Back when I was cab driver, I picked up a lot of drunk people from the DUI checkpoint. I usually avoided the bar areas but for some reason I did get a sadistic pleasure out of picking people up from the DUI checkpoints.
Here is how it would work. In the Phoenix area at the DUI checkpoints they have everything, mobile labs do do blood work and everything else. By the time these peopel are released they have been run through the coals. Their lives are now totally screwed up for the next several years.