Designing a traffic management system to utilize a digital cable network

The City of Walnut Creek is in the process of replacing its existing traffic management system with a new advanced traffic management system. The system will consist of a central control system, Model 2070 controllers, closed circuit television (CCTV) cameras, and a communications network system. The icons/sup TM/ central system was selected by the City to replace the existing VMS-330 system. A key element of the City's new system is the use of a digital cable network for communications between the central system and the field elements. The City's central system will utilize the network of a local digital cable company for the communications between the central system and the field traffic controllers, as well as the CCTV cameras (video signals and control). The digital cable network utilizes standard 10Base-T frames and Internet Protocol (IP) packets for the video and data transmission. At each traffic controller location, an interim solution which "packetizes" the controller's serial data will be implemented which will be replaced when the controllers are able to properly encapsulate data into IP packets for transmission. The video signal at each CCTV location will need to be compressed using readily available equipment. The cable modems proposed for the system can accept up to four devices and multiplex them into a single 10Base-T output. The paper discusses the basic network configuration, the design challenges of the system, and the future enhancements to the system.