Because it is impossible to view the entirety of a
road racing circuit from any one spot, and the nature of such courses make it difficult for any driver to look far ahead, road racing courses are dotted with corner stations, or
flag stations as they are sometimes called.
According to the Sports Car Club of America's General Competition Rules, or GCR corner stations must be sighted to they provide complete visual coverage of the entire course, and ideally should be posted in sight of each other. There are two types of station: Flag stations where informational flags are displayed to the driver. Certain stations may have particular duties, such as the black flag station where individual drivers may be black flagged for some on course offense, or mechanical reasons. Or the station may be an outpost where no flags are displayed, but is operated in order to maintain visual coverage. For example, station 1A at Mid Ohio Sports Car Course is an outpost, because the infield bridge significantly limits the view from the flag station, which is located just before the bridge.
According to the GCR, a flag station must be staffed by a minimum of two workers licensed for flagging and communications, but an outpost need contain only one.
There are four basic jobs at any corner station.
Blue Flag Workers charged with displaying the blue flag will face oncoming traffic, and present the flag as needed when a slower car is being overtaken. The blue flagger is charged with protecting his station in the event that an out-of-control car threatens the station or its workers. He or she will also display other needed flags, such as white or surface, as needed unless the yellow flag is also being displayed.
Yellow Flag The worker carrying the yellow will supervise the area from his position up until the next flag station. If there is an incident between those points he will turn and either present or waive the yellow flag as appropriate. (see Racing Flags)
Communicator The communicator will operate the station's radio or land line phone net. The communicator is responsible for handling all communications to and from the station, including requests for emergency vehicles, flag state changes, and other requests from the steward. If free, they will back up the yellow flagger by watching their area.
Points supervise areas that are hard to see from the station, and are charged with first response to a stopped car in need of immediate assistance. Points are the people who really get to play in traffic, and are often the first people on the scene in the event of a crash.
The Corner Captain is responsible for the operation of the station, including worker rotation and training, and has the final say on the dispatching of any emergency services, or requests that a race session be terminated. Generally the Captain and Communicator will stay together, and either or both may work any the other jobs, except that the Communicator will never be a Point as they are always the last person to leave the station for an emergency.
Stations are equipped with certain standard equipment, including at least one fire extinguisher, brooms to clear debris, the flags, oil dry, report forms and other items as seen as necessary.
Workes manning a corne station are called corner workers or turn marshalls and the activity called flagging or marshalling if you live in Europe. For further information noders are advised to read the GCR.