What does a double yellow line indicate?

A double yellow line indicates that no passing is allowed in either direction. This traffic marking is put in place to enhance safety by preventing vehicles from overtaking each other, particularly in areas where visibility is limited or where there may be increased risks, such as near intersections, highways, or curves. The presence of these lines is a clear signal to drivers that they should remain in their respective lanes and not attempt to cross over, as doing so could lead to dangerous situations, including head-on collisions.

The other choices would suggest scenarios that could lead to confusion and potentially unsafe driving behaviors. For example, having passing allowed on both sides would contradict the purpose of the double yellow line, as would the idea that only the left lane can pass. Similarly, indicating that one lane is for turning does not apply; instead, the double yellow lines serve as a strict no-passing zone for all lanes involved.