Evaluation of traffic signal control systems

Improved traffic signal control using digital computer and microprocessor technology is receiving significant emphasis. The emphasis is being generated by the need to replace aging equipment, much of which was installed in the years following World War II, and by the need to increase the efficiency of road space. This latter element, increased efficiency, is extremely critical today giving increasing congestion in urban areas, resistance to major roadbuilding projects, public demand for cleaner air, and the need to minimize usage of oil. Traffic signal control improvements are being implemented as one element of overall traffic systems management programs because of their cost-effectiveness, relatively low capital requirement, and ease of implementation in terms of public concern. This paper concentrates on a simple description of what is meant by signal control, the difference between "old" and "new" systems, and the effectiveness of the newer systems. With regard to effectiveness, studies have found street performance to be improved by approximately 10 to 25 percent with perhaps 15 percent being the average. Using conservative assumptions, the cost-effectiveness analyses indicates a 5 to 1 payback in one year and over 25 to 1 for the system life. A further extrapolation of data indicates a nationwide potential savings of over 375 million gallons of fuel per year and motorist delay reduction in excess of 624 million gallons.