objective facts exist to create reasonable suspicion that the driver is engaged in criminal activity. If the investigating officer witnesses the driver commit a traffic violation (even if they are mistaken about what constitutes a violation, see Heien v. North Carolina), then said violation generally constitutes probable cause for the officer to stop the vehicle. The officer may detain the driver and any passengers of the vehicle for long enough to confirm and/or deny his or her suspicions. If his or her suspicions are confirmed, then there may be probable cause to either search the vehicle and/or arrest its occupant(s), depending on the nature of the suspected violations. In Illinois v. Caballes, the Supreme Court held that a drug dog may sniff the exterior of a vehicle during a traffic stop so long as any delay in calling the dog to the scene does not unreasonably prolong the traffic stop. The use of a drug dog is sui generis and a dog's sniff is not considered a search in and of itself under the 4th Amendment. Police may also set up roadblocks and stop drivers without particularized reasonable suspicion that the stopped individual is engaged in criminal activity, so long as the plan for the stop is applied neutrally, for instance, driving while intoxicated - so long as all vehicles are stopped or every third vehicle is stopped, or some other reasonably neutral policy is applied for stopping vehicles. Note that some states also impose additional notice requirements for roadblocks, such as appropriate signage and/or flashing blue or red lights. Schools New Jersey has set the precedent that probable cause is not necessary to search a student on school grounds; reasonable suspicion is enough to search a student's belongings. Overly intrusive searches, like a body cavity search, require probable cause. Government workplaces A few years after New Jersey v. T. L. O., the Supreme Court held in O'Connor v. Ortega that while government employees do have Fourth Amendment rights in the workplace, administrative investigations conducted by supervisors looking for evidence of work-related misconduct or violations of an employee policy – unlike investigations by law enforcement looking for evidence of criminal offenses – only require reasonable suspicion to justify a search. Private workplaces Many private employers also use reasonable suspicion in private workplaces to drug and alcohol test their employees. According to the Department of Transportation (DOT), employers must provide training