Over the past week or so, there’s been a big to-do about greater Seattle’s transportation measure—affectionately known as the “RTID”—that’s set to appear on the November ballot. The measure would spend more than $17 billion on new roads, road maintenance, and rail transit, mostly through an increase in sales and vehicle taxes.

To many people’s surprise, King County Executive Ron Sims (a former board chair of Sound Transit) came out against the RTID last week in an op-ed published in the Seattle Times. A chief reason for his opposition: global warming. Said Sims:

Tragically, this plan continues the national policy of ignoring our impacts upon global warming. In a region known for our leadership efforts to reduce greenhouse gases, this plan will actually boost harmful carbon emissions. [Emphasis added.]

On this latter claim, I think that Executive Sims could well be correct.

We recently took a look at the greenhouse gas implications of building a new lane-mile of highway in a congested urban area. Our conclusion—which you can read in full here (pdf link)—is that every extra one-mile stretch of lane added to a congested highway will increase climate-warming CO2 emissions more than 100,000 tons over 50 years. Those emissions are broken out as follows:

  • Road construction and maintenance: 3,500 tons
  • Net congestion relief: -7,000 tons [that’s negative, folks]
  • Additional traffic on the roadway: 90,000 tons
  • Additional traffic off the roadway: 30,000 – 100,000 tons
  • TOTAL: 116,500 – 186,500 tons

For a variety of reasons (which the full memo (pdf, nine pages) discusses in greater depth) these are conservative estimates. And to put all this in context: CO2 emissions in the US currently average about 20 tons per person per year. So 100,000 tons per lane-mile is a fair bit of CO2—not as much as a coal-fired power plant, but worth being concerned about. As I understand the package, the RTID will add over 150 lane-miles of general purpose roadways—which, over the long term, could boost CO2 emissions by some 15 million tons. (Yoiks.)

Obviously, this isn’t a full analysis of the RTID. It doesn’t look at the greenhouse gas impacts of building or operating a train or HOV/HOT lanes, nor of the land-use impacts of more compact development that light rail may help foster. Still, Executive Sims may be on to something; if our estimates are even close to the mark, the greenhouse gas impacts of building new roads are pretty substantial.

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  • The relationship between road building and CO2 emissions has relevance far beyond this year’s RTID debate. British Columbia is considering a massive roadway expansion in greater Vancouver, called the Gateway Program, which includes a controversial twinning of the Port Mann Bridge. And major road widening proposals occasionally rear their heads throughout Cascadia and beyond.

    emissions from lanes 250To me, the most curious thing is that some supporters of this sort of road expansion try to claim the environmental high-ground: adding lanes to crowded highways, they claim, will relieve congestion, which will reduce overall emissions.

    Our analysis shows this claim is bunk. Sure, congestion relief may help in the short term—say, 5 to 10 years. (Even then, it’s pretty slim stuff.) But over the long term, traffic in crowded urban areas tends to fill all available road space. And when roads fill up, we’ll just have an extra highway lane filled with idling traffic—and the extra emissions from new traffic positively dwarf any temporary decline in emissions from congestion relief.

    Just to be clear: Sightline isn’t taking a position on the RTID as a whole. There are a lot of complicated tradeoffs that we just haven’t looked at—and that, frankly, we don’t have time to look at.

    For example, the RTID financing scheme, relying heavily on a sales tax increase, falls most heavily on working families. And that would make our tax system—already the most regressive in the US (pdf link)—even less fair. But building roads and trains can create high-wage jobs for people who don’t have college degrees. The overall economic equity impacts are hard to gauge, without an in-depth look at the regional economy.

    Just so, the long term impacts on land use are hard to judge. Building light rail could foster compact land use, and folks in compact neighborhoods tend to drive less. But this will depend in large measure on what happens to the land surrounding each rail stop: will it be up-zoned and surrounded by complete, compact communities? Or will it become parking lots and kiss-and-ride stations surrounded by sprawl-as-usual? Plus, even if trains do foster compact, pedestrian-friendly neighborhoods, will that offset the car-dependent development made possible by the new highway capacity? (After all, RTID adds more than twice as many lane-miles of roads as of transit.)

    And finally—if the state of Washington (or the US as a whole) does adopt a comprehensive, aggressive greenhouse gas cap, the issue of CO2 from road building is more or less moot. A cap would force overall carbon emissions down, regardless of how many new lanes of highway are built. Sure, highway building could make greenhouse compliance more expensive. But it won’t put it out of reach. That said: who knows how the politics of global warming will play out? We could wind up with no cap, or a phony cap that excludes transportation fuels. If so, extra roads could become a real problem.

    Sure I have some hunches about how these sorts of issues would play out. But hunches shouldn’t substitute for facts. Before Sightline took a position on the RTID overall, we’d want good, reasoned answers to many of these questions—answers that we, regrettably, don’t have time for.

    Still, one thing is clear: building highways for the sake of “congestion relief” will increase CO2 emissions from highways.  And now we have some numbers to back this up.

    Click here to download the full research memo.