[whatshisface]

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.

[Ajedi32]

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

[efxhoy]

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]

We already have this in the form of gas taxes. However, increasing them is politically untenable.

[bobthepanda]

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)

[efxhoy]

An important distinction between specific tolls per road and a general gas tax is that a gas tax funds all roads, not the specific one you're driving on. A toll on a particular road is an informative signal to the market of which particular stretch of road you want to drive on, in theory allowing more "efficient" allocation of roads.

[BoiledCabbage]

> 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 "purpose" of expanding lanes and building alterntae highways is to improve efficiency. For people living in a given area, reduce their time spent commuting. There is large economic cost to having large portions of your population spent 10+ of their waking time commuting to and from work each weekday.

The problem with induced demand is that yes you increase capacity and more people then move clogging up the roads until a similar equilibrum is reached as before. A much better option is both expanding the number of people that can commute by living further out, and reducing the per individual commute time by mass transit. That's the true goal.

[Ajedi32]

> The problem with induced demand is that yes you increase capacity and more people then move clogging up the roads until a similar equilibrum is reached as before.

That's still an improvement over the previous status quo. Commute times are not the only, or even necessarily the most important factor in a transportation system. Your new equilibrium transports a larger number of people than the previous equilibrium. In isolation, that's purely a good thing.

In a world where road users paid for those improvements directly in proportion to their use of the road we could just keep expanding capacity indefinitely until either all the latent demand were met, or until rising construction costs drove demand down to a level where the roads were no longer congested. Since roads are funded by income taxes though, a crucial half of that feedback loop is missing. We can't just keep expanding because there's nothing to stop road users from demanding more and more capacity even after adding that capacity becomes cost-prohibitive.

[BoiledCabbage]

Yes, but that's conveniently ignoring all of the negative externalities produced by it.

So adding roads gets half the benefits (as it doesn't gain any efficiency benefits), and comes with a ton of externalities when compared to mass transit.

[Ajedi32]

What externalities, other than the one I already explained?

Only one I can think of is pollution, but that's not even caused by roads, it's caused by burning gasoline.

[onecommentman]

Or by reducing/rescheduling travel demand by work-from-home, flexible hour hours, and/or devolution of Fed agency HQs to less crowded/costly US regions where their responsibilities better match the activities/needs. Say, moving Fisheries to where they fish, Bureau of Mines to where they mine, DoE to where either energy production or demand is greatest, etc. and keep a skeleton crew of critical Fed functions like White House, Congress, Supreme Court and the Pentagon in The DC area. Perhaps a movable feast with Agencies moving every 25 years to get a fuller outside-the-Beltway American perspective. Like, say, using IT to make that happen…

[ajkjk]

There is a large human cost to having large portions of your population commuting too much, also. I always think it's weird that we tend to justify policy only in terms of its economic (or health) impacts when it is something that people just want for their quality of life.

[nostromo]

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.

[dont__panic]

This is a really good point, but I also want to bring up a (small) counterargument:

I live in Denver, CO. Cars basically make it impossible to walk around most of the city, even in the more residential areas. Walking is an essential part of the public transit/non-car transportation experience because essentially everyone has to walk a few blocks from a bus stop, train station, bike rack, etc. to complete their trip on both ends. If walking those few blocks is unpleasant, unsafe, or impossible, people will (reasonably) prefer cars.

Unfortunately, car and pedestrian traffic are at odds in most cities. Situations that seem better for cars (turning lanes, right-on-red, faster speed limits, street parking) often make life hell for pedestrians who try to cross the road. Or make life very, very noisy for pedestrians who need to walk or live or work near those roads.

I agree wholeheartedly that we can't just make driving suck to encourage more people to walk or take public transit. But there are aspects of driving that need to be sacrificed to make public transit better. A great example: changing 4-lane roads to 2-lane roads -- if you can introduce a bike lane, bus lane, or both, those methods of transportation become significantly faster, safer, and better. Biking is basically a non-starter without lanes; busses can be so slow as to be not worth using when they get stuck in normal traffic. The same argument applies to parking removal -- instead of using an entire effective lane of traffic for parked cars, we can dedicate it to bikes or buses.

