South Australian Numbered Regulations South Australian Numbered Regulations95—Performance and operation of brake lights
(1) When on, a brake light must show a red light visible 30 metres from the rear of the vehicle.
(2) A brake light fitted to a street rod vehicle may incorporate a blue lens not over 20 millimetres in diameter.
(3) A brake light fitted to a motor vehicle must come on, if it is not already on, when—
(a) for a vehicle with 4 or more wheels or built after 1974—a service brake is applied; or
(b) for another vehicle—the rear wheel brake is applied.
(4) Subrule (3) does not apply if the controls in the vehicle that start the engine are in a position that makes it impossible for the engine to operate.
(5) A brake light on a trailer must come on when—
(a) the brake light of the towing vehicle comes on; or
(b) a brake control on the towing vehicle, which independently activates the service brake on the trailer, is operated.
(6) A brake light may be operated by an engine brake, retarder, or similar device if the device does not interfere with the proper operation of the brake light.