A person positioned at a vantage point around the track who communicates with the driver via radio. Spotters relay information about nearby traffic, flag conditions, and incidents the driver may not see.
The HPDE First Timers Guide explains the communication system: "Flags are used by corner/turn workers to communicate with you as you're driving on track. You must understand the use and meaning of all flags; they are used in every and all HPDE on-track sessions." The XX Instructor Handbook describes an alternative approach used by some organizations: "In lieu of physical corner workers, Xtreme Xperience communicates its flagging with in-car radio communications. In the event of any flag, the instructor is responsible for calling in the flag when safe to do so." Whether via visual flags or radio, the spotter/worker provides information the driver cannot see from the cockpit — traffic behind, incidents ahead, debris on the racing surface.