Abstract
The phantom phenomena in light signals are generally divided into 3 types: 1. real phantom; 2. reflex phantom; 3. mirror phantom. They are described in details and their origin is explained. Suitable measured for the prevention of these dangerous phenomena are givenand in particular a new road signal is presented, which completely avoids the dangerous mirror phantom by means of a specially designed disc with a prismatic optic fitted in front of the signal. Measurements of the phantomluminance on this signal as a function of the position of the sun as well as the effect in colour pictures will be shown.