Police in Escondido recently set up a DUI roadblock from 6pm to 12am. The tally:
1,600 cars stopped,
931 drivers screened,
82 drivers pulled aside for extra scrutiny,
32 vehicles impounded,
52 tickets issued to drivers other than those whose vehicles were impounded,
and, drum-roll please….
...one DUI arrest.
Given that the Supreme Court has only ruled on the legitimacy of roadblock checkpoints for DUI policing (it has declared them illegal for the purposes of drug policing, for example), you have to wonder at what point what these roadblocks are achieving in practice begins to make them constitutionally dubious, despite the fact that their stated purpose may be.