Roadway traffic control software

Roadway traffic control is an important practical example of real time control applications, but effective roadway control is hampered by a variety of organizational, financial and technical considerations. One major hurdle is the current reliance on outmoded field hardware and software. A systematic approach to traffic engineering software development could provide significant advantages with regard to software capability, flexibility and maintenance. Improved traffic controllers will likely be essential for many of the proposed intelligent vehicle highway systems (IVHS) applications. This paper describes the roadway traffic control problem generally and introduces a computable language that can be used for constructing real time traffic control software. This computable language is designed to be configured by a graphical user interface that does not require extensive software engineering training to use, yet provides much more flexibility and capability then possible by simply changing program parameters. The model is based upon the function block metaphor commonly used for constructing robust and efficient real time industrial control systems. The software model has been implemented in C on an open architecture traffic controller (OATC) hardware platform and demonstrated under simulated conditions for applications such as signalized intersection control, ramp metering, and communications with existing traffic control devices. System users can construct applications from a library of function blocks. The paper describes a demonstration application to freeway ramp metering control in Sacramento, CA.