References do not need to be included in the lead unless the information there is unique.
Done
Do not use "then" in describing progression of route.
Done
"The roadway then reaches the Turnagain Arm, and turns left, traveling along the arm.", instead of indicating it turns left, indicate what direction the road turns.
Done
The sentence "The highway reaches its northern terminus, an access road to the Porcupine Creek Campgrounds, having spent its entire course inside the national forest" sounds awkward and needs to be reworded.
Done
The traffic counts should be included in the Route description rather than the history.