With a rig your size, you could go thru Tacoma and Seattle during slack time, but if you're coming from the Peninsula, it would actually be cheaper and easier to take the ferry. Fare from Port Townsend to Whidbey Island is $41.00 for a vehicle 20-30' and over 7'6" high and from Bainbridge or Bremerton into the main downtown Seattle , it's $53.00. And having worked for the Bremerton school district, I have driven school buses across all the ferry crossings and in and out of downtown Seattle many times. The most fun is going to Victoria and putting a 40' on the boat out of Port Angeles. You can park your rig in P.A. and ride the boat across to Victoria for an awesome walking tour of the downtown area.