[Unless you have a very small motorhome...] You won't be able to drive it to the top. They will stop all over-sized/over-length vehicles at the Visitors' Center. I will add that the parking at the Visitors' Center is very limited -- we had a hard time turning around (w/toad) to leave and there was only one other car in the parking lot.
Ken & Deb (WIT Club, FMCA, SKP, Harvest Hosts, and grateful volunteers with SOWERs)
2005 Winnebago Vectra 40FD w/400ISL and Allison 3000MH on Freightliner's Evolution chassis, Onan QD7500, 1000w Renogy solar, BlueOx tow gear, and 2015 Cherokee TrailHawk toad.