ON-LINE AND OFF-LINE URBAN TRAFFIC CONTROL.

Computerized traffic signal control systems have become a widespread practice in many urban areas of the world which experience heavy automobile traffic. State-of-the-art control strategies are calculated off-line, stored in the computer's memory and selected for implementation by various real-time criteria such as time-of-day, level of congestion, or special events. Experiments have been conducted with various on-line signal control plan optimization techniques (Second and Third Generation) as opposed to the existing off-line techniques (First Generation). Successful implementation of these strategies depends on both the hardware and software components of the system. This paper presents results from studies conducted in the United States, Canada and the United Kingdom and analyzes their implications with respect to the development of improved generations of urban traffic control strategies.