Took my Subaru Forester 2 miles up the road (from the highway), and parked near the other Subarus there. But hiking up realized I probably could have driven another half mile or so in "X" mode without too much trouble - just a lot of loose cobbles - and a hole or high spot here or there to avoid. It looked to me like any stock SUV or pickup with "real" 4WD (not AWD), sturdy tires, and low range could be driven up to the switchback at about 4.8 miles (from the highway), where the road changes to being much rougher and steeper. There was a Toyota 4x4 pickup, a full size Range Rover, a Jeep Cherokee, and a full size pickup there when we hiked by, and a couple of pickups and 4Runners parked in turnouts below that.