 The last one is the one that really pulls it out of the purview of Fourth Amendment, and it's that. DUI roadblocks must be publicly advertised in advance through local newspapers, news reports, and police department websites to give the public an opportunity to say, I don't want to drive that way. And if they do, then you are, in essence, consenting to the roadblock if adequate public notice was given and you still chose to drive that way.