In Warwick, a Rhode Island State Trooper was running radar. He had a perfect spot to watch for speeders, but wasn't getting any.
Then he discovered the problem. A 12-year-old boy was standing up the road with a hand-painted sign which read 'RADAR TRAP AHEAD!'
The officer later found a young accomplice down the road with a sign reading, 'TIPS' and a bucket full of money. (Beats a lemonade stand!)