storage of privately owned heavy machinery (automobiles) and focus on easily accessible areas of bike & bus friendly infrastructure. The Netherlands was fully capable of transitioning from a nation of car dependent choked cities to a bike first micromobility haven in 30 years. The only thing stopping the USA from doing the same is the enormous government subsidies paid to car owners to keep the roads paved. If the federal government stopped taking 90% of the cost of every road in the US and you had to pay gas tax to support it all do you think you'd still be driving? Do you think you'd support billion dollar bridge extensions and lane additions when it means gas is an extra $5/gallon?
    - 5y ago
mrfusion 5y ago
You’re spot on. Plus the argument doesn’t hold water since there are a finite number of potential drivers.
- asoneth 5y ago
  "Induced demand" doesn't just mean increasing the number of drivers, it means increasing the number of miles driven. In a metro area housing prices are generally correlated with how many minutes it takes to get to a city center. If you add highway capacity then people will choose to move further out to the suburbs. (Though that is great for property values, especially around the periphery of the commuting range.)
ThrustVectoring 5y ago
Taking a trip is a cost, not a benefit. It's evidence that the cost of the trip is considered worth taking and that there's some advantage being gained, but more trips in and of itself is a terrible metric.
tshaddox 5y ago
In some sense I understand what you're saying, but that mode of argument has limitations. Like, you certainly wouldn't say "I don't understand how increasing medical costs doesn't count as success, that means people want to spend their money on medical care, doesn't it?"
- twoodfin 5y ago
  If you doubled the number of hospital beds, doctors, nurses, diagnostic equipment, labs … and demand was high enough to keep prices constant, you’ve doubled healthcare access at a rate patients were already willing to pay. “Induced demand” in every other industry is described as “latent demand”.
  - tshaddox 5y ago
    No one is against increasing access to healthcare. But I deliberately chose the example of healthcare costs to be analogous with people experiencing traffic congestion.
    - twoodfin 5y ago
      Right, and I’m suggesting they are, in fact, quite analogous in this context. If there’s latent, unsatisfied demand for healthcare, and you increase the supply, you shouldn’t be surprised or disappointed if the new supply is consumed. More people are getting the healthcare they wanted!
      - tshaddox 5y ago
        Yes, but people aren’t complaining that more people drove the route. They’re complaining that congestion was not reduced. And congestion is bad.
        twoodfin 5y ago
        Same congestion, more demand being satisfied seems like a win to me—and to the marginal drivers, who decided to start driving when they weren’t before, or the new capacity would not have become congested. This is such an oddball perspective: EDGE, 3G, LTE mobile networks all became increasingly congested as demand rose to meet supply. But nobody thought building out 5G was therefore pointless.
mjmahone17 5y ago
Road usage isn’t necessarily success. For a political region, economic activity is usually considered a success. If by building a larger road through your city, you induce people to live outside of your city instead of in it, then you’ve added costs while reducing your economic activity, while creating more total wasted hours in traffic in the process. Are the trade offs worth it? Sometimes! But induced traffic demand is not by itself a success criteria for regions: it’s only a success if it means more people are able to work and have higher productivity in a region, as opposed to just spreading out the existing workers and reducing their productivity through increased commute times.
- twoodfin 5y ago
  I’m not sure that tracks: If a new road allows me to build a home where I would not have built a home before, that’s economic activity enabled by the new road.
  - alistairSH 5y ago
