The Waipio Valley road on Big Island is considered the steepest road in the US with a maximum gradient of 45%. The official recommendation is to use a 4WD, but is it actually needed in practice?

I've visited this road by foot and while it's indeed very steep, the asphalt is very uniform and it didn't seem like it would be that hard to drive. But I'm curious if this road is actually undrivable with an AWD or 2WD.

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    Probably the main useful feature of 4WD here is that the low range gives you very strong engine braking. First gear on a typical vehicle without low range may not be low enough to keep you from speeding up, and you'll have to use the service brakes, which may then overheat or fade on the long downgrade (800 vertical feet). Commented Jan 24, 2021 at 7:33

1 Answer 1


It's illegal to do so, and I think that settles the question as far as this forum goes.

It was not permitted under local code previously, but as of 2019 under HI HB529 the fine is increased to $250 .

Note that AWD is insufficient, it must be a "low range four-wheel drive" vehicle.

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