> because the route of I5 is fairly arbitrary, geologically speaking You sure about that? From Olympia to the Oregon border I-5 sits on the lowest, flattest s

> because the route of I5 is fairly arbitrary, geologically speaking You sure about that? From Olympia to the Oregon border I-5 sits on the lowest, flattest stretch of land between the coastal range and the cascades. That's why it keeps getting flooded out by the Chehailis river. To the north, through Whatcom County the route is anything but geologically arbitrary: it's the unique route that required the minimum amount of blasting into Chuckanut rock. Parent post seems like a pretty city-centric view of the world. The dozen or so miles that pass through Seattle might be arbitrary to within a Seattle-diameter, but that's an irrelevantly small part of the freeway.