Lowering the speed limit reduces noise at street level, makes streets safer to cross for pedestrians, and allows bikes to peacefully coexist with cars in an environment where you don't need to go that fast anyway.

It would be interesting to hear what holds you back from using buses, walking, or bikes instead of your car to get around town. In Denver, the main issues I encounter are:

- bike theft

- literal crazy people shouting at me on buses/trains

- drivers who park/stop in crosswalks, or try to kill me on my bicycle

- the bus network is extremely slow to get around town

I think there's a fair argument that we should focus on solving these problems first, before we degrade car traffic. Bike theft is a really bike one in Seattle, too, iirc, and a huge blocker for folks trying to switch away from cars. But eventually you need to degrade car traffic to make public transit as good as it can be.

[JPKab]

I live just south of Superior outside of Denver. I lived in DC area for 10 years. For 6 of those years, I commuted on the bus to metro to work.

The DC metro deteriorated markedly, and has continued to. A lot of it is a combination of bad initial designs (lack of surplus tunnel capacity to ease maintenance) along with the aggressive, powerful, and corrupt WMATA employees union. (I was on a project to analyze WMATA's staffing issues, and within the first hour, my team identified that there was a huge incentive to understaff the maintenance/technician teams to allow existing employees to collect massive amounts of overtime. Many would simply hide and sleep during the time they claimed to be "working". Hiring more mechanics/techs was foot-dragged, because it reduced the overtime pay for the existing workers who would interview them.). 2 mechanics working normal hours cost the same as 1 mechanic pulling tons of overtime, but the gap in productivity is huge. The WMATA union doesn't care. The rudeness of the staff is pretty legendary amongst locals as well.

Anyway, all of that is a long winded and detailed way of saying that WMATA gradually became a significantly less reliable means of transportation. My brother was on a car that got stuck in a tunnel that started filling with smoke. He stopped riding. And the buses need the metro to be running well. Without that, the buses become far less reliable. It's a shit show. And it's deteriorated markedly since I last lived there.

[dont__panic]

Hope you're OK after the Marshall Fire -- "just south of Superior" sounds like a very, very good choice compared to "in Superior" these days.

Do you use public transit in the Denver area at all? I find myself biking to most places because the public transit routes don't really get me where I want to go, but a lot of folks I know in the area used to use the buses and light rail in the before times. Seems like it had a pretty good rep before covid.

[JPKab]

Yep, it was spooky. Between my house and the fire was nothing but an open expanse of tall grass prairie and route 128. Had a clear view of the fires, especially at night. We were under pre-evac orders in case the wind shifted. I had a few former colleagues who lost homes. I'm grateful that the loss of life was as low as it was.

Regarding public transit in Denver, I avoid it like the plague. If I'm by myself, I'm a lot more tolerant of it. But I can't take my kids to public places in downtown Denver anymore, including the transit. When my daughter was 4, I had her on my shoulders on Mother's Day while we walked the 16th Street Mall. As we approached the Capitol, a violent altercation occurred within 30 feet of between two chronic drug addicts. One of them had a hiking pole, and he started beating and stabbing the other one. My daughter was terrified. That's just one incident, there are far more like it.

It blows my mind how the current crop of homeless (unhoused, or whatever moronically Orweillian term has been created to signal pious, virtuous sensitivity to ingroup members) activists have pushed the utterly failed policies of San Francisco in other cities. They result is what you and I are complaining about: public spaces that are decidedly unwelcoming and unsafe to children, elderly, and women. The policies seem to do nothing but funnel money to the non-profits that employ the nutbag activists. They certainly don't accomplish anything else. It's the equivalent of the neighborhood cat lady who puts bowls of food out for strays claiming she's a wildlife rehabilitation specialist.

