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ACS Lite is an adaptive control software application that has been developed as a closed-loop system by Siemens under contract to the FHWA Research, Development and Technology Traffic Operations Program. It may be deployed as an on-street field master or on a central server.
The ACS Lite software is designed to adapt the splits and offsets of signal control patterns/plans in a “closed-loop” system. Changes to cycle time are handled on a time-of-day schedule like traditional traffic control systems. At each optimization step, which occurs about every 10 minutes, the system changes the splits and offsets a small amount (e.g. 2-5 seconds) to accommodate changes in traffic flows.
ACS Lite is easy to configure through an HTML browser-based user interface. 75% of the configuration data is uploaded directly from the loacl controllers with no additional user data entry. After uploading configuration data the user configures links, detector locations, and adaptive configuration options through the browser and the system is ready to use for adaptive control.
As the system is running, web pages are updated each cycle to provide status of each intersection performance and track the changes made to the splits and offsets. In addition, the software archives its performance measures and decisions to a data store for future analysis and retrieval.
Browser-based access to operations is available not only locally, but also via the Internet if the master is equipped for remote IP access (e.g., a cellular modem).
Initial field testing of ACS Lite with Siemens control equipment in Houston, TX has shown 5-25% improvement in arterial travel times, significant reduction in stops, and 5%-50% improvements in delays at side streets and left turns. The ACS Lite approach to adaptive control has been designed to provide a significant amount of benefit for a minimum amount of agency investment in additional infrastructure, training, and maintenance by using stop bar detection and advanced loops commonly used for intersection control.
Reference Number: COM MN 2005 03.40 e