What does a solid yellow line indicate?

A solid yellow line on the road is an important traffic control device that indicates no passing is allowed. This marking serves to warn drivers about the potential dangers of crossing that line to overtake other vehicles, which is particularly crucial in areas where visibility is limited or where there may be oncoming traffic. Essentially, it helps maintain safety on the road by preventing collisions that could occur if vehicles were to attempt passing when it is not permitted.

The other options relate to different road regulations, but they do not apply to the context of a solid yellow line. For instance, passing allowed only during daytime would not apply as this line consistently restricts passing at all times. Parking regulations would require specific signage or markings, which a solid yellow line does not indicate. Similarly, a bike lane would typically be designated with different markings, such as bike symbols or dashed lines, making the yellow line unsuitable for this purpose.