From San Francisco, heading east on Interstate 80 to 580 to 205E is the most efficient connecting route to Interstate 5 and Highway 99, which straddle the western side of the Sierra Nevada. To best reach the eastern side from the Bay Area, take Interstate 80 to U.S. 395, then head south.
To get to Mammoth Lakes in summer and early fall (or whenever snows aren't blocking Tioga Road), you can travel via Highway 120 (to U.S. 395 south) through the Yosemite high country; the quickest route in winter is Interstate 80 to U.S. 50 to Highway 207 (Kingsbury Grade) to U.S. 395 south; either route takes about seven hours.
Watch your gas gauge. Gas stations are few and far between in the Sierra, so fill your tank when you can. If you're traveling between October and May, heavy snow may cover mountain roads. Carry tire chains, know how to put them on (on Interstate 80 and U.S. 50 you can pay a chain installer $35 to do it for you, but on other routes you'll have to do it yourself), and always check road conditions before you leave.
Caltrans Current Highway Conditions (800/427–7623. www.dot.ca.gov.)
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