Ok, so maybe you can ride your bike on I-205. I cannot find any legal references to this in WA but I can in OR. What would you like done with that information?  I don't think it's as straightforward solution as marking the road with some kind of bike tag would have routing added to that road.  I'm not sure how the routing works but they should not be recommended as primary routes.  The route to access I 205 north is also convoluted but is on the map.