    But it's activity somewhere other than where part of the road was built. Take DC and NoVA, typical large suburb next to a large city. If DC wants to increase economic activity, does it want to invest in a new bridge that allows more people to live in NoVA (where most of their retail/commercial activity will occur)? Or, would DC be better off spending that money on redeveloping run-down neighborhoods and adding some light rail (or other transit improvements)?
    - kevinmchugh 5y ago
      Doesn't DC have a height limit on buildings? Seems like eliminating that would be a way for the city to increase economic activity without spending any money
      - alistairSH 5y ago
        Yes, that’s a fairly unique rule. IIRC to protect the aesthetics of the downtown monument/lawn zone (which includes the WH and Capitol). Arlington across the river has all the tall office buildings. But I have no idea how much DC “needs” the vertical space for development. It isn’t nearly as dense as NYC - plenty of infill (re)development to be done, I would guess.
zip1234 5y ago
If driving demand can be induced by massively subsidizing it with billions as is currently done, so can other forms of transportation.
bsder 5y ago
> I've never understood how inducing demand doesn't count as success. More lanes generally improves throughput. However, more lanes often increases latency. City planners may prefer this, but individuals may not.
Spooky23 5y ago
The problem is that demand has other consequences. I drive 2-3 times a year from NY to South Carolina or Florida for years, always timing crossing through DC around 5AM. Traffic 15-20 years ago coming into DC extended down to Potomac Mills. When I passed though in 2019 it extended almost 60 miles, well past Fredericksburg! More demand drives more sprawl that drives more demand for roads. Eventually metastasizes into a nightmare like LA or Long Island!
- IdoRA 5y ago
  Part of the reason there is unusually high traffic in that location is the confluence of two things: one is that local traffic doesn’t have a great alternative to 95 over the Rappahannock river (the local Rt. 17/1 interchange is famously awful) so you take 95, and the other is that there is a large amount of truck traffic between Rt. 17 and 95. Basically over the span of the Stafford/F’burg area 95 sees an additional ~30k cars/day. There are road improvements in progress but they are too little, too late.
Ajedi32 5y ago
There was an article[1] posted here a while back which changed my perspective on this issue. Indeed, there's nothing wrong with induced demand on its own. In any other market, more demand induced by lower costs (whether those costs be monetary or in the form of commute times) would almost certainly be a good thing. The only reason it's a potential issue for roads is that road use is an externality. Building and maintaining efficient roadways comes at a significant cost, but our current system of road construction funded primarily by income taxes means road users don't pay that cost in a manner proportional to their use of those roads. Road construction is "free" from their perspective, so there's no incentive to use alternative means of transportation even if those alternatives would be superior overall once road construction and maintenance costs were factored in. Because of this it's hard to be sure whether the demand induced by increased supply of roadways is worth the cost in any particular instance. It could be a worthwhile increase in utility, or it could just be a waste of money. [1]: https://news.ycombinator.com/item?id=28320834 https://news.ycombinator.com/item?id=28320834
- efxhoy 5y ago
  The canonical economist solution to this is to introduce road tolls. Make drivers pay at point of use to fund the road.
  - ravel-bar-foo 5y ago
    We already have this in the form of gas taxes. However, increasing them is politically untenable.
    - bobthepanda 5y ago
      Gas taxes are becoming less of this, though, partially because cars have become more fuel efficient, partially because some cars don't even use gas, and partially because the gas tax has not been raised since 1993 and so has not covered full road spending for a long time. The most "fair" way to do it would be to charge according to road wear and tear, which would look something like axle load ^2 * miles driven, but this would be hard to implement and also widely unpopular with huge swathes of the population (truck driver is the most common profession in many states)
JPKab 5y ago
