United States Department of Transportation
i
Street Deployment of Pedestrian Control Smart Traffic Signals
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2009-04-01
[PDF-780.88 KB]
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Abstract:Smart Signals is a term used to describe the application of network based distributed control technology to the control of traffic signals at signalized intersections. Presently, signalized intersections use a centralized control approach where all of the controls are initiated by a single controller located in a traffic controller cabinet. Dedicated wires are used to turn signal lights on and off. The Smart Signals paradigm uses microprocessors located in the signals to distribute the control intelligence. The advantages of this approach extends the fault coverage, has the potential to reduce the physical size and cost of the traffic controller cabinet, allow for more precise control of intersection movements, and allow the inclusion of future innovations in sensors to traffic control. Our research has explored ways of integrating the new methodologies with existing practices for a more cost effective way of updating intersection traffic controls. We have demonstrated that Smart Signals and conventional traffic signals devices can effectively and reliably simultaneously operate using a single NEMA TS2 traffic controller. For street deployment, the Smart Signals devices must operate with the same degree of reliability as conventional traffic signals do today. Conventional traffic control systems use a malfunction management unit to monitor correctness of traffic controller outputs. However, a new approach to monitoring is required for the distributed control approach used by Smart Signals. We applied Ethernet safety critical control practices to Smart Signals resulting in synchronized time division multiplexing communications to ensure network devices are generating correct outputs.
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