What does a solid yellow line on the road indicate?

A solid yellow line on the road signifies that no passing is allowed in that lane. This marking is used to indicate areas where it is unsafe to overtake another vehicle due to visibility or road conditions. It serves as a warning to drivers that they must remain in their lane and not attempt to pass vehicles ahead. This safety measure helps to reduce the risk of collisions by clearly delineating areas where passing could be hazardous.

In contrast, the other choices reflect different traffic situations. Passing permitted only during the day typically refers to a broken yellow line, which allows for passing when it is safe to do so. Yielding to oncoming traffic is not indicated by a solid yellow line, as this typically relates to intersection signage or road markings that guide drivers to give way. The concept of double lanes in both directions is also unrelated to a solid yellow line since a solid yellow line does not convey information about lane arrangements but rather indicates the limitations on passing.