My father retired from CFHT and I visited the summit on more than one occasion. Easy but winding drive on saddle road. Hit the turn off and see cows. Mauna kea access road is about 8-10 miles long. Head up to about 9000ft and hit the visitor center. Trinkits, displays, snacks, bathrooms, etc...Just up from the visitor center is another facility for employees. Many employees live at this base camp throughout the week. My father lived up there during the week. It is tough to acclimatize on a daily basis to the 14K ft summit. Had his own private lodging and his own company 4wd SUV. 4x4 is highly suggested, but not enforced. The gravel road is pretty well maintained and about 4-5 miles from the visitor center to the summit. It is very steep in some sections and very winding. There are no guard rails and steep drops of hundreds of feet. The drive can be spooky depending on conditions and traffic. My dad drove it daily during the week and it scared the crap out of me the pace he drove it, like no big deal. The road has seen more than its share of casualties. I will say that I grew up skiing at anywhere from 8-12K feet and I will say that despite having a lot of mountainous experience, I was always gassed up at the telescope. I walked up to the upper deck ring of the telescope building (about 4 stories) and I felt like my legs were rocks, I was dizzy and felt like losing my lunch. When we are at my parents place, we always see the snow on the mountain when it gets snow. I used to spend xmas up there until 5 years ago, but now I have to be on Oahu around Xmas thru New Years and don't get up to the Big Island during the winter time. Been meaning to take my kids up there also someday.