Yellow lines separate:

1. Traffic lanes on one-way streets.
2. Traffic moving in opposite directions on two-way roads. ✓
3. All carpool lanes from regular traffic lanes.

Answer: B. Traffic moving in opposite directions on two-way roads.

Yellow lines separate traffic moving in opposite directions on two-way roads.

Why this is the answer

The California Driver Handbook says a single solid yellow line marks the center of a road with two-way traffic. That places yellow lines between lanes where vehicles travel opposite ways. The same section uses white lines for lanes moving in the same direction, including one-way streets, and describes double solid white lines as a barrier between regular and carpool lanes. So yellow marks the divider for opposing traffic, not for same-direction lanes or carpool lanes.

Why the other answers are wrong

• A. Traffic lanes on one-way streets. — Yellow lines do not mark lanes on one-way streets; the handbook says solid white lines mark traffic lanes going in the same direction, including one-way streets.
• C. All carpool lanes from regular traffic lanes. — Yellow lines do not separate all carpool lanes from regular traffic lanes; the handbook says double solid white lines indicate a lane barrier between regular use and preferential use lanes such as carpool lanes.

Remember it

Remember yellow divides opposing traffic; white divides traffic moving the same way.