Where maintenance or construction operations are such that the site of the work moved slowly along the street or highway, or where only momentary (maximum thirty minutes) stops are made, a high level warning device with red flags or a rotating amber beacon mounted on the vehicle being used in the work shall be used. The flags or beacon shall be mounted at least five feet above pavement level and be clearly visible to all approaching traffic; provided that where the hazard is not clearly apparent to motorists, or the sign distance is restricted, advance warning signs shall be installed as required in § 19-129-16.
Haw. Code R. § 19-129-17