Traffic congestion and accidents are major issues in Phnom Penh, the capital city of the Kingdom of Cambodia. An inefficient signal system and lack of traffic discipline contributed to the unfavorable traffic conditions. A comprehensive traffic management project was recently implemented. An area traffic control system that controls traffic signals in the city based on the traffic conditions was introduced, and other traffic management improvement works such as pavement markings, traffic signs, and median dividers were installed. The project is making a positive impact on road users. Efficient operation and maintenance are key factors for the project to sustain its benefits. Keywords: Traffic management, Traffic signal, Area traffic control, Congestion, Adaptive control