What must be clearly displayed at the rear of a vehicle conducting mobile highway works during the day?

The requirement for a clearly displayed "keep left or right" arrow at the rear of a vehicle conducting mobile highway works during the day is to provide essential guidance to traffic. This visual cue helps ensure that road users are informed about the need to navigate safely around the work area, thereby reducing the risk of accidents. Proper direction signage is crucial, especially in dynamic environments where vehicles may be moving and road conditions are changing frequently.

This type of signage plays a vital role in maintaining traffic flow and safety, as it communicates important information quickly and effectively to drivers who may not be aware of the ongoing highway works. The use of directional arrows helps minimize confusion and enhances the overall safety of both the workers and the public.

In contrast, while a red warning sign or an active construction zone alert may serve important functions in different contexts, they do not provide the specific directional guidance that is necessary when vehicles are actively redirecting traffic. A speed limit sign is also essential for road safety but does not directly address the immediate need for drivers to know which side to keep to while passing the mobile works.