Portland mayor says induced demand only matters if vehicles pollute

portland mayor ted wheeler looking into the camera at a meeting

“Induced demand only matters if you’re creating an induced demand for carbon-based vehicles that pollute.”

– Ted Wheeler, mayor of Portland

Portland Mayor Ted Wheeler has some interesting ideas about induced demand. In fact, if you care about building healthy and vibrant cities, his ideas are downright troubling.

For the uninitiated, induced demand is a transportation planning concept. It’s used to describe how the number of driving trips (demand) tends to increase proportionally with the supply of driving space (more lanes). It’s such a well-known phenomenon that Portlander Paul Rippey’s song about it has become a beloved local folk song.

The idea itself isn’t up for debate, neither is the fact that it’s a bad thing. But Wheeler thinks he’s figured out a way to make it A-OK.

Before I share his recent comments, I want to be clear: The list of negative externalities caused by driving trips is miles long. Because of this fact, we have many city plans (which Wheeler has supported) that clearly state Portland’s goal is to drastically reduce the number of cars on our roads.

But at two recent city council meetings Mayor Wheeler has questioned whether induced demand is really such a bad thing. The core of Wheeler’s belief is that induced demand is only problematic if the increase in trips comes from dirty, fossil-fueled vehicles.

Here’s a snip from our story about Wheeler’s comments on the I-5 Rose Quarter project at a June 23rd council meeting (emphases mine):

Toward the end of the meeting, Mayor Wheeler said the only analysis he’d like to see is how many people will be driving “zero emission vehicles” in the future. “Somebody raised during public testimony the issue of induced demand… but my question is demand for what kind of vehicles?… I’d like to know what the assumptions are for zero emissions transportation, because induced demand only matters if you’re creating an induced demand for carbon-based vehicles that pollute,” he said.

And here’s what he said Wednesday during a council discussion on the Interstate Bridge Replacement Program:

“We talk about induced demand. We have the debate about induced demand. It’s an important debate and I happen to support the economics behind the theory of induced demand. I think there is a great deal of evidence to support it. But then the question for me over the long term becomes, demand for what? If the region’s growing, if we care about the economy, if we care about the commerce, the shipment of goods of services, of commuters going back-and-forth — what do they drive? And my hope is we continue to move towards zero emissions. And so while I do expect over the long term there to be more vehicles, which I hope they’re very different than the vehicles we have today.”

I was aghast to hear Mayor Wheeler make these statements. I know how hard it is for political leaders to understand the consequences of driving and expanding freeways, so Wheeler’s lack of seriousness was surprising and disappointing. Nevermind that the he appears to assume “they” will always drive cars as our region grows (a defeatist view for a climate-concerned mayor of a progressive city), his techno-futurist line of thinking is riddled with holes and could reverse years of progress on transportation reform.

I reached out to Portland-based economist and City Observatory founder Joe Cortright, who attended Wednesday’s council meeting, to get his reaction to the comments.

Would it be hyperbolic of me to refer to the comments as “dangerous”? I asked Cortright.

“Yes. I absolutely do think it’s dangerous. It’s like, as if we don’t have to worry about this problem [of induced demand], or about carbon, or any of the other externalities at all… it’s his get-out-of-jail-free card.”

Cortright felt someone like Wheeler with a background as Oregon State Treasurer, should understand the financial repercussions of suggesting that more cars are not bad as long as they are battery-powered.

“If you just care about finances, you shouldn’t build capacity because that will just increase demand for roads, leading to more decentralization, which means people have to spend more money on transportation, making us all worse off,” Cortright added.

The reality of zero emission vehicles (ZEVs) in Oregon is that we are likely at least a decade from them having any serious impact on pollution. Today, 25% of Oregon’s electricity consumption comes from coal-powered sources (PDF) and a 2020 report by the State of Oregon said Oregonians will continue to use coal as an energy source until at least 2030. As EV adoption grows, there will be an even greater strain on all our energy sources and “There’s only so much supply of renewables out there,” Cortright warns.

And while Mayor Wheeler’s neighborhood might be filled with expensive ZEVs (the median household income of ZEV owners in Multnomah County is $69,176), the reality is that there are still only 47,000 of them on the road in Oregon today — just 1.1% of the entire vehicle fleet. Estimates from the Oregon Department of Transportation are that the ZEV fleet will reach only 3% by 2030.

