DWS: Driving While Sleepy?

About a month ago New Jersey put a law on the books that makes it a crime to drive while sleepy. Again, it's a law that takes the place of basic common sense, but this one isn't a bad law, right?

Apparently, the law states that a person must have been awake for at least 24 hours (ok, so far) and must be knowingly driving while drowsy. Now how do you prove, outside of a confession, that someone was knowingly driving while drowsy? It is a very subjective requirement. Without there being an objective standard, I don't see this as being really an enforceable law. I can even see a court striking it down as being too vague as I don't think that there is a reasonable acceptance or standard for "knowingly driving while drowsy."

Like I said before, it is a law that really just codifies common sense. It really says something about how far away from the concept of personal responsibility we are as a society that we need to pass a law like this. But given how far away from that concept we are, I can grudingly accept the need for the law.

It just simply needs to be better written to take away any ambiguity or subjectiveness.