[ThrustVectoring]

Speed limits are far less important than the psychological design of the road - any given section will communicate what hazards are more or less likely, and drivers are very responsive to these cues.

As a concrete example, I grew up near Seattle and regularly drove on East Lake Sammamish Parkway. This road was built and designed to efficiently carry traffic between Redmond and Issaquah at a speed of 45 miles per hour. It has smooth gentle curves, good sightlines, few driveways and intersections, etc. Sometime in the 90s or 00s people built a ton of really expensive lakefront houses between the parkway and the lake, and the new homeowners got the city to lower the speed limit to 35 (presumably to make it easier to get onto the road)

People generally drive 45 on it anyways. It is a road that practically screams "45 mph is safe" at you, and 35 feels downright glacial. If you lowered the limit to 25 people would probably still regularly do 40 on it - you need some kind of traffic calming as park of a major overhaul of the road to get speeds that are safe for pedestrians there. (And even if you could do this, most households in Sammamish travel to or through either Redmond or Issaquah anyhow, so they need some thoroughfare to do so - at best you're overloading and overstressing the other roads in the network)

[dont__panic]

Oh, totally agreed. Denver commits this sin all over the place, too. Honestly, the only place in the US that doesn't commit this is Boston and some parts of New England... because the roads were designed for horses at 10mph max and pedestrians.

[azylman]

> 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.

This is obviously not the solution that anyone is proposing. You're arguing in bad faith against a strawman. The solution to bad public transit is to make public transit better.

[smegsicle]

You mentioned that induced demand is bad; someone pointed out that induced demand is not bad, but actually evidence of increased efficiency; someone else elaborated that the contrapositive is equally insane- if induced demand through efficiency is bad, then reduced demand through inefficiency is good- along with an example of the implementation of what you are asserting noone is proposing.

Caution against the short-sighted pursuit of easily-quantifiable goals at the expense of actual value is not 'arguing in bad faith'.

[ufmace]

How is he arguing against a strawman? He's saying that's exactly what they actually did in his city.

[azylman]

> 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...Transit still mostly sucks, but now driving sucks too...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.

The claim was that they put up speed bumps (and other measures) _with the intent of_ making driving worse to encourage public transit. That's obviously false. Speed bumps get put up to discourage unsafe driving.

If, when forced to drive safely, people would rather take public transit, that's kind of scary, but also a good thing I guess to get unsafe drivers off the road? However, that's not what the claim was (and in reality is unlikely to be true, though I have no data to back that up).

[onecommentman]

Not precisely to discourage unsafe driving. Simply to slow vehicles for any one of several reasons, safety often being an important one. Traffic calming has other benefits, such as more livable residential neighborhoods, and less congested residential side streets, especially during rush hours.

That does have the result of increasing trip times by cars, and thus motivating use of public transit.

Guessing intent is a fool’s game, and can’t really be true or false per se. It does antagonize automobile drivers and, from their valid but particular perspective, makes their life worse in (what would seem to them) a gratuitous fashion. Americans don’t like arbitrary and capricious as a whole.

[asdff]

Go to /r/urbanplanning and you will find this creed of road dieting written in stone tablets by a thundering voice

[kaesar14]

> 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.

It's way more like the driving folks have absolutely ruined transit in almost every single city in the country.

[kmeisthax]

You can't make transit great if cars are also great, because the two are mutually exclusive.

For cars to be good you need lots of space for parking lots and highways. Otherwise, the car is getting you nowhere fast, and there won't be anywhere to park it when you get there. But that also means those parking lots and highways need space. In all but the densest urban metros, that space is two-dimensional, which means all that car infrastructure is spreading out all the buildings.

