Distance from Yosemite: 83 miles (133 km)
Distance from Merced: 15 miles (24 km)
The Merced NWR is arguably too far from Yosemite to make for a pleasant day excursion, but if you're driving to Yosemite in the winter, when the birds are most plentiful, and your route is through Merced and into the park via Highway 140, it's worth the 15-mile detour from Merced. It's not too complicated: you need to make two turns in Merced and another about 8 miles south of Merced. Here's a starting-in-Merced set of driving directions for the refuge:
1) If you're arriving from Yosemite via 140, stay on it until it ends in Merced, just past the 99 freeway, at 16th Street.
1a) If you're arriving via 99, either north or southbound, take the Yosemite exit in Merced (it should be labeled 140 East), and turn west from the off-ramp onto 140, then continue the short distance until 140 ends at 16th Street.
2) However you arrived at the 140/16th intersection, turn right (northwest) onto 16th Street.
3) Take 16th Street approximately half a mile northwest to Highway 59, known as Martin Luther King Jr. Way inside Merced, and turn left (southwest). MLK Jr. Way is between I and K Streets.
4) Take Highway 59 south 8 miles (around 13 km) to Sandy Mush Road, and turn right (west) onto Sandy Mush.
5) Take Sandy Mush Road west for 7.3 miles (11.7 km) to the refuge, which will be on your left.
Yosemite's Arch Rock Entrance - the Arch Rock itself is just to the east but not readily visible on Street View because the driver was exiting the park, rather than entering it, on Highway 140. There's a reason it's not called the Arch Rock Exit.
The brief merger of Highways 140 and 49 as you enter Mariposa - keep going straight here.
Highways 140 and 49 diverging again as you exit Mariposa - keep to the right here.
Highway 140's terminus at 16th Street in Merced - turn right here. This is just past the 99 Freeway, which you'll see if you rotate the street view 180 degrees.
The turnoff from 16th Street onto Highway 59 in Merced - turn left (southwest) here.
The turnoff from Highway 59 onto Sandy Mush Road - turn right (west) here. Watch for the sign in the foreground, which indicates that the refuge is off that way, and for the power plant that will be on your right as you approach the intersection.
The Refuge Entrance from Sandy Mush Road - do as you wish, but turning left here is advised.