What is the longest USA highway?
U.S. Route 20
U.S. Highway 20 (US20) is an east–west United States highway that stretches from the Pacific Northwest all the way to New England. The "0" in its route number indicates that US20 is a coast-to-coast route. Spanning 3,365 miles (5,415km), it is the longest road in the United States,[1] and particularly from Newport, Oregon to Boston, Massachusetts, the route is roughly parallel to that of the newer Interstate 90 (I-90), which is in turn the longest Interstate Highway in the U.S. There is a discontinuity in the official designation of US20 through Yellowstone National Park, with unnumbered roads used to traverse the park.
Interstate 15 in Utah
As of October 2016, the longest continuous high-occupancy-vehicle (HOV) facility in the U.S. is on I-15 in Utah, extending approximately 72.0 mi (115.9 km) from Spanish Fork to Layton with a single HOV lane each direction for a total of 144.0 mi (231.7 km) of HOV lanes.