Induced Demand & Roadway Widening: Everything You Always Wanted to Know (and Weren't Afraid to Ask)

State departments of transportation love to widen freeways. The Katy Freeway in Houston, I-35 in Austin...well, kind of any freeway in Texas when you think about it.
And there's no doubt that certain aspects of roadway capacity projects are futile -- basic microeconomics will tell you that when you increase supply, prices drop and more buyers show up. Or, in the language of traffic, when you add lanes, travel times drop and more drivers show up...until you reach a new travel time equilibrium.
But how many drivers? And do you just reach the same congestion levels again? If there's new traffic, where does it come from? And is "induced demand" even an argument you should be making? I mean...downtown business boosters LOVE the idea of more demand!
We look at how transportation agencies and their consultants analyze -- or don't analyze -- all of the possible sources of what I like to call Induced Traffic, and we'll get deeper than we probably should into the primary analytical tool regions use to identify capacity projects: the travel demand model.
Other CityNerd videos referenced:
- Exponential Traffic: • Why Traffic Congestion...
- Ginormous Interchanges of the US: • Top 10 GINORMOUS Freew...
- Tunnels: • Traffic Tunnel Pros an...
Resources:
- Noland, Robert B. (2001.) “Relationships between highway capacity and induced vehicle travel.” Transportation Research Part A, 35, 47-72.
- Cervero, Robert. (2003.) “Road expansion, urban growth, and induced travel: A path analysis.” Journal of the American Planning Association, 69:2, 145-163.
- Duranton, Gilles, and Matthew A. Turner. 2011. "The Fundamental Law of Road Congestion: Evidence from US Cities." American Economic Review, 101 (6): 2616-52.
- Mokhtarian, Patricia L., Francisco J. Samaniego, Robert H. Shumway, Neil H. Willits (2002) Revisiting the Notion of Induced Traffic through a Matched-Pairs Study. Transportation 29 (2), 193 - 220
- www.bloomberg.com/news/featur...
- www.vox.com/videos/22280067/h...
- www.thestar.com/news/gta/2021...
- www.chron.com/news/houston-te...
- Portland Comprehensive Plan: www.portland.gov/sites/defaul...
Image Credits:
- Atlanta traffic clip Video by citi-flix from Pixabay
- LA traffic clip Video by Ronald Brown from Pixabay
Music:
CityNerd background: Caipirinha in Hawaii by Carmen María and Edu Espinal (KZbin music library)
Twitter: @nerd4cities
Instagram: @nerd4cities
Contact: [e-mail]

[@tekuaniaakab2050]

What also needs to be taken into account is the fact that most of this added volume goes to downtown regions, so now more parking spaces and lanes are demanded. That’s how you turn what should be the heart of a city into Dallas-Fort Worth

[@PSNDonutDude]

You also have to take into account that destination roadways or exits may already be near capacity, and while the highway may not be as congested, the destination roadways might be, leading to worse congestion than before. You might save 10 minutes on your highway trip, but add 15 minutes at highway exits or destination arterial roads. There are also environmental, societal, health, and tax efficiency consequences that are all forgotten. Car travel and car traffic have so many nuanced problems that it's hard to discuss with normal everyday people the numerous problems that car oriented urban areas cause. People are only starting to car because of people like City Nerd and Not Just Bikes but also because car oriented land use has hit its peak, in all the aforementioned consequences. People are thinking more about the environment, more about our society, more about their health, more about the lifestyle they want to live, and more about the absolute shitshow that cars and parking lots are. Not to mention the immense cost of all this.

[@CityNerd]

I was already way over the time I wanted on this video, but yeah, the spillover impacts of increased traffic or really far-reaching and horrendous. Maybe a future video.

[@underground868]

@@PSNDonutDude I'm a native of the DFW area and it's a hellscape under constant and inefficient construction that ultimately makes things worse. The State Longhorn should just be made of sculpted traffic cones

[@saxmanb777]

Hello fellow Dallasites. It’s a Love/Hate relationship here for me.

[@sanderw7153]

Yup and this is also where park and ride can help. Using park and ride to alleviate your freeways while creating rail that is solely based on this type of commuting (see go rail videos from NJB) is probably not great. But using park and ride to keep cars out of the city center is great.

[@thexalon]

I'm reminded of a comment about road expansion that described it as "after months of noise, delays, and confusion, the previously existing traffic jam is relocated by 1/2 mile."

[@CityNerd]

It's a depressingly frequent outcome.

[@benw3864]

And these projects cost in the billions. People can malign transit projects and their overruns all they want, but governments are spending billions to add a few lanes for a few miles. It's insane. A billion dollar project like the green line in Boston may be overpriced, but it's definitely a far better value than a highway widening.

[@pretzels713]

If only these construction projects took 1 month..sometimes they take years

[@spencermovies]

“Orthodox Urbanist teachings require you to be anti-park-and-ride too” Thank you for continuing to spread the good word!

[@tonysoviet3692]

@@JacobGadzella Mass transit conveys the most benefits to those who cannot drive a car, think those with disabilities, children, or senior citizens. Park-and-ride is basically the worst of both world because they REQUIRE you to drive to use public transit, basically exclude population that can benefit the most, while still induces traffic surrounding the sites.

[@CityNerd]

I joke, but it is pretty bad. I mean how do you want to use incredibly valuable land around a high capacity transit station? Housing for people or housing for cars?

[@tonywalters7298]

@@CityNerd In toledo, ohio we have a park and ride/bus transfer area that occupies part of a walmart parking lot

[@sanderw7153]

Nothing wrong with park and ride to keep cars out of your city center. Plenty of parking close to city centers that rarely gets used on normal days (e.g. football stadiums such as Amsterdam Arena P&R). But using park and ride to keep cars off the freeway is problematic. It creates situations like NJB explains in his Go rail video where you have train stations out in the middle of nowhere that can only be reached by car and that have swaths of parking surrounding them. This is bad because you should really build transit oriented communities around train stations.

[@bernardfinucane2061]

Park and ride is ok in small doses. But building train stations in a sea of parking lots is dumb.

[@benroque5378]

Having moved from the Midwest to Massachusetts, one of the biggest culture shocks has been the size and design of Urban Arterial roads that are not Highways. These roads aren't always pleasant to walk or bike along, but they are easier to cross and follow for a short distance than a Midwest "Stroad." I do not study Urban Planning at all, but I do think a comparison between size of Arterial Roads and either efficiency to move people or walkability would be interesting.

