Is induced demand entirely a bad thing?

[plutonicpanda]

Originally Posted by GlassCity

Highway expansion is equivalent to bringing in bigger buses - yes there's more capacity, but it will get filled up, and service isn't any better. There isn't really a way of making highway expansion improve service the way that transit expansion does.

That really isn't an apples to apples comparison there. Buses can't really be compared to freeways which are available to use all the time. The availability on the bus depends on the frequencies.

[plutonicpanda]

Originally Posted by GlassCity

That's actually not it, it's more a matter of people changing their habits due to the increased capacity. So with a congested highway, they might travel at a different time, they might take transit, they might carpool, they might drive the long way around, or they might just make the trip at all. Once a highway's widened, they see that it's now less congested, and they might become more likely to take peak-hour trips, drive alone, drive more often, etc.

It's true of course that there are bad transit projects, and that there are diminishing returns for widening highways. For example, going from 2 lanes each way to four lanes each way doesn't actually double capacity. And I'm not trying to say that induced demand makes highway projects "bad," just that it makes it so that it's almost impossible for them to accomplish their stated goal of reducing congestion. They can have other benefits too. Transportation is a very case-by-case thing.

I've never seen an instance where me or another person have tried to decide where to eat and thought "hey, they widened that freeway that used to be congested all of the time, let's go eat at so and so." That's not to say that doesn't happen, but I'm calling bs on it happening to the extent of so many people doing it that major traffic congestion is a result.

The demand was already there. Whether or not someone decided to use their car to go give their business to a restaurant or store, is irrelevant. I'm sure the business owner sees it as more business and for the consumer they have more options. It's better government all around.

Very small change that person living in the suburbs would have taken light rail or commuter rail if that option was available to them.

Simple math can be used to provide the adequate number of lanes and engineers will design a road so that is functions in a way that gets the most vehicles per hour moving through them.

[plutonicpanda]

Originally Posted by Hindentanic

Perhaps a case study project is Seoul's Cheonggyecheon creek restoration project, which removed the elevated Cheonggyecheon Highway cutting through the central city and restored a former historic creek that had been reduced to a drainage ditch beneath the highway into a modern riverwalk. While the riverwalk itself is a major urban design achievement, a peculiar side-benefit of the project was that the removal of the major highway infrastructure counter-intuitively improved traffic flow in the city. This is Braess' Paradox, where adding major road infrastructure to congested networks instead complicates and worsens the congestion, while removing road infrastructure simplifies the network dynamics and can actually ease congestion. Motorists will always adjust their traffic behavior and routing accordingly, and by simplifying or reducing the network options and capacity, traffic can not only be merely redistributed, but even also dissuaded. Instead of induced demand, it is reduced demand of discretionary, or unnecessary, traffic.

So let's just remove every intercity freeway with that logic and see what happens to traffic.

That said, it's not very fair to compare Asian or European cities to the U.S. Different culture and habits need to be taken into consideration. Those trips didn't just disappear. The traffic went somewhere and made it worse there.

[GlassCity]

Originally Posted by plutonicpanda

I've never seen an instance where me or another person have tried to decide where to eat and thought "hey, they widened that freeway that used to be congested all of the time, let's go eat at so and so." That's not to say that doesn't happen, but I'm calling bs on it happening to the extent of so many people doing it that major traffic congestion is a result.

The demand was already there. Whether or not someone decided to use their car to go give their business to a restaurant or store, is irrelevant. I'm sure the business owner sees it as more business and for the consumer they have more options. It's better government all around.

Very small change that person living in the suburbs would have taken light rail or commuter rail if that option was available to them.

Simple math can be used to provide the adequate number of lanes and engineers will design a road so that is functions in a way that gets the most vehicles per hour moving through them.

That's one of the main points. I'm not saying everyone would've taken transit before, though some certainly would. But in this specific example, you likely just wouldn't have gone to that business. So yes, widening highways enables more trips to be made.