Even if we could wave a magic wand and convert all cars to ZEVs, the vast societal costs associated with accommodating drivers — everything from expensive parking lots, nightmarish land-use, pollution from tires and brake pads, extraction mining for battery materials, deaths of humans and destruction of infrastructure — would still permeate our daily lives.

Adding lanes to our freeway system — auxiliary or not — makes driving easier and more efficient and will lead to more of it. Every time we do that, we sign a contract with those new drivers we cannot afford to pay.

It’s seductive for elected officials to cling onto technology as a quick fix for the serious problems we face, but Mayor Wheeler should know better.


I held this story back and gave Mayor Wheeler a chance to clarify his comments before publication. I just heard back from his Communications Specialist Shuly Wasserstrom:

“Mayor Wheeler supports the City’s goals to reduce carbon emissions and agrees about the adverse impacts of a transportation system overly reliant on personal vehicle use. He views zero emission vehicles as playing a necessary role in our transportation future. The overarching goal is to reduce the number of vehicles needed at all.”

We would also like to add that Mayor Wheeler has been a strong proponent of light rail and public transit, especially in regards to the I-5 Bridge plan. 

Jonathan Maus (Publisher/Editor)

Jonathan Maus (Publisher/Editor)

Founder of BikePortland (in 2005). Father of three. North Portlander. Basketball lover. Car owner and driver. If you have questions or feedback about this site or my work, feel free to contact me at @jonathan_maus on Twitter, via email at maus.jonathan@gmail.com, or phone/text at 503-706-8804. Also, if you read and appreciate this site, please become a supporter.

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soren
soren
1 year ago

Today, 25% of Oregon’s electricity consumption comes from coal-powered sources (PDF) and a 2020 report by the State of Oregon said Oregonians will continue to use coal as an energy source until at least 2030.

Oregon is doomed to use coal into 2030. Nothing to be done about it so we might as well keep on voting for climate arsonist democrats. Maybe some day the democrats will have a super-quorom-super-majority and they can pass legislation that would slowly phase out coal by 2100. That’s probably the best we can do.

And how about that defeatist Mayor…

Watts
Watts
1 year ago
Reply to  Steve

Tire particles are an emerging area of concern, but the only way you can get a headline like that is because modern car exhausts emit very few particles.

Anyone want to compare tire particles to the emissions of a typical American diesel truck?

Orig JF
Orig JF
1 year ago
Reply to  Watts

The SCAQMD has a summary of emissions from heavy duty trucks (HHDT = semi trucks). For fleet mix year 2022, they estimate approximately 25% of the total PM10 emissions from driving is brake and tire-ware.

http://www.aqmd.gov/home/rules-compliance/ceqa/air-quality-analysis-handbook/emfac-2007-(v2-3)-emission-factors-(on-road)

soren
soren
1 year ago
Reply to  Steve

The claims of some random private org in a citation-less opinion piece are not evidence. There is a susbtantial peer-reviewed literature that directly measured tyre/tire-derived particles in air sample and this literature found that only a modest fraction of PM2.5 were derived from tires.

Exaggerating risks based on internet clickbait is a great way to add more confusion and slow transformational changes in our transportation systems.

cc_rider
cc_rider
1 year ago

Wow, I thought Tevis mispoke about the “carbon-based” thing, but he actually thinks electric vehicles aren’t carbon-based. He sure is something isn’t he?

X
X
1 year ago
Reply to  cc_rider

I think he is referring to the vehicles generated when you sprinkle pixie dust on some iron ore. Until the magic goes away.

Christopher of Portland
Christopher of Portland
1 year ago

Things like this along with the glacial pace of adding diverters to greenways, creating physically protected lanes/paths, and maintaining existing paths, then most of the “bike projects” really being about speeding up freight or keeping drivers from killing each other so often make me think that perhaps the people in charge here don’t care about anyone’s ability to ride a bike. Even the guy who rides (rode?) a bike to work.

Serenity
Serenity
1 year ago

Don’t forget about the glacial pace of getting curb cuts fixed. They need time to review a complaint, and *at least* six months to a year to design and build… and that’s if it’s a priority. That’s if you know who to complain to.
Yeah, maybe Teddy boy rode to work once, or twice. Probably decided it wasn’t worth messing up his hair.