[@CityNerd]

Oh I've got a video for you next week.

[@themariokartlick]

@@CityNerd I am so incredibly glad that this channel exists to educate. I love these in depth discussions but don’t have the background knowledge to find this information myself, so it’s great to have a real professional explain it. My only issue is that my demand for your videos is greater than your supply. That’ll change over time I’m sure !

[@aldyftl]

He's right, adding more lane just gonna add more traffic/congestion and attract more cars. I live all my life in big city. Public transportation give people more option and help the environment too

[@justicedemocrat9357]

Nigga, how the hell does a bus give more options than a car?

[@thatguy-notsuraj-6843]

@@justicedemocrat9357 He's saying investing in public transit gives people more options, not the buses themselves, I believe. It would be much, much better if absolutely everyone didn't own a car. It would also take a lot of pressure off of the commuting working class that has available public transit. Also, investing in public transit on a wide scale will reduce the demand for roads and eliminate the need for wide road spaces and create opportunities for other kinds of personal transport, like bikes.

[@mindstalk]

@@justicedemocrat9357 Cars give no options to people who can't drive. Transit let me go around Chicago by myself at age 10.

[@justicedemocrat9357]

@@mindstalk What about the option to let your friend drive?

[@aquaticko]

The lesson I've taken away from looking at induced demand is that it's not really good or bad. As you say, "induced demand" can mean more customers for business or residents for landlords or developers; they want it, and truthfully, anyone interested in growing a city's population should be, too. The problem is capacity: you create a lot more capacity with pedestrian, cycling, or public transit facilities per unit of space consumed than you do with roadways. I think that's an important point to bring up to those parties interested in inducing demand. Public transit can, hypothetically, induce a lot *more* demand than cars can, because it takes a lot more people to fill a bikeway, bus, or train than it does a car.

[@williamchamberlain2263]

The problem is poor town planning - adding capacity ad-hoc without a good plan or building code leads to a town centre that nobody enjoys and is ripe for losing all those customers when someone opens an out-of-town shopping mall.

[@williamchamberlain2263]

e.g. 1:48 for two points of view on the same effects.

[@driley4381]

@@williamchamberlain2263 That is EXACTLY what happened to the town I grew up in. Luckily over the last few years there's been some changing of the hands of power and some reinvestment has been done in the downtown area, as well as other areas outside of town that have similarly deteriorated, and things are slowly but surely coming back. More locals own small businesses downtown now that at any point in the last 30 years, and increased enrollment at and investment by a local college has helped create an entirely new customer base to cater to which has REALLY helped bring life back to downtown.

[@williamchamberlain2263]

@@driley4381 good idea to include young people in it

[@eriklakeland3857]

I’ve loved these refreshing takes on induced demand. As Oh the Urbanity would say, “what kind of demand do you want to induce?”

[@Brmlyklr]

"All models are wrong" is a saying you'll hear sometimes in traffic engineering circles. :) My region is adopting an activity-based model to replace the 4 step model, but I am still learning about it.

[@CityNerd]

It amazes me that the standard practice is to generate a single forecast based on a single set of assumptions rather than some sort of Bayesian/probabilistic approach.

[@brents6993]

@@CityNerd Good point on this. There is work to apply models to show results as a distribution. ABMs have far fewer broad assumptions and are much more flexible in showing the effects of specific changes like tolling and special lanes.

[@emma70707]

The longer saying in science is "all models are wrong but some of them are useful." :D

[@Chris4942Chris]

I've heard that "induced demand" can equally applied to transit in which case it actually is a good thing (maybe it was from a CityNerd video, I can't remember). UTA (Utah Transit Authority) has been working on a project to extend the local commuter rail line 2 cities further south. When they pitched it to the town council in Provo (the current last southern stop), the entire selling point for the project was the trips that would be generated on the rail line or moved away from cars. There's a lot of support and momentum for the project, so I'm pretty sure it will be built. It would be cool to see a video where you talk about "induced demand" in regard to other modes of transit where it would be considered a good thing.

[@henrybrown6480]

Induced transit demand also has few of the negative side-effects of cars (air/noise pollution especially)

[@lensboel]

Or if you look at Amsterdam and Copenhagen for bikes! Using this to the advantage of modes we want to support is great options!

[@rwrunning1813]

@@henrybrown6480 Well, when you have an area where people live, they need to get around somehow, so it's just a matter of inducing demand for the right traffic modes. If there's too much noise, you might want some more walking and biking! One thing to consider is that a city center with many skyscrapers might be too dense to have satisfyingly adequate transportation, even after optimization. (Disclaimer: Just a theory, and I don't even live in a city)

[@dlivingstonmcpherson]

Showing how Induced Demand can be good was done in an excellent "Oh the Urbanity" video. It's "What People Get Wrong about Induced Demand" kzbin.info/www/bejne/bqjPnZdpj56qiMU

[@tonywalters7298]

@@rwrunning1813 Supertall skyscrapers can fall into the "awesome but impractical" category, considering how much space has to go to things like elevator hoistways, safe haven rooms, mechanical floors, and so on, that it may be more efficient to build a smaller building with the same leasable square footage.

[@IamSpiders]

I feel like its hard to talk about highway expansion projects without talking about the opportunity cost for doing something else with that money. Expanding highways is expensive, focus on getting people off their cars and you'll see less traffic (i.e. Induce demand in other modes of transportation, since just about every mode of transport uses less space and less infrastructure than a car)

[@TheOwenMajor]

Highways are profitable. People like driving, and pay tons in taxes and fees to do so. Public transportation? No so much. Usually a massive cost sink even if it gets decent ridership(Which is not always)

[@IamSpiders]

@@TheOwenMajor The subsidized cost of driving is literally $100 billion/year in the US

[@TheOwenMajor]

@@IamSpiders Hmmmm, the interesting thing is that US governments take in about $100,000,000,000 in just fuel taxes..... It's almost like they are designed that way...

[@IamSpiders]

@@TheOwenMajor Yes that takes into account that tax, that's what a subsidy is, the extra to pay for the cost.

[@TheOwenMajor]

@@IamSpiders And your source is?

