Which two special purpose cards are found in traffic signal systems?

Answer: D — Video detector cards and Emergency vehicle pre-emption

In traffic signal systems, special purpose cards are critical for managing various functionalities necessary for efficient operation and safety. One of the primary cards is the video detector card, which is used to analyze real-time traffic conditions through video surveillance. These cards can identify the presence and movement of vehicles at intersections, allowing for adaptive traffic management based on actual traffic flow, thereby improving the overall efficiency of the signal operation. The other special purpose card mentioned is the emergency vehicle pre-emption card. This card is essential for allowing emergency vehicles, such as ambulances and fire trucks, to gain priority at traffic signals. When an emergency vehicle approaches a signalized intersection, the pre-emption system can change the signal to green in the direction of the emergency vehicle, reducing response time and enhancing public safety. Both of these cards play crucial roles in modern traffic signal systems, providing advanced capabilities that enhance traffic management and safety, which is why they are correctly identified as special purpose cards in this context.