The roadside checks themselves are random as they aren't announced to the public, or if they are they're posted somewhere that's non-obvious. What comes afterwa

The roadside checks themselves are random as they aren't announced to the public, or if they are they're posted somewhere that's non-obvious. What comes afterwards when pulled over at one of these stops is inevitably a check to see if you've been drinking. I'm not saying this is fair or in the spirit of the law, but it's how they do this, and they're random enough.