This November, those of us who live in and around Seattle will vote on a $17.7 billion transportation package that would expand light rail (by 50 miles) but also include billions for road expansion — including roads that will primarily serve sprawling developments to Seattle’s south and east, making the package a Hobson’s choice for environmentalists. (The state legislature tied the roads and transit votes together last year, on the theory that road supporters will only support transit if it’s accompanied by pavement, and vice versa.)

A lot of the debate around whether the package is good or bad, environmentally speaking, has centered around whether the roads part of the package (known as the Regional Transportation Investment District, or RTID) consists mostly of "good" or "bad" roads. There are a lot of elements to this debate, the first of which is: What constitutes a "good" road? Are new HOV lanes "good" (because they serve people who are carpooling) or "bad" (because they’re still new road miles), and could they have been created by converting preexisting general-purpose lanes to HOV lanes?

Another issue is whether roads that are designated primarily for freight, but can be used by single-occupancy cars, count as "good" or "bad." Further confusing matters is the question of whether already-clogged roads produce more or fewer greenhouse gases when they’re expanded to accommodate more traffic, because traffic moves more smoothly (at least for a little while.)

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Given all those variables, it’s not surprising that Seattle’s environmental community is split on whether RTID/Sound Transit is a good or a bad thing.

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On the pro side: mainstream enviros like the Transportation Choices Coalition, who argue that most of the roads in RTID are "good," because they include lots of new HOV lanes and freight capacity. By the TCC’s calculation, only 15 percent of the entire joint roads and transit package, or about $2.6 billion, is made up of "bad" roads; according to their analysis, "good" roads make up about 23 percent, or just over $4 billion.

On the other side are environmental purists like (no, really) the local chapter of the Sierra Club, whose own analysis places the percentage of "good" roads at around 8 percent of the entire roads/transit package, or about $1.4 billion, and "bad" roads at around 30 percent, or $5.2 billion.

The primary difference between the Sierra Club’s and TCC’s numbers is that TCC included two expensive road expansions — the extension of SR 167 between Puyallup and the Port of Tacoma, and the proposed new six-lane bridge across SR-520 between Seattle and Bellevue — among their "good" roads. The 520 proposal is controversial because, under the most likely scenario, it would remove 2.3 acres of Seattle’s Arboretum (and include more columns and ramps through the nature preserve) and destroy much of Marsh Island, a wetland near the University of Washington. (In addition, it keeps the number of general-purpose lanes the same, which some argue is hardly an "green" alternative.) Extending 167 is controversial in some circles because there’s no guarantee it would only be used for freight; according to the Sierra Club’s Mike O’Brien, "our concern is, is this corridor going to fill up with new development?"

The larger debate, of course, comes down to whether enviros should stomach a ton of new roads in exchange for transit. The argument for: Sound Transit is shackled to RTID, and if both fail, it’ll be at least 2009 before Sound Transit is on the ballot again. (Washington Gov. Christine Gregoire seems not to recognize that high Democratic turnout in 2008 equals high King County turnout for Gregoire and transit.) And since transit projects historically have not come back to the ballot a second time larger than the first, this is probably our only chance to get 50 miles of light rail. Given that, it’s worth it to bite the bullet and vote for roads.

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The argument against: Building new road capacity cancels out the environmental and climate benefits of building new transit; given that our region’s goal is to reduce greenhouse gases 80 percent by 2050, roads expansion shouldn’t be a priority. Additionally, Sound Transit will be so politically popular once it opens in mid-2009, passing a large expansion a few months later will be a no-brainer. After all, the entire mainstream political establishment in Seattle said a new freeway on the downtown waterfront was "inevitable"; they were wrong, and we’re now moving toward a surface/transit option to replace the Alaskan Way Viaduct instead. Conventional wisdom could be equally wrong here.

Personally, I haven’t decided where I come down on this one. Ideologically, I side with the Sierra Club: We should not be spending a single penny (given what we know in 2007) expanding roads for single-occupancy cars — especially not suburban freeways like I-405, which would get two new general-purpose lanes in each direction. The political will for transit will only grow as climate change becomes accepted as a reality.

Pragmatically, I side with TCC: I don’t want to see light rail sacrificed on the altar of ideological purity. If they’re right, and a 2009 light-rail package would end up smaller and less region-wide than the current Sound Transit II proposal. And maybe some of those roads (like 405 and the controversial Cross Base Highway in Pierce County, south of Seattle) won’t end up getting built anyway; if greens are right about climate change becoming orthodoxy, roads expansion will start to look much less appealing (and much more vulnerable to lawsuits.)

It’s a tough decision.