Transit needs the exact opposite to happen: buildings need to be close-together so that a single line can aggregate more demand, and riders have to walk less when they arrive at their destinations. This is actually how pretty much all cities used to be built, because cars didn't exist yet, so you had to give that space to pedestrian infrastructure. Not coincidentally, those are also the cities with the best transit, and the absolute worst to drive in. You can't have both cars and people sharing the same space.

[throwaway0a5e]

> You can't make transit great if cars are also great, because the two are mutually exclusive.

I disagree. Regardless of your preferred mode of transit, look at the hours just before and after peak. Roads flow smoothly. Trains run at tight intervals and aren't too crowded. It's great for everyone.

Peak demand time will always be a clusterfuck but with enough infrastructure (ignoring petty ideological bickering about which mode should have what market share) we can probably have a system that's pretty damn decent the other 22hr of the day.

[zip1234]

You realize speed bumps are not there to 'ruin driving'--they are mechanical means to stop drivers from speeding as signs are useless and as soon as people are past the cops they speed again.

[Noumenon72]

Let's say they're put there even though they ruin driving for regular people, because they will also stop the few speeders. I don't really speed, but I take a speed bump as a sign someone in the neighborhood is hostile to drivers.

[AnimalMuppet]

I lived in this neighborhood, on a dead-end street. They grew a new subdivision, and put the street through. Now we had people blowing through our neighborhood at non-neighborhood-driving speeds, trying to race between major roads faster than the major roads would take them.

We petitioned to put speed bumps in. Yes, we were hostile to the way at least some people were driving. But also note that we, the people who asked for the bumps, also drove there every day. We weren't hostile to drivers as a class. We were hostile to people trying to drive excessive speeds on suburban side streets.

[alistairSH]

Almost nobody would disagree that making both transit and driving awful is not a good solution.

The real solution is to make transit at least as good as driving (measured roughly by time to get from A-B). Not easy to do in some cities - Seattle has some unique geography to work around. But for someplace like Houston or Dallas? Making transit work shouldn't be that hard (other than the cost to build it out and getting people to agree it can work).

[VintageCool]

> 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.

Seattle just opened light rail from Northgate to the U-District to Downtown this year. We will also have light rail from Downtown Seattle to Bellevue opening next year, and light rail to Redmond the year after that.

And the opening of light rail from Downtown to Capitol Hill to Husky Stadium a few years ago drove some pretty big changes in transit in Seattle.

[robcohen]

> 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]

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?

[twoodfin]

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?

The Federal Highway Trust Fund was fully funded by the gas tax and other user fees until 2008, all while a significant percentage of revenue was allocated not to roads but to mass transit. Congress has topped it up with general revenue since, but the gas tax hike required to eliminate that need would be measured in cents, not dollars.

[pbourke]

> 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.

The Netherlands is smaller than New Jersey and has twice its population - its one of the most densely populated countries. Comparing it to the 3rd largest country on earth is risible.

[crowbahr]

The Netherlands cities are significantly smaller than American cities in terms of population.

NYC doesn't even have good bike infrastructure.

Every major city in America could transition to bike infrastructure and the quality of life would improve across the US. We don't have to cross the great plains on a bike: We're talking micromobility here. Who cares if they're smaller? We have enormous cities choked to death with cars.

Death to cars: cars bring death. Cities are for humans, not cars.

[seanmcdirmid]

> Here in city (Seattle) most people drive because transit tends to be spotty and slow for most people.

I don't drive and I live in Ballard. Driving has always sucked in Seattle since I can remember from the late 1970s. My dad, who lived in Seattle after coming back from Vietnam said the same thing.

[mikestew]

Transit still mostly sucks, but now driving sucks too.

And now bicycling and walking suck just a little less. That is a success.

[potta_coffee]

I've always hated driving around Seattle, but a few years ago I was bumming around for a few days in my Miata and it was a whole different experience. Having a tiny car that can go anywhere and park anywhere is awesome.

[bobthepanda]

The speeds were not reduced because the transit needed to put more people in.