[@sandiegofun1]

As a committed strong town individual, I really appreciate the detail that you went into in this analysis. It's definitely complicated, and I appreciate some of the lane expansions in SoCal, but the lack of any real option for public transport in the sprawl makes lane expansions a 100% given in the current models. More fundamental items need to be changed and lane expansions will continue to be part of that mix, although I hope that the need for that decreases over the next couple of decades in the greater SoCal area.

[@cc_das_me]

Eyyyyyy shout to a fellow San diegan SoCal is so car dependent it’s the saddest thing

[@TexMexTraveler]

I live in Houston. Thanks for doing a great job of explaining how traffic engineering works. I'd like to explain Houston's "Katy Freeway" (I-10) induced demand issue that so many people bring up. While in many cities induced demand happens from the 5 different causes you highlighted, in Houston, the lion's share of the induced demand was from Katy, Texas (a western suburb of Houston) and Houston growing so fast. From 2010 to 2020, Texas grew faster than any other state, we added 4 million new residents in 10 years according to the US Census Bureau. The Houston metro area added just over 1 million people in that time, bringing us to 7.4 million, the nation's 5th largest metro area. The Katy freeway does not have nearby useful large arterial roads that drivers were previously using, and sadly, it also lacks meaningful public transit of any kind, and woefully lacks useful rail services. So there was little to no spillover from alternate routes when the freeway was completed in 2008. In 2008, Katy, Texas was a much smaller bedroom community compared to the large city it is today. Remember from 2010 to 2020, Houston metro added just over 1 million people. So in this case, induced demand was from new residents moving into the metro area who were not here previously. ------ What I'd love to get help with is figuring out how to get HGAC (the regional transit planning authority) to add in regional commuter rail and some meaningful metro rail or light rail for the higher density areas of Houston. So far, my efforts have fallen on deaf ears despite being an engineer that does work with TXDOT on various projects. 1 of the other problem we have here that you previously mentioned was that while most cities have 1 downtown area that people are trying to get in or out of during rush hour, Houston has it's large downtown, but then also has multiple "edge" cities, with 7 that contain at least 10 buildings higher than 100 meters along with lots of smaller buildings. Each one of these have their own rush hour flows as well. Bad planning in my opinion, but fixable if we institute commuter rail and other transit options. I'm not trying to take away cars and trucks from the freeways, just provide alternatives for those who would prefer different transit options. Despite Houston's lower density urban sprawl makeup, I think there are enough people that would use regional commuter rail willingly and without incentives, that it would free up some space on our freeways. Any ideas how to get this started?

[@Maranville]

I think that as far as pitches go, "providing alternative modes for those who want them" might be a slightly easier sell than "rail reduces freeway traffic," which might be hard to prove, and is not really the main reason to do it anyway.

[@justicedemocrat9357]

tl;dr

[@Burt1038]

Katy Freeway is the poster child for "induced demand" but people seem to leave out that half of the expansion went to building toll roads. And the problem with the toll roads is that they exit right back onto the friggin' freeway! So there's virtually no benefit unless you use the toll road and the next available toll exit is close to your intended exit. The pricing on the toll roads is also ridiculous...there's one stretch from beltway 8 to barker cypress that charges five bucks for a whopping six miles; needless to say, the toll road is usually empty.

[@TexMexTraveler]

@@Burt1038 I agree, I don' t think the toll road in the center should be considered a competent of I-10, however, I-10 is not the victim of induced demand in the way city planners are talking, but instead the victim of regional population growth beyond what was predicted. The Houston metro area grew by just over 1 million from 2010 to 2020. At the time I-10 Katy freeway was designed in 2005, the estimates were for the Houston areas to grow by just half of what it did according to H-GAC, the regional transit planning authority. So I-10's congestion is more due to failing to plan for the realistic growth which is new residents moving to the metro area from outside of it rather than induced demand which is existing residents now deciding to take the freeway. What could have helped, is with all the space in the center of the Katy freeway, to put in some type of commuter rail to give people some options.

[@kb_100]

So basically what you're saying is the induced demand was due to reason 5 which he mentions while introducing the topic. I would posit that the Katy region would not have seen as much new home construction and population growth had the Katy freeway not been expanded. So the highway induced demand in the long term because it made Katy an "attractive" place for people to sprawl out to from Houston.

[@evangray8961]

I studied industrial engineering; this video does a great job of relating mathematical models to the real world, much in the same ways that got me interested in the area of study. Love it

[@gamarad]

I've been reading Confessions of a Recovering Engineer and it gives a pretty dismal impression of the state of traffic engineering as a profession in North America.

[@devinfaux6987]

Then you may also find this take on it... well, if not enjoyable, then at least validating: kzbin.info/www/bejne/bqDUYahonpmcfsU

[@skythewonderdog]

is this a book? do you have a link where i could find it? thanks!

[@lamegaming9835]

@@skythewonderdog uhh… amazon?

[@paxundpeace9970]

So much has been left out. General rate of car ownership is rising as well as number of miles traveled. The amount of lane changes and how much trucks run on the road haven't been considered here. How many on and off ramps and of which capacity are on the highway. The travel speed and speed differential is important too. Updated the comment a little bit.

[@bobbyswanson3498]

you should do some more of these types of videos aside from the top 10s. this was really interesting!!

[@CityNerd]

Yeah, I have a few ideas like this. I like to mix it up!

[@rustyshackleford9498]

This is super nerdy but I love how in depth you get on the actual process for measuring traffic dynamics. Got me thinking: I'd love to see a video on top 10 (of course) cities ready for new/expanded rail systems based on the current transportation system i.e. highways, arterial roads, population density, and avg vmt and commute times.

[@CityNerd]

Interesting idea. Thanks!

[@pusheenomics]

As an economist, I have always liked the concept of induced demand. I think it's totally correct and makes sense. Some people may not understand it due to ignorance but that doesn't make it a bad term nor is it difficult to learn the meaning if there's interest.

[@CityNerd]

I guess don't mean to imply that there's no such thing as induced demand (otherwise there'd be no such thing as advertising?), but adding a lane is a shift in the supply curve, not the demand curve.

[@drivers99]

11:45 Eli Goldratt (in "The Goal" etc) wrote about how any system has a bottleneck, and if you fix one bottleneck, it moves the bottleneck somewhere else. (Also, improvements in a place that isn't a bottleneck is wasted.) The throughput of a system as a whole is determined by the capacity of the current bottleneck (although he was talking about like a factory where everything goes through the same system, not traffic which has different things going every direction.) There's a book that talks about that in fewer words (and no framing fictional story) called The Bottleneck Rules which I enjoyed.

