The Southern California Owner Group lists CB radio as required equipment for members. They go on to list to other modes of communication in order of preference.
CB radio
–Very effective, best range
FRS radio
–Moderately effective, limited range
cell phones
–Rarely effective due to coverage
screaming out of the window
–Limited range, especially with diesels
Morse-Code using the horn
–Few understand it, too slow
tin cans tied together with string
–perhaps better then cell phones?
hand gestures
–can get you shot in the inner-city