[Goldie]

TL&DR version:
Open passing, w. point by's in black & instructor run groups
Point by with hand signals or turn signals.

Details: from the 2018 Audi Driving School & Event Guidelines:
A passing vehicle must receive a signal from EACH vehicle being overtaken. EACH vehicle allowing a pass must provide the signal to EACH overtaking vehicle. In groups where turn signals are used, the turn signal will remain on as long as the driver of the vehicle being overtaken wishes to be passed and can be passed in a safe manner.
It is strongly preferred that the passing vehicle goes offline to complete the pass. In
general, offline is defined as the side of the track that is the direction of the next corner.
Pass right if the next corner goes to the right. Pass left if the next corner goes to the
left.

Let-by/Passing is ONLY allowed by clearly defined signal from the driver of the car being
overtaken. The turn signal (blinker) is used to signal the pass. The turn signal indicates
the position/direction that the overtaken car will maintain. The driver of the car being
overtaken is required to facilitate the pass by adjusting their speed and position if
necessary.

Hand signals (point-by) may be used in instructor groups, advanced student groups or in vehicles that do not have turn signals. The hand signal (point by) is given by the driver of the vehicle being overtaken pointing to the side that the passing vehicle should pass.