[@mennoltvanalten7260]

As a factorio player, I agree. There is always a bottleneck somewhere, and if there isn't you will soon create one. In Factorio by building a new bit of factory which needs to be supplied, in the real world by new places being built or places changing use to something that requires different trips.

[@drivers99]

@@mennoltvanalten7260 I play that too and it’s interesting to see it in action after learning about the Theory of Constraints :)

[@CityNerd]

This is true for transit systems as well!

[@andrewstringer5836]

As entertaining as it is to hear people sing songs about induced demand at city council meetings, thank you for articulating these points in a much more meaningful way. To me, the best arguments against freeway expansions in cities are: 1. The project is unlikely to have the desired outcome of reducing congestion and travel times, so the benefits of the projects don't outweigh their [huge] costs. 2. Freeway expansions are likely to increase VMT and all the associated negative effects. The "benefits" of the extra capacity don't justify the negative effects to the environment and to the communities living near the freeway. This is much more a city values argument. Stamping ones feet and shouting "induced demand" an argument does not make. Cheers from a northwestern city whose embattled freeway expansion proposal I'm sure you're very familiar with.

[@jiainsf]

Should transportation planning even be done at the project level? Moving towards a more general comprehensive approach to transportation planning would allow people see the issue of congestion at a more holistic level and in my opinion, an issue of capacity. An issue which, is better solved by changes to networks instead of streets, to mode shifts instead of road expansion.

[@billd9667]

I love this channel and the snarky, yet classy, replies. Tough balance, but you pull it off nicely!

[@adamcapets]

Minneapolis-St Paul where I live now is interesting. From what I can tell, we don't have very wide freeways/widening projects, although we do have a lot of freeways. We are building a lot more managed lanes. We also have a lot of peak hour commuter transit, a lot though involves park n rides. And in the end, our congestion doesn't appear to be the traditional inbound/outbound that I see in places like DC where I used to live.

[@PaulWintz]

I like that this video delves more into analysis and reveals your expertise to provide explanations, in contrast to many of your previous videos that were more often lists of places with bits of trivia thrown in.

[@Ice_Karma]

I live in Metro Vancouver, where we have the *_wonderful_* situation where TransLink is in charge of not just public transit but also roads, highways, and bridges. Transit projects are frequently delayed by years, take longer to complete once started, and frequently bungled--for example, see the fiascos around the Compass card's introduction.

[@pioadventures]

Nice breakdown of everything I definitely learned new stuff from this short video!

[@jasontempest4233]

Interesting that you've used an imager of a PERTH Freeway as the background to many of your data points here. Several of Perth's major freeways like the Kwinana Freeway pictured above could have added additional traffic lanes and even a Traffic "Tidal Flow" lanes were proposed whereby Central lanes would reverse depending on peak traffic times. Fortunately the central median was given over to TRANSPERTH in order to increase the cities rapidly growing Urban Rail Network. So a win for Trains - yeah!

[@3point1415926536]

"Proposed"? It happened! I'm now wondering how many people even remember the bi-directional peak lane that existed before the Narrows duplication...

[@nik257]

Great episode! Love these explainer type videos!

[@AccumulatedGestures]

I enjoyed your video, and I got a bit of a kick out of seeing my home city of Perth being used as the image for traffic congestion! Ironically, the section of the Kwinana Freeway you chose to use is actually one of the most constrained and fixed sections with no further widening possible. They caused environmental destruction to reclaim land from the river to build the freeway in the first place and are likely to never get approvals again to add more lanes. Further south and away from the city, this freeway has been widened continually and yet I don't see great improvements in travel outcomes. All it has done is move the bottleneck further down and encourage more people to drive.

[@AlexanderRafferty]

I also got a nice kick out of that image. I think Perth is a great example of a sprawled car-dependent city that needs a serious rethink of its approach to transit.

[@AccumulatedGestures]

@@AlexanderRafferty I think Perth is a really interesting city from a transit perspective. It is clearly a 1950s planned city that was designed for urban sprawl and car dependency, and yet it has generally fantastic cycling infrastructure and public transport that, in spite of its excellence, is still not chosen by the majority of people who would rather be in bumper to bumper traffic for whatever reason!

[@ivanoffw]

This is probably a video I will have to re-watch several times. In school we did not get this in depth about induced traffic.

[@Secretlyalittleworm]

I am once again seeing, and instantly clicking a great city nerd video

[@joseSanchez-ej2oh]

Yeah given the frequency and quality, he is pretty passionate about the topic

[@Zedprice]

Thanks for this nuanced look at the problem. You've cleared up some of my naive misconceptions.

[@zyadhq8672]

i really enjoy your calm and educated takes on these topics, especially now that they have become more popular to the public(thankfully). you see too many amatuers talking passionatly about these subjects, thinking they know more about theem than they are, it can hurt the new urbanist movment in the long run, since the movement's most popular points would be based on shaky ground.

[@riggo6830]

Fair amount of depth while still being easy to follow. Nice video, thank you!

[@nunyabidness3075]

That was a really good explanation. I can tell you what got my wife to stop driving downtown. It was bad parking choices. She tried the bus. Hated that. Then tried electric bike, and that won. About half the trip was on a bike trail away from traffic. This was the clencher. Also. The Katy freeway is actually not bad in my opinion. It wouldn’t be needed if HISD weren’t awful.

[@roivosemraiva]

I have been watching several of your videos on traffic, CONGESTION and how adding Lanes will not solve traffic problems. i must compliment your knowledge and intelligence on those topics. Again, thank you for your in depth REPORTING !! Where is the resolve to the traffic question?? A problem without an answer. ! Your Channel is a must for everyone driving a vehicle watch. I myself, don't have a car, i walk or ride a Bike to work, or to get groceries.... I planned it that way...Thank you..

[@iseewood]

I live in PDX and have been hearing a lot about ODOT looking at congestion pricing for the region. I’m a big fan. If we can encourage people to use the freeways when they are less congested we’ll get better value out of our rode system. But Clackamas County is already threatening to force it to the ballot and the public opinion on it is dismal. The public complains about traffic congestion, but then don’t want to spend the money to pay for it or enact policies that would encourage better use of the system we have. How do you overcome public opinion to enact policies that is best for them?

