What does a single solid yellow line indicate?

A single solid yellow line indicates that no passing is allowed. This type of line is used to mark the center of a two-way roadway and signifies that crossing this line to pass another vehicle is prohibited. The purpose of this marking is to enhance safety by preventing drivers from attempting to overtake vehicles in situations where visibility is limited or where it would otherwise be dangerous.

The presence of a solid yellow line typically suggests that the conditions might not be safe for passing—for example, on hills, curves, or in areas with heavy traffic. Therefore, it is important for drivers to adhere to this indication and remain in their lane to ensure both their own safety and the safety of others on the road.