It appears to be an attempt to show drunks while they are sober that drinking and driving is a stupid, dangerous idea.
Now, who could possibly think otherwise?
But obviously this person didn't think so.
At a Blood Alcohol Level around 0.28 (2 1/2 times the limit of 0.08; 0.40 is darn-near dead, so this person was major league blotto), he (and I am making an assumption there, although drunk drivers are predominantly if not overwhelmingly male) was hardly in a position to think at all.
But he was able to get into his car and manoeuvre at least this far (I don't know where the trip started).
This is also an odd place for a crash. Straight road, decent visibility, no driveways, not much of anything. I guess he just ran off the road.
There is probably no way to measure the effectiveness of signs like this.
One thing for sure; you can't miss them, and they can't hurt.