2008 Toyota Prius Owners Manual - Page 186

2 -3 . Ope ra t ing t he light s a nd w indshie ld w ipe rs Fog light sw it ch (if e quippe d) The fog lights improve visibility in difficult driving conditions, such as in rain or fog. They can be turned on only when the headlights are on low beam. Type A OFF ON ITY23P004 156 PRIUS_U_(L/O_0802)