Bull Frog Road is one of the few trails from the Sky Oaks trailheads that is not either very steep or too narrow and rough for a wheelchair. From the park entrance, cross a pleasant oak-studded meadow to where the trail splits, and turn left (in the dry season you could take the right turn, Meadow Club Road, and skirt a golf course for about 0.7 mile to reach Bolinas Road, but that’s not a particularly appealing walk). By going left, you’ll take a boardwalk across a seasonal marsh, and continue another few hundred feet through riparian woods to a steep stretch that most wheelchair users won’t want to attempt. Distance to this point is about .4 mile. If you continue, you’ll pass a clearing where maintenance machinery is parked by piles of gravel and lumber, before reaching a parking area overlooking marshes along an arm of Alpine Lake. The map seems to show you can make a loop of this, and I have, more than once, but it’s a mistake. Sky Oaks Road is very narrow, with no shoulder, uncomfortable to walk even though the speed limit is 15 mph.
Details: There is a fee to park; dogs are permitted on leash; bikes are not allowed on this trail. There’s an inaccessible portapotty in the Sky Oaks entrance parking lot.