Apparently, folks in Greater Seattle are responding to congestion by … driving less! Which is, quite literally, no surprise at all. A comprehensive study of transportation patterns in cities across the globe found that high levels of congestion are linked with low overall energy consumption. When roads get congested, people adjust, and find alternatives to long, time-consuming commutes.

And that’s what seems to be happening in Seattle. Highway congestion has grown in the region, as it has virtually everywhere in the U.S. But per-capita car ownership is on the decline, and total vehicle miles per capita has begun to level off. More importantly, the article cites evidence that growth management laws have concentrated much of the region’s recent growth into already-urbanized areas — the sorts of places where people don’t have to make long treks to jobs or stores.

Towards the end of the Seattle Times article comes this telling snippet about a long-time Puget Sound area planner:

Cushman, who studied transportation here for more than 30 years before retiring in July, said he finds a certain irony in what’s transpired, noting that the region’s snail-like pace in making transportation decisions may actually have helped ease congestion. [Emphasis added.]

In the end, Cushman said, people get tired of waiting, and find their own solutions.

I’m not sure what to make of this, especially the bit in italics, since the whole article is premised on the notion that congestion is getting worse.

But really, it may come down to an issue of how to define congestion: Seattle hasn’t built too many big roads recently, so many of its highways really are pretty full, especially at rush hour. But plenty of people are responding by choosing their homes and workplaces so that the congestion doesn’t really affect them that much. Which may be one reason that, when measured per commuter, congestion delays in metro Seattle were, if anything, a bit lower [PDF] in 2005 as in 2000.

So maybe it’s this: the roads are getting more congested, but the people aren’t.