As you say, there's math in capacity. More roads = more space for cars is obvious. What's not obvious is that more roads does not mean there will be less congestion. They encourage people to make more trips, so congestion often goes back to pre-expansion levels in a short while. You can call BS on it all you want, but it's what happens. There is a massive amount of data proving that highway expansion doesn't solve congestion. Obviously it's not because of people eating at restaurants, but there are many many reasons people make trips and these trips fill the space created. Whether this increased amount of people makes up for the congestion is a different conversation.

To be clear, I'm not an anti-highway person. There are times where widening highways makes sense. But induced demand is a real thing that needs to be considered, even if "considered" means "decided it's not a problem," which is a perfectly legitimate position to have.

[GlassCity]

Originally Posted by plutonicpanda

That really isn't an apples to apples comparison there. Buses can't really be compared to freeways which are available to use all the time. The availability on the bus depends on the frequencies.

I'm not trying to compare them directly, I'm trying to show that highway widening doesn't improve service, only capacity. The bigger bus example shows what that would look like in a transit setting, because improving frequencies DOES improve service, while bigger buses only address capacity.

[llamaorama]

What constitutes "congestion" is subjective, thus speeding up traffic as much as possible is not always the goal. Widening a highway may be worthwhile for the sake of increasing capacity to maintain existing travel times even if it doesn't reduce them.

My opinion is that government-funded infrastructure is a public good and the purpose is equity(providing a default, base level of mobility by giving users with less of it more). Toll roads with dynamic pricing schemes offer congestion relief if you can afford it. Plowing a highway through an urban neighborhood offers congestion relief to suburb-suburb commuters. But those things aren't equitable.

[Innsertnamehere]

increased throughput, even if it isn't "faster" throughput still equals greater GDP creation. More people and goods are making more trips too and from destinations.

I never fully understood while "induced demand" is considered such a bad thing. Inducing new trips induces new, more efficient gdp production. It's a good thing! Even if everything takes just as long as before, more people can make the trip.

Highway widening also does tend to reduce congestion in shoulder periods, if not the peak period itself. A lot of people would have had made the trip in the shoulder period as peak period was too bad for traffic - but with a widened highway allows them to make those trips when they prefer, during the peak period.

The part of it I do get is whether making those more trips by automobile is the most desirable way to make those trips. Highway widening isn't an automatically bad thing - it just has to be balanced with other forms of infrastructure.

i'm generally partial to the Dutch model of doing things - they have large freeway networks and regularly widen the roads as traffic growth occurs to allow for the continued flow of traffic - but yet a significant amount of trips in the country aren't made by automobile. Their built form and local roads are configured to be very friendly to active transport and transit trips - while auto trips are generally limited to inter-regional and commercial goods movement. Driving is efficient and fast - but taking transit and biking is made to be an equally attractive choice, reducing the amount of driving that occurs.


Compare to modern North American planning, which seems to be aiming to make driving as difficult and traffic clogged as possible in the hope that some people will shift to other modes in pure frustration. That's not the way to do it in my mind.

[GlassCity]

Originally Posted by llamaorama

What constitutes "congestion" is subjective, thus speeding up traffic as much as possible is not always the goal. Widening a highway may be worthwhile for the sake of increasing capacity to maintain existing travel times even if it doesn't reduce them.

My opinion is that government-funded infrastructure is a public good and the purpose is equity(providing a default, base level of mobility by giving users with less of it more). Toll roads with dynamic pricing schemes offer congestion relief if you can afford it. Plowing a highway through an urban neighborhood offers congestion relief to suburb-suburb commuters. But those things aren't equitable.

Originally Posted by Innsertnamehere

increased throughput, even if it isn't "faster" throughput still equals greater GDP creation. More people and goods are making more trips too and from destinations.

I never fully understood while "induced demand" is considered such a bad thing. Inducing new trips induces new, more efficient gdp production. It's a good thing! Even if everything takes just as long as before, more people can make the trip.

