Final answer:
The best way to combine the two sentences using the subordinate conjunction "while" is to say: While road construction in Seattle has hindered travel around town, streets have become covered with bulldozers, trucks, and cones.
Step-by-step explanation:
The best way to combine the two sentences using the subordinate conjunction "while" would be:
While road construction in Seattle has hindered travel around town, streets have become covered with bulldozers, trucks, and cones.
This sentence combines the two independent clauses into a compound-complex sentence, where the main clause expresses the main idea and the subordinate clause expresses the less important idea.