What are often used to give drivers an advance warning of construction zones?

Flashing arrow signs are specifically designed to alert drivers to upcoming construction zones by providing clear visual cues that indicate a change in traffic flow or detour. These signs typically feature bright, flashing lights in an arrow pattern to direct drivers safely through or around construction areas. They are effective because they can be seen from a distance, giving drivers ample time to prepare for any necessary changes in their driving behavior, such as slowing down or merging into different lanes.

While digital signboards can also provide warning messages and information about road conditions, and traffic cones help to delineate safe zones and guide traffic, flashing arrow signs have a distinct purpose in actively guiding drivers. Roadblocks are used to close off sections of roadway and are not meant to provide advance warnings but rather to physically prevent traffic from entering a certain area. Thus, flashing arrow signs are the most effective tool for warning drivers about the presence of construction zones ahead.