OVI checkpoints or sobriety checkpoints were found legal by the Supreme Court. That article was not about those though it was about a survey ran by the federal government and aided by local police on drivers. Some lady freaked out. If you can believe it the CNN article I linked earlier says:
Deputies were told they were not to make arrests, he said. If a breath sample indicated that a driver was legally intoxicated, "The organization would handle them as far as a ride home."