In Ingersoll v. Palmer (1987) 43 Cal.3d 1321, the Court explained the primary purpose of a sobriety checkpoint is not to detect evidence of crime or arrest drunk drivers, but to "promote public safety by deterring intoxicated persons from driving on the public streets and highways." (Id. at p. 1328.) The court concluded the validity of sobriety checkpoints "is to be determined not by the standard pertinent to traditional criminal investigative stops, but rather by the standard applicable to investigative detentions and inspections conducted as part of a regulatory scheme in furtherance of an administrative purpose." (Ibid.) The Ingersoll court identified eight factors to 'provide functional guidelines for minimizing the intrusiveness of the sobriety checkpoint stop.' These factors are: (1) decisionmaking at the supervisory level; (2) limits on discretion of field officers as to who is to be stopped; (3) maintenance of safety conditions; (4) reasonable location of the checkpoint; (5) a reasonable time and duration of the checkpoint; (6) indicia of the official nature of the roadblock; (7) the length and nature of the detention; (8) advance publicity regarding each checkpoint. " (Id. at p. 876.) "The eight factors identified in Ingersoll provide 'functional guidelines' to assess the intrusiveness of a checkpoint.' " (Id. at p. 877.) In Ingersoll, the court explained "that motorists should not be subject to the unbridled discretion of the officer in the field as to who is to be stopped. Instead, a neutral formula such as every driver or every third, fifth or tenth driver should be employed." (Ingersoll, supra, 43 Cal.3d at p. 1342.)