Automatic Vehicle Identification Systems for Electronic Toll Collection

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California Law requires Caltrans, in cooperation with the state's toll facility operators, to develop functional specifications and standards, i.e., a protocol for automatic vehicle identification (AVI), which would be used for electronic toll collection (ETC). The protocol governs the features of transponders in vehicles and overhead devices (readers) which detect the transponders. California law requires any protocol selected to be an open standard, meaning that toll facility operators must have the ability to select ETC equipment from different manufacturers and vendors.

In 1992, Caltrans developed a protocol for ETC in California which became known as "Title 21" after the section of the California Code of Regulations where the specifications for the standard are listed. Effective January 1, 2019, Caltrans adopted a new protocol known as 6C. The existing Title 21 protocol will continue to be used for seven years after that date, and then be discontinued. The seven-year overlap with the two protocols is intended to give the toll facility operators the necessary time to eliminate their existing inventory of the Title 21 transponders.

California 6C Electronic Toll Collection Standard (PDF)

Compatibility Specifications for Automatic Vehicle Identification Equipment


Extending the Sunset Date for the "Title 21" AVI Protocol

On December 4, 2023, the Office of Administrative Law (OAL) approved a regulatory action to extend the date for discontinuing the Title 21 protocol. The regulatory action was filed with the Secretary of State on December 4, 2023, and took effect upon filing. 

On September1, 2023, Caltrans sent public notice to interested parties related to the proposed regulatory action. The public of this notice initiated a public comment period that ended on October 17, 2023.

Prior to initiating the rulemaking process, Caltrans provided a questionnaire to all potentially affected stakeholders and held a public workshop on February 28, 2023, to obtain initial comments. The responses to the questionnaire and the minutes from the workshop are provided below.

Questionnaire Responses

Title 21 Public Workshop Minutes