Comparative Performance Evaluation of SCATS and Pre-timed Control Systems

Oakland County, one of the largest counties in the State of Michigan, has been experiencing congestion for the past two decades. During the 1990‟s, Oakland County experienced a surge of population growth and economic development. At the current level of funding, it would take 70 years to meet the capacity needs of the Oakland County roadways (2). Looking for innovative and cost effective ways to improve road user mobility and safety, the Road Commission for Oakland County (RCOC) began investigating innovative traffic control strategies associated with Intelligent Transportation Systems (ITS). Subsequently, the County Board of Commissioners approved $2 million for the development of an advanced traffic management system in southeast Oakland County. This commitment by Oakland County toward congestion mitigation, prompted the United States Congress to financially support this effort as a Federal demonstration project with $10 million in funding. The innovative traffic control system created in Oakland County with the Federal and County funds is called “FAST-TRAC”, an acronym which stands for Faster and Safer Travel through Traffic Routing and Advanced Controls. Through a field demonstration project, traffic signals at 28 intersections in the city of Troy within Oakland County were converted from a pre-timed coordinated traffic signal system to SCATS (Sydney Coordinated Adaptive Traffic System) control in 1992. SCAT is a computer controlled traffic signal system, developed in Australia and used widely in the Pacific Rim. SCATS uses anticipatory and adaptive techniques to increase the efficiency of the road network by minimizing the overall number of vehicular stops and delay experienced by motorists. The primary purpose of the SCATS system is to maximize the throughput of a roadway by controlling queue formation. In order to evaluate the performance of SCATS control system a research was conducted to determine the effectiveness of the SCATS signal system as compared to a pre-timed signal system in terms of traffic flow, delay, fuel consumption, emission and other selected measures of effectiveness. The research was conducted through a field experiment along a four-mile segment of M-59 between Pontiac Lake Road West to Pontiac Lake Road East consisting of seven signalized intersections. The M-59 corridor is located in Oakland County, Michigan. The data for the corridor was collected for the two signal system scenarios on a typical weekday and Friday for the noon (12 PM to 1 PM) and PM (4 PM to 6 PM) peak period, as well for a Saturday peak (9 AM to 11 AM). For the purpose of this study, M-59 corridor was converted from SCAT control system to Pre-Timed control system for eight weeks. When comparing the mean values for the various measures of effectiveness, the SCATS signal system, generally, had better performance indicators than the pre-timed signal system based upon the percent differences between the two systems. However, based upon the statistical analysis, the majority of the statistical tests indicated that there was no statistical difference between the two signal systems for any of the measures of effectiveness or peak periods analyzed.