Just to be clear (I lived in DC/northern Virginia for 10 years, and witnessed induced demand over and over), if the goal of widening a highway is to ease traffic congestion, induced demand quickly makes this a failed strategy. In northern Virginia, every project to widen 66 or 95 has always been sold to taxpayers as a move to ease congestion. But the result of that is temporary. As soon as the congestion is eased, cheapish land opens up for new development and more affordable housing. People flock to these new developments, and the cycle repeats. It does result in growth for an area, but quality of life stagnates. The traffic in northern Virginia/DC/Maryland is at a point where it noticeably affects the mood of a bulk of the people who live there. Spending 90 minutes each way day after day after day fucks people's heads up.
- kmeisthax 5y ago
  90 minute commutes not only fuck with people's heads, it also creates Stockholm syndrome where people start talking about how cars are freedom. This isn't directly caused by the commutes. It's more that car-dependent suburbs also can't support transit infrastructure, so not having a car at all is still worse than 90 minutes of lost time.
VintageCool 5y ago
Expanding highways is sold as "making traffic better", or "scaling to day-to-day traffic" as the grandparent poster put it. However, what expanding highways actually accomplishes is incentivizing people to move out of the city because they can have a commute which is longer in miles but shorter in minutes. That lasts until enough people move to the suburb that the commute is now longer in miles AND equal time or longer in minutes. You haven't made traffic any better, you've just made sprawl worse and you've increased the vehicle miles traveled to accomplish the same result of getting people where they want to be. The message of the New Urbanists is that we should make our cities more livable and build/allow more housing units within the cities so that more people can live where their commutes are short (in terms of miles) and the increase in density will make providing transit more cost-effective.
jimmytidey 5y ago
Fascinating that this has generated so many answers, from so many different perspectives. Induced demand is a terrible name for the real issue here. Perhaps the "one more lane fallacy" would be better. The "one more lane fallacy" is not universal, it only applies in cities and other densely populated areas. Imagine you are sitting in a suburban traffic jam, getting slowly more and more annoyed. It's easy to imagine adding marginally more road capacity would put an end to traffic jam. That thought is the 'one more lane fallacy'. That, admittedly attractive, idea is wrong because adding more capacity leaves the traffic jam exactly the same, with more lanes and more cars in them - because of induced demand. The kicker is that in a densely populated area, there is often no realistic prospect of adding enough road capacity to end traffic jams, simply because of there is not enough space. I suspect that in most cases, road building achieves political support through the expectation of ending traffic jams. Nearly always, this expectation will not be met. This is the essence of the induced demand problem - it is not as obvious as is sometimes made out. So, even if you are die hard driver, if you want to reduce traffic jams, you should advocate for other people to use transport methods that are more space efficient than driving. Of course, you might want to live in an area dominated by constantly congested roads, in which case, induced demand isn't a problem.
- benf76 5y ago
  So why bother build any roads larger than one lane?
  - jimmytidey 5y ago
    You need some road capacity for ambulances and Deliveroo.
imgabe 5y ago
The goal of building new roads is to decrease congestion and reduce travel times. If you build a new road and it gets just as congested and it takes just as long to travel from A to B, then what did you accomplish? The number of people who want to use a road is not the metric we're trying to optimize here. If we wanted to do that we should build as few roads as possible. Then there would be tons and tons of people who want to use each road. Hooray! Success!
megablast 5y ago
It is. If you work for an oil company. Or love pollution. Or hate the planet. Getting more people driving is awesome!!

