RCW 46 61 050 is about traffic control devices. I can't see that has any applicability to a no thru traffic sign. You posted this as a speeding ticket problem - was there any other citation to authority on the ticket?
You should consider whether you want to have a ticket attorney deal with this for you. Yes, it will likely cost more than just paying the fine, but it will not negatively impact your driving record or the cost of your insurance if the ticket goes away.
Hope this helps. Elizabeth Powell
Rankin Powell is correct.
The sign can mean a few things - that the property is private (some cities have ordinances against crossing over private property); that the road does not connect; or that drivers are prohibited from driving past the sign in order to reach an egress point to another area or block.
In some jurisdictions these signs are not enforceable. Generally the purpose of such a sign is to control traffic and allow for the orderly flow of traffic on larger, arterial streets (as opposed to narrower residential ones), but in other instances the signs exist to keep people out solely for the benefit of private property owners who wish to 'control' the public streets giving access to their property.
Very likely the sign is not meant to apply to access to residents/visitors of particular homes/businesses, but rather to drivers whose sole purpose is to use the street as a passing zone.
One must look at the entire situation and the statute taken together.