Watts
Watts
1 year ago

He appears to assume “they” will always drive cars as our region grows

He’s wrong. “We” will be the ones driving (or being driven) in cars or car-like vehicles for the foreseeable future*. No one in this forum will live to see the day we abandon great swaths of rural and suburban Portland and crowd into dense urban cores. It just isn’t going to happen.

*Barring the sort of civilizational level meltdown neo-Malthusians perpetually claim is coming, but probably isn’t.

Steve
Steve
1 year ago
Reply to  Watts

You can live in the burbs and still ride a bike (rather than drive) if quality infrastructure exists. Problem is it doesn’t in the US at this moment in time.

soren
soren
1 year ago
Reply to  Steve

if quality infrastructure exists

Building this quality infrastructure is impossible under the capitalist “free”-market that many urban cycling advocates carry water for.

Skid
Skid
1 year ago
Reply to  Steve

I feel safer riding a bicycle in the suburban areas outside of Portland.

SolarEclipse
SolarEclipse
1 year ago

Politicians don’t get a lot of campaign donations from poor transportation wonks or blog writers :-D. They do get a lot from big companies who don’t want anything to interfere with their ability to milk the consumer/tax payer for as much money as they can. Makes one wonder what political office Wheeler is looking to run for next.

Trike Guy
Trike Guy
1 year ago

I’m 55years old. Based on the how long my grandparents & great-grandparents lived I may live another 30-35 years (barring misfortune).

I don’t believe I will see a fleet that’s more than half EV in my lifetime.

The ability of the majority of the human race to make even small concessions to the greater good is nearly non-existent.

Mike Owens
Mike Owens
1 year ago
Reply to  Trike Guy

The sales are doubling every year. Do the math. Look to EU/China to see where US is headed, though lagging due to takes like this.

Trike Guy
Trike Guy
1 year ago
Reply to  Mike Owens

“based on takes like this”?

This take on human nature is based on decades of observing human beings.

I personally don’t own a vehicle over 45lbs and haven’t for 35 years. Nor are any of them powered by anything but me.

Short term lack of lithium, medium term lack of charging infrastructure and long term decrease in gas prices will slow adoption of EV’s – doubling will not continue to happen without a *huge* push from the government.

The reason the EU & China are doing so well in terms of adoptions is because they’re putting huge amounts more money behind it than we are.

Any push we may get from the Biden administration will all but disappear in 2025 when the Republicans return to power. The newest take from conservative think tanks is that all that CO2 is *good* for the planet (courtesy of conservative think tanks funded by the fossil fuel industry, naturally).

All of this is just opinion, of course, but any optimism I used to have has long ago been ground away by the relentless march of human stupidity, greed and narcissism.

ITOTS
ITOTS
1 year ago

We can but don’t need to look beyond the near-term climate implications of his statements to see how not fully thought out they are. The Mayor probably doesn’t know (but his staff should educate him) that the State of Oregon established a schedule of mandated annual vehicle miles traveled reductions specific to the Portland metro area in service of meeting the state’s greenhouse gas emissions reduction targets, a schedule which explicitly accounts for changes in the vehicle fleet (e.g. fuel type, EV, efficiency, etc.):

OAR 660-044-0030

(2) Vehicle Miles Traveled: The greenhouse gas emissions reduction targets as provided in OAR 660-044-0020 and 660-044-0025 are the ratio of future year to base year vehicle miles traveled per capita after controlling for the effects of state and federal policies and other conditions on vehicles, fuels, and pricing.

The upshot is that even if the vehicle fleet converts to EVs and more efficient ICEs at the assumed/hoped for/modeled rate in the Statewide Transportation Strategy (a rate we are not meeting), we still need individuals to drive less than they currently are to meet GHG reduction targets. Given the slower-than-hoped-for uptake of EVs, it’s become even more important we front-load the reduction in vehicle miles traveled to fill the gap.

Serenity
Serenity
1 year ago
Reply to  ITOTS

He has been the mayor for long enough that he should know. There is no good excuse for him not to.

Mike Owens
Mike Owens
1 year ago
Reply to  ITOTS

Sure, and the best way to do so is via policies around remote work (commuters are #1 VMT for personal travel) and cutting back on kids activities that don’t benefit anyone anyhow. (#2). But then…we still have almost 60% of trips that are work vehicles, fleets. The discussions here are literally a few stray cats in a bag who just can’t grasp the bigger picture beyond bikes.

