I was not able to find anything in the Revised Code of Washington (RCW) to support there being a default nor do I believe the Seattle Municipal Code has any application here. I think the best we can do is leave the "maxspeed" tag off these sections. I could also see a case for tagging with the "maxspeed" of I-5 here since a vehicle would be traveling at that speed when entering or leaving the freeway. Hope that helps!