[@keriezy]

Listening to my cousin from Tigard bitch about traffic while he is traffic is a daily.

[@CityNerd]

Good luck with Clackamas County! That board of commissioners is a real piece of work.

[@iseewood]

@@CityNerd I think that is polite way of putting it.

[@mrosskne]

Simple, you get rid of shitty governments like democracy and return to the one true government : autocratic rule by an objectively good philosopher king who is without flaws.

[@SirKenchalot]

Very interesting, thanks. Looking forward to congestion charging video; I only know about London, England as an example of this but must be others.

[@stevengordon3271]

The key point I come away with is that adding capacity in one place creates congestion somewhere else in the network, and then when you add capacity there, another place becomes congested, and so on. It becomes a never-ending drain on resources. The term "induced demand" does not elucidate this key aspect of the problem.

[@jamesmcintosh3832]

Great video. It's also worth mentioning that if a city has a growing population, then traffic congestion will get worse if nothing is done. A lot of the extra traffic when a road is opened is actually extra traffic due to population growth that would have increased congestion on other roads.

[@mostlyguesses8385]

... induced demand means "successful better jobs"... More lanes drops travel time so people can take that better job a bit further than before... From 1900 we went from only working at jobs within half hour 2 mile walk, to trams in 1930 allowing 5 mile in half-hour, to cars allowing 20 miles in half hour. We increased using pir2 the area to work in from pi4 to pi400. Wow.. Cars are sooooo helpful they allowed job specialialization.... Even in W Europe 75% of workers drive to work, cars allowed modern job market, google France Statista How Workers Commute...... Yet transit KZbinrs skip numbers... US lacks dense European cores so cars will always be 90% car... Europeans choose cars too, walking and waiting in cold rain 6 months suckkkkkks.... P.S. we induce demand when build hospitals, let's people get care for minor issues, induced demand is good, letting more use a thing is good!!

[@frankjennings4489]

Thank you for a video that actually explains the benefits and drawbacks of lane capacity, especially the part about bottlenecks. People kept telling me “Adding lanes means more congestion, not less!”, but could never offer an explanation that made sense, almost like it was just a curse from the universe to punish us for not adopting mass transit.

[@fszocelotl]

The title reminded me the road and transit expansions within Tlalnepantla municipality. On the expansion of the México - Querétaro Highway from 3 to 6 lanes per side between Av. Lago de Guadalupe and Av. Central in Tultitlán, the opinion was that drivers could "get faster to the traffic jam"... When the Cuautitlán Suburbano was built, it really helped ease the people mobility around the road mess in the area.

[@fszocelotl]

Suggestion, just for the heck of it. Street markets in the US and Canada... Tianguis here in México are an important option that compliments fresh produce, grocery and even some specific niches for all people's demand, no matter the acquisitive power or location. There are specialized tianguis and many are set outside established markets to vantage from them as visited locations.

[@CityNerd]

It's amazing the public dollars that are invested in just moving bottlenecks around!

[@justinoboyle5767]

This was a very interesting video, thanks for the explainer and lots of thoughtful analysis.

[@martinlisk9913]

Hey CN, it's your Eugene fan, having experienced the Banfield and the building of I 205, (it ended at Foster) it's funny how both have gone beyond their capacity, and it's sad how the US is behind in its urban transportation ... unfortunately, the only time I experience Portland traffic now is when I'm onto further destinations ... I try and schedule my drive through Portland to miss the rush hour, and in some ways, East Portland would be interesting to expand further through the geographical issues, and now I 5 is hosed all the way to Woodburn ... ANYWAY, love the channel, and sorry I'm blathering

[@someguy6075]

Thanks for an in-depth and interesting video. I've always been wary of the idea of induced traffic but I like this analysis. I note that sources 1, 2, and 3 are preexisting trips. 4 might happen with discretionary traffic (e.g. mall) but not non-discretionary (most employment, and employment commuting is what creates rush hour). I expect pretty much all long-term negative effects of capacity planning are due to source 5. It is frustrating that when land use is so heavily regulated in the US we can't get this right. But this does mean that the road itself doesn't directly generate additional traffic. Here's a hot take. Any road network was probably fine when first built, and then development grew beyond its capacity - an argument that roads themselves are not a problem, and if capacity and other development happened hand in hand traffic would stay under control. Adding a lane adds capacity but it is still finite, it is not a cure if you can't keep demand in check. (I am ignoring the land use efficiency argument here, but that is different from the induced traffic argument.) Which leads me to my second hot take. The real failure is lack of coordination of development (traffic capacity vs demand, regardless of mode), and local control ruins city planning in the US. Cities should not be balkanized rivals able to have their cake and eat it too. Many urban cores are anti-road and want everyone to be urbanist like them, while at the same time not zoning enough housing to let people live near jobs. Simultaneously, suburban voters sabotage attempts to build regional transit systems.

[@jarjarbinx79]

The Canadian cities of Vancouver and Victoria actually had always operated under the commitment not to increase vehicle capacity since the late 90s. As a result, traffic volume has remained steady or decreasing even after narrowing more roads and significantly larger population.

[@liesdamnlies3372]

Those SkyTrain extensions can’t happen soon enough, though.

[@CityNerd]

"Don't build it and they won't come"

[@agntdrake]

As a fellow Vancouverite, that's sorta true and sorta not true. There is a *lot* more traffic now than there was 20 years ago, and it's particularly noticeable on each of the bridges south of the Fraser and on the North Shore. For most city streets though, it's about the same. As lies damnlies pointed out though, the Broadway, Surrey, and even North Shore extensions to the Skytrain can't come fast enough.

[@FameyFamous]

I remember when I-696 opened in Southfield near Detroit in 1989. Zero traffic congestion on the roads parallel to the new freeway. Terrible traffic on the roads feeding the new freeway.

[@calvinbarr6919]

Wow its only been around since 89 I had no idea I would have guessed it was built in at least the 60s

[@CityNerd]

Traffic engineering is super difficult and interesting!

[@FameyFamous]

@@calvinbarr6919 confirmed on Wikipedia. Construction started in 1961 before the Berlin Wall went up. The western part opened in in 1963. The eastern part opened in 1979. The middle opened in 1989 after the Berlin Wall came down.

[@henrybrown6480]

I would love to see a video highlighting a case study of highway widening not working, or maybe the history of TX or CA freeway expansion. Great stuff every video!!