animal_spirits 5y ago

Correct, The Downs-Thomson paradox [1] is a known issue in urban planning stating basically unless you improve public transportation car congestion will continue to get worse. > the equilibrium speed of car traffic on a road network is determined by the average door-to-door speed of equivalent journeys taken by public transport. NotJustBikes has a good introduction to it [2] [1] https://en.wikipedia.org/wiki/Downs%E2%80%93Thomson_paradox https://en.wikipedia.org/wiki/Downs%E2%80%93Thomson_paradox [2] https://youtu.be/RQY6WGOoYis https://youtu.be/RQY6WGOoYis

andrewflnr 5y ago

I don't understand why public transit doesn't have exactly the same induced demand problem as highways. If there's enough people to fill up new highways, they'll also fill up the public transit... Unless the plan is to make public transit miserable enough that only outside with no better options will use it, in which case it seems like it's all going according to plan already.

meheleventyone 5y ago
Improving public transport absolutely does induce demand and that’s part of the point of making it better. In particular because it’s much more space efficient it also reduces congestion as people switch to it. Same thing with improving cycling facilities. It’s just inducing demand on an already overused system like private cars doesn’t fix the system being overused unless you can get beyond the desired capacity.
azylman 5y ago
The way that public transit scales to meet higher demand is different than roads. Whereas roads require more lanes, public transit such as trains can scale by either adding more train cars to existing trains or adding more frequent service. More frequent service, in addition to improving throughput, also helps everyone else using the system by making it more convenient. And, if it "induces" people to move from roads to trains, that also reduces congestion on the roads. So induced demand for rail lines is a good thing. If induced demand is high enough even that, too, may not be enough - but then building a new rail line is at least no harder than adding a new highway lane (in most cases), and can support substantially more throughput with equal or lower travel times.
- njarboe 5y ago
  Before COVID, BART in the Bay Area was completely full during peak hours. You had to wait for multiple trains to finally pack into the car. That, or take the train the opposite direction for a few stops from downtown and then get back on in the other direction. They are starting to remove more and more seats to pack in more people, but eventually if use keeps increasing you will have to build a new subway and who knows how much that will cost or how long it will take. It is probably not really possible right now. See the failure of California's bullet train.

njarboe 5y ago

Most people prefer individual transport systems for many good reasons. "Induced demand" is just more people using new roads because they get to do what they need/want to do. If we build enough roads (maybe using tunnels underground, a la The Boring Company) for everyone to go where they want, when they want, with up to 40 tons of cargo with them, there won't be any traffic congestion. This happened when the interstates were first built in the US and we could have that again if we decided to build thousands of miles of new tunnels. That would be a true national infrastructure project that would make everyone's lives much better. Sitting in traffic is a scourge on humanity. These tunnels could also have buses and groups of buses (trains?) in them for people who would rather travel with strangers, following a schedule set by someone else, and not carrying many objects with them. Could constructing this system also be called large-scale investment in public transportation then we could get everyone on board? Win-win solutions in society are still possible I hope.

bluGill 5y ago
individual transport vs shared is a matter of compromise. Human drivers only go fast (when there is no congestion the autobahn with no speed limit doesn't in practice move any faster than US freeways for the majority of users of each). Trains today have the ability to go faster than human drivers. Trains carry far more people than cars. Thus replacing most trips with train trips would be faster and cheaper for most people. Note that I said most trips there. If you don't have a system useful enough that most people use it most of the time then people still need cars to get around and that changes the calculation. it can be very hard to get there.

adventured 5y ago

> never a solution, due to induced demand That's false. The mistake universally made by people repeating that claim is a failure to account for the fact that vehicles and population are finite. In the US there isn't much population growth, except for in a select few urban areas. It's baffling that it gets repeated so often as though it's always true, when it's not. You can swamp the amount of induced demand with additional roads, it all depends on the number of vehicles you're dealing with. Which is to say, it depends on context and it's incorrect to suggest matter-of-fact that induced demand defeats additional roads. You'd need to run a study on the traffic potential and local + regional population growth to know one way or another what additional roads might do as it pertains to inducing demand over time and whether you can overcome the expected increased demand. The demand doesn't just keep rising forever as you build more roads.

_dain_ 5y ago
>You can swamp the amount of induced demand with additional roads, it all depends on the number of vehicles you're dealing with Do you realize just how extravagantly expensive that would be?

dave_aiello 5y ago

HOV lanes, special toll lanes, driverless vehicles, new alternative means of transportation that never quite materialize, etc., don’t cut it and never did.

