Don't stop me, I'm on a roll

Here's the SLOG comment I made yesterday about RTID and global warming:

Make no mistake: I'm supporting this because I support ST2, and because I believe that it will will not come back in similar form in 2008 if this measure goes down.

However, I'm trying to think about the real impact of RTID. As I noted before, it makes my head hurt, but please chip in if you have any constructive feedback.

I'd hoped that the Stranger, or somebody, would talk to some experts and report on this, but I guess I'll have to do it myself.

(1) The type of road project that is most destructive to the environment is probably new roads through virgin territory, like the old I-605 proposal. What's most bad about this is that sprawl develops around these highways because they provide easy access to everything else.

As far as I can tell, the only RTID project anything like this is the Cross-Base Highway. While this will reduce travel times (see below), the ability for developers to add parking lots and strip malls is severely limited by the fact that it's, you know, across a base. And I'm fairly skeptical that that project will ever get really started.

(2) The type that's almost certainly good for the environment is HOV improvements, because they encourage bus and carpool use. A significant chunk of RTID falls in this category (SR 520, BRT on SR 99 in Shoreline, 167/405 interchange, etc.)

(3) That leaves the great middle: projects that increase capacity and/or improve traffic flow of general-purpose lanes, which amount to two sides of the same coin. The net effect of doing this over doing nothing is:

- Somewhat more people move to the Puget Sound region. I think this is a net plus (?), given the relatively high proportion of carbon-neutral energy production here.

- Car capacity increases: it takes more cars to get to bad congestion, shifting the equilibrium point where people shift to transit. Almost certainly a net minus.

- Growing suburbs: favors lower-density development in existing outer suburbs, rather than more density in inner suburbs and Seattle. A minus for the environment, but the neighborhood movement will like it, and probably results in more affordable housing.

- Less idling in traffic: congestion isn't binary; there's slow traffic and very slow traffic. Wider roads result in more cars, but quite probably a shorter commute for each of those cars. Probably a net plus.

Taking all this together (and I wish I had numbers to make this more certain), I can't conclude anything other than that RTID is a mild net minus taken in isolation. Throw in 50 miles of light rail, and it's a no-brainer.