[@wihistorybuff]

Do a video on Wisconsin and their lack of transit outside the Madison and Milwaukee area. They are so concerned with those two cities but forgot about the rest of the state.

[@pinkjuano]

Knowing that you are(/were?) a traffic engineer perfectly explains your deadpan comedy and monotone content delivery lol. I thoroughly enjoy it though. For a suggestion: I’d like to see a video covering bike lanes, sidewalks, shared use paths, and when it’s typically best to use each one.

[@ttopero]

I think a great benchmark of understandable for a video like this is if a new traffic engineering intern could follow & explain the slides without the audio after a little practice. My guess is that this is practically there-great work!

[@pablouribe1522]

Finally a great explenation about the topic! People just said it time and time again without a great understanding of the actual meaning.

[@guidoenriquez3076]

I'd love to see a video about Intermodal Public Transport Transfer Centres, I know Mexico uses them a lot but i'd love to see similar places in the rest of NA.

[@bearcubdaycare]

Rail has capacity limits too, such as station size, or minimum train separation. I think that one thing to be careful about, is that removing bottlenecks allows cities to grow and to trade. The flip side of "build more, and you'll get more vehicle miles" is, in part, you'll limit city growth if you don't allow more traffic, trains, whatever it is that you're providing capacity for. Maybe that's good, maybe that's bad, but urbanists often seem to extol the biggest cities as the most interesting, so be careful in how much you wish to limit capacity. Maybe those park and rides like at the northwest end of the Orange line in greater Boston, where a highway reduces lanes and diverts traffic into an enormous parking garage with escalators down to the subway, aren't all bad. Could the drivers instead just get on a bus from their suburban home to their local suburban rail, in to the city? Probably not, not enough density to support a good bus network in many burbs. Could everybody just be forced to live in tightly packed multi family housing close in to city center? Even with London's many attractions, and England's severe hurdles to development, loads of people who work in the London metropolis choose to live out in leafy semi rural areas. I think that a pragmatic approach that recognizes that a desirable, and economically strong, city will induce growth, and that people have a spectrum of different priorities, can yield a sensibly balanced outcome with good characteristics on several fronts.

[@matthays7800]

Very useful video! One element you allude to but might expand on is how expanding one road will influence other roads. It's sort of an extension of your note about pinch points.

[@CityNerd]

I might do something more expansive looking at networks, but it's really hard to do it concisely.

[@flavious27]

I am in Delaware and "induced demand" with DelDot has not happened as much as roads were built out after growth occurred without the infrastructure in place when residential developments were zoned. The issues with DelDot has been the amount and length of projects on the same roads.

[@bhig3]

I do live near there. Thanks for the episode!

[@RossSpeirs]

The pinchpoint upstream/bottleneck downstream thing is what always stops this from working. We had a project here to widen highway lanes and added cloverleaf exits instead of just traffic signals and nothing changed because 5 km down the road it’s still the exact same road the entire rest of the way in either direction.

[@yottanuclei]

Nice video. I really learnt a lot about how to think about road widening.

[@KevinButler55]

Thank you for this explanation. I thought I knew enough about induced demand...

[@dominik262]

great video! There is an obvious relation between road capacity and VMT for all, so environmental argument ultimately supports transit projects.

[@rebeccawinter472]

Ray - in r’t the livestream last week - this is one of your videos that I was thinking of where you definitely help to build folks skills and knowledge to better understand and advocate. All your vids inspire and entertain. This does that and more. You could even create a new playlist with some that delve into planning topics / fundamentals. 🤔 Also, have noticed that the playlists on nebula are… yeah.

[@CityNerd]

oh that's a good idea. Yeah I definitely have certain videos that are intended to help expand people's vocab and understanding around a lot of this stuff, I'll figure out how to categorize!

[@DiogenesOfCa]

This was a really nerdy video, great job.

[@storploin3860]

I like this video. I dont have much to say, but I want to post a comment to help feed the algorithm, and create Induced Views. All hail the machine. Thanks for the technical breakdown!

[@MusicalInquisit]

Thank you for mentioning the seemingly nonsense use of demand, especially those with economics background (e.g. me). I have a passion for economics, and having first heard the term, I immediately wanted to call nonsense on it because adding supply does not shift demand. I agree people really should call Induced Traffic.

[@heinuchung8680]

Txdot hasn’t never seen a ride they wouldn’t expand . They will expand it if they have the space, best thing I like are flex lanes charge people for congestion.

[@vaiyaktikasolarbeam1906]

Thank You!!! Thx for the Explanation!!

[@pwhnckexstflajizdryvombqug9042]

It's also worth pointing out that because traffic follows the supply and demand system, traffic is only ever as bad as people are willing to put up with. Every day there are thousands of people that choose not to travel because of the hassle of traffic, and as soon as the disadvantage of sitting through traffic is less significant then the benefit gained from traveling in it, people will choose to drive. Same goes the other way, if people have a choice other than driving and you make a road significantly more congested (due to narrowing) people will choose to take other options rather than sitting in traffic. The important things is that there are other options and no one is forced to sit in traffic because there is literally nothing else they can do.

[@CityNerd]

There really is basic math at the root of all this, as much as it appears to be randomness moment to moment.

[@danellis-jones1591]

Happy that you used a pic of Perth Australia. It's got a Houston level of road addiction. So many people literally laugh at indiced demand, because they're so brainwashed into big roads

[@jasonhilgefort5184]

just seeing this now. just wanna give you credit. i cannot believe you got 76k folks to watch an 'induced demand' video. wildly impressive.

[@misterflibble9799]

There's a major junction near me that has had at least four significant "capacity improvement" schemes in the 20 or so years that I've been here. Each time the council suggest a new scheme, I ask "when is this junction going to have *enough* capacity?"

[@htraygo]

I got an answer to traffic. Move over after you pass someone not matter what lane you’re in. Obviously not but the US loves going the same speed in every lane holding up miles of freeway all for 100’s of cars to try and pass everyone in the fast lane. Then it’s basically open freeway after you pass the group.

[@ryanseidel7436]

Great explanation, thanks

[@marjae2767]

If you're only considering cars and buses, that will leave out people who can't drive or take the bus, who may have to take longer detours to avoid the traffic, or may have to stop going places, cancel trips, etc., or may get hit because of the wider roads, faster traffic, or new safety signals.