Highway widening also does tend to reduce congestion in shoulder periods, if not the peak period itself. A lot of people would have had made the trip in the shoulder period as peak period was too bad for traffic - but with a widened highway allows them to make those trips when they prefer, during the peak period.

The part of it I do get is whether making those more trips by automobile is the most desirable way to make those trips. Highway widening isn't an automatically bad thing - it just has to be balanced with other forms of infrastructure.

i'm generally partial to the Dutch model of doing things - they have large freeway networks and regularly widen the roads as traffic growth occurs to allow for the continued flow of traffic - but yet a significant amount of trips in the country aren't made by automobile. Their built form and local roads are configured to be very friendly to active transport and transit trips - while auto trips are generally limited to inter-regional and commercial goods movement. Driving is efficient and fast - but taking transit and biking is made to be an equally attractive choice, reducing the amount of driving that occurs.


Compare to modern North American planning, which seems to be aiming to make driving as difficult and traffic clogged as possible in the hope that some people will shift to other modes in pure frustration. That's not the way to do it in my mind.

That's exactly what I've been trying to say. Induced demand is bad in that it means highway widening doesn't solve congestion, but it doesn't mean that there aren't other benefits to increasing highway capacity.

I agree that mobility and sustainable transportation use has lots to do with land use planning, and not just making driving suck.

[electricron]

Originally Posted by GlassCity

That's exactly what I've been trying to say. Induced demand is bad in that it means highway widening doesn't solve congestion, but it doesn't mean that there aren't other benefits to increasing highway capacity.

I agree that mobility and sustainable transportation use has lots to do with land use planning, and not just making driving suck.

Induced demand is NOT bad!
You shouldn’t take one item, aka congestion, of the transportation issues as the only solution to how your city moves both people and goods. I have never seen one light rail train or bus move your next meal, computer, or phone from the manufacturing plant to your store, to your home and finally to the city’s dump.
The health of your city’s economy isn’t measured by how easy it is for people to move throughout your city, it is measured by how many good and services are sold in your city. And to do that goods must be moved throughout your city from the point of origin to its’ final destination and all the destinations in between.

Congestion is just one aspect to consider in that entire process, not the only aspect. Efficiency of movement maybe more valuable than just reducing congestion.

[GlassCity]

Originally Posted by electricron

Induced demand is NOT bad!
You shouldn’t take one item, aka congestion, of the transportation issues as the only solution to how your city moves both people and goods. I have never seen one light rail train or bus move your next meal, computer, or phone from the manufacturing plant to your store, to your home and finally to the city’s dump.
The health of your city’s economy isn’t measured by how easy it is for people to move throughout your city, it is measured by how many good and services are sold in your city. And to do that goods must be moved throughout your city from the point of origin to its’ final destination and all the destinations in between.

Congestion is just one aspect to consider in that entire process, not the only aspect. Efficiency of movement maybe more valuable than just reducing congestion.

I don't disagree with any of that. I'm just saying congestion is the one factor where induced demand means that highway expansion may not have the traffic-improving qualities people might hope for.

[electricron]

Originally Posted by GlassCity

I don't disagree with any of that. I'm just saying congestion is the one factor where induced demand means that highway expansion may not have the traffic-improving qualities people might hope for.

Hope for. 3Golly, anybody in the world should recognize that a 10 lane freeway moves more traffic than an 8 lane freeway, that an 8 lane freeway moves more traffic than a 6 lane freeway, that a 6 lane freeway moves more traffic than a 4 lane freeway, a 4 lane freeway moves more traffic than a 2 lane highway, and finally a 2 lane highway moves more traffic than an 1 lane street.