ITOTS
ITOTS
1 year ago
Reply to  Mike Owens

I must have been in a different bag of cats when someone in your bag of cats said something like “we need to get everyone currently driving a car onto a bike, regardless of their trip purpose”. In my cat bag, we are talking—quite amicably so far—about how climate-wise we need folks overall to drive less while those who still need to drive transition to EVs—and that we shouldn’t make any more transportation or land use decisions that require more folks to drive or enable those who already do to drive more often/for longer distances than necessary. 

Not sure whose point of view you are trying to throw into relief, but I want no part of the cat fight you seem to be trying to start.

I am interested in learning more about the UC Davis and other sources you mention in your thread below with Jonathan, but would like to avoid the heat from that particular fire. Could you share them? (yes, I tried searching and am a bit lost in the thicket)

Middle of the Road Guy
Middle of the Road Guy
1 year ago
Reply to  ITOTS

Let’s just admit it is not going to happen.

David Hampsten
1 year ago

When I was a MURP student at PSU (1997-2003) I was taught that gentrification, involuntary economic displacement, induced demand, and sprawl were all evils that needed to be prevented or at least mitigated by public policies and through intelligent facility provision. This was further enforced in my mind by my living in Portland and my travels to similar cities.

And then I moved to mediocreville North Carolina (Greensboro), a city with nearly no traffic congestion, where it takes no more than 20 minutes to drive clear across town by car (an area as large as Portland but with half as many people), and where the city has unsuccessfully attempted for decades to gentrify large parts of the city, trying to get poor (mostly black) residents to move away in favor of richer newcomers (also mostly black but better educated). There are homeless here, but most leave for more generous services in other cities or cheaper rent and/or less harassment in rural areas.

I still think sprawl is a bad thing for our society as it increases the costs of delivering public services, but I’m no longer so certain about gentrification and induced demand as I once was. Part of the problem is that adding bike facilities and making it easier and efficient to walk and use public transit does in fact add a certain capacity to the overall transportation system, something we all advocate for other reasons, but to a certain limited extent also contributes to induced demand in a way similar to adding freeway lanes or a new roadway.

I have no doubt that EV’s, including eBikes, contribute marginally to our ever-increasing levels of air pollution and global warming, but is induced demand in and of itself such a bad thing we make it out to be? Shouldn’t we be focusing on reducing VMT instead?

Luke
Luke
1 year ago
Reply to  David Hampsten

Induced demand isn’t the problem, no. The problem is inducing demand in a mode type with a very low capacity. If we induce demand on a cycleway, bus, or rail line, it’s a long ways to go before those capacities are filled and we need to add more. It’s that by-now well-known photo of how much space 150 pedestrians/cyclists/bus riders/rail passengers/cars take up: you need so much infrastructure to accommodate 150 cars that if the people in those cars were forced to pay the full cost of that accommodation, there’s no way they would; they would be aghast, refuse to pay, and then find other ways to get around.

Aside from placating industry interests and avoiding having to tell Portlanders what they’d discover for themselves if their electeds had the spine to tell them–that autocentric infrastructure hasn’t, won’t, can’t pay for itself–I don’t know how someone with the self-proclaimed politics of Mayor Wheeler sleeps at night.

chris
chris
1 year ago
Reply to  David Hampsten

Figuring out that induced demand isn’t really a thing is as easy as crossing the river and visiting Vancouver and noticing how smooth sailing it is compared to Portland.

Middle of the Road Guy
Middle of the Road Guy
1 year ago
Reply to  David Hampsten

When I was a grad student back in the mid-90’s studying transportation policy and alternative fuels, it struck me that the root cause of just about everything was VMT. I mean really it is population growth but we are not allowed to discuss that.

Watts
Watts
1 year ago

Interesting that adding bike lanes has not induced bicycle demand. Quite the opposite, it would appear; ridership was more robust before we started building all these fancy facilities.

