A traffic signal is an electrically operated device using colored lights to control traffic flow, typically at intersections. The standard sequence—green (proceed), yellow (caution/prepare to stop), red (stop)—is universally understood. Traffic signals manage competing traffic movements, improving safety and efficiency at busy intersections. Signal timing balances service to different approaches and movements. Protected phases provide exclusive green lights for turning movements. Pedestrian phases allow safe crossing. Signal systems range from simple fixed-timing controllers to sophisticated adaptive systems responding to real-time conditions. Signal infrastructure includes poles, controller cabinets, detection equipment, and communication systems. Proper signal maintenance is essential for safety—malfunctioning signals require immediate response.