<P> Some jurisdictions use special small blue lights on the reverse of signal heads to indicate a red light lit on that head . They are used to communicate the presence of a red signal to police so they can view the situation without having to traverse the intersection . Other jurisdictions simply drill a small hole in the red signal visor to allow police to see the status of the signal from a wide angle (but not directly opposite the signal). In France and, perhaps, Vietnam, the back of the red lights are sometimes designed with a red cross to indicate that the light is red . </P> <P> In Austria, Cambodia, Estonia, Latvia, Lithuania, Russia, most of Israel, Malaysia, parts of Mexico, Turkey, and in certain other parts of Europe, the green lights will start flashing at the end of the Go or Turn phase to indicate that the yellow (Caution phase) lights are about to be engaged . This is useful in fast - paced roads to allow for longer slowing down time, and for pedestrians crossing broad streets . Some traffic lights in Pennsylvania illuminate the yellow light a few seconds before the green light turns off, to give this same warning . </P> <P> Note that the 2009 Manual of Uniform Traffic Control Devices prohibits any display that gives warning of an upcoming signal change, unless that display is placed well upstream of the signal (See "Warnings of traffic light ahead" below), so traffic at the stop line cannot see it . </P> <P> At some intersections in Quebec, Canada, the yellow and red lights will appear together to indicate that the light is about to change to red . This mitigates the fact that at most Quebec intersections, there is no delay between the time that the lights in one direction turn red and the lights in the perpendicular direction turn green . However, this is considered redundant in other places, as the yellow light itself indicates that the light is about to change to red . </P>

Where do you start when its red and stop when its green