rayiner 5y ago

I grew up in Northern VA. Public transit here is a solution looking for a problem. The job centers and commercial are too spread out for public transit to make any sense. Most of the population and jobs in the DC metro area aren’t in DC but spread around in Tysons, Loudoun, Reston, Arlington, Bethesda, etc. The state spent billions building the Silver line out to Tysons, Reston, and Loudoun, and ridership was disappointing even before COVID. (And it’s approximately zero now.) In a traditional hub-and-spoke city like Chicago, heavy rail can bring tons of commuters down to where the jobs are in the core. But when the jobs are spread out all over the spokes, that model breaks down. It’s impossible to take Metro to Reston from most of the surrounding residential areas (all the ones except the narrow slice on the Silver line itself). And it’s a huge pain in the ass to do the spoke-hub-spoke commute and take Metro from a different suburb to Reston. And for married couples, it’s a real roll of the dice whether both your jobs will be easily accessible via Metro. Rail transit is an anachronism, best suited for the 1950s when life involved a woman staying home with the kids while dad took the train into the city for work. I did that for a year before my wife started her job and it was lovely (took Metro North down from Westchester to Manhattan every day). But in a modern family with two jobs in two locations, plus kids with daycare and school and after school activities, it’s not scalable. My wife and I are “city people.” We really tried to scale the transit lifestyle. We lived in downtown Baltimore for two years and took Amtrak to work each day. We lived in downtown DC and took Metro. We’ve commutes in the Silver line, Orange line, Blue line, MARC, etc. And every year the service got worse, and every time we had another kid the equation got harder to balance. Eventually we threw in the towel, moved to a red county, and bought an SUV that gets 13 mpg. And we’ve never looked back. You want to know what the future of America looks like? Go to the Dallas suburbs. That’s where all the immigrants with kids are, and where the next generation of Americans are being raised. It’s a glorious place. And it doesn’t involve public transit.

vjust 5y ago
Right on. I lived literally next to Dulles International Airport - ~8 miles. Yet, to get to Dulles (or Reston/Herndon) by Public transit, would've taken me 2 hours perhaps, or more.
- 5y ago

trhway 5y ago

public transportation doesn't work for people with pets, in many situations for people with children, people with various health issues.

enragedcacti 5y ago
they can still drive?
acdha 5y ago
> public transportation doesn't work for people with pets, in many situations for people with children Do you mean the millions of people who do this every day don't exist? You might personally prefer that and it's certainly an opinion which has been lavishly subsidized in the U.S. but this is a lifestyle choice, not a truth. > people with various health issues. How many of the people who cannot take transit are capable of safely driving cars? Public transportation — whether bus/rail mass transit or on-demand access services — is key for a large number of people who cannot drive themselves and a large number of people who could but are not affluent enough to afford the $10K/year or more that personal car ownership (considerably more if you need a vehicle customized with assistive technologies). Again, you obviously have an opinion on this issue but that doesn't make such blanket statements less incorrect.
- trhway 5y ago
  It isn't a preference nor choice. It is direct experience. More than half of my life i was using public transportation in USSR/Russia, no issues, we'd take our cats/dogs when needed. Not the case in US. >How many of the people who cannot take transit are capable of safely driving cars? It doesn't matter how many (though a lot of people for example develop back issues by mid age and beyond so prolonged walking/standing is much harder than sitting in the car especially after a workday). The point is you just dismiss them. And this is why those tone-deaf public transportation proponents like you aren't going anywhere - you dismiss all those supposedly small groups and thus as a result left with pretty much no support. And just a bit of meta to illustrate the point - notice that i'm telling you about the issues with your approach and instead of addressing them, you're dismissing them outright as supposedly just "my preferences".

AnthonyMouse 5y ago

> Additional highways are at-best a stop-gap for day-to-day traffic, never a solution, due to induced demand This continues to be wrong every time someone brings it up. If you have insufficient road capacity, you have congestion, and congestion suppresses demand. If you increase capacity, some of the congestion goes away, and then some of the demand comes back. What this looks like is that you currently have enough cars to require three lanes but have two lanes, so you build a third lane. The reduction in congestion causes you to have enough cars to require four lanes, leading to the fool's conclusion that adding enough lanes is impossible. But that's not it. It's that you needed four from the beginning to handle the amount of traffic that occurs there in the absence of congestion, but you only had three, or two. Sometimes building a four (or five or six) lane highway isn't the best solution. Sometimes it's better to build more housing near the jobs so people have shorter commutes, or build mass transit etc. Sometimes you just need a wider road. Pretending that's never the case is preposterous. If that was true then why do we keep multi-lane highways open instead of closing all but one of the lanes? Wouldn't that improve traffic, under this theory?

