It is no secret that there is much controversy surrounding a visit to the Central part of the Big Island. To do so you must drive the Saddle, a road that connects the east and west sides of the island passing between the island's two largest mountains, Mauna Loa (13,680 feet) and Mauna Kea (13,796 feet).
It's a 53-mile two-lane and two-faced road. Two-faced literally because approximately only half of it is 'safe' for all traffic. The newly resurfaced Hilo-side which begins in Hilo on Kaumana Road and ends at the Mauna Kea Science Reserve International Astronomical Observatory Complex (the road to the summit of Mauna Kea; yeah, the name is ridiculously long) is in great driving condition. Unfortunately the Kona-side (meaning all of the highway west of the Mauna Kea Observatory Access Road) of the Highway is not in as good condition.
The Kona side of the highway is also two lanes, but is notoriously known as "Straddle Road" due to the fact that only the center of the highway is in good driving condition. To avoid the ruts and grooves on the edges of the pavement (likely caused by tanks, more on that in a second) most drivers will straddle the center line until they reach the Hilo segment of the Highway, moving over only when another vehicle approaches. Though plans exist to resurface and improve the entire road, don't expect changes anytime soon. As of this posting (and for the foreseeable future) the road will remain in poor condition.
Well, Saddle Road was first carved out of the lava in 1942 as both an access road to the Pohakuloa Army Base (located in the center of the island) along with a way to quickly travel between East and West Hawai'i. Saddle Road was constructed by the Federal Government and was eventually turned over to the Territory of Hawaii in 1945. However by 1957, when funds for maintenance ran low, duties were transferred to the County of Hawai'i. Today Saddle Road provides the only access to the Army Base, residential areas of Waiki'i Ranch, Mauna Kea State Recreation Area, portions of Parker Ranch, Kilohana Girl Scout Camp, Kaumana City and Kaumana Caves County Park. So why all the controversy? Though Saddle Road is the shortest route between the east and west side of the island the poor condition of the Kona-side of the highway makes the road quite dangerous to visitors and sight-seers. That makes the rental companies nervous and thus they have banned (there are some exceptions) all visitors from driving on this road. Even though several miles of the highway have been resurfaced between Hilo and the Mauna Kea Access Road, as of press time, you cannot drive it without violating most rental agreements. We talk a bit more on the debacle of 4x4 versus a regular car on the Hawaii rental tips page. We always rent with Turo before we drive the Saddle, normally because we like having a 4x4 to reach the summit of Mauna Kea (in fact, never try and visit the summit without a 4x4!). Just check with your rental company before-hand if you plan to make any journey on the Saddle Road; as a few are actually now allowing Hilo-side driving. It's a part of the island you shouldn't miss if you can afford the time to see it.