Likewise, a 4 lane freeway moves more traffic over a distance of 10 miles quicker than a 4 lane street with signal lights every half mile. Just last month I was on I-20 in Texas where the speed limit was 75 mph just east of Abilene. Traffic here is far less than it is in the DFW area. There was an accident on the freeway, the DPS troopers blockade both lanes at the scene, and detoured all traffic onto the two way two lane service road at the previous intersection, allowing traffic back on the freeway at the next intersection, a distance of several miles. The amount of traffic was able to move without too much delay through the detour once traffic was aligned into a single lane. But the speed was much slower, like 50 mph vs 75 mph. Most of the delay experienced by the traffic was merging into a single lane. Never the less, there was a delay traveling slower once it started moving again. When the detouring single lane traffic returned to the freeway, speeds increased to what it was before. And this was what was experienced in the middle of nowhere, after twilight, on a rural freeway.
That was with just loosing one lane. Well, adding just one lane to a freeway in an urban area moves traffic faster likewise, with far more room. Before the accident scene, traffic was not congested. On the detour traffic was congested. After the detour, traffic returned to what it was before. Induced demand did not cause that congestion that evening, a traffic accident did!

[huggkruka]

Maybe this is the North American mindset in this thread, but no-one has stated the obvious: if there is a big demand to get from A to B, and enabling this demand is a good thing, why do it in the most polluting and CO2-releasing way we know of(highways)? Why not take that demand and funnel it into transit projects, which are cost-effective and environmentally better?

[BrownTown]

Originally Posted by huggkruka

Maybe this is the North American mindset in this thread, but no-one has stated the obvious: if there is a big demand to get from A to B, and enabling this demand is a good thing, why do it in the most polluting and CO2-releasing way we know of(highways)? Why not take that demand and funnel it into transit projects, which are cost-effective and environmentally better?

1. US transit projects are almost never cost effective.

2. The people on the highway aren't going from A to B, they are coming from 100 different suburbs. Theoretically commuter rail could work, but it's far slower than a highway.

[Rizzo]

Originally Posted by llamaorama

"Induced Demand" is a concept in transportation planning roughly defined as "if you build it they will come".

An expanded highway will attract new users who previously avoided it due to congestion, e.g. induced demand. This is considered a problem because it means that expansion may not solve congestion. Thus induced demand is treated as an altogether bad thing, a derogative term in modern urbanist circles, and the concept is used to justify highway teardowns and oppose road expansion.

But should it? Certainly some new usage of an expanded highway may be wasteful: suburban commuters who choose sprawl over urban living, or people wasting gas and creating emissions just for the sake of eating out in a different neighborhood. But, some of those new users could also be commercial ones, who are able to expand business to new territories. They could be people driving to jobs while living in a neighborhood they can afford.

In the latter case, the highway expansion could be creating new economic gains through an increase in productivity. The business can compete further afield, the worker can optimally participate in the labor force. However, highway opponents and those who favor highway teardowns don't seem to incorporate this in their analysis.

Are they being fair?

Discuss.

Induced demand is never good, even if that has some sort of economic benefit, because the gains of one area come at the loss of another. From a regional perspective, the government (or taxpayers) become burdened by excessive infrastructure costs as a result of inefficient spatial planning.

Induced demand is best explained by theories of triple convergence. So this is a psychology argument. People will choose their modes and routes on their personal needs and desires and engineers and policy makers will make the users happy through planning

For example, when a lane is added people will:
1. Leave later than earlier
2. Take advantage of the new lane, vs taking other streets
3. Switch to driving

It’s a shame we’ve departed from the grid as it could handle near limitless load of annexations and regional expansion. Our piecemeal assembly of large disjointed subdivisions strung along collector roads connected to freeways makes planning difficult and unpredictable.

[emathias]

I'd say it partly depends on what sort of demand it induces.

If a region is economically constrained in a way that damages residents and can only be effectively improved by added capacity, then induced demand might be a good thing. If a new road just causes existing economic activity to travel greater distances, then that's not good. Or if the lack of capacity is damaging a region in non-economic ways, that could be bad, too. For example, when I290 heading die West from Chicago's Loop was constructed, there was more travel but a dramatic reduction in over all traffic deaths and injuries because the limited-access expressway was so much safer than the surface streets.

[electricron]

Originally Posted by Rizzo

It’s a shame we’ve departed from the grid as it could handle near limitless load of annexations and regional expansion. Our piecemeal assembly of large disjointed subdivisions strung along collector roads connected to freeways makes planning difficult and unpredictable.