azylman 5y ago
> Sometimes you just need a wider road. Pretending that's never the case is preposterous. If that was true then why do we keep multi-lane highways open instead of closing all but one of the lanes? Wouldn't that improve traffic, under this theory? You're setting up this strawman where the argument is "improve roads" vs. "do nothing". That's obviously not the case. The argument is "improve roads" vs. "improve public transit". Demonstrably, improving roads is worse than improving public transit. You refer to this as a "fool's conclusion" yet this has been a well-known fact in the field for almost a century. The wikipedia article I linked has some good information on this if you'd like to learn more.
- AnthonyMouse 5y ago
  > Your setting up this strawman where the argument is "improve roads" vs. "do nothing". Your claim is this: > Additional highways are at-best a stop-gap for day-to-day traffic, never a solution, due to induced demand That claim is false and is not a straw man because you actually claim it. Improving mass transit might work as an alternate solution, sometimes, in specific contexts. That doesn't prove that adding more lanes wouldn't also work, and it's also not universally true. A large fraction of the traffic on I-95 is trucks. How many semi truck drivers and their loads can you fit on a public bus? Many highways are congested at a specific choke point. You could make a completely free thousand mile an hour bullet train to transport people from one side of the choke point to the other and solve nothing because people would get to the other side without a car and be unable to get the last ten miles to their destination. But once you get past the choke point, the traffic diverges in every direction and there is no longer enough density to justify a mass transit route. Sometimes you just need a wider road.

mrfusion 5y ago

I love how people think induced demand is an iron clad argument against any road building. What about the induced demand of going from 0 lanes to 1 lane?

yifanl 5y ago
Depends on where that 0 lanes is initially I guess. You can bulldoze a housing block to add a new lane, that's not necessarily an economic success.
- asdff 5y ago
  It is if destroying those ten houses relieved a trucking bottleneck at the train yard.

erik_seaberg 5y ago

“People drive more instead of giving up and staying home” is latent demand being met. “People drive more because building the highways made everything farther apart” is induced demand being created.

wyager 5y ago

There is no economical way for public transportation to cover the kind of transit patterns serviced by highways. If I had to take buses from Bozeman, MT to Boise, ID, any plausible bus network would take 5x as long to get me from A to B. Making everyone ride busses and bicycles in a country with the geography of America is a fantasy, even if you buy the premise that this is otherwise desirable. I don't even buy the premise, because things that are valuable to me include: 1. Expediency 2. Comfort 3. Not being subject to timetables decided by other people 4. Not having to deal with homeless or crazy people while transiting 5. Sanitation. Public transit and pandemic mitigation measures are mutually incompatible While driving, I only have to deal with one network topology (the road system) instead of two (the bus network on top of the road network), leading to vastly shorter travel times in practice. My vehicles are customized to my comfort. I don't have to get permission or wait on someone else to use them. I don't have to share them with anyone. I can keep them as clean as I please.

yuliyp 5y ago

Is there really that much induced demand in rural interstate highways? They're congested rarely enough and still almost everywhere the standard 4 lane interstate can handle things without seeing demand fill the available capacity. Certain corridors see increased demand at times but that's because of the surrounding communities happening to grow (and thus need more goods delivered / ability to ship goods) more than the highways necessarily inducing that growth. I understand that induced demand is a thing in sprawling metropolis where transport is the bottleneck preventing growth in certain areas, but this feels like a different situation.

massysett 5y ago

The idea that highways are “never” a solution due to induced demand is an utter falsehood. It may well be that the expense of sufficient highway capacity is, in some cases, more than society is willing to bear. But that does not mean that highway construction is “never” a solution.