Which line indicates that a driver should enter a roundabout with caution?

The line that indicates a driver should enter a roundabout with caution is the roundabout holding line. This line is specifically designed to alert drivers to prepare for entering the roundabout. It serves as a visual cue that emphasizes the need for caution and careful observation of other vehicles and pedestrians in the area before proceeding. By heeding this line, drivers are reminded to yield to traffic already in the roundabout, ensuring a safer merging process and reducing the risk of accidents.

Other types of lines, such as broken white lines, center lines, and holding lines, serve different functions in traffic management. For instance, a broken white line indicates that lane changes are permitted, while a center line typically marks the separation of traffic moving in opposite directions. None of these lines pertain specifically to the cautionary measures needed when approaching a roundabout like the roundabout holding line does.