Do Jeep Wranglers have this restriction? If so, it's pretty much useless to rent one. As far as 2WD vehicles, on Maui, they used to say that driving on "unpaved roads" violates the contract. And then when they paved most of the Kahekili and Pi‘ilani Highways, they changed the language on the maps they give you at the rental car office to say that driving on "unauthorized roads" violates the rental car contract. Although I've not actually noticed any fine print in the contract language that specifically mentions the Kahekili or Pi‘ilani Highways. If I have a rental car break down on one of those roads at some point it would probably make for an interesting legal dispute over who is responsible for the towing bill. In any case, to get to the Maunakea summit, I rented a Wrangler from Hertz and drove it to the top.