Can a stop be made based on a police officer's visual estimation that a vehicle code violation has occurred?

Federal courts likewise hold that a stop cannot be based on an officer's unsupported opinion that a traffic violation has occurred. (See United States v. Sowards (4th Cir. 2012) 690 F.3d 583, 592, 594 [officer's visual estimation that vehicle was traveling 5 miles past the speed limit held an insufficient basis to stop vehicle absent "additional indicia of reliability to support probable cause" because otherwise it was a conclusory guess without appropriate foundation); U.S. v. Lopez-Valdez (5th Cir. 1999) 178 F.3d 282, 289 [good faith but wrongful belief that broken taillight constituted vehicle code violation held insufficient where "no well-trained Texas police officer" would believe a traffic violation had occurred: although "a traffic infraction can justify a stop even where the police officer made the stop for a reason other than the occurrence of the traffic infraction . . . if officers are allowed to stop vehicles based upon their subjective belief that traffic laws have been violated even where no such violation has, in fact, occurred, the potential for abuse of traffic infractions as pretext for effecting stops seems boundless and the costs to privacy rights excessive"].)