What does a solid white line signify?

A solid white line is used to indicate that drivers should remain in their lane except when it is necessary to change lanes, such as to avoid an obstacle or to respond to an emergency situation. This line acts as a visual barrier that advises drivers against unnecessary lane changes, promoting safety and consistency on the road.

While other choices might seem relevant, they do not accurately define the purpose of a solid white line. It doesn’t designate a no-passing zone (which is generally marked by a solid yellow line), nor does it specify lane restrictions such as staying in the right lane or prohibiting left turns. Overall, the presence of a solid white line encourages careful lane discipline without the absolute restrictions implied by some of those other options.