The speeds were reduced because people keep dying when getting hit by speeding cars. And this problem has gotten worse with Americans shifting to SUVs and crossovers that hit humans higher up and toss them under the wheels.

[animal_spirits]

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

[criddell]

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.

[massysett]

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]

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

[mjmahone17]

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]

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]

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]

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]

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.

[massysett]

The workers have spread out because they prefer spread-out housing. They prefer larger homes on larger lots. Roads allow people to live where they wish in the housing they want. People are willing to accept longer commutes so they have the housing they want. This is a success.

[VintageCool]

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.

[NikolaeVarius]

If the point of adding lanes is to reduce delays, and induced demand prevents that, you have failed in the task.

[dragontamer]

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.

[NikolaeVarius]

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

[azylman]

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.

[bluGill]

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.

[dragontamer]

> You need to get ahead of induced demand, otherwise you city isn't meeting the needs of the people who live there.

Well, there's an annoying edge case that must be considered as well. In some cases, "induced demand" is "stealing demand from somewhere else".

Lets say you have Town Foo and Town Bar. If you build a highway to Foo, all the additional traffic might be "stealing" traffic from Town Bar and benefiting Town Foo. Especially if people emigrate out of Town Bar for closer housing to Town Foo, you didn't really improve the lives of anyone. You just caused everyone to migrate over.

---------

Ideally, you want to build highways / roads / transportation in ways that benefits people, and causes the least inconvenience to other towns.

[bluGill]

Only if town bar isn't a place people want to be. I call it a good thing is bad towns die.

[NikolaeVarius]

Well sadly, roads have a bad habit of being confined by physical time and space and cannot just be arbitrarily widened.

[bluGill]

You can go up and down though.

Again, I'm not making a value judgement here. Transit is a valid option that could be better

[ryukafalz]

Up is expensive and rather unpleasant for those walking nearby on the surface. Down is even more expensive.

Don't forget that no matter how many lanes you add to a highway heading into a city, eventually that highway ends up... in the city. Too many cars in a city makes for a loud and dangerous-to-navigate environment for those who live there.

[asdff]

The point of adding lanes is not to improve commutes. It's to improve thoroughput. If you add more lanes, and traffic moves at the exact same speed as it did before, guess what that's a win. Your throughput is now higher, more vehicles are moving per hour, and that ultimately means fewer trucks clogging up the port across town (or across the country).

[rootusrootus]

If induced demand is going to negate the improvements from adding capacity, then why not just reduce capacity to one lane? Or less?

[nostromo]

The point of adding lanes is to increase throughput.

[zip1234]

If driving demand can be induced by massively subsidizing it with billions as is currently done, so can other forms of transportation.

[Spooky23]

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]

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.

[azylman]

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.

[mrfusion]

But those extra people are choosing to be there so there must be some benefit.

[tshaddox]

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.

[seanmcdirmid]

> 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]

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]

> 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]

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.

[njarboe]

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]

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]

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.

[jimmytidey]

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]

So why bother build any roads larger than one lane?

[jimmytidey]

You need some road capacity for ambulances and Deliveroo.

[JPKab]

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]

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.

[ThrustVectoring]

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]

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]

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”.

[sagarm]

Induced demand actually does happen in American healthcare: spending goes up with healthcare availability, but health outcomes do not improve past a fairly low level of usage. This is a waste, not productive economic activity.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8057171/

The situation with roads is not that different: building more road capacity incentivizes sprawl, leaving the entire network more congested than it was when you started.

Roads just don't scale. The daily commute is like a distributed shuffle: time to complete the shuffle scales superlinearly, probably quadratically given the limited topologies possible with roads. It's not like you can build a hypercube road network.

[tshaddox]

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]

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]

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]

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.

[shkkmo]

> 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]

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]

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.

