Check Mate

We've all seen checkpoints on roads, usually for sobriety, but I've lately seen signs in some places well ahead of the checkpoint identifying what's ahead.  I guess it varies by state and the purpose of the roadblock, but whether two miles ahead for immigration (used to see that one in Southern California), or two blocks for DMV, who exactly do you catch when you tell them you're going to catch them?

Image from shubtastic.blogspot.com