The Pritchett Canyon trail is a mixture of jeep-road on open mesa, intermediate technical ledge dropping, rolling rock, sand digs, and insane technical rock. We describe the main trail (following the trail signs), which is 22 miles. You'll descend about 1400 feet from the mesa down to the Colorado, but you'll also do a bit of climbing, too.
Two authoritative guidebooks give the riding time for this trail as "2 hours." Make that FOUR hours if you're in good shape.
To leave a shuttle car, drive south on Moab's main drag (US-191) to the McDonald's, and turn right onto Kane Creek Blvd. After 1.5 miles, go straight at the "Yield" sign where the road seems to turn right. Continue along the Colorado River until the road turns to gravel. There's a parking area on the right. The trail's end is about 100 feet back, on the south side of the street where it exits private property.
Now drive your second vehicle to the trailhead.Head back to Highway 191 and turn right (south). Drive 12.5 miles, and watch for a small road on your right. You should see a sign that (among other destinations) says Pritchett Arch. GPS is N 38° 25.301' W 109° 25.995'. Park near the cattle guard and begin riding.