[tshaddox]

Yes, but if you reduced the average amount of time stuck in traffic while the total number and distance of trips remained the same, you certainly wouldn't say that your local city is doing worse. Moreover, if you replaced some car trips with other ways of transporting the same person or freight, that certainly isn't a loss for your local city simply because the number of people driving decreased.

[kmeisthax]

Cars don't have an individual latency advantage. If you want to travel somewhere during rush hour, you still have an hour of latency, even if the trip would ordinarily be 15 minutes.

What they do have an advantage on is not having to synchronize with a schedule. If you need to travel 15 minutes by light rail, but the train only comes around once an hour, then missing the train adds an hour to your trip. It doesn't matter if the train never breaks down and has separated right-of-way - running on time is useless if you're not.

The way you work around that is by running more trains so that they can come more frequently. My rule of thumb is that if a transit line has a frequency of 15 minutes or less, I don't need to worry about the schedule because the time spent waiting for the train or bus is less than the time of the overall trip.

However, this is expensive; it only makes economic sense if you actually have that many riders that need to travel along that line. In other words, demand needs to be aggregated. The problem is that cars work the opposite way: they exist specifically to segregate demand. This occurs both directly and indirectly. The direct effect is the ability to immediately depart, which I already mentioned; but the indirect effect is the result of all the infrastructure that cars need in order to work at all. Things like wide highways and parking lots spread out where people need to go and make it far more dangerous to walk from a train or bus stop to your final destination.

In other words, cars cheat - they don't make your commute better, they make anyone who does not own a car have a worse one.

[asdff]

Freeways also carry significant trucking traffic. Like iPhones and food? Increasing throughput makes these things cheaper to deliver into your home from where they are produced.

[mrfusion]

But more people wouldn’t drive if there wasn’t a benefit to it. So you’re benefiting more people.

[kaesar14]

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]

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.

[seanmcdirmid]

> 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.

They tried this in Beijing. People would just buy second cars so they could drive on both days. Eventually they had to restrict new license plates as well.

[tshaddox]

I don't think anyone is claiming that is literally the only metric, because if it were, you could also just ban driving completely, or kill a bunch of people, etc.

[kaesar14]

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]

why would you count that as a win? you almost certainly wouldn't be one of those 20 people allowed on the road

[kaesar14]

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.

[sokoloff]

Having lived through it all and seeing the outcome, the Big Dig was a pain while it was happening, but a smashing success now that it’s done. A later removal of some of the toll booths in favor of automated tolling has made the road network even more effective.

Is there still some traffic? Yes. Is it better than it was 30 years ago, even as the roads handle way more traffic? Absolutely.

[kaesar14]

I'd rather the T be functional and get me to where I need to be, and a better commuter rail system, then having to drive to and fro on Storrow at rush hour. There's no amount of bridges or expansions to the roads that would make it better short of leveling the city to build a giant highway, which I'm sure some percentage of Massachusetts drivers would be in favor of.

[sokoloff]

You prefer the T or commuter rail. That's fine and improving those modes of transit seems a fine goal as well. That preference/goal doesn't support an argument that the Big Dig solved nothing for those who choose to drive.

[kaesar14]

The only goal is to get in and out of Boston in a reasonable amount of time. I wasn't around for pre Big Dig Boston but it's still dangerous and time-consuming driving to get out of Boston by car. The Big Dig might've made it _less_ dangerous and time-consuming, but the point is the solution barely scales since the total number of people driving just increased instead. If they spent those 20 years and billions of dollars on burying and expanding the T lines, and improving the commuter rail offerings, I wager we'd have achieved a lot more towards the aforementioned goal of getting in and out of Boston quickly.

[imgabe]

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!

[bsder]

> 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.

[megablast]

It is. If you work for an oil company. Or love pollution. Or hate the planet. Getting more people driving is awesome!!

[mrfusion]

You’re spot on. Plus the argument doesn’t hold water since there are a finite number of potential drivers.

[asoneth]

"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.)