Don't think it's going to be easy, either. This sign is a strict form. Three lines, seven characters max per line. That's tighter than haiku. It would take six or seven of them to add up to one 140-character Twitter tweet.
So here's your assignment,which could go two ways.
1) Compose a highway sign that will actually prevent collisions and save lives with a useful warning.
or 2) Write the coolest sign imaginable.
Got it? I'll go first:
NEXT 3 MI
BEAR O MY
Now your turn. If my comments box gives you any trouble, email sign copy to me at firstname.lastname@example.org