Where there are street grids in Dallas neighborhoods there are usually speed bumps and/or 4 way stops at every intersection to slow traffic down. They call it traffic calming. Residential neighborhoods like walkability, but definitely do not like drive-ability. These neighborhoods mainly want peace and quiet, and traffic flowing at a crawl through them.

Just the opposite desires of the interstate trucking industry, who would rather be driving on controlled access freeways without signal lights and stop signs at every intersection. Truckers moving tons of goods in their trailers don't care how easy your neighborhood is to walk.

Please do not suggest gridded streets can move as much traffic as fast through neighborhoods that a freeway can. If they could, your neighbors would make sure they couldn't.

[Rizzo]

Originally Posted by electricron

Where there are street grids in Dallas neighborhoods there are usually speed bumps and/or 4 way stops at every intersection to slow traffic down. They call it traffic calming. Residential neighborhoods like walkability, but definitely do not like drive-ability. These neighborhoods mainly want peace and quiet, and traffic flowing at a crawl through them.

Just the opposite desires of the interstate trucking industry, who would rather be driving on controlled access freeways without signal lights and stop signs at every intersection. Truckers moving tons of goods in their trailers don't care how easy your neighborhood is to walk.

Please do not suggest gridded streets can move as much traffic as fast through neighborhoods that a freeway can. If they could, your neighbors would make sure they couldn't.

I see you misread my point.

[GlassCity]

Originally Posted by Rizzo

Induced demand is never good, even if that has some sort of economic benefit, because the gains of one area come at the loss of another. From a regional perspective, the government (or taxpayers) become burdened by excessive infrastructure costs as a result of inefficient spatial planning.

Induced demand is best explained by theories of triple convergence. So this is a psychology argument. People will choose their modes and routes on their personal needs and desires and engineers and policy makers will make the users happy through planning

For example, when a lane is added people will:
1. Leave later than earlier
2. Take advantage of the new lane, vs taking other streets
3. Switch to driving

It’s a shame we’ve departed from the grid as it could handle near limitless load of annexations and regional expansion. Our piecemeal assembly of large disjointed subdivisions strung along collector roads connected to freeways makes planning difficult and unpredictable.

This is the single greatest problem we have in urban planning today.

[digitallagasse]

Originally Posted by GlassCity

This is the single greatest problem we have in urban planning today.

Correct and it is also why those same areas are not able to densify well and are stuck being car based. Limited access neighborhoods simply doesn't work for walk-ability and transit use. That really isn't easy to fix short of tearing most if not all of it up and redoing the the whole thing. Hence it doesn't really happen and when it does thee process is so slow.

In the Vegas metro thankfully the major streets are mostly a grind except for the edges of the valley. Within the major blocks it is still limited access twisty neighborhoods, low rise tower in the parking lot apartment complexes and strip mall commercial spaces. At least some mix use projects are showing up more.

[GlassCity]

Originally Posted by digitallagasse

Correct and it is also why those same areas are not able to densify well and are stuck being car based. Limited access neighborhoods simply doesn't work for walk-ability and transit use. That really isn't easy to fix short of tearing most if not all of it up and redoing the the whole thing. Hence it doesn't really happen and when it does thee process is so slow.

In the Vegas metro thankfully the major streets are mostly a grind except for the edges of the valley. Within the major blocks it is still limited access twisty neighborhoods, low rise tower in the parking lot apartment complexes and strip mall commercial spaces. At least some mix use projects are showing up more.

I grew up in a neighbourhood like this (in the Vancouver metro) and I think (hope) it's the future of suburbia. Phoenix and Salt Lake City have a lot of suburbia that looks like this as well. You get most of the benefits of an arterial grid system (through-transit access, integrated neighbourhoods, etc.), while also getting most of the benefits of cul-de-sac land (quiet streets, less cost to developers). I'm currently doing my master's thesis on this, so I hope the results are positive!

I agree with the rest of your post too.