[@scooter32145]

Well done - a side note could be on how these same weaknesses (in the analysis tools) can over-estimate the severity of congestion when a traffic lane is taken away to build transit or bike lanes. I also like your point that traffic engineers are criticized unfairly. Your channel takes a fair tone - contrary to the hatred and scapegoating, most or all traffic engineers these days mainly want safer roads, protected bike facilities, traffic calming, lower speeds, and optimizing traffic but in the context of the best solution for all users. And are also appalled at the difficulty of getting these things done.

[@CityNerd]

Good comment. The traffic/transportation engineering profession is constantly evolving, but there's definitely an "old guard" that's aging out and being replaced by engineers who have grown up in a different world and -- I think -- had an education that really emphasizes context sensitivity. Not to be ageist about it -- some of the most forward-thinking engineers I've met have been around the industry for 30+ years, but in general, the dynamic seems generational.

[@MarloSoBalJr]

One of the issues we have in Baltimore is that a lot traffic from I-70 [ends at the city border] floods onto I-695 with many wanting to head east (that would be I-95) but because of the abrupt end to I-70 they are forced onto the Beltway. Now the reason for that abrupt cut-off is due to public resistance [unfortunately, it didn't stop the 'Highway to Nowhere' from happening] so that was a positive BUT it's a double-edged sword.

[@kevinwoolley7960]

I'm curious about induced demand in locations that are either not growing or actually losing population. My anecdotal experience is that stagnant cities and shrinking cities in the US have much better traffic than rapidly growing cities, in fact, growth seems to be the most important factor for traffic congestion outside of the 3 largest metro areas, which are so large and congested that they are in a different category. Maybe a future topic? Correlation of metro area growth with congestion?

[@mauricio4619]

Thank you so much mr. engineer man!!

[@nickduma3049]

Something I feel like I never see mentioned also is that driving on 3 and 4 lane freeways feels significantly more dangerous than driving on 2 lanes where I really just need to keep my eye on the passing lane and ramps.

[@EmilyChandlerj]

I love this. At the start of the video I had a thought that this should be more integrated into middle and high school education. We balanced checkbooks and had the opportunity to do home economics (I didn't take it, ha!). But we didn't learn about these basics which impact our lives and impact the world we live in. Thank you. I feel like I'm getting a good education here. And I do realize you made a joke but if there is a good place for "chatachism for urbanism" I would read it!

[@mostlyguesses8385]

... Europe is denser than US. Even there per statista com on France and Italy and Finland 80% of workers drive to work. Transit don't work for more than this in any rich country.. I walk, I'm a weirdo, cars are by far what any European or American will use.... Our cities post1950 grew from 5 miles radius mostly downtown to 20 mile radius all sppreadout, only cars let us avoid awful 3 hour bus rides, thank you cars! ... It's scary how transit people spin fables, all my family in Finland drive. Even in Japan half the people have cars, in a country smaller than Florida with 120m people. Nonpoor people choice cars the world over, it's not unique to US. I guess fables are fun, I want a subway in Wyoming!!

[@TheNotverysocial]

I say this much: Street parking does not help matters at all. Streets exist for the purpose of getting individuals from one address to the next. Cargo from one precise location of choice to the next. They were not made to be giant parking lots. That is the purpose of garages and driveways. Especially in residential places, suburban ones and the like. The outlawing of using public streets as places to park your car would greatly improve city and residential street traffic at any rate. One more lane made without needing to do any construction whatever. Places that lack frontal driveways usually have alleys in the rear, and their own lots and garages.

[@chengyanboon]

When looking at your supply-demand curve I wonder if the extremely simplified situation in North America is that we already have so many lane-miles built that you'd need to build an absurd amount more lane-miles to have a perceptible delta in delay. So we're nowhere near the middle of the curve but rather all the way on the right.

[@chris57035]

Wow this is, like, no shit analysis with a real model and real parameters. I feel like I’m back in Grad school all of the sudden. Fantastic!

[@dungandonuts]

nice pic of the Kwinana Freeway, Perth

[@CentralPASpotter]

I loved the amount of data you used even though most of it went over my head. Most urbanist channels just say "Cars are bad, trains are good. [Insert European country] uses [insert mode of transit] so it'll work for us."

[@Twentydragon]

2:30 - I never understood this graph at all, until I saw the Steam marketplace's breakdowns on item prices and item orders. They had the axes reversed, and it finally clicked for me.

[@nicomol4882]

The problem of congestion begins with the necessity of going from point A to point B. When you get those closer together, other forms of transportation become more logical. Build schools, shops and businesses, restaurants in the places where you live. Then you can walk or take a bike. You now have decimated the miles you need to make. Kids can go to school without the need of a car, groceries don't take an hour to get to the store and back etc.. Use al the billions that are now used for highway expansion, to create a viable and safe infrastructure for cyclist and pedestrians. Make sure there is a variety of public transport options when distances are much further than 5 miles. Make bus lanes so they can follow a predictable schedule, and don't get stuck in traffic as well. In the US gas prices are ridiculously low, increase taxes on fuel to help pay for these changes., but also to induce economic incentive for using other forms of transportation than a car. And than, when you do have to, or want to use the car you than will not get stuck in traffic on a road half the size, and with half the maintenance costs.

[@beardannyboy]

The dry sarcasm of "Review the catechisms", perfection.

[@rodlavery509]

I feel like this video would have pre-empted Economics Explained's video about induced demand if he had seen it. You do such a great job of addressing EE's exact problem, that "the demand is always there, you don't create it from nothing", while also explaining that that's just a problem with terminology. And you then give us the nerdy evidence that the actual point remains true: adding lanes adds traffic, and the solution is more non-car transit. You accidentally made a killer response video, a year before it was needed!

