Interstate H-201 (H-201) is the only auxiliary Interstate Highway located outside the contiguous United States, serving the island of Oʻahu in the US state of Hawaii. The H-201 designation is also known as the Moanalua Freeway. The loop route connects exits 13 and 19 on H-1, passing Fort Shafter, Tripler Army Medical Center, and the Red Hill Underground Fuel Storage Facility. Despite being designated an Interstate in 1989, until mid-2004, the route was an unsigned Interstate, signed only as Route 78. The section of the Moanalua Freeway between Route 99 (Kamehameha Highway) and the western H-1 interchange remains designated as Route 78. Route description H-201 serves as an alternate route to H-1 near Downtown Honolulu, traveling on the Moanalua Freeway around the northeast side of Salt Lake. It begins at a junction with Route 99 on the north side of Aloha Stadium, located near Joint Base Pearl Harbor–Hickam. The freeway travels east through an interchange with H-1, which continues west toward Kapolei and south to Daniel K. Inouye International Airport, and H-3. H-201 and H-3 briefly run parallel to each other through Halawa, where the former intersects Kahuapaani Street, before H-3 splits to continue northeast across the Koʻolau Range. H-201 turns southeast to avoid Red Hill and travels through Moanalua, a residential neighborhood with hospitals operated by Kaiser Permanente, the US Department of Veterans Affairs, and the US Army (including Tripler Army Medical Center). The freeway continues southeast, passing Moanalua Gardens and an industrial area, before it bisects Fort Shafter, a military installation in the Kalihi valley. H-201 then terminates on the south side of Fort Shafter at an interchange with H-1, which continues southeast towards Downtown Honolulu on the Lunalilo Freeway. The freeway is maintained by the Hawaii Department of Transportation (HDOT) and is designated as part of the National Highway System, a network of strategic highways in the US. H-201 is generally six to eight lanes wide with an eastbound high-occupancy vehicle (HOV) lane during the morning rush hour from Halawa to Puuloa Road. Traffic volumes on the highway, measured in terms of annual average daily traffic, ranged in 2020 from a minimum of 19,800 vehicles at its western terminus to a maximum of 136,100 vehicles near H-3. History Moanalua Road, the direct predecessor to H-201, was an unpaved road constructed in the late 19th century to connect Honolulu's King Street to Aiea. The road was macadamized in