Center to Center Standards

Center-to-Center communication involves the communication between two or more central management systems. Examples of Center-to-Center communication applicable to the Bay Area ITS Architecture include:

• Two or more traffic signal management systems exchanging information (including second-by-second status changes) to achieve coordinated operation of traffic signals managed by the different systems and to enable personnel at one center to monitor the status of signals operated from another center.
• Sharing of transportation related information with other Bay Area agencies or centers such as 511.
• Providing traffic signal priority for selected (e.g., behind schedule) transit vehicles.
• Posting a warning message on another agency’s changeable message sign.

The NTCIP Center-to-Center protocols are particularly relevant as they allow agencies to exchange information, to monitor conditions in other agencies’ systems, and to implement coordinated responses to incidents and other changes in field conditions when needed. Such data exchange and coordinated response can be implemented either manually or automatically. One agency can monitor, and issue basic commands to field devices (if authorized) operated by another agency, even though those devices may be from a different vendor than those used by the monitoring agency.

For Example

If Agency A wants to control Agency B’s traffic signals, Agency A sends a message to Agency B to ask for permission to control the signals. This is an example of Center-to-Center communication.

NTCIP Center-to-Center protocols are implemented currently though multiple standards. More information on the current status of NTCIP standards can be found at NTCIP.org. The major Center-to-Center projects in the Bay Area use a variety of standards. DATEX ASN (Data Exchange protocol/Abstract Syntex) is used by Silicon Valley-ITS, East Bay SMART Corridors, and the Bay Area Center-to-Center System. The Bay Area Center-to-Center System includes 511 and East Bay SMART Corridors. The SFgo connection to the Center-to-Center system is a DATEX to eXtensible Markup Language (XML) conversion. XML is also emerging as a Center-to-Center communications protocol. It has the advantage of being an industry wide standard (across all Microsoft Windows-based systems regardless of the application) and can be implemented relatively easily with “typical” information systems staff. Until XML becomes an accepted standard in the Bay Area, it is recommended that a Center to Center Task Force be developed to monitor changes in standard development and deployment and make recommendations to agencies implementing projects. The existing Center to Center Working Group could be expanded beyond the interim Center to Center project to take on the new responsibility of recommending Center to Center standards for projects throughout the region. This Task Force or Working Group would be coordinated with Architecture Maintenance efforts to ensure that the Architecture is updated accordingly.