It's okay to cross a double yellow line to turn left. YOU CANNOT cross a double yellow line to pass another vehicle.
Two sets of solid double yellow lines that are two or more feet apart sometimes appear as a road marking. Such lines stand for a solid wall. Don't drive on or over these road markings. You may not make a left turn or U-turn across it.
Turn lanes are found in the middle of some two-way streets. The lane is marked on both sides by two painted lines—inner line broken, outer line solid. Use this lane only for making left turns.