My grandparents will drive only on roads recommended in printed travel guides; they'll ask the rental car company if Waipio Valley Road and the road to the top of Mauna Kea are sanctioned.

9. Re: Car Rental - is 4WD Really Necessary? Apr. 19, 2010, 5:19 a.m.

A rented 4WD vehicle is allowed by law to travel ANY public roadway in Hawaii. AND there are some places that require a 4WD vehicle.


If you travel down into Waipio Valley or to the top of Mauna Kea, you are legally allowed to do so, but your rental company will expect you to pay for any damage incurred whether you selected the insurance or not, as the insurance is null and void when you violate the contract.

16. Re: Car Rental - is 4WD Really Necessary? Apr. 19, 2010, 10:01 p.m.

I do not believe a 4x4 rental is necessary for 99% of visitors. For the other 1%, "necessary" is too strong a word!

But, being in that "1%" category, there ARE worthy places to go on the BI that require 4x4 (the kind you can rent from a normal rental outlet, not the kind locals may drive). I won't publicize those places because I don't want such places to become overused. [I bolded.] Just don't believe it when you read here that there is absolutely no place at all worth visiting that would require 4x4.

  1. I doubt the Tripadvisor comments overhead, as none of them discussed potholes:

I was there two weeks ago and got an SUV so I could drive to the Mauna Loa Observatory and do some hiking. We didn't need the SUV, although it made it easier to go over the potholes.

  1. Please see the bolded phrase. Where on the BI requires an SUV?
  • 1
    What do you mean by "require"? There's a distinction between "all vehicles must have 4WD by law", "rental car companies won't let you take conventional-drive vehicles on these roads", and "it's probably a good idea to have 4WD on this road." Nov 11, 2018 at 23:08
  • There's some commentary re Mauna Kea on the answer to this question: travel.stackexchange.com/questions/121742/… Nov 11, 2018 at 23:12
  • 2
    Also, note that there's a distinction between the Visitor Center and the Observatories on Mauna Kea. You definitely don't need 4WD to get up to the Visitor Center, but I'd recommend it for the Observatories themselves. Since that last post you quoted put the road on the wrong mountain, I suspect they might have meant the Visitor Center rather than the Observatory. See here for further description (also, note the concern about elderly folks and altitude sickness there.) Nov 11, 2018 at 23:12
  • @MichaelSeifert Thanks for raising that distinction!
    – user13759
    Nov 12, 2018 at 5:28

1 Answer 1


A 4x4 is required to go into Waipio Valley. There is a police officer at the top of the road who will not let you drive down into the valley unless you're in a 4x4. The road is well paved but extremely steep. I would not want to attempt to drive it without a 4x4 anyway.

The road to the Mauna Kea visitor information station (very high but not at the top) is just a regular road. No need for any special vehicle. If you want to go past the VIS up to the very top, it's a steep gravel road which needs a 4x4, according to the official website http://www.ifa.hawaii.edu/info/vis/visiting-mauna-kea/visiting-the-summit.html The visitor information center is where the telescopes for tourists are. The telescopes at the summit are not open to the public.

  • As most cars and even some SUVs are front-wheel drive only, the fact that the road is well paved but extremely steep. makes it foolhardy to attempt it even if you are an accomplished driver. Nov 12, 2018 at 5:28
  • @BurhanKhalid Why not rent an AWD vehicle, sedan or SUV?
    – user13759
    Nov 12, 2018 at 6:22
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    AWD vehicles (I owned two) typically don't have separate gearing for things like controlled descent and engine braking (sometimes called ascent / descent control). Of course this not universal. The WRX STi my friend has can run circles (literally, and figuratively) around my AWD sedan. Nov 12, 2018 at 7:03
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    Note that the Waipio Valley (the falls and the black sand beach) is accessible by foot. It is a tough but quite short hike, and young grandparents can do it.
    – Taladris
    Feb 9, 2019 at 0:46