"its for the children" huh?
how about instead of sitting around, hoping to nab a couple badguys and generate a buttload if income from seatbelt tickets, those cops went out and caught the CRIMINALS that were causing the problems.
besides, most criminals will know 15 minutes after a roadblock is set up, and find alternative routes.
It's a nice and easy way for the cops to not only generate money but they can sweep up people who have warrants as well as nab some moron for transporting drugs in the car.