How to . . . The primary purpose of Roadside sobriety checkpoints is not to arrest impaired drivers. Certainly, that is one results. But the primary purpose is to put the public on notice that law enforcement is watching. Worldwide, DUI incidents are reduced by a consistent use of sobriety checkpoints.
Laguna Beach is a good example.
Communities which consistently use checkpoints have experienced reductions as much as 8 times greater than communities that depend on roving patrols. The reason for the effectiveness of the sobriety checkpoints has to do with the perception of how likely one is to be stopped and arrested when driving while impaired. One of the most important requirements for deterring potential drunk drivers is to convince them that if they drive while impaired, there is a strong probability that they will be arrested and lose their license to drive. Sobriety checkpoints are not expensive, comparatively. And nothing prevents DUI as effectively as checkpoints.