Is Questioning during a routine traffic stop on a subject unrelated to the purpose of the stop a Fourth Amendment violation?

^3. "Questioning during the routine traffic stop on a subject unrelated to the purpose of the stop is not itself a Fourth Amendment violation. Mere questioning is neither a search nor a seizure. [Citations.] While the traffic detainee is under no obligation to answer unrelated questions, the Constitution does not prohibit law enforcement officers from asking. [Citations.] [] Obviously, this rule must be applied in light of the companion rule that the length of a detention must be reasonably related in scope to the circumstances which justified the interference in the first place. [Citations.]" (People v. Brown, supra, 62 Cal.App.4th at p. 499.)