[Alberta's Child]

. . . I do not see how the random searches are any different than "roving road blocks," where cops randomly pull over drivers without any probable cause in the hopes nailing a drunk driver.

That's a very good point. I don't think a roadside checkpoint of any kind can pass legal muster unless they stop EVERY driver, and not just random ones (this was the basis of a decision in a landmark case in New York or New Jersey a few years ago, in which a random drug-enforcement checkpoint on the George Washington Bridge was determined to be illegal).

[Labyrinthos]

Actually, the Supreme Court has upheld "roving road blocks" provided the selection process is objective, i.e., the cops pull over every 4th car that passes through a particular intersection or every 9th car that leaves the shopping mall.