Lisa Caballero (Assistant Editor)
Editor
Reply to  Watts

New bike facilities do, with statistical significance, associate with robust increases in ridership according to a study published recently in PNAS. I mention it this article I wrote last year about the Biden infrastructure bill:

https://bikeportland.org/2021/04/05/caution-blumenauer-and-bikes-lets-talk-bidens-infrastructure-plan-329630

dwk
dwk
1 year ago

There are numerous reasons its not working here but it isn’t… Infrastructure like Broadway is just embarrassing,, Tons of paint and cones and stripes and NO bike riders..
The new infrastructure in Hollywood is really stupid and embarrassing.
Projects like these are ruining future cycling infrastructure plans because the average voter sees no one in the huge green striped things and just thinks it is a waste of spending which it is….

Watts
Watts
1 year ago

New bike facilities do, with statistical significance, associate with robust increases in ridership…

This may well be true elsewhere, but not so here. If infrastructure drives ridership (a claim I am skeptical of based on my keen participant and observer of cycling since before the Hawthorne bridge got its “wide” sidewalks), that suggests what we’ve been building is so bad it’s causing people to quit riding (and that, frankly, is implausible).

Or the picture is much more complex than advocates like to admit (or are aware of), and infrastructure is not the prime driver of demand. I believe in the nuanced view, so take the whole induced demand argument, in both driving and biking, with a container load of salt.

Will
Will
1 year ago
Reply to  Watts

There’s a pretty convincing body of research that says that, absent a well connected and truly protected network, ridership tops out around 5-7% and skews towards young men. Both the connectivity and safety of the network matter.

Will
Will
1 year ago
Reply to  Watts

Also a good point! In a vein similar to how reducing street parking doesn’t reduce trips to an area, but it does reduce car trips to an area.

Tomas Paella
Tomas Paella
1 year ago
Reply to  Watts

PBOT lost the script around the time they shoehorned the left-side bike lane into Williams Ave. It’s been more awkward unpleasantness ever since. All the work they’ve put into Division recently has done nothing to make me feel safe; it’s just convoluted and confusing and there’s a driveway every 100 feet.

Serenity
Serenity
1 year ago
Reply to  Watts

You’ve got to remember that drivers have also gone much more aggressive.

Yes, some of those bike lanes are great *pieces* of bike infrastructure, but don’t connect well.

Jakob Bernardson
Jakob Bernardson
1 year ago

Good to be aghast, JM!

If we, like the nabobs of Arabia, forbade driving to persons who can become pregnant, VMT would be halved, with pollution, crashes, deaths following suit.

Also we could reduce the size of freeways, rather than increasing them.

Just thinking!

Jim
Jim
1 year ago

Do something about the out of control homeless problem and the out of control crime problem first.

Steve
Steve
1 year ago
Reply to  Jim

Fun fact: wage theft by employers is the largest category of theft by far. Or are you not counting that as a crime for…reasons?

Chris I
Chris I
1 year ago

Tevis is a typical Portlander here. They will buy an electric car so they don’t have to feel bad about driving everywhere. Literally doing the bare minimum to feel better about climate change.

Just a reminder that 27 pedestrians were killed by motor vehicle operators in 2021 in Portland. A Tesla is just as good at killing pedestrians as any other modern car. The power source doesn’t matter.

Matt
Matt
1 year ago
Reply to  Chris I

Exactly. As well as sticking signs in their yard or windows. Not really moving the needle.

Watts
Watts
1 year ago
Reply to  Matt

Black Lives Matter!

Peter W
Peter W
1 year ago

> “Induced demand only matters if you’re creating an induced demand for carbon-based vehicles that pollute.”

The chemical process of creating cement (a key ingredient in the concrete these freeways are made of) emits carbon dioxide into the atmosphere.

So yes Ted, it does matter, even if all those vehicles are battery powered Teslas, because the roads they’re driving on are ‘carbon-based’ roads (to use your phrasing).

Middle of the Road Guy
Middle of the Road Guy
1 year ago
Reply to  Peter W

Doesn’t building bike infrastructure fall under the same reasoning?

Babygorilla
Babygorilla
1 year ago

Aren’t we trying to induce demand for trips by bicycle by building bike infrastructure and induce demand for trips by transit by building lightrail, red lane projects, streetcar infrastructure?

David Hampsten
1 year ago
Reply to  Babygorilla

As long as humans continue to procreate, move about, and drive to Sunday Parkways and the beach, travel demand will continue to be induced.

