 The route serves as a southern bypass of Smithtown and as a direct link between Nesconset and Port Jefferson.Along the way, NY 347 intersects NY 25 in Nesconset and Nicolls Road (County Route 97 or CR 97) in Lake Grove.The westernmost of NY 347 is concurrent with NY 454 while the portion northeast of NY 25 parallels NY 25A, which follows a more northerly alignment through the town of Brookhaven than NY 347.