Urban traffic congestion is a major transportation problem caused by increasing vehicle ownership, fixed-time traffic signals, irregular traffic demand, and inefficient allocation of green time. Conventional traffic lights operate according to predetermined timing plans and may continue displaying a green signal even when no vehicles are present. This results in unnecessary vehicle idling, increased fuel consumption, longer travel time, and reduced road-user satisfaction. This paper presents the design and working of a density-based intelligent traffic-light control system that dynamically adjusts signal timing according to the number of vehicles waiting on each approach. The proposed system uses vehicle-detection sensors, a microcontroller, signal-control hardware, and programming or simulation tools to monitor traffic conditions and determine the appropriate signal sequence. The controller assigns longer green periods to approaches with higher traffic density while maintaining minimum green time, yellow transition time, pedestrian safety, and maximum waiting limits. The system is evaluated under low, medium, and high traffic-load conditions. The proposed approach demonstrates the application of embedded control and intelligent transportation concepts to real-time traffic management. It can reduce unnecessary waiting, improve traffic flow, minimize idling, and support safer and more sustainable urban transportation.