Four of the 12 tollbooths on the Interstate 80 Carquinez Bridge in Northern California are using photonics technology to catch drivers who do not pay the toll. Caltrans is testing a new automatic toll-collection system that recognizes transponders in cars whose drivers have prepaid their tolls. The system, from MFS Network Technologies of Omaha, Neb., includes an infrared sensor to determine when a car passes through the booth and overhead monochrome and color video cameras to record license plate numbers and colors of vehicles that don't have transponders and, thus, haven't paid the toll.