What does a single broken white line on the road indicate?

A single broken white line on the road indicates that drivers are permitted to change lanes if it is safe to do so. This line serves as a guide, allowing for movements between lanes as long as drivers check their surroundings and ensure that it is safe to make the maneuver. The presence of the broken line signifies that lane changes are allowed, making it important for drivers to remain vigilant and responsible.

The other options suggest restrictions that are not applicable to a single broken white line. The solid nature of the line instead is what would inform a driver to stay within lanes, but that is not the case with the broken line. Thus, the broken line clearly communicates the flexibility and permission to change lanes under safe conditions.