Route 200, known locally as Saddle Road, traverses the width of the Island of Hawaii, from downtown Hilo to its junction with Hawaii Route 190 near Waimea. The road was once considered one of the most dangerous paved roads in the state, with many one-lane bridges and areas of marginally maintained pavement. Most of the road has now been repaved, and major parts have new re-alignments to modern standards. The highway is mostly one-lane in each direction, but there are two lanes on the uphill portions. The highway reaches a maximum elevation of and is subject to fog and low visibility. Many rental car companies used to prohibit use of their cars on Saddle Road, but now allow use of the road. The highway experiences heavy use as it provides the shortest driving route from Hilo to Kailua-Kona and access to the slopes of Mauna Loa and the Mauna Kea Observatories.
Route description
Waiānuenue Avenue
The mile marker 0 is posted in Hilo on the traffic signal at the intersection of Waiānuenue Avenue, Kamehameha Avenue and Bayfront Highway at coordinates . The route continues mauka along Waiānuenue Avenue to a little over a half-mile past the mile 1 where it veers left onto Kaūmana Drive near Gilbert Carvalho Park. Further along Waiānuenue Avenue is Rainbow Falls Park (Wai means "water" (fresh) in the Hawaiian language; ānuenue means "rainbow". Thus "Rainbow Falls" is rendered as Waiānuenue). Total miles = 1.7 (2.7 km)
Kaūmana Drive
Starting at the “Y” junction adjacent to Gilbert Carvalho Park, Highway 200 continues mauka (uphill) on Kaūmana Drive and provides access to neighborhoods overlooking Hilo. The road is quite narrow and windy with many blind corners, hidden driveways and open drainage ditches. Near mile 4 it passes Kaumana Cave, a lava tube. Just past mile 6 (coordinates ) is the junction with Pūainakō Street Extension, (Hawaii Route 2000), completed in September 2004 as a bypass of the above-mentioned windy sections. The intersection with Ua Nahele Street at mile 8 marks the mauka terminus of Kaūmana Drive. Total miles =
Saddle Road
The official start of Saddle Road is at the “T” intersection of Ua Nahele Street at mile 8. This is the last neighborhood through which the route will pass. As it has from its beginning in Hilo, Route 200 continues to climb towards the Humuula Saddle between Mauna Kea and Mauna Loa. The rainforest of the Hilo Forest Reserve and Upper Waiākea Forest Reserve surround the roadway and begin to thin as the elevation increases. Quality of the asphalt surface is quite good on this side of the crest but there are many curves and rises with limited visual distances. There are no tourist services or other infrastructure on the Saddle Road.
Reconstruction of the sections from mileposts 11 to 19 and 19 to 28 was finished in November 2011 and October 2008, respectively.
The terrain becomes the high lava desert of the Humuula Saddle. Two roads intersect Saddle Road close to Puu Huluhulu at its crest near mile 28 at above sea level, the Mauna Loa Observatory Road to the south, and the Mauna Kea Summit Road to the north.
The Mauna Loa Observatory Road is an unmarked long narrow rough (but paved) road which winds its way towards Mauna Loa Solar Observatory, Mauna Loa Atmospheric Observatory, and AMiBA on the slopes of Mauna Loa. It was connected in 1963 to the old Tom Vance road from 1950.
The Mauna Kea Summit Road (known as John A. Burns Way) provides access to the Onizuka Center for International Astronomy (at elevation then climbs Mauna Kea past the Mauna Kea Ice Age Reserve to the height of at grades averaging 17% making this the third highest public road in the United States. The road is long, of which the first 6 miles (to the Onizuka Center) and the last are paved. Puu Wēkiu is the highest point in Hawaii at and is home to Poliahu, Goddess of Snow. Mauna Kea Observatory on the summit, an ideal location for astronomical seeing, is under the jurisdiction of the University of Hawaii Institute for Astronomy.