There is a signed (from eastbound US 101) Truck US 101, explicitly following WA 117. No signage along WA 117, and from westbound US 101, only a generic Truck Route marker. On the ground, the route would follow Marine to downtown Port Angeles to meet with US 101 there. With only signage approaching the WA 117 exit going eastbound, however, I can see justification in not adding it, particularly along Marine.
What are the determinations for Olympic NP roads? We have only two: Upper Hoh Road, and Hurricane Ridge Road, but there are a number that probably could be included, as they are signed as park destinations from US 101, WA 110, 110S, 112, or 119.
From the Olympic NP map, these include:
--US 101
·South Shore Road/Graves Creek Road
·North Shore Road
·NFS 21, 2180, 2180-010, 2100 (all one road), connecting from US 101 to Upper Queets Valley Road in the park
·Lower Queets Valley Road
·Sol Duc Hot Springs Road
·Olympic Hot Springs Road
·Race Street (access to Hurricane Ridge Road)*
--WA 110
·La Push Road from the end of 110 to First Beach
--WA 110S
·Mora Road from the end of 110S to Rialto Beach
--WA 112
·Hoko-Ozette Road
--WA 119
·NFS 24 from the end of 119 to Staircase Ranger Station
I'll note that some are not within the Park itself, but are the connection from the Park to their respective routes, but Upper Hoh Road is already providing a precedent here.