The western end of Interstate 90 is in down town Seattle, Washington*; near where the King Dome was.  As you drive east from Seattle you cross I-5, go a short distance and come to a tunnel, a bridge that floats on Lake Washington, and yet another tunnel on Mercer Island before you cross I-405.  There's even a tunnel for the bike path that runs parallel to I-90.  These tunnels were not made so much to beat the altitude game, but to conserve valuable real-estate.

     As you drive west from Portland, Oregon* on US 26, you will pass through two tunnels before you reach the Pacific Ocean.  These tunnels do take the strain off your Buick.