The Oregon Department of Transportation (ODOT) has recently begun changing their standard traffic signal control systems from the 170 controller running the Wapiti W4IKS firmware to 2070 controllers operating the Northwest Signal Supply Corporation’s Voyage software. Concurrent with this change in standard signal control systems, ODOT has taken the opportunity to install test sites with adaptive signal control systems and evaluate advanced features in the Voyage software. The evaluation of advanced features and adaptive signal control systems has led to a series of questions about how to measure performance, when to apply a given feature, and when should one system be preferred over another. To answer these questions a survey of literature and practising professionals was conducted to determine the current state of the practice regarding conventional and adaptive signal control systems. The survey of practitioners indicated that practitioners in general were seeking answers regarding when and how to implement adaptive systems. To assist ODOT’s engineers in selecting when and which systems to evaluate more closely, a methodology frame work has been developed and implemented in a Microsoft Excel based evaluation tool. This framework uses queuing models and simplified control logic to estimate corridor performance. Selected additional features have also been enabled to allow engineers to evaluate the performance benefits that may be realized through enabling them with the existing systems. Finally, to compare performance across different systems and different measures of effectiveness, the research team implemented a cost to benefit ratio calculation. This calculation encompasses performance measures produced by the evaluation model as well as external data regarding existing equipment, required upgrades, and additional costs such as those associated with retiming operations. By including as many cost factors as practical, the methodological framework and its Excel-based implementation may offer a means to make the selection of systems to evaluate as simple and straightforward as possible. (Author/publisher)
Abstract