RipCityBassWorks
RipCityBassWorks
1 year ago

“ZEV” is an oxymoron:

““Currently, the electric vehicle in the U.S., on average, would emit about 200 grams of CO2 per mile,” he said. “We are projecting that with cleaning up the grid, we can reduce emissions from electric vehicles by 75%, from about 200 (grams) today to about 50 grams of CO2 per mile in 2050.””

https://www.cnbc.com/2021/07/26/lifetime-emissions-of-evs-are-lower-than-gasoline-cars-experts-say.html

We should be planning cities around walkable/bikeable neighborhoods and transit, not around increasingly destructive single occupancy vehicles.

Watts
Watts
1 year ago

We should be planning cities around walkable/bikeable neighborhoods and transit, not around increasingly destructive single occupancy vehicles.

I totally agree with this, but the horse has already left the barn. The suburbs have been built, and most people still long for a single family house. Those huge areas, like much of Portland proper, would be impossible to serve with transit to the extent that most people would stop driving.

I see no viable way of eliminating cars in any but the most central parts of Portland, and maybe not even there. The question to me is how do we change cars to make living with them more acceptable? Transitioning to smaller, lighter electric cars seems feasible with the right incentives. This should seem no more offensive to this community than those large heavy e-motorbikes that are currently in vogue.

Zac S
Zac S
1 year ago

What exactly is “aghastly?”

HA
HA
1 year ago

Also the fact that there is no such thing as a zero-emission vehicle.

Mike Quigley
Mike Quigley
1 year ago

Does induced demand really matter anymore now that Manchin alone has squelched Biden’s meager attempt to address climate change?

Or, the way humans worldwide are trying every angle to avoid addressing climate change just one small part of how nature is beginning to deal with the planet’s human overpopulation problem?

ro
ro
1 year ago

Two former Portland Mayors now work for the giant highway engineering firm – HDR – who is leading the Rose Quarter I-5 expansion. Perhaps Mayor Wheeler is setting himself up for a job. The highway building industry’s “revolving door” is always open to well connected politicians. That is the only logic I can see in his statement about induced demand.

Sigma
Sigma
1 year ago
Reply to  ro

Charlie Hales and ?

ActualPractical
ActualPractical
1 year ago

Yes, induced demand is fine with qualifiers…. specifically it is transit, biking, or walking!

Matthew
Matthew
1 year ago

Electricty is a carbon-based fuel and electric cars kill people just the same as their combustion engine cousins

Mike Owens
Mike Owens
1 year ago

Jonathan hasn’t read the studies from UC Davis or Climate Solutions about EVs in the PNW, clearly. This piece is full of disinformation.

Top blind spots?

  1. Work/fleet trips are the majority of VMT and mode shift doesn’t apply
  2. EVs can attain 90% of our emissions reductions needed by 2040 when including entire LCA
  3. Local and national grid are a non-issue for EV deployment. EV adoption parallels the cleaning grid very well, and complements/stabilizes it

Why do you continue to spout disinformation Jonathan?

Tomas Paella
Tomas Paella
1 year ago
Reply to  Mike Owens

BikePortland has never been a fact-based publication, it’s mostly about feels

Steve
Steve
1 year ago

Yeah, Wasserstrom is obviously bullshitting us. Even if Wheeler misspoke the first time, he had three whole weeks to mull it over and doubled down on expecting “more vehicles” as inevitable. He clearly does not understand “the adverse impacts of a transportation system overly reliant on personal vehicle use”.

Mark smith
Mark smith
1 year ago

So tires aren’t pollution? Interesting.

Racer X
Racer X
1 year ago

Wow!…such a dated comment perhaps even out of touch technically. (I would hope he just has not ‘thunk’ about this topic much…vs. being totally in the dark, but then again it might be telling a lot about his period of administration.)

Rob W
Rob W
1 year ago

Our region is likely to have climate in migration. The Water Bureau has a plan for massive growth. There is nothing which can prevent it. That is why the lanes.

Skid
Skid
1 year ago

Induced demand is an utter fallacy

GR
GR
1 year ago

Induced demand is OK with electric cars because building an interstate highway doesn’t require any carbon….since when? “constructing 1 lane- mile of highway and maintaining it for 50 years releases roughly 3,500 tons of CO2.”

Increases in greenhouse-gas emissions from highway-widening projects. Sightline institute. 2007.

https://transdef.org/media/Sightline-GHG-analysis.pdf