10.12.060   Yellow alone—Caution.
   A yellow alone or "caution" signal, when shown following the green or "go" signal, shall indicate as follows:
   Vehicular traffic facing the signal is thereby warned that the red or "stop" signal will be exhibited immediately thereafter and such vehicular traffic shall not enter or be crossing the intersection when the red or "stop" signal is exhibited.
(Ord. 321 Art. 2 § 3 (b), 1974).