Round traffic lights mean the following:
A green light allows traffic to move;
A flashing green light allows traffic to move. It also warns that the green light is ending and a red or yellow light will turn on soon. Digital countdown timers may be used to show drivers how many seconds are left for the green light;
A yellow light means do not drive, except in cases described in paragraph 6.14 of the Traffic rules. It warns that the light is about to change;
A flashing yellow light allows traffic to move. It warns drivers about an uncontrolled intersection, a crosswalk, or a danger;
A red light, including a flashing red light, means do not drive;
A red and yellow light together mean do not drive. It warns that the green light will turn on soon.