[@TychoRVT]

Wow, two minutes in and you described almost exactly the response I got from a car traffic project manager. Where I typed "induced demand" he responded with 'bla-bla-bla - current and future commercial - whatever"

[@danwylie-sears1134]

From an Econ 101 perspective, one way to make sense of the concept of induced demand is to distinguish between short-term and long-term demand. At any moment, there is a short-term demand curve: a function that gives a quantity demanded for any price. It depends on people's beliefs about alternatives, and about the good that we're looking at demand for. If price is the only thing that changes, then quantity demanded will vary along that curve. That definition has nothing to do with time, only with whether anything else changes. But it can be called a "short-term" demand curve because changes in price can be assumed to happen faster than other changes, or because price changes that aren't expected to last will have very little effect on anything else. A long-term demand curve describes what quantity will be demanded if the price stays at a particular level indefinitely, accounting for all the other changes that may eventually happen as a result of the change in price. So a change in supply can gradually induce a change in short-term demand, where the new short-term demand curve intersects the supply curve where the long-term demand curve does, instead of where the old short-term demand curve did. As for traffic, my impression is that the main problem is how capacity works. If you add lanes, that gives a nearly proportional increase in the maximum amount of traffic a road could carry, if metered entrance ramps functioned perfectly to let vehicles on at the rate that maximizes throughput. But it gives very little increase, if any, in the amount of traffic that the road can carry when fully congested. A four-lane parking lot is a parking lot, and a six-lane parking lot is still a parking lot.

[@steveprice9737]

We have an example of wishful thinking road expansion on one major junction on the M6 motorway just north of Birmingham UK , they have expanded the size of the interchange island area and slip roads but they can't do anything about the gridlocked motorway (notoriously bad section) and a similar situation on adjoining main roads... even people without much interest in transport who live here are asking " how's that going to work then?" The only positive thing is the possible improvement for bikes and pedestrians crossing, this motorway is a massive blight and block to getting from one part of the Borough to the other. Our council is in love with cars unfortunately and they'll keep on with the nonsense for as long as they can. Great vids, cheers.

[@roaringchicken4219]

Great video as usual! As for topics, how do cities implement Vision Zero programs? Where I live, we had a record number of traffic fatalities in 2021, six years after the city began its VZ program. What tools do local gov’t have to achieve their goal?

[@CityNerd]

Oooh, VZ is a hot topic. Not sure I want to wade in, but I'll think about it!

[@Redmage913]

Small city region, here. The Charleston, WV region at this point doesn't have a huge problem with capacity, as long as you know to use parallel roads along the river instead of the interstate at 745am and 515pm, but instead it has issues with degredation. Our roads and streets are getting bad to the point of damaging cars from the physical stress of the potholes, crumbling shoulders eating into single lanes on 40+mph twisty roads, I could go on. The sections of interstate in the metro area that aren't bridges are getting especially bad in the truck lanes until you get a few miles west of town. It's difficult watching conditions in the region deteriorate. The streets around the Capitol are shiny and fresh, while our Piggly Wiggly has to complain on their advertising banner to get the governor to repave WV 61 in maybe a few years.

[@iCleanHitz]

How cities solve congestion in my area: Take a freeway thats three lanes. Remove one lane and make that lane a pay to use lane to make traffic worse and encourage people to pay the state money to use a lane. Thats what they do in Colorado.

[@dumbobg]

Great content! Really insightful. Do you know if and what differences exist in traffic management between US and Europe?

[@steveszigethy]

Excellent work. Similar to Henry's comment below, a lookback at the before/after performance of past expressway capacity projects would be interesting. Or more appropriately: before, after, and a few years after. And include some with tolls (like MD 200 Intercounty Connector, the Orange County tollways) and some without. That would be hard of course, with pesky external factors like recessions, pandemic, gas price fluctuations, etc. But nothing that City Nerd couldn't handle.

[@CityNerd]

Wait, are you asking me to do data analysis? I think I need a scope and budget for that. jk -- I'll add this idea to the list

[@dannyegold]

Induced demand actually makes a lot of sense from a more advanced economics background. You can’t survive your first-year PhD micro sequence without learning L’Chatelier’s principle, which states that long-run supply/demand is more elastic than short-run supply/demand. So while the increased quantity demanded from expanding capacity *is* a movement down the short-run demand curve, in the long-run, travelers take the expanded capacity into account when re-optimizing. Since they don’t account for their congestion externalities, the result is an outward shift in the demand curve. So even if you don’t have to worry about all of the other factors you mentioned, in a simple dynamic model, you’d see no long-run congestion benefits from widening a freeway

[@LucarioBoricua]

Not just that, we also have to consider that land use plans often have conditions put on land development based on the supply of public infrastructure, like utilities and transportation. Say, a suburban developer or a retail developer might not be authorized to build that new subdivision or shopping mall unless they invest in expanding the road capacity along their access routes; or until the DOT expands the freeways or arterials passing near the development sites. This sort of thing is what's happening under the hood in the long-term supply and demand elasticity.

[@someguy6075]

IMO you hit a key word here: externalities. I disagree with the elasticity analysis. Short-term demand is inelastic - at least when talking about people commuting to work. Long-term demand is more elastic but under regulatory control. Consider this - if people are commuting to jobs in the urban core, the core city cannot prevent suburban housing development (or existing workers moving out of the city), but it can absolutely control how many new jobs can be added in the city. While there are some things they cannot control, they typically fail to use the levers at their disposal either, so it is not surprising when the new capacity limit is hit.

[@dannyegold]

​@@someguy6075 I didn't say demand was elastic in the short run. I said that long-run demand is more elastic than short-run demand (which is true regardless of how elastic or inelastic short-run demand is). And the thing is that long-run elasticity accounts for the regulatory barriers you mentioned. Those barriers are inputs in the optimization problem that determines the shape of the demand curve. What makes long-run demand more elastic than short-run demand is that workers can move, or buy (or sell) a car, or find a new job, in the long run. No matter the regulatory regime, you would see induced demand. It's an axiomatic reality of transportation demand.

[@dannyegold]

@@LucarioBoricua Sure, but the point is that *even absent those second-order effects*, you would see an increase in highway demand in the long term as a direct result of capacity expansion. I mentioned this in my reply to @someguy's reply to my comment, but long-run demand is more elastic not because of knock-on policy choices or whatever, but simply because commuters are less constrained by long-run investments (e.g. where they live).

[@someguy6075]

@@dannyegold Your statement of _no_ long-term benefit removes all agency and culpability from regulators. I don't see how that attitude is useful.

[@neilpacheco622]

In Denver they built E470 to reduce congestion on other roads like I25 and I225, but they built the business and housing up along it so fast that the on and off ramps were already over capacity in less than 1 year. Too many exits to make it an efficient way to go around Denver. It was made too small for the demand from day 1.

[@artman40]

Would be interesting to try another angle from time to time: How to widen a particular road in order to maximize traffic congestion?

[@gytan2221]

Lol this video reminded me of my economics lesson today 😂… the demand curve.