For problems of greater urgency, the course marshal may choose to call a full course caution period. A full course caution is typically signified by two yellow flags waved by each of the corner workers, as well as a yellow flag at the main starter's stand or yellow lights at some circuits. A full course caution will often be associated with emergency vehicles on track and is the signal of an incident deemed serious enough to place the entire track under caution conditions. A full course caution period also involves the deployment of a pace car to gather or bunch up the field before a restart.
As with corner or local yellows, speed should be reduced, and there's no passing permitted anywhere on the circuit. Drivers should be prepared to drive off line as the problem area may block much of the circuit.
The problem with full course cautions is in fact the bunching up of the field. Especially for the driver who was running away with the event! While it certainly is a mandatory part of the full course caution and subsequent restart equation, it often forces cars that are caught just in front of the pace car to have to hustle to catch the group before the restart.
At a long circuit like Road America in Wisconsin or VIR in Virginia, it might mean having to drive near race pace to catch the group. At the 24 hours of Le Mans, the 8.5-mile Circuit de la Sarthe in Le Mans, France, is so long that two pace cars are deployed during full course cautions to allow cars the chance to catch the group without having to turn qualifying times to get there.
That, in a rather small nutshell, is what yellow flags are about. It is, of course, the drivers' responsibility to slow to a prudent and safe speed without becoming a rolling chicane. Spotters aside, it is also the drivers' responsibility to see the yellow flags and interpret the situation for what it is.
Yellow flags also offer strategic opportunities to pit for fuel and tires in races that require such stops. Many a race has been won or lost based on a particular race team's strategist. The irony is that under full course caution, when the cars are running at their slowest speed, some of the fastest decisions need to be made regarding pit stops and overall pit strategy.
And finally, as SPEED commentator, veteran Skip Barber instructor and multi-time championship race driver Dorsey Schroeder so often says, "Yellows breed yellows," and few statements are as true. So often, yellow flags interrupt the rhythm and flow of a driver, and the slower speeds allow the various components of the car to cool and at times fall out of their optimum operating temperature range. Track surfaces may also change as a result of crashed cars and the lightly perceptible introduction of fluids such as a light haze of oil from engine or gearbox. Sure enough, when cars are then released-again in tight formation with questionable handling characteristics-mistakes are made and another yellow is likely to be thrown.
For those of you new to the sport, be sure to make yourself very familiar with those yellow flag rules and especially how they are set up for your particular series. To those who have a few races under your belt, maybe this discussion can help you to become more strategic in your races, making the most of those performance mods by driving the car that much better.